merge trunk

1 files changed, 1706 insertions, 1981 deletions

diff --git a/generic/tclIO.c b/generic/tclIO.c
index f1d85bf..aad576a 100644
--- a/generic/tclIO.c
+++ b/generic/tclIO.c
@@ -6,6 +6,7 @@
  *
  * Copyright (c) 1998-2000 Ajuba Solutions
  * Copyright (c) 1995-1997 Sun Microsystems, Inc.
+ * Contributions from Don Porter, NIST, 2014. (not subject to US copyright)
  *
  * See the file "license.terms" for information on usage and redistribution of
  * this file, and for a DISCLAIMER OF ALL WARRANTIES.
@@ -34,15 +35,15 @@ typedef struct ChannelHandler {
 
 /*
  * This structure keeps track of the current ChannelHandler being invoked in
- * the current invocation of ChannelHandlerEventProc. There is a potential
+ * the current invocation of Tcl_NotifyChannel. There is a potential
  * problem if a ChannelHandler is deleted while it is the current one, since
- * ChannelHandlerEventProc needs to look at the nextPtr field. To handle this
+ * Tcl_NotifyChannel needs to look at the nextPtr field. To handle this
  * problem, structures of the type below indicate the next handler to be
  * processed for any (recursively nested) dispatches in progress. The
  * nextHandlerPtr field is updated if the handler being pointed to is deleted.
- * The nextPtr field is used to chain together all recursive invocations, so
- * that Tcl_DeleteChannelHandler can find all the recursively nested
- * invocations of ChannelHandlerEventProc and compare the handler being
+ * The nestedHandlerPtr field is used to chain together all recursive
+ * invocations, so that Tcl_DeleteChannelHandler can find all the recursively
+ * nested invocations of Tcl_NotifyChannel and compare the handler being
  * deleted against the NEXT handler to be invoked in that invocation; when it
  * finds such a situation, Tcl_DeleteChannelHandler updates the nextHandlerPtr
  * field of the structure to the next handler.
@@ -53,21 +54,10 @@ typedef struct NextChannelHandler {
 					 * this invocation. */
     struct NextChannelHandler *nestedHandlerPtr;
 					/* Next nested invocation of
-					 * ChannelHandlerEventProc. */
+					 * Tcl_NotifyChannel. */
 } NextChannelHandler;
 
 /*
- * The following structure describes the event that is added to the Tcl
- * event queue by the channel handler check procedure.
- */
-
-typedef struct ChannelHandlerEvent {
-    Tcl_Event header;		/* Standard header for all events. */
-    Channel *chanPtr;		/* The channel that is ready. */
-    int readyMask;		/* Events that have occurred. */
-} ChannelHandlerEvent;
-
-/*
  * The following structure is used by Tcl_GetsObj() to encapsulates the
  * state for a "gets" operation.
  */
@@ -129,7 +119,7 @@ typedef struct CopyState {
 typedef struct ThreadSpecificData {
     NextChannelHandler *nestedHandlerPtr;
 				/* This variable holds the list of nested
-				 * ChannelHandlerEventProc invocations. */
+				 * Tcl_NotifyChannel invocations. */
     ChannelState *firstCSPtr;	/* List of all channels currently open,
 				 * indexed by ChannelState, as only one
 				 * ChannelState exists per set of stacked
@@ -162,11 +152,14 @@ typedef struct CloseCallback {
  */
 
 static ChannelBuffer *	AllocChannelBuffer(int length);
+static void		PreserveChannelBuffer(ChannelBuffer *bufPtr);
+static void		ReleaseChannelBuffer(ChannelBuffer *bufPtr);
+static int		IsShared(ChannelBuffer *bufPtr);
+static void		ChannelFree(Channel *chanPtr);
 static void		ChannelTimerProc(ClientData clientData);
+static int		ChanRead(Channel *chanPtr, char *dst, int dstSize);
 static int		CheckChannelErrors(ChannelState *statePtr,
 			    int direction);
-static int		CheckFlush(Channel *chanPtr, ChannelBuffer *bufPtr,
-			    int newlineFlag);
 static int		CheckForDeadChannel(Tcl_Interp *interp,
 			    ChannelState *statePtr);
 static void		CheckForStdChannelsBeingClosed(Tcl_Channel chan);
@@ -178,10 +171,15 @@ static int		CloseChannelPart(Tcl_Interp *interp, Channel *chanPtr,
 			    int errorCode, int flags);
 static int		CloseWrite(Tcl_Interp *interp, Channel *chanPtr);
 static void		CommonGetsCleanup(Channel *chanPtr);
-static int		CopyAndTranslateBuffer(ChannelState *statePtr,
-			    char *result, int space);
-static int		CopyBuffer(Channel *chanPtr, char *result, int space);
 static int		CopyData(CopyState *csPtr, int mask);
+static int		MoveBytes(CopyState *csPtr);
+
+static void		MBCallback(CopyState *csPtr, Tcl_Obj *errObj);
+static void		MBError(CopyState *csPtr, int mask, int errorCode);
+static int		MBRead(CopyState *csPtr);
+static int		MBWrite(CopyState *csPtr);
+static void		MBEvent(ClientData clientData, int mask);
+
 static void		CopyEventProc(ClientData clientData, int mask);
 static void		CreateScriptRecord(Tcl_Interp *interp,
 			    Channel *chanPtr, int mask, Tcl_Obj *scriptPtr);
@@ -193,16 +191,16 @@ static int		DetachChannel(Tcl_Interp *interp, Tcl_Channel chan);
 static void		DiscardInputQueued(ChannelState *statePtr,
 			    int discardSavedBuffers);
 static void		DiscardOutputQueued(ChannelState *chanPtr);
-static int		DoRead(Channel *chanPtr, char *srcPtr, int slen, int allowShortReads);
-static int		DoWrite(Channel *chanPtr, const char *src, int srcLen);
+static int		DoRead(Channel *chanPtr, char *dst, int bytesToRead,
+			    int allowShortReads);
 static int		DoReadChars(Channel *chan, Tcl_Obj *objPtr, int toRead,
 			    int appendFlag);
-static int		DoWriteChars(Channel *chan, const char *src, int len);
 static int		FilterInputBytes(Channel *chanPtr,
 			    GetsState *statePtr);
 static int		FlushChannel(Tcl_Interp *interp, Channel *chanPtr,
 			    int calledFromAsyncFlush);
 static int		TclGetsObjBinary(Tcl_Channel chan, Tcl_Obj *objPtr);
+static Tcl_Encoding	GetBinaryEncoding();
 static void		FreeBinaryEncoding(ClientData clientData);
 static Tcl_HashTable *	GetChannelTable(Tcl_Interp *interp);
 static int		GetInput(Channel *chanPtr);
@@ -211,29 +209,30 @@ static int		HaveVersion(const Tcl_ChannelType *typePtr,
 static void		PeekAhead(Channel *chanPtr, char **dstEndPtr,
 			    GetsState *gsPtr);
 static int		ReadBytes(ChannelState *statePtr, Tcl_Obj *objPtr,
-			    int charsLeft, int *offsetPtr);
+			    int charsLeft);
 static int		ReadChars(ChannelState *statePtr, Tcl_Obj *objPtr,
-			    int charsLeft, int *offsetPtr, int *factorPtr);
+			    int charsLeft, int *factorPtr);
 static void		RecycleBuffer(ChannelState *statePtr,
 			    ChannelBuffer *bufPtr, int mustDiscard);
 static int		StackSetBlockMode(Channel *chanPtr, int mode);
 static int		SetBlockMode(Tcl_Interp *interp, Channel *chanPtr,
 			    int mode);
 static void		StopCopy(CopyState *csPtr);
-static int		TranslateInputEOL(ChannelState *statePtr, char *dst,
-			    const char *src, int *dstLenPtr, int *srcLenPtr);
-static int		TranslateOutputEOL(ChannelState *statePtr, char *dst,
+static void		TranslateInputEOL(ChannelState *statePtr, char *dst,
 			    const char *src, int *dstLenPtr, int *srcLenPtr);
 static void		UpdateInterest(Channel *chanPtr);
-static int		WriteBytes(Channel *chanPtr, const char *src,
-			    int srcLen);
-static int		WriteChars(Channel *chanPtr, const char *src,
-			    int srcLen);
+static int		Write(Channel *chanPtr, const char *src,
+			    int srcLen, Tcl_Encoding encoding);
 static Tcl_Obj *	FixLevelCode(Tcl_Obj *msg);
 static void		SpliceChannel(Tcl_Channel chan);
 static void		CutChannel(Tcl_Channel chan);
 static int              WillRead(Channel *chanPtr);
 
+#define WriteChars(chanPtr, src, srcLen) \
+			Write(chanPtr, src, srcLen, chanPtr->state->encoding)
+#define WriteBytes(chanPtr, src, srcLen) \
+			Write(chanPtr, src, srcLen, tclIdentityEncoding)
+
 /*
  * Simplifying helper macros. All may use their argument(s) multiple times.
  * The ANSI C "prototypes" for the macros are listed below, together with a
@@ -286,7 +285,7 @@ static int              WillRead(Channel *chanPtr);
 
 #define IsBufferEmpty(bufPtr)	((bufPtr)->nextAdded == (bufPtr)->nextRemoved)
 
-#define IsBufferFull(bufPtr)	((bufPtr)->nextAdded >= (bufPtr)->bufLength)
+#define IsBufferFull(bufPtr)	((bufPtr) && (bufPtr)->nextAdded >= (bufPtr)->bufLength)
 
 #define IsBufferOverflowing(bufPtr) ((bufPtr)->nextAdded>(bufPtr)->bufLength)
 
@@ -323,14 +322,13 @@ static int              WillRead(Channel *chanPtr);
 static void		DupChannelIntRep(Tcl_Obj *objPtr, Tcl_Obj *copyPtr);
 static int		SetChannelFromAny(Tcl_Interp *interp,
 			    Tcl_Obj *objPtr);
-static void		UpdateStringOfChannel(Tcl_Obj *objPtr);
 static void		FreeChannelIntRep(Tcl_Obj *objPtr);
 
-static const Tcl_ObjType tclChannelType = {
+static const Tcl_ObjType chanObjType = {
     "channel",			/* name for this type */
     FreeChannelIntRep,		/* freeIntRepProc */
     DupChannelIntRep,		/* dupIntRepProc */
-    NULL,			/* updateStringProc UpdateStringOfChannel */
+    NULL,			/* updateStringProc */
     NULL			/* setFromAnyProc SetChannelFromAny */
 };
 
@@ -339,7 +337,7 @@ static const Tcl_ObjType tclChannelType = {
 #define SET_CHANNELSTATE(objPtr, storePtr) \
     ((objPtr)->internalRep.twoPtrValue.ptr1 = (void *) (storePtr))
 #define GET_CHANNELINTERP(objPtr) \
-    ((Interp *) (objPtr)->internalRep.twoPtrValue.ptr2)
+    ((Tcl_Interp *) (objPtr)->internalRep.twoPtrValue.ptr2)
 #define SET_CHANNELINTERP(objPtr, storePtr) \
     ((objPtr)->internalRep.twoPtrValue.ptr2 = (void *) (storePtr))
 
@@ -382,19 +380,87 @@ ChanCloseHalf(
     return chanPtr->typePtr->close2Proc(chanPtr->instanceData, interp, flags);
 }
 
-static inline int
+/*
+ *---------------------------------------------------------------------------
+ *
+ * ChanRead --
+ *
+ *	Read up to dstSize bytes using the inputProc of chanPtr, store
+ *	them at dst, and return the number of bytes stored.
+ *
+ * Results:
+ *	The return value of the driver inputProc,
+ *	  - number of bytes stored at dst, ot
+ *	  - -1 on error, with a Posix error code available to the
+ *	    caller by calling Tcl_GetErrno().
+ *
+ * Side effects:
+ *	The CHANNEL_BLOCKED and CHANNEL_EOF flags of the channel state are
+ *	set as appropriate.
+ *	On EOF, the inputEncodingFlags are set to perform ending operations
+ *	on decoding.
+ *	TODO - Is this really the right place for that?
+ *
+ *---------------------------------------------------------------------------
+ */
+static int
 ChanRead(
     Channel *chanPtr,
     char *dst,
-    int dstSize,
-    int *errnoPtr)
+    int dstSize)
 {
+    int bytesRead, result;
+
+    /*
+     * If the caller asked for zero bytes, we'd force the inputProc
+     * to return zero bytes, and then misinterpret that as EOF.
+     */
+    assert(dstSize > 0);
+
+    /*
+     * Each read op must set the blocked and eof states anew, not let
+     * the effect of prior reads leak through.
+     */
+    if (GotFlag(chanPtr->state, CHANNEL_EOF)) {
+        chanPtr->state->inputEncodingFlags |= TCL_ENCODING_START;
+    }
+    ResetFlag(chanPtr->state, CHANNEL_BLOCKED | CHANNEL_EOF);
+    chanPtr->state->inputEncodingFlags &= ~TCL_ENCODING_END;
     if (WillRead(chanPtr) < 0) {
         return -1;
     }
 
-    return chanPtr->typePtr->inputProc(chanPtr->instanceData, dst, dstSize,
-	    errnoPtr);
+    bytesRead = chanPtr->typePtr->inputProc(chanPtr->instanceData,
+	    dst, dstSize, &result);
+
+    /* Stop any flag leakage through stacked channel levels */
+    if (GotFlag(chanPtr->state, CHANNEL_EOF)) {
+        chanPtr->state->inputEncodingFlags |= TCL_ENCODING_START;
+    }
+    ResetFlag(chanPtr->state, CHANNEL_BLOCKED | CHANNEL_EOF);
+    chanPtr->state->inputEncodingFlags &= ~TCL_ENCODING_END;
+    if (bytesRead > 0) {
+	/*
+	 * If we get a short read, signal up that we may be BLOCKED.
+	 * We should avoid calling the driver because on some
+	 * platforms we will block in the low level reading code even
+	 * though the channel is set into nonblocking mode.
+	 */
+
+	if (bytesRead < dstSize) {
+	    SetFlag(chanPtr->state, CHANNEL_BLOCKED);
+	}
+    } else if (bytesRead == 0) {
+	SetFlag(chanPtr->state, CHANNEL_EOF);
+	chanPtr->state->inputEncodingFlags |= TCL_ENCODING_END;
+    } else if (bytesRead < 0) {
+	if ((result == EWOULDBLOCK) || (result == EAGAIN)) {
+	    SetFlag(chanPtr->state, CHANNEL_BLOCKED);
+	    result = EAGAIN;
+	}
+	Tcl_SetErrno(result);
+    }
+    return bytesRead;
 }
 
 static inline Tcl_WideInt
@@ -512,11 +578,11 @@ TclFinalizeIOSubsystem(void)
     int active = 1;		/* Flag == 1 while there's still work to do */
     int doflushnb;
 
-    /* Fetch the pre-TIP#398 compatibility flag */ 
+    /* Fetch the pre-TIP#398 compatibility flag */
     {
         const char *s;
         Tcl_DString ds;
-        
+
         s = TclGetEnv("TCL_FLUSH_NONBLOCKING_ON_EXIT", &ds);
         doflushnb = ((s != NULL) && strcmp(s, "0"));
         if (s != NULL) {
@@ -558,6 +624,7 @@ TclFinalizeIOSubsystem(void)
 
 	if (active) {
 
+	    TclChannelPreserve((Tcl_Channel)chanPtr);
 	    /*
 	     * TIP #398:  by default, we no  longer set the  channel back into
              * blocking  mode.  To  restore  the old  blocking  behavior,  the
@@ -568,9 +635,9 @@ TclFinalizeIOSubsystem(void)
                     /* Set the channel back into blocking mode to ensure that we wait
                      * for all data to flush out.
                      */
-                
+
                 (void) Tcl_SetChannelOption(NULL, (Tcl_Channel) chanPtr,
-                                            "-blocking", "on");                    
+                                            "-blocking", "on");
             }
 
 	    if ((chanPtr == (Channel *) tsdPtr->stdinChannel) ||
@@ -616,6 +683,7 @@ TclFinalizeIOSubsystem(void)
 		chanPtr->instanceData = NULL;
 		SetFlag(statePtr, CHANNEL_DEAD);
 	    }
+	    TclChannelRelease((Tcl_Channel)chanPtr);
 	}
     }
 
@@ -954,8 +1022,7 @@ DeleteChannelTable(
 
 	Tcl_DeleteHashEntry(hPtr);
 	SetFlag(statePtr, CHANNEL_TAINTED);
-	statePtr->refCount--;
-	if (statePtr->refCount <= 0) {
+	if (statePtr->refCount-- <= 1) {
 	    if (!GotFlag(statePtr, BG_FLUSH_SCHEDULED)) {
 		(void) Tcl_Close(interp, (Tcl_Channel) chanPtr);
 	    }
@@ -1177,15 +1244,6 @@ Tcl_UnregisterChannel(
      */
 
     if (statePtr->refCount <= 0) {
-	/*
-	 * Ensure that if there is another buffer, it gets flushed whether or
-	 * not we are doing a background flush.
-	 */
-
-	if ((statePtr->curOutPtr != NULL) &&
-		IsBufferReady(statePtr->curOutPtr)) {
-	    SetFlag(statePtr, BUFFER_READY);
-	}
 	Tcl_Preserve(statePtr);
 	if (!GotFlag(statePtr, BG_FLUSH_SCHEDULED)) {
 	    /*
@@ -1497,6 +1555,22 @@ Tcl_CreateChannel(
      */
 
     assert(sizeof(Tcl_ChannelTypeVersion) == sizeof(Tcl_DriverBlockModeProc *));
+    assert(typePtr->typeName != NULL);
+    if (NULL == typePtr->closeProc) {
+	Tcl_Panic("channel type %s must define closeProc", typePtr->typeName);
+    }
+    if ((TCL_READABLE & mask) && (NULL == typePtr->inputProc)) {
+	Tcl_Panic("channel type %s must define inputProc when used for reader channel", typePtr->typeName);
+    }
+    if ((TCL_WRITABLE & mask) &&  (NULL == typePtr->outputProc)) {
+	Tcl_Panic("channel type %s must define outputProc when used for writer channel", typePtr->typeName);
+    }
+    if (NULL == typePtr->watchProc) {
+	Tcl_Panic("channel type %s must define watchProc", typePtr->typeName);
+    }
+    if ((NULL!=typePtr->wideSeekProc) && (NULL == typePtr->seekProc)) {
+	Tcl_Panic("channel type %s must define seekProc if defining wideSeekProc", typePtr->typeName);
+    }
 
     /*
      * JH: We could subsequently memset these to 0 to avoid the numerous
@@ -1581,11 +1655,7 @@ Tcl_CreateChannel(
     statePtr->timer		= NULL;
     statePtr->csPtrR		= NULL;
     statePtr->csPtrW		= NULL;
-
     statePtr->outputStage	= NULL;
-    if ((statePtr->encoding != NULL) && GotFlag(statePtr, TCL_WRITABLE)) {
-	statePtr->outputStage = ckalloc(statePtr->bufSize + 2);
-    }
 
     /*
      * As we are creating the channel, it is obviously the top for now.
@@ -1597,6 +1667,7 @@ Tcl_CreateChannel(
     chanPtr->upChanPtr		= NULL;
     chanPtr->inQueueHead	= NULL;
     chanPtr->inQueueTail	= NULL;
+    chanPtr->refCount		= 0;
 
     /*
      * TIP #219, Tcl Channel Reflection API
@@ -1750,6 +1821,10 @@ Tcl_StackChannel(
 	statePtr->csPtrR = NULL;
 	statePtr->csPtrW = NULL;
 
+	/*
+	 * TODO: Examine what can go wrong if Tcl_Flush() call disturbs
+	 * the stacking state of this channel during its operations.
+	 */
 	if (Tcl_Flush((Tcl_Channel) prevChanPtr) != TCL_OK) {
 	    statePtr->csPtrR = csPtrR;
 	    statePtr->csPtrW = csPtrW;
@@ -1781,17 +1856,17 @@ Tcl_StackChannel(
      */
 
     if (((mask & TCL_READABLE) != 0) && (statePtr->inQueueHead != NULL)) {
+
 	/*
-	 * Remark: It is possible that the channel buffers contain data from
-	 * some earlier push-backs.
+	 * When statePtr->inQueueHead is not NULL, we know
+	 * prevChanPtr->inQueueHead must be NULL.
 	 */
 
-	statePtr->inQueueTail->nextPtr = prevChanPtr->inQueueHead;
-	prevChanPtr->inQueueHead = statePtr->inQueueHead;
+	assert(prevChanPtr->inQueueHead == NULL);
+	assert(prevChanPtr->inQueueTail == NULL);
 
-	if (prevChanPtr->inQueueTail == NULL) {
-	    prevChanPtr->inQueueTail = statePtr->inQueueTail;
-	}
+	prevChanPtr->inQueueHead = statePtr->inQueueHead;
+	prevChanPtr->inQueueTail = statePtr->inQueueTail;
 
 	statePtr->inQueueHead = NULL;
 	statePtr->inQueueTail = NULL;
@@ -1813,6 +1888,7 @@ Tcl_StackChannel(
     chanPtr->upChanPtr		= NULL;
     chanPtr->inQueueHead	= NULL;
     chanPtr->inQueueTail	= NULL;
+    chanPtr->refCount		= 0;
 
     /*
      * Place new block at the head of a possibly existing list of previously
@@ -1837,6 +1913,41 @@ Tcl_StackChannel(
 
     return (Tcl_Channel) chanPtr;
 }
+
+void
+TclChannelPreserve(
+    Tcl_Channel chan)
+{
+    ((Channel *)chan)->refCount++;
+}
+
+void
+TclChannelRelease(
+    Tcl_Channel chan)
+{
+    Channel *chanPtr = (Channel *) chan;
+
+    if (chanPtr->refCount == 0) {
+	Tcl_Panic("Channel released more than preserved");
+    }
+    if (--chanPtr->refCount) {
+	return;
+    }
+    if (chanPtr->typePtr == NULL) {
+	ckfree(chanPtr);
+    }
+}
+
+static void
+ChannelFree(
+    Channel *chanPtr)
+{
+    if (chanPtr->refCount == 0) {
+	ckfree(chanPtr);
+	return;
+    }
+    chanPtr->typePtr = NULL;
+}
 
 /*
  *----------------------------------------------------------------------
@@ -1879,6 +1990,13 @@ Tcl_UnstackChannel(
 	 * into the old structure.
 	 */
 
+	/*
+	 * TODO: Figure out how to handle the situation where the chan
+	 * operations called below by this unstacking operation cause
+	 * another unstacking recursively.  In that case the downChanPtr
+	 * value we're holding on to will not be the right thing.
+	 */
+
 	Channel *downChanPtr = chanPtr->downChanPtr;
 
 	/*
@@ -1976,14 +2094,9 @@ Tcl_UnstackChannel(
 	 */
 
 	result = ChanClose(chanPtr, interp);
-	chanPtr->typePtr = NULL;
-
-	/*
-	 * AK: Tcl_NotifyChannel may hold a reference to this block of memory
-	 */
+	ChannelFree(chanPtr);
 
-	Tcl_EventuallyFree(chanPtr, TCL_DYNAMIC);
-	UpdateInterest(downChanPtr);
+	UpdateInterest(statePtr->topChanPtr);
 
 	if (result != 0) {
 	    Tcl_SetErrno(result);
@@ -2295,8 +2408,36 @@ AllocChannelBuffer(
     bufPtr->nextRemoved	= BUFFER_PADDING;
     bufPtr->bufLength	= length + BUFFER_PADDING;
     bufPtr->nextPtr	= NULL;
+    bufPtr->refCount	= 1;
     return bufPtr;
 }
+
+static void
+PreserveChannelBuffer(
+    ChannelBuffer *bufPtr)
+{
+    if (bufPtr->refCount == 0) {
+	Tcl_Panic("Reuse of ChannelBuffer! %p", bufPtr);
+    }
+    bufPtr->refCount++;
+}
+
+static void
+ReleaseChannelBuffer(
+    ChannelBuffer *bufPtr)
+{
+    if (--bufPtr->refCount) {
+	return;
+    }
+    ckfree(bufPtr);
+}
+
+static int
+IsShared(
+    ChannelBuffer *bufPtr)
+{
+    return bufPtr->refCount > 1;
+}
 
 /*
  *----------------------------------------------------------------------
@@ -2327,20 +2468,23 @@ RecycleBuffer(
     /*
      * Do we have to free the buffer to the OS?
      */
+    if (IsShared(bufPtr)) {
+	mustDiscard = 1;
+    }
 
     if (mustDiscard) {
-	ckfree(bufPtr);
+	ReleaseChannelBuffer(bufPtr);
 	return;
     }
 
     /*
-     * Only save buffers which are at least as big as the requested buffersize
-     * for the channel. This is to honor dynamic changes of the buffersize
+     * Only save buffers which have the requested buffersize for the
+     * channel. This is to honor dynamic changes of the buffersize
      * made by the user.
      */
 
-    if ((bufPtr->bufLength - BUFFER_PADDING) < statePtr->bufSize) {
-	ckfree(bufPtr);
+    if ((bufPtr->bufLength - BUFFER_PADDING) != statePtr->bufSize) {
+	ReleaseChannelBuffer(bufPtr);
 	return;
     }
 
@@ -2375,7 +2519,7 @@ RecycleBuffer(
      * If we reached this code we return the buffer to the OS.
      */
 
-    ckfree(bufPtr);
+    ReleaseChannelBuffer(bufPtr);
     return;
 
   keepBuffer:
@@ -2413,6 +2557,11 @@ DiscardOutputQueued(
     }
     statePtr->outQueueHead = NULL;
     statePtr->outQueueTail = NULL;
+    bufPtr = statePtr->curOutPtr;
+    if (bufPtr && BytesLeft(bufPtr)) {
+	statePtr->curOutPtr = NULL;
+	RecycleBuffer(statePtr, bufPtr, 0);
+    }
 }
 
 /*
@@ -2480,8 +2629,6 @@ FlushChannel(
     ChannelState *statePtr = chanPtr->state;
 				/* State of the channel stack. */
     ChannelBuffer *bufPtr;	/* Iterates over buffered output queue. */
-    int toWrite;		/* Amount of output data in current buffer
-				 * available to be written. */
     int written;		/* Amount of output data actually written in
 				 * current round. */
     int errorCode = 0;		/* Stores POSIX error codes from channel
@@ -2501,63 +2648,61 @@ FlushChannel(
     }
 
     /*
-     * Loop over the queued buffers and attempt to flush as much as possible
-     * of the queued output to the channel.
-     */
-
-    Tcl_Preserve(chanPtr);
-    while (1) {
-	/*
-	 * If the queue is empty and there is a ready current buffer, OR if
-	 * the current buffer is full, then move the current buffer to the
-	 * queue.
-	 */
-
-	if (((statePtr->curOutPtr != NULL) &&
-		IsBufferFull(statePtr->curOutPtr))
-		|| (GotFlag(statePtr, BUFFER_READY) &&
-			(statePtr->outQueueHead == NULL))) {
-	    ResetFlag(statePtr, BUFFER_READY);
-	    statePtr->curOutPtr->nextPtr = NULL;
-	    if (statePtr->outQueueHead == NULL) {
-		statePtr->outQueueHead = statePtr->curOutPtr;
-	    } else {
-		statePtr->outQueueTail->nextPtr = statePtr->curOutPtr;
-	    }
-	    statePtr->outQueueTail = statePtr->curOutPtr;
-	    statePtr->curOutPtr = NULL;
+     * Should we shift the current output buffer over to the output queue?
+     * First check that there are bytes in it.  If so then...
+     * If the output queue is empty, then yes, trusting the caller called
+     * us only when written bytes ought to be flushed.
+     * If the current output buffer is full, then yes, so we can meet
+     * the post-condition that on a successful return to caller we've
+     * left space in the current output buffer for more writing (the flush
+     * call was to make new room).
+     * If the channel is blocking, then yes, so we guarantee that
+     * blocking flushes actually flush all pending data.
+     * Otherwise, no.  Keep the current output buffer where it is so more
+     * can be written to it, possibly filling it, to promote more efficient
+     * buffer usage.
+     */
+
+    bufPtr = statePtr->curOutPtr;
+    if (bufPtr && BytesLeft(bufPtr) && /* Keep empties off queue */
+	    (statePtr->outQueueHead == NULL || IsBufferFull(bufPtr)
+		    || !GotFlag(statePtr, CHANNEL_NONBLOCKING))) {
+	if (statePtr->outQueueHead == NULL) {
+	    statePtr->outQueueHead = bufPtr;
+	} else {
+	    statePtr->outQueueTail->nextPtr = bufPtr;
 	}
-	bufPtr = statePtr->outQueueHead;
+	statePtr->outQueueTail = bufPtr;
+	statePtr->curOutPtr = NULL;
+    }
 
-	/*
-	 * If we are not being called from an async flush and an async flush
-	 * is active, we just return without producing any output.
-	 */
+    assert(!IsBufferFull(statePtr->curOutPtr));
 
-	if (!calledFromAsyncFlush && GotFlag(statePtr, BG_FLUSH_SCHEDULED)) {
-	    errorCode = 0;
-	    goto done;
-	}
+    /*
+     * If we are not being called from an async flush and an async flush
+     * is active, we just return without producing any output.
+     */
 
-	/*
-	 * If the output queue is still empty, break out of the while loop.
-	 */
+    if (!calledFromAsyncFlush && GotFlag(statePtr, BG_FLUSH_SCHEDULED)) {
+	return 0;
+    }
 
-	if (bufPtr == NULL) {
-	    break;		/* Out of the "while (1)". */
-	}
+    /*
+     * Loop over the queued buffers and attempt to flush as much as possible
+     * of the queued output to the channel.
+     */
+
+    TclChannelPreserve((Tcl_Channel)chanPtr);
+    while (statePtr->outQueueHead) {
+	bufPtr = statePtr->outQueueHead;
 
 	/*
 	 * Produce the output on the channel.
 	 */
 
-	toWrite = BytesLeft(bufPtr);
-	if (toWrite == 0) {
-            written = 0;
-	} else {
-	    written = ChanWrite(chanPtr, RemovePoint(bufPtr), toWrite,
-		    &errorCode);
-	}
+	PreserveChannelBuffer(bufPtr);
+	written = ChanWrite(chanPtr, RemovePoint(bufPtr), BytesLeft(bufPtr),
+		&errorCode);
 
 	/*
 	 * If the write failed completely attempt to start the asynchronous
@@ -2572,6 +2717,7 @@ FlushChannel(
 
 	    if (errorCode == EINTR) {
 		errorCode = 0;
+		ReleaseChannelBuffer(bufPtr);
 		continue;
 	    }
 
@@ -2593,6 +2739,7 @@ FlushChannel(
 		    UpdateInterest(chanPtr);
 		}
 		errorCode = 0;
+		ReleaseChannelBuffer(bufPtr);
 		break;
 	    }
 
@@ -2654,14 +2801,15 @@ FlushChannel(
 	     */
 
 	    DiscardOutputQueued(statePtr);
-	    continue;
+	    ReleaseChannelBuffer(bufPtr);
+	    break;
 	} else {
+	    /* TODO: Consider detecting and reacting to short writes
+	     * on blocking channels.  Ought not happen.  See iocmd-24.2. */
 	    wroteSome = 1;
 	}
 
-	if (!IsBufferEmpty(bufPtr)) {
-	    bufPtr->nextRemoved += written;
-	}
+	bufPtr->nextRemoved += written;
 
 	/*
 	 * If this buffer is now empty, recycle it.
@@ -2674,7 +2822,8 @@ FlushChannel(
 	    }
 	    RecycleBuffer(statePtr, bufPtr, 0);
 	}
-    }	/* Closes "while (1)". */
+	ReleaseChannelBuffer(bufPtr);
+    }	/* Closes "while". */
 
     /*
      * If we wrote some data while flushing in the background, we are done.
@@ -2689,6 +2838,25 @@ FlushChannel(
 	} else if (statePtr->outQueueHead == NULL) {
 	    ResetFlag(statePtr, BG_FLUSH_SCHEDULED);
 	    ChanWatch(chanPtr, statePtr->interestMask);
+	} else {
+
+	    /*
+	     * When we are calledFromAsyncFlush, that means a writable
+	     * state on the channel triggered the call, so we should be
+	     * able to write something.  Either we did write something
+	     * and wroteSome should be set, or there was nothing left to
+	     * write in this call, and we've completed the BG flush.
+	     * These are the two cases above.  If we get here, that means
+	     * there is some kind failure in the writable event machinery.
+	     *
+	     * The tls extension indeed suffers from flaws in its channel
+	     * event mgmt.  See http://core.tcl.tk/tcl/info/c31ca233ca.
+	     * Until that patch is broadly distributed, disable the
+	     * assertion checking here, so that programs using Tcl and
+	     * tls can be debugged.
+
+	    assert(!calledFromAsyncFlush);
+	     */
 	}
     }
 
@@ -2721,7 +2889,7 @@ FlushChannel(
     }
 
   done:
-    Tcl_Release(chanPtr);
+    TclChannelRelease((Tcl_Channel)chanPtr);
     return errorCode;
 }
 
@@ -2775,7 +2943,7 @@ CloseChannel(
      */
 
     if (statePtr->curOutPtr != NULL) {
-	ckfree(statePtr->curOutPtr);
+	ReleaseChannelBuffer(statePtr->curOutPtr);
 	statePtr->curOutPtr = NULL;
     }
 
@@ -2838,10 +3006,6 @@ CloseChannel(
 	}
 
 	Tcl_FreeEncoding(statePtr->encoding);
-	if (statePtr->outputStage != NULL) {
-	    ckfree(statePtr->outputStage);
-	    statePtr->outputStage = NULL;
-	}
     }
 
     /*
@@ -2891,9 +3055,9 @@ CloseChannel(
 
 	statePtr->topChanPtr = downChanPtr;
 	downChanPtr->upChanPtr = NULL;
-	chanPtr->typePtr = NULL;
 
-	Tcl_EventuallyFree(chanPtr, TCL_DYNAMIC);
+	ChannelFree(chanPtr);
+
 	return Tcl_Close(interp, (Tcl_Channel) downChanPtr);
     }
 
@@ -2901,13 +3065,11 @@ CloseChannel(
      * There is only the TOP Channel, so we free the remaining pointers we
      * have and then ourselves. Since this is the last of the channels in the
      * stack, make sure to free the ChannelState structure associated with it.
-     * We use Tcl_EventuallyFree to allow for any last references.
      */
 
-    chanPtr->typePtr = NULL;
+    ChannelFree(chanPtr);
 
     Tcl_EventuallyFree(statePtr, TCL_DYNAMIC);
-    Tcl_EventuallyFree(chanPtr, TCL_DYNAMIC);
 
     return errorCode;
 }
@@ -3191,10 +3353,18 @@ Tcl_Close(
 
     stickyError = 0;
 
-    if ((statePtr->encoding != NULL) && (statePtr->curOutPtr != NULL)
-	    && (CheckChannelErrors(statePtr, TCL_WRITABLE) == 0)) {
-	statePtr->outputEncodingFlags |= TCL_ENCODING_END;
-	if (WriteChars(chanPtr, "", 0) < 0) {
+    if (GotFlag(statePtr, TCL_WRITABLE) && (statePtr->encoding != NULL)
+	    && !(statePtr->outputEncodingFlags & TCL_ENCODING_START)) {
+
+	int code = CheckChannelErrors(statePtr, TCL_WRITABLE);
+
+	if (code == 0) {
+	    statePtr->outputEncodingFlags |= TCL_ENCODING_END;
+	    code = WriteChars(chanPtr, "", 0);
+	    statePtr->outputEncodingFlags &= ~TCL_ENCODING_END;
+	    statePtr->outputEncodingFlags |= TCL_ENCODING_START;
+	}
+	if (code < 0) {
 	    stickyError = Tcl_GetErrno();
 	}
 
@@ -3229,14 +3399,6 @@ Tcl_Close(
     ResetFlag(statePtr, CHANNEL_INCLOSE);
 
     /*
-     * Ensure that the last output buffer will be flushed.
-     */
-
-    if ((statePtr->curOutPtr != NULL) && IsBufferReady(statePtr->curOutPtr)) {
-	SetFlag(statePtr, BUFFER_READY);
-    }
-
-    /*
      * If this channel supports it, close the read side, since we don't need
      * it anymore and this will help avoid deadlocks on some channel types.
      */
@@ -3281,7 +3443,17 @@ Tcl_Close(
 	    Tcl_SetObjResult(interp,
 			     Tcl_NewStringObj(Tcl_PosixError(interp), -1));
 	}
-	flushcode = -1;
+	return TCL_ERROR;
+    }
+    /*
+     * Bug 97069ea11a: set error message if a flush code is set and no error
+     * message set up to now.
+     */
+    if (flushcode != 0 && interp != NULL
+	    && 0 == Tcl_GetCharLength(Tcl_GetObjResult(interp)) ) {
+	Tcl_SetErrno(flushcode);
+	Tcl_SetObjResult(interp,
+		Tcl_NewStringObj(Tcl_PosixError(interp), -1));
     }
     if ((flushcode != 0) || (result != 0)) {
 	return TCL_ERROR;
@@ -3394,10 +3566,6 @@ Tcl_CloseEx(
 
 	return CloseChannelPart(interp, chanPtr, 0, flags);
     } else if (flags & TCL_CLOSE_WRITE) {
-	if ((statePtr->curOutPtr != NULL) &&
-		IsBufferReady(statePtr->curOutPtr)) {
-	    SetFlag(statePtr, BUFFER_READY);
-	}
 	Tcl_Preserve(statePtr);
 	if (!GotFlag(statePtr, BG_FLUSH_SCHEDULED)) {
 	    /*
@@ -3459,14 +3627,6 @@ CloseWrite(
     int result = 0;
 
     /*
-     * Ensure that the last output buffer will be flushed.
-     */
-
-    if ((statePtr->curOutPtr != NULL) && IsBufferReady(statePtr->curOutPtr)) {
-	SetFlag(statePtr, BUFFER_READY);
-    }
-
-    /*
      * The call to FlushChannel will flush any queued output and invoke the
      * close function of the channel driver, or it will set up the channel to
      * be flushed and closed asynchronously.
@@ -3778,7 +3938,10 @@ Tcl_Write(
     if (srcLen < 0) {
 	srcLen = strlen(src);
     }
-    return DoWrite(chanPtr, src, srcLen);
+    if (WriteBytes(chanPtr, src, srcLen) < 0) {
+	return -1;
+    }
+    return srcLen;
 }
 
 /*
@@ -3869,82 +4032,40 @@ Tcl_WriteChars(
     int len)			/* Length of string in bytes, or < 0 for
 				 * strlen(). */
 {
-    ChannelState *statePtr;	/* State info for channel */
-
-    statePtr = ((Channel *) chan)->state;
+    Channel *chanPtr = (Channel *) chan;
+    ChannelState *statePtr = chanPtr->state;	/* State info for channel */
+    int result;
+    Tcl_Obj *objPtr;
 
     if (CheckChannelErrors(statePtr, TCL_WRITABLE) != 0) {
 	return -1;
     }
 
-    return DoWriteChars((Channel *) chan, src, len);
-}
-
-/*
- *---------------------------------------------------------------------------
- *
- * DoWriteChars --
- *
- *	Takes a sequence of UTF-8 characters and converts them for output
- *	using the channel's current encoding, may queue the buffer for output
- *	if it gets full, and also remembers whether the current buffer is
- *	ready e.g. if it contains a newline and we are in line buffering mode.
- *	Compensates stacking, i.e. will redirect the data from the specified
- *	channel to the topmost channel in a stack.
- *
- * Results:
- *	The number of bytes written or -1 in case of error. If -1,
- *	Tcl_GetErrno will return the error code.
- *
- * Side effects:
- *	May buffer up output and may cause output to be produced on the
- *	channel.
- *
- *----------------------------------------------------------------------
- */
-
-static int
-DoWriteChars(
-    Channel *chanPtr,		/* The channel to buffer output for. */
-    const char *src,		/* UTF-8 characters to queue in output
-				 * buffer. */
-    int len)			/* Length of string in bytes, or < 0 for
-				 * strlen(). */
-{
-    /*
-     * Always use the topmost channel of the stack
-     */
-
-    ChannelState *statePtr;	/* State info for channel */
-
-    statePtr = chanPtr->state;
     chanPtr = statePtr->topChanPtr;
 
     if (len < 0) {
 	len = strlen(src);
     }
-    if (statePtr->encoding == NULL) {
-	/*
-	 * Inefficient way to convert UTF-8 to byte-array, but the code
-	 * parallels the way it is done for objects.
-	 * Special case for 1-byte (used by eg [puts] for the \n) could
-	 * be extended to more efficient translation of the src string.
-	 */
-
-	int result;
+    if (statePtr->encoding) {
+	return WriteChars(chanPtr, src, len);
+    }
 
-	if ((len == 1) && (UCHAR(*src) < 0xC0)) {
-	    result = WriteBytes(chanPtr, src, len);
-	} else {
-	    Tcl_Obj *objPtr = Tcl_NewStringObj(src, len);
+    /*
+     * Inefficient way to convert UTF-8 to byte-array, but the code
+     * parallels the way it is done for objects.  Special case for 1-byte
+     * (used by eg [puts] for the \n) could be extended to more efficient
+     * translation of the src string.
+     */
 
-	    src = (char *) Tcl_GetByteArrayFromObj(objPtr, &len);
-	    result = WriteBytes(chanPtr, src, len);
-	    TclDecrRefCount(objPtr);
-	}
-	return result;
+    if ((len == 1) && (UCHAR(*src) < 0xC0)) {
+	return WriteBytes(chanPtr, src, len);
     }
-    return WriteChars(chanPtr, src, len);
+
+    objPtr = Tcl_NewStringObj(src, len);
+    src = (char *) Tcl_GetByteArrayFromObj(objPtr, &len);
+    result = WriteBytes(chanPtr, src, len);
+    TclDecrRefCount(objPtr);
+    return result;
 }
 
 /*
@@ -4020,12 +4141,25 @@ static int
 WillRead(
     Channel *chanPtr)
 {
+    if (chanPtr->typePtr == NULL) {
+	/* Prevent read attempts on a closed channel */
+        DiscardInputQueued(chanPtr->state, 0);
+	Tcl_SetErrno(EINVAL);
+	return -1;
+    }
     if ((chanPtr->typePtr->seekProc != NULL)
             && (Tcl_OutputBuffered((Tcl_Channel) chanPtr) > 0)) {
-        if ((chanPtr->state->curOutPtr != NULL)
-                && IsBufferReady(chanPtr->state->curOutPtr)) {
-            SetFlag(chanPtr->state, BUFFER_READY);
-        }
+
+	/*
+	 * CAVEAT - The assumption here is that FlushChannel() will
+	 * push out the bytes of any writes that are in progress.
+	 * Since this is a seekable channel, we assume it is not one
+	 * that can block and force bg flushing.  Channels we know that
+	 * can do that -- sockets, pipes -- are not seekable.  If the
+	 * assumption is wrong, more drastic measures may be required here
+	 * like temporarily setting the channel into blocking mode.
+	 */
+
         if (FlushChannel(NULL, chanPtr, 0) != 0) {
             return -1;
         }
@@ -4036,110 +4170,9 @@ WillRead(
 /*
  *----------------------------------------------------------------------
  *
- * WriteBytes --
- *
- *	Write a sequence of bytes into an output buffer, may queue the buffer
- *	for output if it gets full, and also remembers whether the current
- *	buffer is ready e.g. if it contains a newline and we are in line
- *	buffering mode.
- *
- * Results:
- *	The number of bytes written or -1 in case of error. If -1,
- *	Tcl_GetErrno will return the error code.
- *
- * Side effects:
- *	May buffer up output and may cause output to be produced on the
- *	channel.
- *
- *----------------------------------------------------------------------
- */
-
-static int
-WriteBytes(
-    Channel *chanPtr,		/* The channel to buffer output for. */
-    const char *src,		/* Bytes to write. */
-    int srcLen)			/* Number of bytes to write. */
-{
-    ChannelState *statePtr = chanPtr->state;
-				/* State info for channel */
-    ChannelBuffer *bufPtr;
-    char *dst;
-    int dstMax, sawLF, savedLF, total, dstLen, toWrite, translate;
-
-    if (srcLen) {
-        WillWrite(chanPtr);
-    }
-
-    total = 0;
-    sawLF = 0;
-    savedLF = 0;
-    translate = GotFlag(statePtr, CHANNEL_LINEBUFFERED)
-	    || (statePtr->outputTranslation != TCL_TRANSLATE_LF);
-
-    /*
-     * Loop over all bytes in src, storing them in output buffer with proper
-     * EOL translation.
-     */
-
-    while (srcLen + savedLF > 0) {
-	bufPtr = statePtr->curOutPtr;
-	if (bufPtr == NULL) {
-	    bufPtr = AllocChannelBuffer(statePtr->bufSize);
-	    statePtr->curOutPtr = bufPtr;
-	}
-	dst = InsertPoint(bufPtr);
-	dstMax = SpaceLeft(bufPtr);
-	dstLen = dstMax;
-
-	toWrite = dstLen;
-	if (toWrite > srcLen) {
-	    toWrite = srcLen;
-	}
-
-	if (translate) {
-	    if (savedLF) {
-		/*
-		 * A '\n' was left over from last call to TranslateOutputEOL()
-		 * and we need to store it in this buffer. If the channel is
-		 * line-based, we will need to flush it.
-		 */
-
-		*dst++ = '\n';
-		dstLen--;
-		sawLF++;
-	    }
-	    if (TranslateOutputEOL(statePtr, dst, src, &dstLen, &toWrite)) {
-		sawLF++;
-	    }
-	    dstLen += savedLF;
-	    savedLF = 0;
-	    if (dstLen > dstMax) {
-		savedLF = 1;
-		dstLen = dstMax;
-	    }
-	} else {
-	    memcpy(dst, src, toWrite);
-	    dstLen = toWrite;
-	}
-
-	bufPtr->nextAdded += dstLen;
-	if (CheckFlush(chanPtr, bufPtr, sawLF) != 0) {
-	    return -1;
-	}
-	total += dstLen;
-	src += toWrite;
-	srcLen -= toWrite;
-	sawLF = 0;
-    }
-    return total;
-}
-
-/*
- *----------------------------------------------------------------------
- *
- * WriteChars --
+ * Write --
  *
- *	Convert UTF-8 bytes to the channel's external encoding and write the
+ *	Convert srcLen bytes starting at src according to encoding and write
  *	produced bytes into an output buffer, may queue the buffer for output
  *	if it gets full, and also remembers whether the current buffer is
  *	ready e.g. if it contains a newline and we are in line buffering mode.
@@ -4156,381 +4189,175 @@ WriteBytes(
  */
 
 static int
-WriteChars(
+Write(
     Channel *chanPtr,		/* The channel to buffer output for. */
     const char *src,		/* UTF-8 string to write. */
-    int srcLen)			/* Length of UTF-8 string in bytes. */
+    int srcLen,			/* Length of UTF-8 string in bytes. */
+    Tcl_Encoding encoding)
 {
     ChannelState *statePtr = chanPtr->state;
 				/* State info for channel */
-    ChannelBuffer *bufPtr;
-    char *dst, *stage;
-    int saved, savedLF, sawLF, total, dstLen, stageMax, dstWrote;
-    int stageLen, toWrite, stageRead, endEncoding, result;
-    int consumedSomething, translate;
-    Tcl_Encoding encoding;
-    char safe[BUFFER_PADDING];
+    char *nextNewLine = NULL;
+    int endEncoding, saved = 0, total = 0, flushed = 0, needNlFlush = 0;
 
     if (srcLen) {
         WillWrite(chanPtr);
     }
 
-    total = 0;
-    sawLF = 0;
-    savedLF = 0;
-    saved = 0;
-    encoding = statePtr->encoding;
-
     /*
      * Write the terminated escape sequence even if srcLen is 0.
      */
 
     endEncoding = ((statePtr->outputEncodingFlags & TCL_ENCODING_END) != 0);
 
-    translate = GotFlag(statePtr, CHANNEL_LINEBUFFERED)
-	    || (statePtr->outputTranslation != TCL_TRANSLATE_LF);
+    if (GotFlag(statePtr, CHANNEL_LINEBUFFERED)
+	    || (statePtr->outputTranslation != TCL_TRANSLATE_LF)) {
+	nextNewLine = memchr(src, '\n', srcLen);
+    }
 
-    /*
-     * Loop over all UTF-8 characters in src, storing them in staging buffer
-     * with proper EOL translation.
-     */
+    while (srcLen + saved + endEncoding > 0) {
+	ChannelBuffer *bufPtr;
+	char *dst, safe[BUFFER_PADDING];
+	int result, srcRead, dstLen, dstWrote, srcLimit = srcLen;
 
-    consumedSomething = 1;
-    while (consumedSomething && (srcLen + savedLF + endEncoding > 0)) {
-	consumedSomething = 0;
-	stage = statePtr->outputStage;
-	stageMax = statePtr->bufSize;
-	stageLen = stageMax;
+	if (nextNewLine) {
+	    srcLimit = nextNewLine - src;
+	}
 
-	toWrite = stageLen;
-	if (toWrite > srcLen) {
-	    toWrite = srcLen;
+	/* Get space to write into */
+	bufPtr = statePtr->curOutPtr;
+	if (bufPtr == NULL) {
+	    bufPtr = AllocChannelBuffer(statePtr->bufSize);
+	    statePtr->curOutPtr = bufPtr;
 	}
+	if (saved) {
+	    /*
+	     * Here's some translated bytes left over from the last buffer
+	     * that we need to stick at the beginning of this buffer.
+	     */
 
-	if (translate) {
-	    if (savedLF) {
-		/*
-		 * A '\n' was left over from last call to TranslateOutputEOL()
-		 * and we need to store it in the staging buffer. If the
-		 * channel is line-based, we will need to flush the output
-		 * buffer (after translating the staging buffer).
-		 */
+	    memcpy(InsertPoint(bufPtr), safe, (size_t) saved);
+	    bufPtr->nextAdded += saved;
+	    saved = 0;
+	}
+	PreserveChannelBuffer(bufPtr);
+	dst = InsertPoint(bufPtr);
+	dstLen = SpaceLeft(bufPtr);
 
-		*stage++ = '\n';
-		stageLen--;
-		sawLF++;
-	    }
-	    if (TranslateOutputEOL(statePtr, stage, src, &stageLen,
-		    &toWrite)) {
-		sawLF++;
-	    }
+	result = Tcl_UtfToExternal(NULL, encoding, src, srcLimit,
+		statePtr->outputEncodingFlags,
+		&statePtr->outputEncodingState, dst,
+		dstLen + BUFFER_PADDING, &srcRead, &dstWrote, NULL);
 
-	    stage -= savedLF;
-	    stageLen += savedLF;
-	    savedLF = 0;
+	/* See chan-io-1.[89]. Tcl Bug 506297. */
+	statePtr->outputEncodingFlags &= ~TCL_ENCODING_START;
 
-	    if (stageLen > stageMax) {
-		savedLF = 1;
-		stageLen = stageMax;
+	if ((result != TCL_OK) && (srcRead + dstWrote == 0)) {
+	    /* We're reading from invalid/incomplete UTF-8 */
+	    ReleaseChannelBuffer(bufPtr);
+	    if (total == 0) {
+		Tcl_SetErrno(EINVAL);
+		return -1;
 	    }
-	} else {
-	    memcpy(stage, src, toWrite);
-	    stageLen = toWrite;
+	    break;
 	}
-	src += toWrite;
-	srcLen -= toWrite;
 
-	/*
-	 * Loop over all UTF-8 characters in staging buffer, converting them
-	 * to external encoding, storing them in output buffer.
-	 */
+	bufPtr->nextAdded += dstWrote;
+	src += srcRead;
+	srcLen -= srcRead;
+	total += dstWrote;
+	dst += dstWrote;
+	dstLen -= dstWrote;
 
-	while (stageLen + saved + endEncoding > 0) {
-	    bufPtr = statePtr->curOutPtr;
-	    if (bufPtr == NULL) {
-		bufPtr = AllocChannelBuffer(statePtr->bufSize);
-		statePtr->curOutPtr = bufPtr;
-	    }
-	    dst = InsertPoint(bufPtr);
-	    dstLen = SpaceLeft(bufPtr);
+	if (src == nextNewLine && dstLen > 0) {
+	    static char crln[3] = "\r\n";
+	    char *nl = NULL;
+	    int nlLen = 0;
 
-	    if (saved != 0) {
-		/*
-		 * Here's some translated bytes left over from the last buffer
-		 * that we need to stick at the beginning of this buffer.
-		 */
-
-		memcpy(dst, safe, (size_t) saved);
-		bufPtr->nextAdded += saved;
-		dst += saved;
-		dstLen -= saved;
-		saved = 0;
+	    switch (statePtr->outputTranslation) {
+	    case TCL_TRANSLATE_LF:
+		nl = crln + 1;
+		nlLen = 1;
+		break;
+	    case TCL_TRANSLATE_CR:
+		nl = crln;
+		nlLen = 1;
+		break;
+	    case TCL_TRANSLATE_CRLF:
+		nl = crln;
+		nlLen = 2;
+		break;
+	    default:
+		Tcl_Panic("unknown output translation requested");
+		break;
 	    }
 
-	    result = Tcl_UtfToExternal(NULL, encoding, stage, stageLen,
-		    statePtr->outputEncodingFlags,
-		    &statePtr->outputEncodingState, dst,
-		    dstLen + BUFFER_PADDING, &stageRead, &dstWrote, NULL);
-
-	    /*
-	     * Fix for SF #506297, reported by Martin Forssen
-	     * <ruric@users.sourceforge.net>.
-	     *
-	     * The encoding chosen in the script exposing the bug writes out
-	     * three intro characters when TCL_ENCODING_START is set, but does
-	     * not consume any input as TCL_ENCODING_END is cleared. As some
-	     * output was generated the enclosing loop calls UtfToExternal
-	     * again, again with START set. Three more characters in the out
-	     * and still no use of input ... To break this infinite loop we
-	     * remove TCL_ENCODING_START from the set of flags after the first
-	     * call (no condition is required, the later calls remove an unset
-	     * flag, which is a no-op). This causes the subsequent calls to
-	     * UtfToExternal to consume and convert the actual input.
-	     */
-
-	    statePtr->outputEncodingFlags &= ~TCL_ENCODING_START;
-
-	    /*
-	     * The following code must be executed only when result is not 0.
-	     */
+	    result |= Tcl_UtfToExternal(NULL, encoding, nl, nlLen,
+		statePtr->outputEncodingFlags,
+		&statePtr->outputEncodingState, dst,
+		dstLen + BUFFER_PADDING, &srcRead, &dstWrote, NULL);
 
-	    if ((result != 0) && (stageRead + dstWrote == 0)) {
-		/*
-		 * We have an incomplete UTF-8 character at the end of the
-		 * staging buffer. It will get moved to the beginning of the
-		 * staging buffer followed by more bytes from src.
-		 */
+	    assert (srcRead == nlLen);
 
-		src -= stageLen;
-		srcLen += stageLen;
-		stageLen = 0;
-		savedLF = 0;
-		break;
-	    }
 	    bufPtr->nextAdded += dstWrote;
-	    if (IsBufferOverflowing(bufPtr)) {
-		/*
-		 * When translating from UTF-8 to external encoding, we
-		 * allowed the translation to produce a character that crossed
-		 * the end of the output buffer, so that we would get a
-		 * completely full buffer before flushing it. The extra bytes
-		 * will be moved to the beginning of the next buffer.
-		 */
-
-		saved = -SpaceLeft(bufPtr);
-		memcpy(safe, dst + dstLen, (size_t) saved);
-		bufPtr->nextAdded = bufPtr->bufLength;
-	    }
-	    if (CheckFlush(chanPtr, bufPtr, sawLF) != 0) {
-		return -1;
-	    }
-
+	    src++;
+	    srcLen--;
 	    total += dstWrote;
-	    stage += stageRead;
-	    stageLen -= stageRead;
-	    sawLF = 0;
-
-	    consumedSomething = 1;
+	    dst += dstWrote;
+	    dstLen -= dstWrote;
+	    nextNewLine = memchr(src, '\n', srcLen);
+	    needNlFlush = 1;
+	}
 
+	if (IsBufferOverflowing(bufPtr)) {
 	    /*
-	     * If all translated characters are written to the buffer,
-	     * endEncoding is set to 0 because the escape sequence may be
-	     * output.
+	     * When translating from UTF-8 to external encoding, we
+	     * allowed the translation to produce a character that crossed
+	     * the end of the output buffer, so that we would get a
+	     * completely full buffer before flushing it. The extra bytes
+	     * will be moved to the beginning of the next buffer.
 	     */
 
-	    if ((stageLen + saved == 0) && (result == 0)) {
-		endEncoding = 0;
-	    }
+	    saved = -SpaceLeft(bufPtr);
+	    memcpy(safe, dst + dstLen, (size_t) saved);
+	    bufPtr->nextAdded = bufPtr->bufLength;
 	}
-    }
-
-    /*
-     * If nothing was written and it happened because there was no progress in
-     * the UTF conversion, we throw an error.
-     */
-
-    if (!consumedSomething && (total == 0)) {
-	Tcl_SetErrno(EINVAL);
-	return -1;
-    }
-    return total;
-}
-
-/*
- *---------------------------------------------------------------------------
- *
- * TranslateOutputEOL --
- *
- *	Helper function for WriteBytes() and WriteChars(). Converts the '\n'
- *	characters in the source buffer into the appropriate EOL form
- *	specified by the output translation mode.
- *
- *	EOL translation stops either when the source buffer is empty or the
- *	output buffer is full.
- *
- *	When converting to CRLF mode and there is only 1 byte left in the
- *	output buffer, this routine stores the '\r' in the last byte and then
- *	stores the '\n' in the byte just past the end of the buffer. The
- *	caller is responsible for passing in a buffer that is large enough to
- *	hold the extra byte.
- *
- * Results:
- *	The return value is 1 if a '\n' was translated from the source buffer,
- *	or 0 otherwise -- this can be used by the caller to decide to flush a
- *	line-based channel even though the channel buffer is not full.
- *
- *	*dstLenPtr is filled with how many bytes of the output buffer were
- *	used. As mentioned above, this can be one more that the output
- *	buffer's specified length if a CRLF was stored.
- *
- *	*srcLenPtr is filled with how many bytes of the source buffer were
- *	consumed.
- *
- * Side effects:
- *	It may be obvious, but bears mentioning that when converting in CRLF
- *	mode (which requires two bytes of storage in the output buffer), the
- *	number of bytes consumed from the source buffer will be less than the
- *	number of bytes stored in the output buffer.
- *
- *---------------------------------------------------------------------------
- */
 
-static int
-TranslateOutputEOL(
-    ChannelState *statePtr,	/* Channel being read, for translation and
-				 * buffering modes. */
-    char *dst,			/* Output buffer filled with UTF-8 chars by
-				 * applying appropriate EOL translation to
-				 * source characters. */
-    const char *src,		/* Source UTF-8 characters. */
-    int *dstLenPtr,		/* On entry, the maximum length of output
-				 * buffer in bytes. On exit, the number of
-				 * bytes actually used in output buffer. */
-    int *srcLenPtr)		/* On entry, the length of source buffer. On
-				 * exit, the number of bytes read from the
-				 * source buffer. */
-{
-    char *dstEnd;
-    int srcLen, newlineFound;
-
-    newlineFound = 0;
-    srcLen = *srcLenPtr;
-
-    switch (statePtr->outputTranslation) {
-    case TCL_TRANSLATE_LF:
-	for (dstEnd = dst + srcLen; dst < dstEnd; ) {
-	    if (*src == '\n') {
-		newlineFound = 1;
-	    }
-	    *dst++ = *src++;
-	}
-	*dstLenPtr = srcLen;
-	break;
-    case TCL_TRANSLATE_CR:
-	for (dstEnd = dst + srcLen; dst < dstEnd;) {
-	    if (*src == '\n') {
-		*dst++ = '\r';
-		newlineFound = 1;
-		src++;
-	    } else {
-		*dst++ = *src++;
-	    }
+	if ((srcLen + saved == 0) && (result == TCL_OK)) {
+	    endEncoding = 0;
 	}
-	*dstLenPtr = srcLen;
-	break;
-    case TCL_TRANSLATE_CRLF: {
-	/*
-	 * Since this causes the number of bytes to grow, we start off trying
-	 * to put 'srcLen' bytes into the output buffer, but allow it to store
-	 * more bytes, as long as there's still source bytes and room in the
-	 * output buffer.
-	 */
-
-	char *dstStart, *dstMax;
-	const char *srcStart;
-
-	dstStart = dst;
-	dstMax = dst + *dstLenPtr;
 
-	srcStart = src;
-
-	if (srcLen < *dstLenPtr) {
-	    dstEnd = dst + srcLen;
-	} else {
-	    dstEnd = dst + *dstLenPtr;
-	}
-	while (dst < dstEnd) {
-	    if (*src == '\n') {
-		if (dstEnd < dstMax) {
-		    dstEnd++;
-		}
-		*dst++ = '\r';
-		newlineFound = 1;
-	    }
-	    *dst++ = *src++;
-	}
-	*srcLenPtr = src - srcStart;
-	*dstLenPtr = dst - dstStart;
-	break;
-    }
-    default:
-	break;
-    }
-    return newlineFound;
-}
-
-/*
- *---------------------------------------------------------------------------
- *
- * CheckFlush --
- *
- *	Helper function for WriteBytes() and WriteChars(). If the channel
- *	buffer is ready to be flushed, flush it.
- *
- * Results:
- *	The return value is -1 if there was a problem flushing the channel
- *	buffer, or 0 otherwise.
- *
- * Side effects:
- *	The buffer will be recycled if it is flushed.
- *
- *---------------------------------------------------------------------------
- */
-
-static int
-CheckFlush(
-    Channel *chanPtr,		/* Channel being read, for buffering mode. */
-    ChannelBuffer *bufPtr,	/* Channel buffer to possibly flush. */
-    int newlineFlag)		/* Non-zero if a the channel buffer contains a
-				 * newline. */
-{
-    ChannelState *statePtr = chanPtr->state;
-				/* State info for channel */
-
-    /*
-     * The current buffer is ready for output:
-     * 1. if it is full.
-     * 2. if it contains a newline and this channel is line-buffered.
-     * 3. if it contains any output and this channel is unbuffered.
-     */
-
-    if (!GotFlag(statePtr, BUFFER_READY)) {
 	if (IsBufferFull(bufPtr)) {
-	    SetFlag(statePtr, BUFFER_READY);
-	} else if (GotFlag(statePtr, CHANNEL_LINEBUFFERED)) {
-	    if (newlineFlag != 0) {
-		SetFlag(statePtr, BUFFER_READY);
+	    if (FlushChannel(NULL, chanPtr, 0) != 0) {
+		ReleaseChannelBuffer(bufPtr);
+		return -1;
 	    }
-	} else if (GotFlag(statePtr, CHANNEL_UNBUFFERED)) {
-	    SetFlag(statePtr, BUFFER_READY);
-	}
-    }
-    if (GotFlag(statePtr, BUFFER_READY)) {
+	    flushed += statePtr->bufSize;
+
+	    /*
+ 	     * We just flushed.  So if we have needNlFlush set to record
+ 	     * that we need to flush because theres a (translated) newline
+ 	     * in the buffer, that's likely not true any more.  But there
+ 	     * is a tricky exception.  If we have saved bytes that did not
+ 	     * really get flushed and those bytes came from a translation
+ 	     * of a newline as the last thing taken from the src array,
+ 	     * then needNlFlush needs to remain set to flag that the
+ 	     * next buffer still needs a newline flush.
+ 	     */
+	    if (needNlFlush && (saved == 0 || src[-1] != '\n')) {
+		needNlFlush = 0;
+	    }
+	}
+	ReleaseChannelBuffer(bufPtr);
+    }
+    if ((flushed < total) && (GotFlag(statePtr, CHANNEL_UNBUFFERED) ||
+	    (needNlFlush && GotFlag(statePtr, CHANNEL_LINEBUFFERED)))) {
 	if (FlushChannel(NULL, chanPtr, 0) != 0) {
 	    return -1;
 	}
     }
-    return 0;
+
+    return total;
 }
 
 /*
@@ -4612,8 +4439,22 @@ Tcl_GetsObj(
     Tcl_EncodingState oldState;
 
     if (CheckChannelErrors(statePtr, TCL_READABLE) != 0) {
-	copiedTotal = -1;
-	goto done;
+	return -1;
+    }
+
+    /*
+     * If we're sitting ready to read the eofchar, there's no need to
+     * do it.
+     */
+
+    if (GotFlag(statePtr, CHANNEL_STICKY_EOF)) {
+	SetFlag(statePtr, CHANNEL_EOF);
+	assert( statePtr->inputEncodingFlags & TCL_ENCODING_END );
+	assert( !GotFlag(statePtr, CHANNEL_BLOCKED|INPUT_SAW_CR) );
+
+	/* TODO: Do we need this? */
+	UpdateInterest(chanPtr);
+	return -1;
     }
 
     /*
@@ -4633,6 +4474,7 @@ Tcl_GetsObj(
      */
 
     chanPtr = statePtr->topChanPtr;
+    TclChannelPreserve((Tcl_Channel)chanPtr);
 
     bufPtr = statePtr->inQueueHead;
     encoding = statePtr->encoding;
@@ -4656,16 +4498,7 @@ Tcl_GetsObj(
      */
 
     if (encoding == NULL) {
-	ThreadSpecificData *tsdPtr = TCL_TSD_INIT(&dataKey);
-
-	if (tsdPtr->binaryEncoding == NULL) {
-	    tsdPtr->binaryEncoding = Tcl_GetEncoding(NULL, "iso8859-1");
-	    Tcl_CreateThreadExitHandler(FreeBinaryEncoding, NULL);
-	}
-	encoding = tsdPtr->binaryEncoding;
-	if (encoding == NULL) {
-	    Tcl_Panic("attempted gets on binary channel where no iso8859-1 encoding available");
-	}
+	encoding = GetBinaryEncoding();
     }
 
     /*
@@ -4690,6 +4523,7 @@ Tcl_GetsObj(
     eof = NULL;
     inEofChar = statePtr->inEofChar;
 
+    ResetFlag(statePtr, CHANNEL_BLOCKED);
     while (1) {
 	if (dst >= dstEnd) {
 	    if (FilterInputBytes(chanPtr, &gs) != 0) {
@@ -4781,14 +4615,14 @@ Tcl_GetsObj(
 		     * Skip the raw bytes that make up the '\n'.
 		     */
 
-		    char tmp[1 + TCL_UTF_MAX];
+		    char tmp[TCL_UTF_MAX];
 		    int rawRead;
 
 		    bufPtr = gs.bufPtr;
 		    Tcl_ExternalToUtf(NULL, gs.encoding, RemovePoint(bufPtr),
-			    gs.rawRead, statePtr->inputEncodingFlags,
-			    &gs.state, tmp, 1 + TCL_UTF_MAX, &rawRead, NULL,
-			    NULL);
+			    gs.rawRead, statePtr->inputEncodingFlags
+				| TCL_ENCODING_NO_TERMINATE, &gs.state, tmp,
+			    TCL_UTF_MAX, &rawRead, NULL, NULL);
 		    bufPtr->nextRemoved += rawRead;
 		    gs.rawRead -= rawRead;
 		    gs.bytesWrote--;
@@ -4841,6 +4675,7 @@ Tcl_GetsObj(
 	    dstEnd = eof;
 	    SetFlag(statePtr, CHANNEL_EOF | CHANNEL_STICKY_EOF);
 	    statePtr->inputEncodingFlags |= TCL_ENCODING_END;
+	    ResetFlag(statePtr, CHANNEL_BLOCKED|INPUT_SAW_CR);
 	}
 	if (GotFlag(statePtr, CHANNEL_EOF)) {
 	    skip = 0;
@@ -4854,6 +4689,7 @@ Tcl_GetsObj(
 		Tcl_SetObjLength(objPtr, oldLength);
 		CommonGetsCleanup(chanPtr);
 		copiedTotal = -1;
+		ResetFlag(statePtr, CHANNEL_BLOCKED);
 		goto done;
 	    }
 	    goto gotEOL;
@@ -4875,7 +4711,11 @@ Tcl_GetsObj(
      * self-modifying reflected transforms.
      */
 
-    chanPtr = statePtr->topChanPtr;
+    if (chanPtr != statePtr->topChanPtr) {
+	TclChannelRelease((Tcl_Channel)chanPtr);
+	chanPtr = statePtr->topChanPtr;
+	TclChannelPreserve((Tcl_Channel)chanPtr);
+    }
 
     bufPtr = gs.bufPtr;
     if (bufPtr == NULL) {
@@ -4883,8 +4723,9 @@ Tcl_GetsObj(
     }
     statePtr->inputEncodingState = gs.state;
     Tcl_ExternalToUtf(NULL, gs.encoding, RemovePoint(bufPtr), gs.rawRead,
-	    statePtr->inputEncodingFlags, &statePtr->inputEncodingState, dst,
-	    eol - dst + skip + TCL_UTF_MAX, &gs.rawRead, NULL,
+	    statePtr->inputEncodingFlags | TCL_ENCODING_NO_TERMINATE,
+	    &statePtr->inputEncodingState, dst,
+	    eol - dst + skip + TCL_UTF_MAX - 1, &gs.rawRead, NULL,
 	    &gs.charsWrote);
     bufPtr->nextRemoved += gs.rawRead;
 
@@ -4909,16 +4750,18 @@ Tcl_GetsObj(
      * Regenerate the top channel, in case it was changed due to
      * self-modifying reflected transforms.
      */
-
-    chanPtr = statePtr->topChanPtr;
-
+    if (chanPtr != statePtr->topChanPtr) {
+	TclChannelRelease((Tcl_Channel)chanPtr);
+	chanPtr = statePtr->topChanPtr;
+	TclChannelPreserve((Tcl_Channel)chanPtr);
+    }
     bufPtr = statePtr->inQueueHead;
-    if (bufPtr == NULL) {
-	Tcl_Panic("Tcl_GetsObj: restore reached with bufPtr==NULL");
+    if (bufPtr != NULL) {
+	bufPtr->nextRemoved = oldRemoved;
+	bufPtr = bufPtr->nextPtr;
     }
-    bufPtr->nextRemoved = oldRemoved;
 
-    for (bufPtr = bufPtr->nextPtr; bufPtr != NULL; bufPtr = bufPtr->nextPtr) {
+    for ( ; bufPtr != NULL; bufPtr = bufPtr->nextPtr) {
 	bufPtr->nextRemoved = BUFFER_PADDING;
     }
     CommonGetsCleanup(chanPtr);
@@ -4947,14 +4790,24 @@ Tcl_GetsObj(
      */
 
   done:
+	assert(!GotFlag(statePtr, CHANNEL_EOF)
+		|| GotFlag(statePtr, CHANNEL_STICKY_EOF)
+		|| Tcl_InputBuffered((Tcl_Channel)chanPtr) == 0);
+
+	assert( !(GotFlag(statePtr, CHANNEL_EOF|CHANNEL_BLOCKED)
+		== (CHANNEL_EOF|CHANNEL_BLOCKED)) );
+
     /*
      * Regenerate the top channel, in case it was changed due to
      * self-modifying reflected transforms.
      */
-
-    chanPtr = statePtr->topChanPtr;
-
+    if (chanPtr != statePtr->topChanPtr) {
+	TclChannelRelease((Tcl_Channel)chanPtr);
+	chanPtr = statePtr->topChanPtr;
+	TclChannelPreserve((Tcl_Channel)chanPtr);
+    }
     UpdateInterest(chanPtr);
+    TclChannelRelease((Tcl_Channel)chanPtr);
     return copiedTotal;
 }
 
@@ -4967,6 +4820,11 @@ Tcl_GetsObj(
  *	end-of-line or end-of-file has been seen. Bytes read from the input
  *	channel return as a ByteArray obj.
  *
+ *	WARNING!  The notion of "binary" used here is different from
+ *	notions of "binary" used in other places.  In particular, this
+ *	"binary" routine may be called when an -eofchar is set on the
+ * 	channel.
+ *
  * Results:
  *	Number of characters accumulated in the object or -1 if error,
  *	blocked, or EOF. If -1, use Tcl_GetErrno() to retrieve the POSIX error
@@ -5000,6 +4858,7 @@ TclGetsObjBinary(
      */
 
     chanPtr = statePtr->topChanPtr;
+    TclChannelPreserve((Tcl_Channel)chanPtr);
 
     bufPtr = statePtr->inQueueHead;
 
@@ -5027,6 +4886,7 @@ TclGetsObjBinary(
 
     eolChar = (statePtr->inputTranslation == TCL_TRANSLATE_LF) ? '\n' : '\r';
 
+    ResetFlag(statePtr, CHANNEL_BLOCKED);
     while (1) {
 	/*
 	 * Subtract the number of bytes that were removed from channel
@@ -5046,17 +4906,24 @@ TclGetsObjBinary(
 	     * hasn't seen EOL. Need to read more bytes from the channel
 	     * device. Side effect is to allocate another channel buffer.
 	     */
-
-	    if (GotFlag(statePtr, CHANNEL_BLOCKED)) {
-		if (GotFlag(statePtr, CHANNEL_NONBLOCKING)) {
-		    goto restore;
-		}
-		ResetFlag(statePtr, CHANNEL_BLOCKED);
-	    }
 	    if (GetInput(chanPtr) != 0) {
 		goto restore;
 	    }
 	    bufPtr = statePtr->inQueueTail;
+	    if (bufPtr == NULL) {
+		goto restore;
+	    }
+	} else {
+	    /*
+	     * Incoming CHANNEL_STICKY_EOF is filtered out on entry.
+	     * A new CHANNEL_STICKY_EOF set in this routine leads to
+	     * return before coming back here.  When we are not dealing
+	     * with CHANNEL_STICKY_EOF, a CHANNEL_EOF implies an
+	     * empty buffer.  Here the buffer is non-empty so we know
+	     * we're a non-EOF */
+
+	    assert ( !GotFlag(statePtr, CHANNEL_STICKY_EOF) );
+	    assert ( !GotFlag(statePtr, CHANNEL_EOF) );
 	}
 
 	dst = (unsigned char *) RemovePoint(bufPtr);
@@ -5098,6 +4965,7 @@ TclGetsObjBinary(
 
 	    SetFlag(statePtr, CHANNEL_EOF | CHANNEL_STICKY_EOF);
 	    statePtr->inputEncodingFlags |= TCL_ENCODING_END;
+	    ResetFlag(statePtr, CHANNEL_BLOCKED|INPUT_SAW_CR);
 	}
 	if (GotFlag(statePtr, CHANNEL_EOF)) {
 	    skip = 0;
@@ -5111,10 +4979,15 @@ TclGetsObjBinary(
 		byteArray = Tcl_SetByteArrayLength(objPtr, oldLength);
 		CommonGetsCleanup(chanPtr);
 		copiedTotal = -1;
+		ResetFlag(statePtr, CHANNEL_BLOCKED);
 		goto done;
 	    }
 	    goto gotEOL;
 	}
+	if (GotFlag(statePtr, CHANNEL_BLOCKED|CHANNEL_NONBLOCKING)
+		== (CHANNEL_BLOCKED|CHANNEL_NONBLOCKING)) {
+	    goto restore;
+	}
 
 	/*
 	 * Copy bytes from the channel buffer to the ByteArray.
@@ -5169,12 +5042,12 @@ TclGetsObjBinary(
 
   restore:
     bufPtr = statePtr->inQueueHead;
-    if (bufPtr == NULL) {
-	Tcl_Panic("TclGetsObjBinary: restore reached with bufPtr==NULL");
+    if (bufPtr) {
+	bufPtr->nextRemoved = oldRemoved;
+	bufPtr = bufPtr->nextPtr;
     }
-    bufPtr->nextRemoved = oldRemoved;
 
-    for (bufPtr = bufPtr->nextPtr; bufPtr != NULL; bufPtr = bufPtr->nextPtr) {
+    for ( ; bufPtr != NULL; bufPtr = bufPtr->nextPtr) {
 	bufPtr->nextRemoved = BUFFER_PADDING;
     }
     CommonGetsCleanup(chanPtr);
@@ -5202,7 +5075,13 @@ TclGetsObjBinary(
      */
 
   done:
+	assert(!GotFlag(statePtr, CHANNEL_EOF)
+		|| GotFlag(statePtr, CHANNEL_STICKY_EOF)
+		|| Tcl_InputBuffered((Tcl_Channel)chanPtr) == 0);
+	assert( !(GotFlag(statePtr, CHANNEL_EOF|CHANNEL_BLOCKED)
+		== (CHANNEL_EOF|CHANNEL_BLOCKED)) );
     UpdateInterest(chanPtr);
+    TclChannelRelease((Tcl_Channel)chanPtr);
     return copiedTotal;
 }
 
@@ -5231,6 +5110,21 @@ FreeBinaryEncoding(
 	tsdPtr->binaryEncoding = NULL;
     }
 }
+
+static Tcl_Encoding
+GetBinaryEncoding()
+{
+    ThreadSpecificData *tsdPtr = TCL_TSD_INIT(&dataKey);
+
+    if (tsdPtr->binaryEncoding == NULL) {
+	tsdPtr->binaryEncoding = Tcl_GetEncoding(NULL, "iso8859-1");
+	Tcl_CreateThreadExitHandler(FreeBinaryEncoding, NULL);
+    }
+    if (tsdPtr->binaryEncoding == NULL) {
+	Tcl_Panic("binary encoding is not available");
+    }
+    return tsdPtr->binaryEncoding;
+}
 
 /*
  *---------------------------------------------------------------------------
@@ -5264,7 +5158,7 @@ FilterInputBytes(
     ChannelState *statePtr = chanPtr->state;
 				/* State info for channel */
     ChannelBuffer *bufPtr;
-    char *raw, *rawStart, *dst;
+    char *raw, *dst;
     int offset, toRead, dstNeeded, spaceLeft, result, rawLen;
     Tcl_Obj *objPtr;
 #define ENCODING_LINESIZE 20	/* Lower bound on how many bytes to convert at
@@ -5298,13 +5192,11 @@ FilterInputBytes(
 	 */
 
     read:
-	if (GotFlag(statePtr, CHANNEL_BLOCKED)) {
-	    if (GotFlag(statePtr, CHANNEL_NONBLOCKING)) {
-		gsPtr->charsWrote = 0;
-		gsPtr->rawRead = 0;
-		return -1;
-	    }
-	    ResetFlag(statePtr, CHANNEL_BLOCKED);
+	if (GotFlag(statePtr, CHANNEL_NONBLOCKING|CHANNEL_BLOCKED)
+		== (CHANNEL_NONBLOCKING|CHANNEL_BLOCKED)) {
+	    gsPtr->charsWrote = 0;
+	    gsPtr->rawRead = 0;
+	    return -1;
 	}
 	if (GetInput(chanPtr) != 0) {
 	    gsPtr->charsWrote = 0;
@@ -5313,6 +5205,22 @@ FilterInputBytes(
 	}
 	bufPtr = statePtr->inQueueTail;
 	gsPtr->bufPtr = bufPtr;
+	if (bufPtr == NULL) {
+	    gsPtr->charsWrote = 0;
+	    gsPtr->rawRead = 0;
+	    return -1;
+	}
+    } else {
+	/*
+	 * Incoming CHANNEL_STICKY_EOF is filtered out on entry.
+	 * A new CHANNEL_STICKY_EOF set in this routine leads to
+	 * return before coming back here.  When we are not dealing
+	 * with CHANNEL_STICKY_EOF, a CHANNEL_EOF implies an
+	 * empty buffer.  Here the buffer is non-empty so we know
+	 * we're a non-EOF */
+
+	assert ( !GotFlag(statePtr, CHANNEL_STICKY_EOF) );
+	assert ( !GotFlag(statePtr, CHANNEL_EOF) );
     }
 
     /*
@@ -5321,8 +5229,7 @@ FilterInputBytes(
      * string rep if we need more space.
      */
 
-    rawStart = RemovePoint(bufPtr);
-    raw = rawStart;
+    raw = RemovePoint(bufPtr);
     rawLen = BytesLeft(bufPtr);
 
     dst = *gsPtr->dstPtr;
@@ -5350,9 +5257,9 @@ FilterInputBytes(
     }
     gsPtr->state = statePtr->inputEncodingState;
     result = Tcl_ExternalToUtf(NULL, gsPtr->encoding, raw, rawLen,
-	    statePtr->inputEncodingFlags, &statePtr->inputEncodingState,
-	    dst, spaceLeft+1, &gsPtr->rawRead, &gsPtr->bytesWrote,
-	    &gsPtr->charsWrote);
+	    statePtr->inputEncodingFlags | TCL_ENCODING_NO_TERMINATE,
+	    &statePtr->inputEncodingState, dst, spaceLeft, &gsPtr->rawRead,
+	    &gsPtr->bytesWrote, &gsPtr->charsWrote);
 
     /*
      * Make sure that if we go through 'gets', that we reset the
@@ -5389,7 +5296,7 @@ FilterInputBytes(
 	    } else {
 		/*
 		 * There are no more cached raw bytes left. See if we can get
-		 * some more.
+		 * some more, but avoid blocking on a non-blocking channel.
 		 */
 
 		goto read;
@@ -5630,134 +5537,87 @@ Tcl_Read(
 int
 Tcl_ReadRaw(
     Tcl_Channel chan,		/* The channel from which to read. */
-    char *bufPtr,		/* Where to store input read. */
+    char *readBuf,		/* Where to store input read. */
     int bytesToRead)		/* Maximum number of bytes to read. */
 {
     Channel *chanPtr = (Channel *) chan;
     ChannelState *statePtr = chanPtr->state;
 				/* State info for channel */
-    int nread, result, copied, copiedNow;
-
-    /*
-     * The check below does too much because it will reject a call to this
-     * function with a channel which is part of an 'fcopy'. But we have to
-     * allow this here or else the chaining in the transformation drivers will
-     * fail with 'file busy' error instead of retrieving and transforming the
-     * data to copy.
-     *
-     * We let the check procedure now believe that there is no fcopy in
-     * progress. A better solution than this might be an additional flag
-     * argument to switch off specific checks.
-     */
+    int copied = 0;
 
+    assert(bytesToRead > 0);
     if (CheckChannelErrors(statePtr, TCL_READABLE | CHANNEL_RAW_MODE) != 0) {
 	return -1;
     }
 
-    /*
-     * Check for information in the push-back buffers. If there is some, use
-     * it. Go to the driver only if there is none (anymore) and the caller
-     * requests more bytes.
-     */
+    /* First read bytes from the push-back buffers. */
 
-    for (copied = 0; copied < bytesToRead; copied += copiedNow) {
-	copiedNow = CopyBuffer(chanPtr, bufPtr + copied,
-		bytesToRead - copied);
-	if (copiedNow == 0) {
-	    if (GotFlag(statePtr, CHANNEL_EOF)) {
-		goto done;
-	    }
-	    if (GotFlag(statePtr, CHANNEL_BLOCKED)) {
-		if (GotFlag(statePtr, CHANNEL_NONBLOCKING)) {
-		    goto done;
-		}
-		ResetFlag(statePtr, CHANNEL_BLOCKED);
-	    }
+    while (chanPtr->inQueueHead && bytesToRead > 0) {
+	ChannelBuffer *bufPtr = chanPtr->inQueueHead;
+	int bytesInBuffer = BytesLeft(bufPtr);
+	int toCopy = (bytesInBuffer < bytesToRead) ? bytesInBuffer
+		: bytesToRead;
 
-#ifdef TCL_IO_TRACK_OS_FOR_DRIVER_WITH_BAD_BLOCKING
-	    /*
-	     * [Bug 943274]. Better emulation of non-blocking channels for
-	     * channels without BlockModeProc, by keeping track of true
-	     * fileevents generated by the OS == Data waiting and reading if
-	     * and only if we are sure to have data.
-	     */
+	/* Copy the current chunk into the read buffer. */
 
-	    if (GotFlag(statePtr, CHANNEL_NONBLOCKING) &&
-		    (Tcl_ChannelBlockModeProc(chanPtr->typePtr) == NULL) &&
-		    !GotFlag(statePtr, CHANNEL_HAS_MORE_DATA)) {
-		/*
-		 * We bypass the driver; it would block as no data is
-		 * available.
-		 */
+	memcpy(readBuf, RemovePoint(bufPtr), (size_t) toCopy);
+	bufPtr->nextRemoved += toCopy;
+	copied += toCopy;
+	readBuf += toCopy;
+	bytesToRead -= toCopy;
 
-		nread = -1;
-		result = EWOULDBLOCK;
-	    } else
-#endif /* TCL_IO_TRACK_OS_FOR_DRIVER_WITH_BAD_BLOCKING */
-	    {
-		/*
-		 * Now go to the driver to get as much as is possible to fill
-		 * the remaining request. Do all the error handling by
-		 * ourselves. The code was stolen from 'GetInput' and slightly
-		 * adapted (different return value here).
-		 *
-		 * The case of 'bytesToRead == 0' at this point cannot happen.
-		 */
+	/* If the current buffer is empty recycle it. */
 
-		nread = ChanRead(chanPtr, bufPtr + copied,
-			bytesToRead - copied, &result);
+	if (IsBufferEmpty(bufPtr)) {
+	    chanPtr->inQueueHead = bufPtr->nextPtr;
+	    if (chanPtr->inQueueHead == NULL) {
+		chanPtr->inQueueTail = NULL;
 	    }
+	    RecycleBuffer(chanPtr->state, bufPtr, 0);
+	}
+    }
 
-	    if (nread > 0) {
-		/*
-		 * If we get a short read, signal up that we may be BLOCKED.
-		 * We should avoid calling the driver because on some
-		 * platforms we will block in the low level reading code even
-		 * though the channel is set into nonblocking mode.
-		 */
-
-		if (nread < (bytesToRead - copied)) {
-		    SetFlag(statePtr, CHANNEL_BLOCKED);
-		}
-
-#ifdef TCL_IO_TRACK_OS_FOR_DRIVER_WITH_BAD_BLOCKING
-		if (nread <= (bytesToRead - copied)) {
-		    /*
-		     * [Bug 943274] We have read the available data, clear
-		     * flag.
-		     */
+    /*
+     * Go to the driver only if we got nothing from pushback.
+     * Have to do it this way to avoid EOF mis-timings when we
+     * consider the ability that EOF may not be a permanent
+     * condition in the driver, and in that case we have to
+     * synchronize.
+     */
 
-		    ResetFlag(statePtr, CHANNEL_HAS_MORE_DATA);
-		}
-#endif /* TCL_IO_TRACK_OS_FOR_DRIVER_WITH_BAD_BLOCKING */
-	    } else if (nread == 0) {
-		SetFlag(statePtr, CHANNEL_EOF);
-		statePtr->inputEncodingFlags |= TCL_ENCODING_END;
-
-	    } else if (nread < 0) {
-		if ((result == EWOULDBLOCK) || (result == EAGAIN)) {
-		    if (copied > 0) {
-			/*
-			 * Information that was copied earlier has precedence
-			 * over EAGAIN/WOULDBLOCK handling.
-			 */
+    if (copied) {
+	return copied;
+    }
 
-			return copied;
-		    }
+    /* This test not needed. */
+    if (bytesToRead > 0) {
 
-		    SetFlag(statePtr, CHANNEL_BLOCKED);
-		    result = EAGAIN;
-		}
+	int nread = ChanRead(chanPtr, readBuf, bytesToRead);
 
-		Tcl_SetErrno(result);
-		return -1;
+	if (nread > 0) {
+	    /* Successful read (short is OK) - add to bytes copied */
+	    copied += nread;
+	} else if (nread < 0) {
+	    /*
+	     * An error signaled.  If CHANNEL_BLOCKED, then the error
+	     * is not real, but an indication of blocked state.  In
+	     * that case, retain the flag and let caller receive the
+	     * short read of copied bytes from the pushback.
+	     * HOWEVER, if copied==0 bytes from pushback then repeat
+	     * signalling the blocked state as an error to caller so
+	     * there is no false report of an EOF.
+	     * When !CHANNEL_BLOCKED, the error is real and passes on
+	     * to caller.
+	     */
+	    if (!GotFlag(statePtr, CHANNEL_BLOCKED) || copied == 0) {
+		copied = -1;
 	    }
-
-	    return copied + nread;
+	} else {
+	    /*
+	     * nread == 0.  Driver is at EOF. Let that state filter up.
+	     */
 	}
     }
-
-  done:
     return copied;
 }
 
@@ -5854,20 +5714,18 @@ DoReadChars(
     ChannelState *statePtr = chanPtr->state;
 				/* State info for channel */
     ChannelBuffer *bufPtr;
-    int offset, factor, copied, copiedNow, result;
-    Tcl_Encoding encoding;
+    int copied, copiedNow, result;
+    Tcl_Encoding encoding = statePtr->encoding;
+    int binaryMode;
 #define UTF_EXPANSION_FACTOR	1024
+    int factor = UTF_EXPANSION_FACTOR;
 
-    /*
-     * This operation should occur at the top of a channel stack.
-     */
-
-    chanPtr = statePtr->topChanPtr;
-    encoding = statePtr->encoding;
-    factor = UTF_EXPANSION_FACTOR;
+    binaryMode = (encoding == NULL)
+	    && (statePtr->inputTranslation == TCL_TRANSLATE_LF)
+	    && (statePtr->inEofChar == '\0');
 
     if (appendFlag == 0) {
-	if (encoding == NULL) {
+	if (binaryMode) {
 	    Tcl_SetByteArrayLength(objPtr, 0);
 	} else {
 	    Tcl_SetObjLength(objPtr, 0);
@@ -5876,27 +5734,61 @@ DoReadChars(
 	     * We're going to access objPtr->bytes directly, so we must ensure
 	     * that this is actually a string object (otherwise it might have
 	     * been pure Unicode).
+	     *
+	     * Probably not needed anymore.
 	     */
 
 	    TclGetString(objPtr);
 	}
-	offset = 0;
-    } else {
-	if (encoding == NULL) {
-	    Tcl_GetByteArrayFromObj(objPtr, &offset);
-	} else {
-	    TclGetStringFromObj(objPtr, &offset);
+    }
+
+    /*
+     * Early out when next read will see eofchar.
+     *
+     * NOTE: See DoRead for argument that it's a bug (one we're keeping)
+     * to have this escape before the one for zero-char read request.
+     */
+
+    if (GotFlag(statePtr, CHANNEL_STICKY_EOF)) {
+	SetFlag(statePtr, CHANNEL_EOF);
+	assert( statePtr->inputEncodingFlags & TCL_ENCODING_END );
+	assert( !GotFlag(statePtr, CHANNEL_BLOCKED|INPUT_SAW_CR) );
+
+	UpdateInterest(chanPtr);
+	return 0;
+    }
+
+    /* Special handling for zero-char read request. */
+    if (toRead == 0) {
+	if (GotFlag(statePtr, CHANNEL_EOF)) {
+	    statePtr->inputEncodingFlags |= TCL_ENCODING_START;
 	}
+	ResetFlag(statePtr, CHANNEL_BLOCKED|CHANNEL_EOF);
+	statePtr->inputEncodingFlags &= ~TCL_ENCODING_END;
+	UpdateInterest(chanPtr);
+	return 0;
     }
 
+    /*
+     * This operation should occur at the top of a channel stack.
+     */
+
+    chanPtr = statePtr->topChanPtr;
+    TclChannelPreserve((Tcl_Channel)chanPtr);
+
+    /* Must clear the BLOCKED|EOF flags here since we check before reading */
+    if (GotFlag(statePtr, CHANNEL_EOF)) {
+	statePtr->inputEncodingFlags |= TCL_ENCODING_START;
+    }
+    ResetFlag(statePtr, CHANNEL_BLOCKED|CHANNEL_EOF);
+    statePtr->inputEncodingFlags &= ~TCL_ENCODING_END;
     for (copied = 0; (unsigned) toRead > 0; ) {
 	copiedNow = -1;
 	if (statePtr->inQueueHead != NULL) {
-	    if (encoding == NULL) {
-		copiedNow = ReadBytes(statePtr, objPtr, toRead, &offset);
+	    if (binaryMode) {
+		copiedNow = ReadBytes(statePtr, objPtr, toRead);
 	    } else {
-		copiedNow = ReadChars(statePtr, objPtr, toRead, &offset,
-			&factor);
+		copiedNow = ReadChars(statePtr, objPtr, toRead, &factor);
 	    }
 
 	    /*
@@ -5919,19 +5811,21 @@ DoReadChars(
 	    if (GotFlag(statePtr, CHANNEL_EOF)) {
 		break;
 	    }
-	    if (GotFlag(statePtr, CHANNEL_BLOCKED)) {
-		if (GotFlag(statePtr, CHANNEL_NONBLOCKING)) {
-		    break;
-		}
-		ResetFlag(statePtr, CHANNEL_BLOCKED);
+	    if (GotFlag(statePtr, CHANNEL_NONBLOCKING|CHANNEL_BLOCKED)
+		    == (CHANNEL_NONBLOCKING|CHANNEL_BLOCKED)) {
+		break;
 	    }
 	    result = GetInput(chanPtr);
+	    if (chanPtr != statePtr->topChanPtr) {
+		TclChannelRelease((Tcl_Channel)chanPtr);
+		chanPtr = statePtr->topChanPtr;
+		TclChannelPreserve((Tcl_Channel)chanPtr);
+	    }
 	    if (result != 0) {
-		if (result == EAGAIN) {
-		    break;
+		if (!GotFlag(statePtr, CHANNEL_BLOCKED)) {
+		    copied = -1;
 		}
-		copied = -1;
-		goto done;
+		break;
 	    }
 	} else {
 	    copied += copiedNow;
@@ -5939,27 +5833,36 @@ DoReadChars(
 	}
     }
 
-    ResetFlag(statePtr, CHANNEL_BLOCKED);
-    if (encoding == NULL) {
-	Tcl_SetByteArrayLength(objPtr, offset);
-    } else {
-	Tcl_SetObjLength(objPtr, offset);
-    }
-
     /*
-     * Update the notifier state so we don't block while there is still data
-     * in the buffers.
+     * Failure to fill a channel buffer may have left channel reporting
+     * a "blocked" state, but so long as we fulfilled the request here,
+     * the caller does not consider us blocked.
      */
+    if (toRead == 0) {
+	ResetFlag(statePtr, CHANNEL_BLOCKED);
+    }
 
-  done:
     /*
      * Regenerate the top channel, in case it was changed due to
      * self-modifying reflected transforms.
      */
+    if (chanPtr != statePtr->topChanPtr) {
+	TclChannelRelease((Tcl_Channel)chanPtr);
+	chanPtr = statePtr->topChanPtr;
+	TclChannelPreserve((Tcl_Channel)chanPtr);
+    }
 
-    chanPtr = statePtr->topChanPtr;
-
+    /*
+     * Update the notifier state so we don't block while there is still data
+     * in the buffers.
+     */
+	assert(!GotFlag(statePtr, CHANNEL_EOF)
+		|| GotFlag(statePtr, CHANNEL_STICKY_EOF)
+		|| Tcl_InputBuffered((Tcl_Channel)chanPtr) == 0);
+	assert( !(GotFlag(statePtr, CHANNEL_EOF|CHANNEL_BLOCKED)
+		== (CHANNEL_EOF|CHANNEL_BLOCKED)) );
     UpdateInterest(chanPtr);
+    TclChannelRelease((Tcl_Channel)chanPtr);
     return copied;
 }
 
@@ -5977,13 +5880,11 @@ DoReadChars(
  *	allocated to hold data read from the channel as needed.
  *
  * Results:
- *	The return value is the number of bytes appended to the object and
- *	*offsetPtr is filled with the total number of bytes in the object
- *	(greater than the return value if there were already bytes in the
- *	object).
+ *	The return value is the number of bytes appended to the object, or
+ *	-1 to indicate that zero bytes were read due to an EOF.
  *
  * Side effects:
- *	None.
+ *	The storage of bytes in objPtr can cause (re-)allocation of memory.
  *
  *---------------------------------------------------------------------------
  */
@@ -5996,72 +5897,22 @@ ReadBytes(
 				 * been allocated to hold data, not how many
 				 * bytes of data have been stored in the
 				 * object. */
-    int bytesToRead,		/* Maximum number of bytes to store, or < 0 to
+    int bytesToRead)		/* Maximum number of bytes to store, or < 0 to
 				 * get all available bytes. Bytes are obtained
 				 * from the first buffer in the queue - even
 				 * if this number is larger than the number of
 				 * bytes available in the first buffer, only
 				 * the bytes from the first buffer are
 				 * returned. */
-    int *offsetPtr)		/* On input, contains how many bytes of objPtr
-				 * have been used to hold data. On output,
-				 * filled with how many bytes are now being
-				 * used. */
 {
-    int toRead, srcLen, offset, length, srcRead, dstWrote;
-    ChannelBuffer *bufPtr;
-    char *src, *dst;
-
-    offset = *offsetPtr;
-
-    bufPtr = statePtr->inQueueHead;
-    src = RemovePoint(bufPtr);
-    srcLen = BytesLeft(bufPtr);
-
-    toRead = bytesToRead;
-    if ((unsigned) toRead > (unsigned) srcLen) {
-	toRead = srcLen;
-    }
-
-    dst = (char *) Tcl_GetByteArrayFromObj(objPtr, &length);
-    if (toRead > length - offset - 1) {
-	/*
-	 * Double the existing size of the object or make enough room to hold
-	 * all the characters we may get from the source buffer, whichever is
-	 * larger.
-	 */
-
-	length = offset * 2;
-	if (offset < toRead) {
-	    length = offset + toRead + 1;
-	}
-	dst = (char *) Tcl_SetByteArrayLength(objPtr, length);
-    }
-    dst += offset;
-
-    if (GotFlag(statePtr, INPUT_NEED_NL)) {
-	ResetFlag(statePtr, INPUT_NEED_NL);
-	if ((srcLen == 0) || (*src != '\n')) {
-	    *dst = '\r';
-	    *offsetPtr += 1;
-	    return 1;
-	}
-	*dst++ = '\n';
-	src++;
-	srcLen--;
-	toRead--;
-    }
+    ChannelBuffer *bufPtr = statePtr->inQueueHead;
+    int srcLen = BytesLeft(bufPtr);
+    int toRead = bytesToRead>srcLen || bytesToRead<0 ? srcLen : bytesToRead;
 
-    srcRead = srcLen;
-    dstWrote = toRead;
-    if (TranslateInputEOL(statePtr, dst, src, &dstWrote, &srcRead) != 0) {
-	if (dstWrote == 0) {
-	    return -1;
-	}
-    }
-    bufPtr->nextRemoved += srcRead;
-    *offsetPtr += dstWrote;
-    return dstWrote;
+    TclAppendBytesToByteArray(objPtr, (unsigned char *) RemovePoint(bufPtr),
+	    toRead);
+    bufPtr->nextRemoved += toRead;
+    return toRead;
 }
 
 /*
@@ -6105,35 +5956,35 @@ ReadChars(
 				 * is larger than the number of characters
 				 * available in the first buffer, only the
 				 * characters from the first buffer are
-				 * returned. */
-    int *offsetPtr,		/* On input, contains how many bytes of objPtr
-				 * have been used to hold data. On output,
-				 * filled with how many bytes are now being
-				 * used. */
+				 * returned. The execption is when there is
+				 * not any complete character in the first
+				 * buffer.  In that case, a recursive call
+				 * effectively obtains chars from the
+				 * second buffer. */
     int *factorPtr)		/* On input, contains a guess of how many
 				 * bytes need to be allocated to hold the
 				 * result of converting N source bytes to
 				 * UTF-8. On output, contains another guess
 				 * based on the data seen so far. */
 {
-    int toRead, factor, offset, spaceLeft, srcLen, dstNeeded;
-    int srcRead, dstWrote, numChars, dstRead;
-    ChannelBuffer *bufPtr;
-    char *src, *dst;
-    Tcl_EncodingState oldState;
-    int encEndFlagSuppressed = 0;
-
-    factor = *factorPtr;
-    offset = *offsetPtr;
+    Tcl_Encoding encoding = statePtr->encoding? statePtr->encoding
+	    : GetBinaryEncoding();
+    Tcl_EncodingState savedState = statePtr->inputEncodingState;
+    ChannelBuffer *bufPtr = statePtr->inQueueHead;
+    int savedIEFlags = statePtr->inputEncodingFlags;
+    int savedFlags = statePtr->flags;
+    char *dst, *src = RemovePoint(bufPtr);
+    int numBytes, srcLen = BytesLeft(bufPtr);
 
-    bufPtr = statePtr->inQueueHead;
-    src = RemovePoint(bufPtr);
-    srcLen = BytesLeft(bufPtr);
+    /*
+     * One src byte can yield at most one character.  So when the
+     * number of src bytes we plan to read is less than the limit on
+     * character count to be read, clearly we will remain within that
+     * limit, and we can use the value of "srcLen" as a tighter limit
+     * for sizing receiving buffers.
+     */
 
-    toRead = charsToRead;
-    if ((unsigned) toRead > (unsigned) srcLen) {
-	toRead = srcLen;
-    }
+    int toRead = ((charsToRead<0)||(charsToRead > srcLen)) ? srcLen : charsToRead;
 
     /*
      * 'factor' is how much we guess that the bytes in the source buffer will
@@ -6141,226 +5992,335 @@ ReadChars(
      * how many characters were produced by the previous pass.
      */
 
-    dstNeeded = TCL_UTF_MAX - 1 + toRead * factor / UTF_EXPANSION_FACTOR;
-    spaceLeft = objPtr->length - offset;
-
-    if (dstNeeded > spaceLeft) {
-	/*
-	 * Double the existing size of the object or make enough room to hold
-	 * all the characters we want from the source buffer, whichever is
-	 * larger.
-	 */
-
-	int length = offset + ((offset < dstNeeded) ? dstNeeded : offset);
+    int factor = *factorPtr;
+    int dstLimit = TCL_UTF_MAX - 1 + toRead * factor / UTF_EXPANSION_FACTOR;
 
-	if (Tcl_AttemptSetObjLength(objPtr, length) == 0) {
-	    length = offset + dstNeeded;
-	    if (Tcl_AttemptSetObjLength(objPtr, length) == 0) {
-		dstNeeded = TCL_UTF_MAX - 1 + toRead;
-		length = offset + dstNeeded;
-		Tcl_SetObjLength(objPtr, length);
-	    }
-	}
-	spaceLeft = length - offset;
-    }
+    (void) TclGetStringFromObj(objPtr, &numBytes);
+    Tcl_AppendToObj(objPtr, NULL, dstLimit);
     if (toRead == srcLen) {
-	/*
-	 * Want to convert the whole buffer in one pass. If we have enough
-	 * space, convert it using all available space in object rather than
-	 * using the factor.
-	 */
-
-	dstNeeded = spaceLeft;
+	unsigned int size;
+	dst = TclGetStringStorage(objPtr, &size) + numBytes;
+	dstLimit = size - numBytes;
+    } else {
+	dst = TclGetString(objPtr) + numBytes;
     }
-    dst = objPtr->bytes + offset;
 
     /*
-     * [Bug 1462248]: The cause of the crash reported in this bug is this:
-     *
-     * - ReadChars, called with a single buffer, with a incomplete
-     *	 multi-byte character at the end (only the first byte of it).
-     * - Encoding translation fails, asks for more data
-     * - Data is read, and eof is reached, TCL_ENCODING_END (TEE) is set.
-     * - ReadChar is called again, converts the first buffer, but due to TEE
-     *	 it does not check for incomplete multi-byte data, and the character
-     *	 just after the end of the first buffer is a valid completion of the
-     *	 multi-byte header in the actual buffer. The conversion reads more
-     *	 characters from the buffer then present. This causes nextRemoved to
-     *	 overshoot nextAdded and the next reads compute a negative srcLen,
-     *	 cause further translations to fail, causing copying of data into the
-     *	 next buffer using bad arguments, causing the mecpy for to eventually
-     *	 fail.
-     *
-     * In the end it is a memory access bug spiraling out of control if the
-     * conditions are _just so_. And ultimate cause is that TEE is given to a
-     * conversion where it should not. TEE signals that this is the last
-     * buffer. Except in our case it is not.
+     * This routine is burdened with satisfying several constraints.
+     * It cannot append more than 'charsToRead` chars onto objPtr.
+     * This is measured after encoding and translation transformations
+     * are completed.  There is no precise number of src bytes that can
+     * be associated with the limit.  Yet, when we are done, we must know
+     * precisely the number of src bytes that were consumed to produce
+     * the appended chars, so that all subsequent bytes are left in
+     * the buffers for future read operations.
      *
-     * My solution is to suppress TEE if the first buffer is not the last. We
-     * will eventually need it given that EOF has been reached, but not right
-     * now. This is what the new flag "endEncSuppressFlag" is for.
-     *
-     * The bug in 'Tcl_Utf2UtfProc' where it read from memory behind the
-     * actual buffer has been fixed as well, and fixes the problem with the
-     * crash too, but this would still allow the generic layer to
-     * accidentially break a multi-byte sequence if the conditions are just
-     * right, because again the ExternalToUtf would be successful where it
-     * should not.
+     * The consequence is that we have no choice but to implement a
+     * "trial and error" approach, where in general we may need to
+     * perform transformations and copies multiple times to achieve
+     * a consistent set of results.  This takes the shape of a loop.
      */
 
-    if ((statePtr->inputEncodingFlags & TCL_ENCODING_END) &&
-	    (bufPtr->nextPtr != NULL)) {
+    while (1) {
+	int dstDecoded, dstRead, dstWrote, srcRead, numChars, code;
+	int flags = statePtr->inputEncodingFlags | TCL_ENCODING_NO_TERMINATE;
+
+	if (charsToRead > 0) {
+	    flags |= TCL_ENCODING_CHAR_LIMIT;
+	    numChars = charsToRead;
+	}
+
 	/*
-	 * TEE is set for a buffer which is not the last. Squash it for now,
-	 * and restore it later, before yielding control to our caller.
+	 * Perform the encoding transformation.  Read no more than
+	 * srcLen bytes, write no more than dstLimit bytes.
+	 *
+	 * Some trickiness with encoding flags here.  We do not want
+	 * the end of a buffer to be treated as the end of all input
+	 * when the presence of bytes in a next buffer are already
+	 * known to exist.  This is checked with an assert() because
+	 * so far no test case causing the assertion to be false has
+	 * been created.  The normal operations of channel reading
+	 * appear to cause EOF and TCL_ENCODING_END setting to appear
+	 * only in situations where there are no further bytes in
+	 * any buffers.
 	 */
 
-	statePtr->inputEncodingFlags &= ~TCL_ENCODING_END;
-	encEndFlagSuppressed = 1;
-    }
+	assert(bufPtr->nextPtr == NULL || BytesLeft(bufPtr->nextPtr) == 0
+		|| (statePtr->inputEncodingFlags & TCL_ENCODING_END) == 0);
+
+	code = Tcl_ExternalToUtf(NULL, encoding, src, srcLen,
+		flags, &statePtr->inputEncodingState,
+		dst, dstLimit, &srcRead, &dstDecoded, &numChars);
 
-    oldState = statePtr->inputEncodingState;
-    if (GotFlag(statePtr, INPUT_NEED_NL)) {
 	/*
-	 * We want a '\n' because the last character we saw was '\r'.
+	 * Perform the translation transformation in place.  Read no more
+	 * than the dstDecoded bytes the encoding transformation actually
+	 * produced.  Capture the number of bytes written in dstWrote.
+	 * Capture the number of bytes actually consumed in dstRead.
 	 */
 
-	ResetFlag(statePtr, INPUT_NEED_NL);
-	Tcl_ExternalToUtf(NULL, statePtr->encoding, src, srcLen,
-		statePtr->inputEncodingFlags, &statePtr->inputEncodingState,
-		dst, TCL_UTF_MAX + 1, &srcRead, &dstWrote, &numChars);
-	if ((dstWrote > 0) && (*dst == '\n')) {
+	dstWrote = dstLimit;
+	dstRead = dstDecoded;
+	TranslateInputEOL(statePtr, dst, dst, &dstWrote, &dstRead);
+
+	if (dstRead < dstDecoded) {
+
 	    /*
-	     * The next char was a '\n'. Consume it and produce a '\n'.
+	     * The encoding transformation produced bytes that the
+	     * translation transformation did not consume.  Why did
+	     * this happen?
 	     */
 
-	    bufPtr->nextRemoved += srcRead;
-	} else {
+	    if (statePtr->inEofChar && dst[dstRead] == statePtr->inEofChar) {
+		/*
+		 * 1) There's an eof char set on the channel, and
+		 *    we saw it and stopped translating at that point.
+		 *
+		 * NOTE the bizarre spec of TranslateInputEOL in this case.
+		 * Clearly the eof char had to be read in order to account
+		 * for the stopping, but the value of dstRead does not
+		 * include it.
+		 *
+		 * Also rather bizarre, our caller can only notice an
+		 * EOF condition if we return the value -1 as the number
+		 * of chars read.  This forces us to perform a 2-call
+		 * dance where the first call can read all the chars
+		 * up to the eof char, and the second call is solely
+		 * for consuming the encoded eof char then pointed at
+		 * by src so that we can return that magic -1 value.
+		 * This seems really wasteful, especially since
+		 * the first decoding pass of each call is likely to
+		 * decode many bytes beyond that eof char that's all we
+		 * care about.
+		 */
+
+		if (dstRead == 0) {
+		    /*
+		     * Curious choice in the eof char handling.  We leave
+		     * the eof char in the buffer.  So, no need to compute
+		     * a proper srcRead value.  At this point, there
+		     * are no chars before the eof char in the buffer.
+		     */
+		    Tcl_SetObjLength(objPtr, numBytes);
+		    return -1;
+		}
+
+		{
+		    /*
+		     * There are chars leading the buffer before the eof
+		     * char.  Adjust the dstLimit so we go back and read
+		     * only those and do not encounter the eof char this
+		     * time.
+		     */
+
+		    dstLimit = dstRead - 1 + TCL_UTF_MAX;
+		    statePtr->flags = savedFlags;
+		    statePtr->inputEncodingFlags = savedIEFlags;
+		    statePtr->inputEncodingState = savedState;
+		    continue;
+		}
+	    }
+
 	    /*
-	     * The next char was not a '\n'. Produce a '\r'.
+	     * 2) The other way to read fewer bytes than are decoded
+	     *    is when the final byte is \r and we're in a CRLF
+	     *    translation mode so we cannot decide whether to
+	     *	  record \r or \n yet.
 	     */
 
-	    *dst = '\r';
-	}
-	statePtr->inputEncodingFlags &= ~TCL_ENCODING_START;
-	*offsetPtr += 1;
+	    assert(dst[dstRead] == '\r');
+	    assert(statePtr->inputTranslation == TCL_TRANSLATE_CRLF);
 
-	if (encEndFlagSuppressed) {
-	    statePtr->inputEncodingFlags |= TCL_ENCODING_END;
-	}
-	return 1;
-    }
+	    if (dstWrote > 0) {
+		/*
+		 * There are chars we can read before we hit the bare cr.
+		 * Go back with a smaller dstLimit so we get them in the
+		 * next pass, compute a matching srcRead, and don't end
+		 * up back here in this call.
+		 */
 
-    Tcl_ExternalToUtf(NULL, statePtr->encoding, src, srcLen,
-	    statePtr->inputEncodingFlags, &statePtr->inputEncodingState, dst,
-	    dstNeeded + 1, &srcRead, &dstWrote, &numChars);
+		dstLimit = dstRead - 1 + TCL_UTF_MAX;
+		statePtr->flags = savedFlags;
+		statePtr->inputEncodingFlags = savedIEFlags;
+		statePtr->inputEncodingState = savedState;
+		continue;
+	    }
 
-    if (encEndFlagSuppressed) {
-	statePtr->inputEncodingFlags |= TCL_ENCODING_END;
-    }
+	    assert(dstWrote == 0);
+	    assert(dstRead == 0);
 
-    if (srcRead == 0) {
-	/*
-	 * Not enough bytes in src buffer to make a complete char. Copy the
-	 * bytes to the next buffer to make a new contiguous string, then tell
-	 * the caller to fill the buffer with more bytes.
-	 */
+	    /*
+	     * We decoded only the bare cr, and we cannot read a
+	     * translated char from that alone.  We have to know what's
+	     * next.  So why do we only have the one decoded char?
+	     */
 
-	ChannelBuffer *nextPtr;
+	    if (code != TCL_OK) {
+		char buffer[TCL_UTF_MAX + 1];
+		int read, decoded, count;
 
-	nextPtr = bufPtr->nextPtr;
-	if (nextPtr == NULL) {
-	    if (srcLen > 0) {
 		/*
-		 * There isn't enough data in the buffers to complete the next
-		 * character, so we need to wait for more data before the next
-		 * file event can be delivered. [Bug 478856]
-		 *
-		 * The exception to this is if the input buffer was completely
-		 * empty before we tried to convert its contents. Nothing in,
-		 * nothing out, and no incomplete character data. The
-		 * conversion before the current one was complete.
+		 * Didn't get everything the buffer could offer
 		 */
 
-		SetFlag(statePtr, CHANNEL_NEED_MORE_DATA);
+		statePtr->flags = savedFlags;
+		statePtr->inputEncodingFlags = savedIEFlags;
+		statePtr->inputEncodingState = savedState;
+
+		assert(bufPtr->nextPtr == NULL
+			|| BytesLeft(bufPtr->nextPtr) == 0 || 0 ==
+			(statePtr->inputEncodingFlags & TCL_ENCODING_END));
+
+		Tcl_ExternalToUtf(NULL, encoding, src, srcLen,
+		(statePtr->inputEncodingFlags | TCL_ENCODING_NO_TERMINATE),
+		&statePtr->inputEncodingState, buffer, TCL_UTF_MAX + 1,
+		&read, &decoded, &count);
+
+		if (count == 2) {
+		    if (buffer[1] == '\n') {
+			/* \r\n translate to \n */
+			dst[0] = '\n';
+			bufPtr->nextRemoved += read;
+		    } else {
+			dst[0] = '\r';
+			bufPtr->nextRemoved += srcRead;
+		    }
+
+		    statePtr->inputEncodingFlags &= ~TCL_ENCODING_START;
+
+		    Tcl_SetObjLength(objPtr, numBytes + 1);
+		    return 1;
+		}
+
+	    } else if (statePtr->flags & CHANNEL_EOF) {
+
+		/*
+		 * The bare \r is the only char and we will never read
+		 * a subsequent char to make the determination.
+		 */
+
+		dst[0] = '\r';
+		bufPtr->nextRemoved = bufPtr->nextAdded;
+		Tcl_SetObjLength(objPtr, numBytes + 1);
+		return 1;
 	    }
-	    return -1;
+
+	    /*
+	     * Revise the dstRead value so that the numChars calc
+	     * below correctly computes zero characters read.
+	     */
+
+	    dstRead = numChars;
+
+	    /* FALL THROUGH - get more data (dstWrote == 0) */
 	}
 
 	/*
-	 * Space is made at the beginning of the buffer to copy the previous
-	 * unused bytes there. Check first if the buffer we are using actually
-	 * has enough space at its beginning for the data we are copying.
-	 * Because if not we will write over the buffer management
-	 * information, especially the 'nextPtr'.
-	 *
-	 * Note that the BUFFER_PADDING (See AllocChannelBuffer) is used to
-	 * prevent exactly this situation. I.e. it should never happen.
-	 * Therefore it is ok to panic should it happen despite the
-	 * precautions.
+	 * The translation transformation can only reduce the number
+	 * of chars when it converts \r\n into \n.  The reduction in
+	 * the number of chars is the difference in bytes read and written.
 	 */
 
-	if (nextPtr->nextRemoved - srcLen < 0) {
-	    Tcl_Panic("Buffer Underflow, BUFFER_PADDING not enough");
-	}
+	numChars -= (dstRead - dstWrote);
 
-	nextPtr->nextRemoved -= srcLen;
-	memcpy(RemovePoint(nextPtr), src, (size_t) srcLen);
-	RecycleBuffer(statePtr, bufPtr, 0);
-	statePtr->inQueueHead = nextPtr;
-	return ReadChars(statePtr, objPtr, charsToRead, offsetPtr, factorPtr);
-    }
+	if (charsToRead > 0 && numChars > charsToRead) {
 
-    dstRead = dstWrote;
-    if (TranslateInputEOL(statePtr, dst, dst, &dstWrote, &dstRead) != 0) {
-	/*
-	 * Hit EOF char. How many bytes of src correspond to where the EOF was
-	 * located in dst? Run the conversion again with an output buffer just
-	 * big enough to hold the data so we can get the correct value for
-	 * srcRead.
-	 */
+	    /*
+	     * TODO: This cannot happen anymore.
+	     *
+	     * We read more chars than allowed.  Reset limits to
+	     * prevent that and try again.  Don't forget the extra
+	     * padding of TCL_UTF_MAX bytes demanded by the
+	     * Tcl_ExternalToUtf() call!
+	     */
 
-	if (dstWrote == 0) {
-	    return -1;
+	    dstLimit = Tcl_UtfAtIndex(dst, charsToRead) - 1 + TCL_UTF_MAX - dst;
+	    statePtr->flags = savedFlags;
+	    statePtr->inputEncodingFlags = savedIEFlags;
+	    statePtr->inputEncodingState = savedState;
+	    continue;
 	}
-	statePtr->inputEncodingState = oldState;
-	Tcl_ExternalToUtf(NULL, statePtr->encoding, src, srcLen,
-		statePtr->inputEncodingFlags, &statePtr->inputEncodingState,
-		dst, dstRead + TCL_UTF_MAX, &srcRead, &dstWrote, &numChars);
-	TranslateInputEOL(statePtr, dst, dst, &dstWrote, &dstRead);
-    }
 
-    /*
-     * The number of characters that we got may be less than the number that
-     * we started with because "\r\n" sequences may have been turned into just
-     * '\n' in dst.
-     */
+	if (dstWrote == 0) {
+	    ChannelBuffer *nextPtr;
 
-    numChars -= dstRead - dstWrote;
+	    /* We were not able to read any chars. */
 
-    if ((unsigned) numChars > (unsigned) toRead) {
-	/*
-	 * Got too many chars.
-	 */
+	    assert (numChars == 0);
 
-	const char *eof = Tcl_UtfAtIndex(dst, toRead);
+	    /*
+	     * There is one situation where this is the correct final
+	     * result.  If the src buffer contains only a single \n
+	     * byte, and we are in TCL_TRANSLATE_AUTO mode, and
+	     * when the translation pass was made the INPUT_SAW_CR
+	     * flag was set on the channel.  In that case, the
+	     * correct behavior is to consume that \n and produce the
+	     * empty string.
+	     */
 
-	statePtr->inputEncodingState = oldState;
-	Tcl_ExternalToUtf(NULL, statePtr->encoding, src, srcLen,
-		statePtr->inputEncodingFlags, &statePtr->inputEncodingState,
-		dst, eof - dst + TCL_UTF_MAX, &srcRead, &dstWrote, &numChars);
-	dstRead = dstWrote;
-	TranslateInputEOL(statePtr, dst, dst, &dstWrote, &dstRead);
-	numChars -= (dstRead - dstWrote);
-    }
-    statePtr->inputEncodingFlags &= ~TCL_ENCODING_START;
+	    if (dstRead == 1 && dst[0] == '\n') {
+		assert(statePtr->inputTranslation == TCL_TRANSLATE_AUTO);
+
+		goto consume;
+	    }
+
+	    /* Otherwise, reading zero characters indicates there's
+	     * something incomplete at the end of the src buffer.
+	     * Maybe there were not enough src bytes to decode into
+	     * a char.  Maybe a lone \r could not be translated (crlf
+	     * mode).  Need to combine any unused src bytes we have
+	     * in the first buffer with subsequent bytes to try again.
+	     */
+
+	    nextPtr = bufPtr->nextPtr;
+
+	    if (nextPtr == NULL) {
+		if (srcLen > 0) {
+		    SetFlag(statePtr, CHANNEL_NEED_MORE_DATA);
+		}
+		Tcl_SetObjLength(objPtr, numBytes);
+		return -1;
+	    }
+
+	    /*
+	     * Space is made at the beginning of the buffer to copy the
+	     * previous unused bytes there. Check first if the buffer we
+	     * are using actually has enough space at its beginning for
+	     * the data we are copying.  Because if not we will write over
+	     * the buffer management information, especially the 'nextPtr'.
+	     *
+	     * Note that the BUFFER_PADDING (See AllocChannelBuffer) is
+	     * used to prevent exactly this situation. I.e. it should never
+	     * happen.  Therefore it is ok to panic should it happen despite
+	     * the precautions.
+	     */
+
+	    if (nextPtr->nextRemoved - srcLen < 0) {
+		Tcl_Panic("Buffer Underflow, BUFFER_PADDING not enough");
+	    }
+
+	    nextPtr->nextRemoved -= srcLen;
+	    memcpy(RemovePoint(nextPtr), src, (size_t) srcLen);
+	    RecycleBuffer(statePtr, bufPtr, 0);
+	    statePtr->inQueueHead = nextPtr;
+	    Tcl_SetObjLength(objPtr, numBytes);
+	    return ReadChars(statePtr, objPtr, charsToRead, factorPtr);
+	}
 
-    bufPtr->nextRemoved += srcRead;
-    if (dstWrote > srcRead + 1) {
-	*factorPtr = dstWrote * UTF_EXPANSION_FACTOR / srcRead;
+	statePtr->inputEncodingFlags &= ~TCL_ENCODING_START;
+
+    consume:
+	bufPtr->nextRemoved += srcRead;
+	/*
+	 * If this read contained multibyte characters, revise factorPtr
+	 * so the next read will allocate bigger buffers.
+	 */
+	if (numChars && numChars < srcRead) {
+	    *factorPtr = srcRead * UTF_EXPANSION_FACTOR / numChars;
+	}
+	Tcl_SetObjLength(objPtr, numBytes + dstWrote);
+	return numChars;
     }
-    *offsetPtr += dstWrote;
-    return numChars;
 }
 
 /*
@@ -6381,7 +6341,7 @@ ReadChars(
  *---------------------------------------------------------------------------
  */
 
-static int
+static void
 TranslateInputEOL(
     ChannelState *statePtr,	/* Channel being read, for EOL translation and
 				 * EOF character. */
@@ -6390,132 +6350,138 @@ TranslateInputEOL(
 				 * characters. */
     const char *srcStart,	/* Source characters. */
     int *dstLenPtr,		/* On entry, the maximum length of output
-				 * buffer in bytes; must be <= *srcLenPtr. On
-				 * exit, the number of bytes actually used in
-				 * output buffer. */
+				 * buffer in bytes. On exit, the number of
+				 * bytes actually used in output buffer. */
     int *srcLenPtr)		/* On entry, the length of source buffer. On
 				 * exit, the number of bytes read from the
 				 * source buffer. */
 {
-    int dstLen, srcLen, inEofChar;
-    const char *eof;
+    const char *eof = NULL;
+    int dstLen = *dstLenPtr;
+    int srcLen = *srcLenPtr;
+    int inEofChar = statePtr->inEofChar;
 
-    dstLen = *dstLenPtr;
+    /*
+     * Depending on the translation mode in use, there's no need
+     * to scan more srcLen bytes at srcStart than can possibly transform
+     * to dstLen bytes.  This keeps the scan for eof char below from
+     * being pointlessly long.
+     */
+
+    switch (statePtr->inputTranslation) {
+    case TCL_TRANSLATE_LF:
+    case TCL_TRANSLATE_CR:
+	if (srcLen > dstLen) {
+	/* In these modes, each src byte become a dst byte. */
+	    srcLen = dstLen;
+	}
+	break;
+    default:
+	/* In other modes, at most 2 src bytes become a dst byte. */
+	if (srcLen > 2 * dstLen) {
+	    srcLen = 2 * dstLen;
+	}
+	break;
+    }
 
-    eof = NULL;
-    inEofChar = statePtr->inEofChar;
     if (inEofChar != '\0') {
 	/*
-	 * Find EOF in translated buffer then compress out the EOL. The source
-	 * buffer may be much longer than the destination buffer - we only
-	 * want to return EOF if the EOF has been copied to the destination
-	 * buffer.
+	 * Make sure we do not read past any logical end of channel input
+	 * created by the presence of the input eof char.
 	 */
 
-	const char *src, *srcMax = srcStart + *srcLenPtr;
-
-	for (src = srcStart; src < srcMax; src++) {
-	    if (*src == inEofChar) {
-		eof = src;
-		srcLen = src - srcStart;
-		if (srcLen < dstLen) {
-		    dstLen = srcLen;
-		}
-		*srcLenPtr = srcLen;
-		break;
-	    }
+	if ((eof = memchr(srcStart, inEofChar, srcLen))) {
+	    srcLen = eof - srcStart;
 	}
     }
+
     switch (statePtr->inputTranslation) {
     case TCL_TRANSLATE_LF:
+    case TCL_TRANSLATE_CR:
 	if (dstStart != srcStart) {
-	    memcpy(dstStart, srcStart, (size_t) dstLen);
+	    memcpy(dstStart, srcStart, (size_t) srcLen);
 	}
-	srcLen = dstLen;
-	break;
-    case TCL_TRANSLATE_CR: {
-	char *dst, *dstEnd;
+	if (statePtr->inputTranslation == TCL_TRANSLATE_CR) {
+	    char *dst = dstStart;
+	    char *dstEnd = dstStart + srcLen;
 
-	if (dstStart != srcStart) {
-	    memcpy(dstStart, srcStart, (size_t) dstLen);
-	}
-	dstEnd = dstStart + dstLen;
-	for (dst = dstStart; dst < dstEnd; dst++) {
-	    if (*dst == '\r') {
-		*dst = '\n';
+	    while ((dst = memchr(dst, '\r', dstEnd - dst))) {
+		*dst++ = '\n';
 	    }
 	}
-	srcLen = dstLen;
+	dstLen = srcLen;
 	break;
-    }
     case TCL_TRANSLATE_CRLF: {
-	char *dst;
-	const char *src, *srcEnd, *srcMax;
-
-	dst = dstStart;
-	src = srcStart;
-	srcEnd = srcStart + dstLen;
-	srcMax = srcStart + *srcLenPtr;
-
-	for ( ; src < srcEnd; ) {
-	    if (*src == '\r') {
-		src++;
-		if (src >= srcMax) {
-		    SetFlag(statePtr, INPUT_NEED_NL);
-		} else if (*src == '\n') {
-		    *dst++ = *src++;
-		} else {
+	const char *crFound, *src = srcStart;
+	char *dst = dstStart;
+	int lesser = (dstLen < srcLen) ? dstLen : srcLen;
+
+	while ((crFound = memchr(src, '\r', lesser))) {
+	    int numBytes = crFound - src;
+	    memmove(dst, src, numBytes);
+
+	    dst += numBytes; dstLen -= numBytes;
+	    src += numBytes; srcLen -= numBytes;
+	    if (srcLen == 1) {
+		/* valid src bytes end in \r */
+		if (eof) {
 		    *dst++ = '\r';
+		    src++; srcLen--;
+		} else {
+		    lesser = 0;
+		    break;
 		}
+	    } else if (src[1] == '\n') {
+		*dst++ = '\n';
+		src += 2; srcLen -= 2;
 	    } else {
-		*dst++ = *src++;
+		*dst++ = '\r';
+		src++; srcLen--;
 	    }
+	    dstLen--;
+	    lesser = (dstLen < srcLen) ? dstLen : srcLen;
 	}
-	srcLen = src - srcStart;
-	dstLen = dst - dstStart;
+	memmove(dst, src, lesser);
+	srcLen = src + lesser - srcStart;
+	dstLen = dst + lesser - dstStart;
 	break;
     }
     case TCL_TRANSLATE_AUTO: {
-	char *dst;
-	const char *src, *srcEnd, *srcMax;
-
-	dst = dstStart;
-	src = srcStart;
-	srcEnd = srcStart + dstLen;
-	srcMax = srcStart + *srcLenPtr;
+	const char *crFound, *src = srcStart;
+	char *dst = dstStart;
+	int lesser;
 
-	if (GotFlag(statePtr, INPUT_SAW_CR) && (src < srcMax)) {
-	    if (*src == '\n') {
-		src++;
-	    }
+	if ((statePtr->flags & INPUT_SAW_CR) && srcLen) {
+	    if (*src == '\n') { src++; srcLen--; }
 	    ResetFlag(statePtr, INPUT_SAW_CR);
 	}
-	for ( ; src < srcEnd; ) {
-	    if (*src == '\r') {
-		src++;
-		if (src >= srcMax) {
-		    SetFlag(statePtr, INPUT_SAW_CR);
-		} else if (*src == '\n') {
-		    if (srcEnd < srcMax) {
-			srcEnd++;
-		    }
-		    src++;
-		}
-		*dst++ = '\n';
-	    } else {
-		*dst++ = *src++;
+	lesser = (dstLen < srcLen) ? dstLen : srcLen;
+	while ((crFound = memchr(src, '\r', lesser))) {
+	    int numBytes = crFound - src;
+	    memmove(dst, src, numBytes);
+
+	    dst[numBytes] = '\n';
+	    dst += numBytes + 1; dstLen -= numBytes + 1;
+	    src += numBytes + 1; srcLen -= numBytes + 1;
+	    if (srcLen == 0) {
+		SetFlag(statePtr, INPUT_SAW_CR);
+	    } else if (*src == '\n') {
+		src++; srcLen--;
 	    }
+	    lesser = (dstLen < srcLen) ? dstLen : srcLen;
 	}
-	srcLen = src - srcStart;
-	dstLen = dst - dstStart;
+	memmove(dst, src, lesser);
+	srcLen = src + lesser - srcStart;
+	dstLen = dst + lesser - dstStart;
 	break;
     }
     default:
-	return 0;
+	Tcl_Panic("unknown input translation %d", statePtr->inputTranslation);
     }
     *dstLenPtr = dstLen;
+    *srcLenPtr = srcLen;
 
-    if ((eof != NULL) && (srcStart + srcLen >= eof)) {
+    if (srcStart + srcLen == eof) {
 	/*
 	 * EOF character was seen in EOL translated range. Leave current file
 	 * position pointing at the EOF character, but don't store the EOF
@@ -6524,12 +6490,8 @@ TranslateInputEOL(
 
 	SetFlag(statePtr, CHANNEL_EOF | CHANNEL_STICKY_EOF);
 	statePtr->inputEncodingFlags |= TCL_ENCODING_END;
-	ResetFlag(statePtr, INPUT_SAW_CR | INPUT_NEED_NL);
-	return 1;
+	ResetFlag(statePtr, CHANNEL_BLOCKED|INPUT_SAW_CR);
     }
-
-    *srcLenPtr = srcLen;
-    return 0;
 }
 
 /*
@@ -6583,16 +6545,15 @@ Tcl_Ungets(
     statePtr->flags = flags;
 
     /*
-     * If we have encountered a sticky EOF, just punt without storing (sticky
-     * EOF is set if we have seen the input eofChar, to prevent reading beyond
-     * the eofChar). Otherwise, clear the EOF flags, and clear the BLOCKED
-     * bit. We want to discover these conditions anew in each operation.
+     * Clear the EOF flags, and clear the BLOCKED bit.
      */
 
-    if (GotFlag(statePtr, CHANNEL_STICKY_EOF)) {
-	goto done;
+    if (GotFlag(statePtr, CHANNEL_EOF)) {
+	statePtr->inputEncodingFlags |= TCL_ENCODING_START;
     }
-    ResetFlag(statePtr, CHANNEL_BLOCKED | CHANNEL_EOF);
+    ResetFlag(statePtr,
+	    CHANNEL_BLOCKED | CHANNEL_STICKY_EOF | CHANNEL_EOF | INPUT_SAW_CR);
+    statePtr->inputEncodingFlags &= ~TCL_ENCODING_END;
 
     bufPtr = AllocChannelBuffer(len);
     memcpy(InsertPoint(bufPtr), str, (size_t) len);
@@ -6657,14 +6618,6 @@ Tcl_Flush(
 	return -1;
     }
 
-    /*
-     * Force current output buffer to be output also.
-     */
-
-    if ((statePtr->curOutPtr != NULL) && IsBufferReady(statePtr->curOutPtr)) {
-	SetFlag(statePtr, BUFFER_READY);
-    }
-
     result = FlushChannel(NULL, chanPtr, 0);
     if (result != 0) {
 	return TCL_ERROR;
@@ -6715,7 +6668,7 @@ DiscardInputQueued(
      */
 
     if (discardSavedBuffers && statePtr->saveInBufPtr != NULL) {
-	ckfree(statePtr->saveInBufPtr);
+	ReleaseChannelBuffer(statePtr->saveInBufPtr);
 	statePtr->saveInBufPtr = NULL;
     }
 }
@@ -6727,6 +6680,9 @@ DiscardInputQueued(
  *
  *	Reads input data from a device into a channel buffer.
  *
+ *	IMPORTANT!  This routine is only called on a chanPtr argument
+ *	that is the top channel of a stack!
+ *
  * Results:
  *	The return value is the Posix error code if an error occurred while
  *	reading from the file, or 0 otherwise.
@@ -6749,6 +6705,14 @@ GetInput(
 				/* State info for channel */
 
     /*
+     * Verify that all callers know better than to call us when
+     * it's recorded that the next char waiting to be read is the
+     * eofchar.
+     */
+
+    assert( !GotFlag(statePtr, CHANNEL_STICKY_EOF) );
+
+    /*
      * Prevent reading from a dead channel -- a channel that has been closed
      * but not yet deallocated, which can happen if the exit handler for
      * channel cleanup has run but the channel is still registered in some
@@ -6760,20 +6724,34 @@ GetInput(
     }
 
     /*
+     * WARNING: There was once a comment here claiming that it was
+     * a bad idea to make another call to the inputproc of a channel
+     * driver when EOF has already been detected on the channel.  Through
+     * much of Tcl's history, this warning was then completely negated
+     * by having all (most?) read paths clear the EOF setting before
+     * reaching here.  So we had a guard that was never triggered.
+     *
+     * Don't be tempted to restore the guard.  Even if EOF is set on
+     * the channel, continue through and call the inputproc again.  This
+     * is the way to enable the ability to [read] again beyond the EOF,
+     * which seems a strange thing to do, but for which use cases exist
+     * [Tcl Bug 5adc350683] and which may even be essential for channels
+     * representing things like ttys or other devices where the stream
+     * might take the logical form of a series of 'files' separated by
+     * an EOF condition.
+     */
+
+    /*
      * First check for more buffers in the pushback area of the topmost
      * channel in the stack and use them. They can be the result of a
      * transformation which went away without reading all the information
      * placed in the area when it was stacked.
-     *
-     * Two possibilities for the state: No buffers in it, or a single empty
-     * buffer. In the latter case we can recycle it now.
      */
 
     if (chanPtr->inQueueHead != NULL) {
-	if (statePtr->inQueueHead != NULL) {
-	    RecycleBuffer(statePtr, statePtr->inQueueHead, 0);
-	    statePtr->inQueueHead = NULL;
-	}
+
+	/* TODO: Tests to cover this. */
+	assert(statePtr->inQueueHead == NULL);
 
 	statePtr->inQueueHead = chanPtr->inQueueHead;
 	statePtr->inQueueTail = chanPtr->inQueueTail;
@@ -6794,21 +6772,21 @@ GetInput(
      */
 
     bufPtr = statePtr->inQueueTail;
-    if ((bufPtr != NULL) && !IsBufferFull(bufPtr)) {
-	toRead = SpaceLeft(bufPtr);
-    } else {
+
+    if ((bufPtr == NULL) || IsBufferFull(bufPtr)) {
 	bufPtr = statePtr->saveInBufPtr;
 	statePtr->saveInBufPtr = NULL;
 
 	/*
 	 * Check the actual buffersize against the requested buffersize.
-	 * Buffers which are smaller than requested are squashed. This is done
+	 * Saved buffers of the wrong size are squashed. This is done
 	 * to honor dynamic changes of the buffersize made by the user.
+	 * TODO: Tests to cover this.
 	 */
 
 	if ((bufPtr != NULL)
-		&& (bufPtr->bufLength - BUFFER_PADDING < statePtr->bufSize)) {
-	    ckfree(bufPtr);
+		&& (bufPtr->bufLength - BUFFER_PADDING != statePtr->bufSize)) {
+	    ReleaseChannelBuffer(bufPtr);
 	    bufPtr = NULL;
 	}
 
@@ -6817,21 +6795,8 @@ GetInput(
 	}
 	bufPtr->nextPtr = NULL;
 
-	/*
-	 * SF #427196: Use the actual size of the buffer to determine the
-	 * number of bytes to read from the channel and not the size for new
-	 * buffers. They can be different if the buffersize was changed
-	 * between reads.
-	 *
-	 * Note: This affects performance negatively if the buffersize was
-	 * extended but this small buffer is reused for all subsequent reads.
-	 * The system never uses buffers with the requested bigger size in
-	 * that case. An adjunct patch could try and delete all unused buffers
-	 * it encounters and which are smaller than the formally requested
-	 * buffersize.
-	 */
-
 	toRead = SpaceLeft(bufPtr);
+	assert(toRead == statePtr->bufSize);
 
 	if (statePtr->inQueueTail == NULL) {
 	    statePtr->inQueueHead = bufPtr;
@@ -6839,75 +6804,22 @@ GetInput(
 	    statePtr->inQueueTail->nextPtr = bufPtr;
 	}
 	statePtr->inQueueTail = bufPtr;
+    } else {
+	toRead = SpaceLeft(bufPtr);
     }
 
-    /*
-     * If EOF is set, we should avoid calling the driver because on some
-     * platforms it is impossible to read from a device after EOF.
-     */
-
-    if (GotFlag(statePtr, CHANNEL_EOF)) {
-	return 0;
-    }
-
-#ifdef TCL_IO_TRACK_OS_FOR_DRIVER_WITH_BAD_BLOCKING
-    /*
-     * [Bug 943274]: Better emulation of non-blocking channels for channels
-     * without BlockModeProc, by keeping track of true fileevents generated by
-     * the OS == Data waiting and reading if and only if we are sure to have
-     * data.
-     */
+    PreserveChannelBuffer(bufPtr);
+    nread = ChanRead(chanPtr, InsertPoint(bufPtr), toRead);
 
-    if (GotFlag(statePtr, CHANNEL_NONBLOCKING) &&
-	    (Tcl_ChannelBlockModeProc(chanPtr->typePtr) == NULL) &&
-	    !GotFlag(statePtr, CHANNEL_HAS_MORE_DATA)) {
-	/*
-	 * Bypass the driver, it would block, as no data is available
-	 */
-
-	nread = -1;
-	result = EWOULDBLOCK;
-    } else
-#endif /* TCL_IO_TRACK_OS_FOR_DRIVER_WITH_BAD_BLOCKING */
-    {
-	nread = ChanRead(chanPtr, InsertPoint(bufPtr), toRead, &result);
-    }
-
-    if (nread > 0) {
+    if (nread < 0) {
+	result = Tcl_GetErrno();
+    } else {
+	result = 0;
 	bufPtr->nextAdded += nread;
-
-	/*
-	 * If we get a short read, signal up that we may be BLOCKED. We should
-	 * avoid calling the driver because on some platforms we will block in
-	 * the low level reading code even though the channel is set into
-	 * nonblocking mode.
-	 */
-
-	if (nread < toRead) {
-	    SetFlag(statePtr, CHANNEL_BLOCKED);
-	}
-
-#ifdef TCL_IO_TRACK_OS_FOR_DRIVER_WITH_BAD_BLOCKING
-	if (nread <= toRead) {
-	    /*
-	     * [Bug 943274]: We have read the available data, clear flag.
-	     */
-
-	    ResetFlag(statePtr, CHANNEL_HAS_MORE_DATA);
-	}
-#endif /* TCL_IO_TRACK_OS_FOR_DRIVER_WITH_BAD_BLOCKING */
-    } else if (nread == 0) {
-	SetFlag(statePtr, CHANNEL_EOF);
-	statePtr->inputEncodingFlags |= TCL_ENCODING_END;
-    } else if (nread < 0) {
-	if ((result == EWOULDBLOCK) || (result == EAGAIN)) {
-	    SetFlag(statePtr, CHANNEL_BLOCKED);
-	    result = EAGAIN;
-	}
-	Tcl_SetErrno(result);
-	return result;
     }
-    return 0;
+
+    ReleaseChannelBuffer(bufPtr);
+    return result;
 }
 
 /*
@@ -7011,8 +6923,12 @@ Tcl_Seek(
      * point. Also clear CR related flags.
      */
 
+    if (GotFlag(statePtr, CHANNEL_EOF)) {
+	statePtr->inputEncodingFlags |= TCL_ENCODING_START;
+    }
     ResetFlag(statePtr, CHANNEL_EOF | CHANNEL_STICKY_EOF | CHANNEL_BLOCKED |
 	    INPUT_SAW_CR);
+    statePtr->inputEncodingFlags &= ~TCL_ENCODING_END;
 
     /*
      * If the channel is in asynchronous output mode, switch it back to
@@ -7035,15 +6951,6 @@ Tcl_Seek(
     }
 
     /*
-     * If there is data buffered in statePtr->curOutPtr then mark the channel
-     * as ready to flush before invoking FlushChannel.
-     */
-
-    if ((statePtr->curOutPtr != NULL) && IsBufferReady(statePtr->curOutPtr)) {
-	SetFlag(statePtr, BUFFER_READY);
-    }
-
-    /*
      * If the flush fails we cannot recover the original position. In that
      * case the seek is not attempted because we do not know where the access
      * position is - instead we return the error. FlushChannel has already
@@ -7367,17 +7274,7 @@ CheckChannelErrors(
     }
 
     if (direction == TCL_READABLE) {
-	/*
-	 * If we have not encountered a sticky EOF, clear the EOF bit (sticky
-	 * EOF is set if we have seen the input eofChar, to prevent reading
-	 * beyond the eofChar). Also, always clear the BLOCKED bit. We want to
-	 * discover these conditions anew in each operation.
-	 */
-
-	if (!GotFlag(statePtr, CHANNEL_STICKY_EOF)) {
-	    ResetFlag(statePtr, CHANNEL_EOF);
-	}
-	ResetFlag(statePtr, CHANNEL_BLOCKED | CHANNEL_NEED_MORE_DATA);
+	ResetFlag(statePtr, CHANNEL_NEED_MORE_DATA);
     }
 
     return 0;
@@ -7406,9 +7303,7 @@ Tcl_Eof(
     ChannelState *statePtr = ((Channel *) chan)->state;
 				/* State of real channel structure. */
 
-    return (GotFlag(statePtr, CHANNEL_STICKY_EOF) ||
-	    (GotFlag(statePtr, CHANNEL_EOF) &&
-	    (Tcl_InputBuffered(chan) == 0))) ? 1 : 0;
+    return GotFlag(statePtr, CHANNEL_EOF) ? 1 : 0;
 }
 
 /*
@@ -7593,14 +7488,26 @@ Tcl_SetChannelBufferSize(
     }
 
     statePtr = ((Channel *) chan)->state;
+
+    if (statePtr->bufSize == sz) {
+	return;
+    }
     statePtr->bufSize = sz;
 
-    if (statePtr->outputStage != NULL) {
-	ckfree(statePtr->outputStage);
-	statePtr->outputStage = NULL;
+    /*
+     * If bufsize changes, need to get rid of old utility buffer.
+     */
+
+    if (statePtr->saveInBufPtr != NULL) {
+	RecycleBuffer(statePtr, statePtr->saveInBufPtr, 1);
+	statePtr->saveInBufPtr = NULL;
     }
-    if ((statePtr->encoding != NULL) && GotFlag(statePtr, TCL_WRITABLE)) {
-	statePtr->outputStage = ckalloc(statePtr->bufSize + 2);
+    if ((statePtr->inQueueHead != NULL)
+	    && (statePtr->inQueueHead->nextPtr == NULL)
+	    && IsBufferEmpty(statePtr->inQueueHead)) {
+	RecycleBuffer(statePtr, statePtr->inQueueHead, 1);
+	statePtr->inQueueHead = NULL;
+	statePtr->inQueueTail = NULL;
     }
 }
 
@@ -8036,6 +7943,7 @@ Tcl_SetChannelOption(
 	    return TCL_ERROR;
 	}
 	Tcl_SetChannelBufferSize(chan, newBufferSize);
+	return TCL_OK;
     } else if (HaveOpt(2, "-encoding")) {
 	Tcl_Encoding encoding;
 
@@ -8053,7 +7961,8 @@ Tcl_SetChannelOption(
 	 * iso2022, the terminated escape sequence must write to the buffer.
 	 */
 
-	if ((statePtr->encoding != NULL) && (statePtr->curOutPtr != NULL)
+	if ((statePtr->encoding != NULL)
+		&& !(statePtr->outputEncodingFlags & TCL_ENCODING_START)
 		&& (CheckChannelErrors(statePtr, TCL_WRITABLE) == 0)) {
 	    statePtr->outputEncodingFlags |= TCL_ENCODING_END;
 	    WriteChars(chanPtr, "", 0);
@@ -8066,6 +7975,7 @@ Tcl_SetChannelOption(
 	statePtr->outputEncodingFlags = TCL_ENCODING_START;
 	ResetFlag(statePtr, CHANNEL_NEED_MORE_DATA);
 	UpdateInterest(chanPtr);
+	return TCL_OK;
     } else if (HaveOpt(2, "-eofchar")) {
 	if (Tcl_SplitList(interp, newValue, &argc, &argv) == TCL_ERROR) {
 	    return TCL_ERROR;
@@ -8112,7 +8022,11 @@ Tcl_SetChannelOption(
 	 * ahead'. Ditto for blocked.
 	 */
 
+	if (GotFlag(statePtr, CHANNEL_EOF)) {
+	    statePtr->inputEncodingFlags |= TCL_ENCODING_START;
+	}
 	ResetFlag(statePtr, CHANNEL_EOF|CHANNEL_STICKY_EOF|CHANNEL_BLOCKED);
+	statePtr->inputEncodingFlags &= ~TCL_ENCODING_END;
 	return TCL_OK;
     } else if (HaveOpt(1, "-translation")) {
 	const char *readMode, *writeMode;
@@ -8226,33 +8140,6 @@ Tcl_SetChannelOption(
 	return Tcl_BadChannelOption(interp, optionName, NULL);
     }
 
-    /*
-     * If bufsize changes, need to get rid of old utility buffer.
-     */
-
-    if (statePtr->saveInBufPtr != NULL) {
-	RecycleBuffer(statePtr, statePtr->saveInBufPtr, 1);
-	statePtr->saveInBufPtr = NULL;
-    }
-    if ((statePtr->inQueueHead != NULL)
-	    && (statePtr->inQueueHead->nextPtr == NULL)
-	    && IsBufferEmpty(statePtr->inQueueHead)) {
-	RecycleBuffer(statePtr, statePtr->inQueueHead, 1);
-	statePtr->inQueueHead = NULL;
-	statePtr->inQueueTail = NULL;
-    }
-
-    /*
-     * If encoding or bufsize changes, need to update output staging buffer.
-     */
-
-    if (statePtr->outputStage != NULL) {
-	ckfree(statePtr->outputStage);
-	statePtr->outputStage = NULL;
-    }
-    if ((statePtr->encoding != NULL) && GotFlag(statePtr, TCL_WRITABLE)) {
-	statePtr->outputStage = ckalloc(statePtr->bufSize + 2);
-    }
     return TCL_OK;
 }
 
@@ -8344,21 +8231,6 @@ Tcl_NotifyChannel(
     Channel *upChanPtr;
     const Tcl_ChannelType *upTypePtr;
 
-#ifdef TCL_IO_TRACK_OS_FOR_DRIVER_WITH_BAD_BLOCKING
-    /*
-     * [SF Tcl Bug 943274] For a non-blocking channel without blockmodeproc we
-     * keep track of actual input coming from the OS so that we can do a
-     * credible imitation of non-blocking behaviour.
-     */
-
-    if ((mask & TCL_READABLE) &&
-	    GotFlag(statePtr, CHANNEL_NONBLOCKING) &&
-	    (Tcl_ChannelBlockModeProc(chanPtr->typePtr) == NULL) &&
-	    !GotFlag(statePtr, CHANNEL_TIMER_FEV)) {
-	SetFlag(statePtr, CHANNEL_HAS_MORE_DATA);
-    }
-#endif /* TCL_IO_TRACK_OS_FOR_DRIVER_WITH_BAD_BLOCKING */
-
     /*
      * In contrast to the other API functions this procedure walks towards the
      * top of a stack and not down from it.
@@ -8408,7 +8280,7 @@ Tcl_NotifyChannel(
      * Preserve the channel struct in case the script closes it.
      */
 
-    Tcl_Preserve(channel);
+    TclChannelPreserve((Tcl_Channel)channel);
     Tcl_Preserve(statePtr);
 
     /*
@@ -8418,13 +8290,14 @@ Tcl_NotifyChannel(
      */
 
     if (GotFlag(statePtr, BG_FLUSH_SCHEDULED) && (mask & TCL_WRITABLE)) {
-	FlushChannel(NULL, chanPtr, 1);
-	mask &= ~TCL_WRITABLE;
+	if (0 == FlushChannel(NULL, chanPtr, 1)) {
+	    mask &= ~TCL_WRITABLE;
+	}
     }
 
     /*
      * Add this invocation to the list of recursive invocations of
-     * ChannelHandlerEventProc.
+     * Tcl_NotifyChannel.
      */
 
     nh.nextHandlerPtr = NULL;
@@ -8439,7 +8312,7 @@ Tcl_NotifyChannel(
 
 	if ((chPtr->mask & mask) != 0) {
 	    nh.nextHandlerPtr = chPtr->nextPtr;
-	    chPtr->proc(chPtr->clientData, mask);
+	    chPtr->proc(chPtr->clientData, chPtr->mask & mask);
 	    chPtr = nh.nextHandlerPtr;
 	} else {
 	    chPtr = chPtr->nextPtr;
@@ -8457,7 +8330,7 @@ Tcl_NotifyChannel(
     }
 
     Tcl_Release(statePtr);
-    Tcl_Release(channel);
+    TclChannelRelease(channel);
 
     tsdPtr->nestedHandlerPtr = nh.nestedHandlerPtr;
 }
@@ -8487,6 +8360,11 @@ UpdateInterest(
 				/* State info for channel */
     int mask = statePtr->interestMask;
 
+    if (chanPtr->typePtr == NULL) {
+	/* Do not update interest on a closed channel */
+	return;
+    }
+
     /*
      * If there are flushed buffers waiting to be written, then we need to
      * watch for the channel to become writable.
@@ -8594,29 +8472,8 @@ ChannelTimerProc(
 
 	statePtr->timer = Tcl_CreateTimerHandler(SYNTHETIC_EVENT_TIME,
                 ChannelTimerProc,chanPtr);
-
-#ifdef TCL_IO_TRACK_OS_FOR_DRIVER_WITH_BAD_BLOCKING
-	/*
-	 * Set the TIMER flag to notify the higher levels that the driver
-	 * might have no data for us. We do this only if we are in
-	 * non-blocking mode and the driver has no BlockModeProc because only
-	 * then we really don't know if the driver will block or not. A
-	 * similar test is done in "PeekAhead".
-	 */
-
-	if (GotFlag(statePtr, CHANNEL_NONBLOCKING) &&
-		(Tcl_ChannelBlockModeProc(chanPtr->typePtr) == NULL)) {
-	    SetFlag(statePtr, CHANNEL_TIMER_FEV);
-	}
-#endif /* TCL_IO_TRACK_OS_FOR_DRIVER_WITH_BAD_BLOCKING */
-
 	Tcl_Preserve(statePtr);
 	Tcl_NotifyChannel((Tcl_Channel) chanPtr, TCL_READABLE);
-
-#ifdef TCL_IO_TRACK_OS_FOR_DRIVER_WITH_BAD_BLOCKING
-	ResetFlag(statePtr, CHANNEL_TIMER_FEV);
-#endif /* TCL_IO_TRACK_OS_FOR_DRIVER_WITH_BAD_BLOCKING */
-
 	Tcl_Release(statePtr);
     } else {
 	statePtr->timer = NULL;
@@ -8759,7 +8616,7 @@ Tcl_DeleteChannelHandler(
     }
 
     /*
-     * If ChannelHandlerEventProc is about to process this handler, tell it to
+     * If Tcl_NotifyChannel is about to process this handler, tell it to
      * process the next one instead - we are going to delete *this* one.
      */
 
@@ -8955,7 +8812,7 @@ TclChannelEventScriptInvoker(
      */
 
     Tcl_Preserve(interp);
-    Tcl_Preserve(chanPtr);
+    TclChannelPreserve((Tcl_Channel)chanPtr);
     result = Tcl_EvalObjEx(interp, esPtr->scriptPtr, TCL_EVAL_GLOBAL);
 
     /*
@@ -8972,7 +8829,7 @@ TclChannelEventScriptInvoker(
 	}
 	Tcl_BackgroundException(interp, result);
     }
-    Tcl_Release(chanPtr);
+    TclChannelRelease((Tcl_Channel)chanPtr);
     Tcl_Release(interp);
 }
 
@@ -9147,6 +9004,7 @@ TclCopyChannel(
     int readFlags, writeFlags;
     CopyState *csPtr;
     int nonBlocking = (cmdPtr) ? CHANNEL_NONBLOCKING : 0;
+    int moveBytes;
 
     inStatePtr = inPtr->state;
     outStatePtr = outPtr->state;
@@ -9198,13 +9056,24 @@ TclCopyChannel(
 	    | CHANNEL_UNBUFFERED;
 
     /*
+     * Test for conditions where we know we can just move bytes from input
+     * channel to output channel with no transformation or even examination
+     * of the bytes themselves.
+     */
+
+    moveBytes = inStatePtr->inEofChar == '\0'	/* No eofChar to stop input */
+	    && inStatePtr->inputTranslation == TCL_TRANSLATE_LF
+	    && outStatePtr->outputTranslation == TCL_TRANSLATE_LF
+	    && inStatePtr->encoding == outStatePtr->encoding;
+
+    /*
      * Allocate a new CopyState to maintain info about the current copy in
      * progress. This structure will be deallocated when the copy is
      * completed.
      */
 
-    csPtr = ckalloc(sizeof(CopyState) + inStatePtr->bufSize);
-    csPtr->bufSize = inStatePtr->bufSize;
+    csPtr = ckalloc(sizeof(CopyState) + !moveBytes * inStatePtr->bufSize);
+    csPtr->bufSize = !moveBytes * inStatePtr->bufSize;
     csPtr->readPtr = inPtr;
     csPtr->writePtr = outPtr;
     csPtr->readFlags = readFlags;
@@ -9220,6 +9089,10 @@ TclCopyChannel(
     inStatePtr->csPtrR  = csPtr;
     outStatePtr->csPtrW = csPtr;
 
+    if (moveBytes) {
+	return MoveBytes(csPtr);
+    }
+
     /*
      * Special handling of -size 0 async transfers, so that the -command is
      * still called asynchronously.
@@ -9254,6 +9127,236 @@ TclCopyChannel(
  *----------------------------------------------------------------------
  */
 
+static void
+MBCallback(
+    CopyState *csPtr,
+    Tcl_Obj *errObj)
+{
+    Tcl_Obj *cmdPtr = Tcl_DuplicateObj(csPtr->cmdPtr);
+    Tcl_WideInt total = csPtr->total;
+    Tcl_Interp *interp = csPtr->interp;
+    int code;
+
+    Tcl_IncrRefCount(cmdPtr);
+    StopCopy(csPtr);
+
+    /* TODO: What if cmdPtr is not a list?! */
+
+    Tcl_ListObjAppendElement(NULL, cmdPtr, Tcl_NewWideIntObj(total));
+    if (errObj) {
+	Tcl_ListObjAppendElement(NULL, cmdPtr, errObj);
+    }
+
+    Tcl_Preserve(interp);
+    code = Tcl_EvalObjEx(interp, cmdPtr, TCL_EVAL_GLOBAL);
+    if (code != TCL_OK) {
+	Tcl_BackgroundException(interp, code);
+    }
+    Tcl_Release(interp);
+    TclDecrRefCount(cmdPtr);
+}
+
+static void
+MBError(
+    CopyState *csPtr,
+    int mask,
+    int errorCode)
+{
+    Tcl_Channel inChan = (Tcl_Channel) csPtr->readPtr;
+    Tcl_Channel outChan = (Tcl_Channel) csPtr->writePtr;
+    Tcl_Obj *errObj;
+
+    Tcl_SetErrno(errorCode);
+
+    errObj = Tcl_ObjPrintf( "error %sing \"%s\": %s",
+	    (mask & TCL_READABLE) ? "read" : "writ",
+	    Tcl_GetChannelName((mask & TCL_READABLE) ? inChan : outChan),
+	    Tcl_PosixError(csPtr->interp));
+
+    if (csPtr->cmdPtr) {
+	MBCallback(csPtr, errObj);
+    } else {
+	Tcl_SetObjResult(csPtr->interp, errObj);
+	StopCopy(csPtr);
+    }
+}
+
+static void
+MBEvent(
+    ClientData clientData,
+    int mask)
+{
+    CopyState *csPtr = (CopyState *) clientData;
+    Tcl_Channel inChan = (Tcl_Channel) csPtr->readPtr;
+    Tcl_Channel outChan = (Tcl_Channel) csPtr->writePtr;
+    ChannelState *inStatePtr = csPtr->readPtr->state;
+
+    if (mask & TCL_WRITABLE) {
+	Tcl_DeleteChannelHandler(inChan, MBEvent, csPtr);
+	Tcl_DeleteChannelHandler(outChan, MBEvent, csPtr);
+	switch (MBWrite(csPtr)) {
+	case TCL_OK:
+	    MBCallback(csPtr, NULL);
+	    break;
+	case TCL_CONTINUE:
+	    Tcl_CreateChannelHandler(inChan, TCL_READABLE, MBEvent, csPtr);
+	    break;
+	}
+    } else if (mask & TCL_READABLE) {
+	if (TCL_OK == MBRead(csPtr)) {
+	    /* When at least one full buffer is present, stop reading. */
+	    if (IsBufferFull(inStatePtr->inQueueHead)
+		    || !Tcl_InputBlocked(inChan)) {
+		Tcl_DeleteChannelHandler(inChan, MBEvent, csPtr);
+	    }
+
+	    /* Successful read -- set up to write the bytes we read */
+	    Tcl_CreateChannelHandler(outChan, TCL_WRITABLE, MBEvent, csPtr);
+	}
+    }
+}
+
+static int
+MBRead(
+    CopyState *csPtr)
+{
+    ChannelState *inStatePtr = csPtr->readPtr->state;
+    ChannelBuffer *bufPtr = inStatePtr->inQueueHead;
+    int code;
+
+    if (bufPtr && BytesLeft(bufPtr) > 0) {
+	return TCL_OK;
+    }
+
+    code = GetInput(inStatePtr->topChanPtr);
+    if (code == 0 || GotFlag(inStatePtr, CHANNEL_BLOCKED)) {
+	return TCL_OK;
+    } else {
+	MBError(csPtr, TCL_READABLE, code);
+	return TCL_ERROR;
+    }
+}
+
+static int
+MBWrite(
+    CopyState *csPtr)
+{
+    ChannelState *inStatePtr = csPtr->readPtr->state;
+    ChannelState *outStatePtr = csPtr->writePtr->state;
+    ChannelBuffer *bufPtr = inStatePtr->inQueueHead;
+    ChannelBuffer *tail = NULL;
+    int code;
+    Tcl_WideInt inBytes = 0;
+
+    /* Count up number of bytes waiting in the input queue */
+    while (bufPtr) {
+	inBytes += BytesLeft(bufPtr);
+	tail = bufPtr;
+	if (csPtr->toRead != -1 && csPtr->toRead < inBytes) {
+	    /* Queue has enough bytes to complete the copy */
+	    break;
+	}
+	bufPtr = bufPtr->nextPtr;
+    }
+
+    if (bufPtr) {
+	/* Split the overflowing buffer in two */
+	int extra = (int) (inBytes - csPtr->toRead);
+        /* Note that going with int for extra assumes that inBytes is not too
+         * much over toRead to require a wide itself. If that gets violated
+         * then the calculations involving extra must be made wide too.
+         *
+         * Noted with Win32/MSVC debug build treating the warning (possible of
+         * data in int64 to int conversion) as error.
+         */
+
+	bufPtr = AllocChannelBuffer(extra);
+
+	tail->nextAdded -= extra;
+	memcpy(InsertPoint(bufPtr), InsertPoint(tail), extra);
+	bufPtr->nextAdded += extra;
+	bufPtr->nextPtr = tail->nextPtr;
+	tail->nextPtr = NULL;
+	inBytes = csPtr->toRead;
+    }
+
+    /* Update the byte counts */
+    if (csPtr->toRead != -1) {
+	csPtr->toRead -= inBytes;
+    }
+    csPtr->total += inBytes;
+
+    /* Move buffers from input to output channels */
+    if (outStatePtr->outQueueTail) {
+	outStatePtr->outQueueTail->nextPtr = inStatePtr->inQueueHead;
+    } else {
+	outStatePtr->outQueueHead = inStatePtr->inQueueHead;
+    }
+    outStatePtr->outQueueTail = tail;
+    inStatePtr->inQueueHead = bufPtr;
+    if (inStatePtr->inQueueTail == tail) {
+	inStatePtr->inQueueTail = bufPtr;
+    }
+    if (bufPtr == NULL) {
+	inStatePtr->inQueueTail = NULL;
+    }
+
+    code = FlushChannel(csPtr->interp, outStatePtr->topChanPtr, 0);
+    if (code) {
+	MBError(csPtr, TCL_WRITABLE, code);
+	return TCL_ERROR;
+    }
+    if (csPtr->toRead == 0 || GotFlag(inStatePtr, CHANNEL_EOF)) {
+	return TCL_OK;
+    }
+    return TCL_CONTINUE;
+}
+
+static int
+MoveBytes(
+    CopyState *csPtr)		/* State of copy operation. */
+{
+    ChannelState *outStatePtr = csPtr->writePtr->state;
+    ChannelBuffer *bufPtr = outStatePtr->curOutPtr;
+    int errorCode;
+
+    if (bufPtr && BytesLeft(bufPtr)) {
+	/* If we start with unflushed bytes in the destination
+	 * channel, flush them out of the way first. */
+
+	errorCode = FlushChannel(csPtr->interp, outStatePtr->topChanPtr, 0);
+	if (errorCode != 0) {
+	    MBError(csPtr, TCL_WRITABLE, errorCode);
+	    return TCL_ERROR;
+	}
+    }
+
+    if (csPtr->cmdPtr) {
+	Tcl_Channel inChan = (Tcl_Channel) csPtr->readPtr;
+	Tcl_CreateChannelHandler(inChan, TCL_READABLE, MBEvent, csPtr);
+	return TCL_OK;
+    }
+
+    while (1) {
+	int code;
+
+	if (TCL_ERROR == MBRead(csPtr)) {
+	    return TCL_ERROR;
+	}
+	code = MBWrite(csPtr);
+	if (code == TCL_OK) {
+	    Tcl_SetObjResult(csPtr->interp, Tcl_NewWideIntObj(csPtr->total));
+	    StopCopy(csPtr);
+	    return TCL_OK;
+	}
+	if (code == TCL_ERROR) {
+	    return TCL_ERROR;
+	}
+	/* code == TCL_CONTINUE --> continue the loop */
+    }
+    return TCL_OK;	/* Silence compiler warnings */
+}
+
 static int
 CopyData(
     CopyState *csPtr,		/* State of copy operation. */
@@ -9379,6 +9482,10 @@ CopyData(
 			csPtr);
 	    }
 	    if (size == 0) {
+		if (!GotFlag(inStatePtr, CHANNEL_NONBLOCKING)) {
+		    /* We allowed a short read.  Keep trying. */
+		    continue;
+		}
 		if (bufObj != NULL) {
 		    TclDecrRefCount(bufObj);
 		    bufObj = NULL;
@@ -9399,9 +9506,9 @@ CopyData(
 	}
 
 	if (outBinary || sameEncoding) {
-	    sizeb = DoWrite(outStatePtr->topChanPtr, buffer, sizeb);
+	    sizeb = WriteBytes(outStatePtr->topChanPtr, buffer, sizeb);
 	} else {
-	    sizeb = DoWriteChars(outStatePtr->topChanPtr, buffer, sizeb);
+	    sizeb = WriteChars(outStatePtr->topChanPtr, buffer, sizeb);
 	}
 
 	/*
@@ -9556,12 +9663,23 @@ CopyData(
  *
  * DoRead --
  *
- *	Reads a given number of bytes from a channel. No encoding conversions
+ *	Stores up to "bytesToRead" bytes in memory pointed to by "dst".
+ *	These bytes come from reading the channel "chanPtr" and
+ *	performing the configured translations.  No encoding conversions
  *	are applied to the bytes being read.
  *
  * Results:
- *	The number of characters read, or -1 on error. Use Tcl_GetErrno() to
- *	retrieve the error code for the error that occurred.
+ *	The number of bytes actually stored (<= bytesToRead),
+ * 	or -1 if there is an error in reading the channel.  Use
+ * 	Tcl_GetErrno() to retrieve the error code for the error
+ *	that occurred.
+ *
+ *	The number of bytes stored can be less than the number
+ * 	requested when
+ *	  - EOF is reached on the channel; or
+ *	  - the channel is non-blocking, and we've read all we can
+ *	    without blocking.
+ *	  - a channel reading error occurs (and we return -1)
  *
  * Side effects:
  *	May cause input to be buffered.
@@ -9572,538 +9690,197 @@ CopyData(
 static int
 DoRead(
     Channel *chanPtr,		/* The channel from which to read. */
-    char *bufPtr,		/* Where to store input read. */
-    int toRead,			/* Maximum number of bytes to read. */
+    char *dst,			/* Where to store input read. */
+    int bytesToRead,		/* Maximum number of bytes to read. */
     int allowShortReads)	/* Allow half-blocking (pipes,sockets) */
 {
     ChannelState *statePtr = chanPtr->state;
-				/* State info for channel */
-    int copied;			/* How many characters were copied into the
-				 * result string? */
-    int copiedNow;		/* How many characters were copied from the
-				 * current input buffer? */
-    int result;			/* Of calling GetInput. */
+    char *p = dst;
 
-    /*
-     * If we have not encountered a sticky EOF, clear the EOF bit. Either way
-     * clear the BLOCKED bit. We want to discover these anew during each
-     * operation.
-     */
-
-    if (!GotFlag(statePtr, CHANNEL_STICKY_EOF)) {
-	ResetFlag(statePtr, CHANNEL_EOF);
-    }
-    ResetFlag(statePtr, CHANNEL_BLOCKED | CHANNEL_NEED_MORE_DATA);
-
-    for (copied = 0; copied < toRead; copied += copiedNow) {
-	copiedNow = CopyAndTranslateBuffer(statePtr, bufPtr + copied,
-		toRead - copied);
-	if (copiedNow == 0) {
-	    if (GotFlag(statePtr, CHANNEL_EOF)) {
-		goto done;
-	    }
-	    if (GotFlag(statePtr, CHANNEL_BLOCKED)) {
-		if (GotFlag(statePtr, CHANNEL_NONBLOCKING)) {
-		    goto done;
-		}
-		ResetFlag(statePtr, CHANNEL_BLOCKED);
-	    }
-	    result = GetInput(chanPtr);
-	    if (result != 0) {
-		if (result != EAGAIN) {
-		    copied = -1;
-		}
-		goto done;
-	    }
-	} else if (allowShortReads) {
-            copied += copiedNow;
-            break;
-        }
-    }
-
-    ResetFlag(statePtr, CHANNEL_BLOCKED);
+    assert (bytesToRead >= 0);
 
     /*
-     * Update the notifier state so we don't block while there is still data
-     * in the buffers.
+     * Early out when we know a read will get the eofchar.
+     *
+     * NOTE: This seems to be a bug.  The special handling for
+     * a zero-char read request ought to come first.  As coded
+     * the EOF due to eofchar has distinguishing behavior from
+     * the EOF due to reported EOF on the underlying device, and
+     * that seems undesirable.  However recent history indicates
+     * that new inconsistent behavior in a patchlevel has problems
+     * too.  Keep on keeping on for now.
      */
 
-  done:
-    UpdateInterest(chanPtr);
-    return copied;
-}
-
-/*
- *----------------------------------------------------------------------
- *
- * CopyAndTranslateBuffer --
- *
- *	Copy at most one buffer of input to the result space, doing eol
- *	translations according to mode in effect currently.
- *
- * Results:
- *	Number of bytes stored in the result buffer (as opposed to the number
- *	of bytes read from the channel). May return zero if no input is
- *	available to be translated.
- *
- * Side effects:
- *	Consumes buffered input. May deallocate one buffer.
- *
- *----------------------------------------------------------------------
- */
-
-static int
-CopyAndTranslateBuffer(
-    ChannelState *statePtr,	/* Channel state from which to read input. */
-    char *result,		/* Where to store the copied input. */
-    int space)			/* How many bytes are available in result to
-				 * store the copied input? */
-{
-    ChannelBuffer *bufPtr;	/* The buffer from which to copy bytes. */
-    int bytesInBuffer;		/* How many bytes are available to be copied
-				 * in the current input buffer? */
-    int copied;			/* How many characters were already copied
-				 * into the destination space? */
-    int i;			/* Iterates over the copied input looking for
-				 * the input eofChar. */
-
-    /*
-     * If there is no input at all, return zero. The invariant is that either
-     * there is no buffer in the queue, or if the first buffer is empty, it is
-     * also the last buffer (and thus there is no input in the queue). Note
-     * also that if the buffer is empty, we leave it in the queue.
-     */
+    if (GotFlag(statePtr, CHANNEL_STICKY_EOF)) {
+	SetFlag(statePtr, CHANNEL_EOF);
+	assert( statePtr->inputEncodingFlags & TCL_ENCODING_END );
+	assert( !GotFlag(statePtr, CHANNEL_BLOCKED|INPUT_SAW_CR) );
 
-    if (statePtr->inQueueHead == NULL) {
+	UpdateInterest(chanPtr);
 	return 0;
     }
-    bufPtr = statePtr->inQueueHead;
-    bytesInBuffer = BytesLeft(bufPtr);
 
-    copied = 0;
-    switch (statePtr->inputTranslation) {
-    case TCL_TRANSLATE_LF:
-	if (bytesInBuffer == 0) {
-	    return 0;
+    /* Special handling for zero-char read request. */
+    if (bytesToRead == 0) {
+	if (GotFlag(statePtr, CHANNEL_EOF)) {
+	    statePtr->inputEncodingFlags |= TCL_ENCODING_START;
 	}
+	ResetFlag(statePtr, CHANNEL_BLOCKED|CHANNEL_EOF);
+	statePtr->inputEncodingFlags &= ~TCL_ENCODING_END;
+	UpdateInterest(chanPtr);
+	return 0;
+    }
 
+    TclChannelPreserve((Tcl_Channel)chanPtr);
+    while (bytesToRead) {
 	/*
-	 * Copy the current chunk into the result buffer.
+	 * Each pass through the loop is intended to process up to
+	 * one channel buffer.
 	 */
 
-	if (bytesInBuffer < space) {
-	    space = bytesInBuffer;
-	}
-	memcpy(result, RemovePoint(bufPtr), (size_t) space);
-	bufPtr->nextRemoved += space;
-	copied = space;
-	break;
-    case TCL_TRANSLATE_CR: {
-	char *end;
-
-	if (bytesInBuffer == 0) {
-	    return 0;
-	}
+	int bytesRead, bytesWritten;
+	ChannelBuffer *bufPtr = statePtr->inQueueHead;
 
 	/*
-	 * Copy the current chunk into the result buffer, then replace all \r
-	 * with \n.
+	 * Don't read more data if we have what we need.
 	 */
 
-	if (bytesInBuffer < space) {
-	    space = bytesInBuffer;
-	}
-	memcpy(result, RemovePoint(bufPtr), (size_t) space);
-	bufPtr->nextRemoved += space;
-	copied = space;
+	while (!bufPtr ||			/* We got no buffer!   OR */
+		(!IsBufferFull(bufPtr) && 	/* Our buffer has room AND */
+		(BytesLeft(bufPtr) < bytesToRead) ) ) {
+						/* Not enough bytes in it
+						 * yet to fill the dst */
+	    int code;
 
-	for (end = result + copied; result < end; result++) {
-	    if (*result == '\r') {
-		*result = '\n';
-	    }
-	}
-	break;
-    }
-    case TCL_TRANSLATE_CRLF: {
-	char *src, *end, *dst;
-	int curByte;
+	moreData:
+	    code = GetInput(chanPtr);
+	    bufPtr = statePtr->inQueueHead;
 
-	/*
-	 * If there is a held-back "\r" at EOF, produce it now.
-	 */
+	    assert (bufPtr != NULL);
 
-	if (bytesInBuffer == 0) {
-	    if ((statePtr->flags & (INPUT_SAW_CR | CHANNEL_EOF)) ==
-		    (INPUT_SAW_CR | CHANNEL_EOF)) {
-		result[0] = '\r';
-		ResetFlag(statePtr, INPUT_SAW_CR);
-		return 1;
+	    if (GotFlag(statePtr, CHANNEL_EOF|CHANNEL_BLOCKED)) {
+		/* Further reads cannot do any more */
+		break;
 	    }
-	    return 0;
-	}
-
-	/*
-	 * Copy the current chunk and replace "\r\n" with "\n" (but not
-	 * standalone "\r"!).
-	 */
-
-	if (bytesInBuffer < space) {
-	    space = bytesInBuffer;
-	}
-	memcpy(result, RemovePoint(bufPtr), (size_t) space);
-	bufPtr->nextRemoved += space;
-	copied = space;
 
-	end = result + copied;
-	dst = result;
-	for (src = result; src < end; src++) {
-	    curByte = *src;
-	    if (curByte == '\n') {
-		ResetFlag(statePtr, INPUT_SAW_CR);
-	    } else if (GotFlag(statePtr, INPUT_SAW_CR)) {
-		ResetFlag(statePtr, INPUT_SAW_CR);
-		*dst = '\r';
-		dst++;
-	    }
-	    if (curByte == '\r') {
-		SetFlag(statePtr, INPUT_SAW_CR);
-	    } else {
-		*dst = (char) curByte;
-		dst++;
+	    if (code) {
+		/* Read error */
+		UpdateInterest(chanPtr);
+		TclChannelRelease((Tcl_Channel)chanPtr);
+		return -1;
 	    }
-	}
-	copied = dst - result;
-	break;
-    }
-    case TCL_TRANSLATE_AUTO: {
-	char *src, *end, *dst;
-	int curByte;
 
-	if (bytesInBuffer == 0) {
-	    return 0;
+	    assert (IsBufferFull(bufPtr));
 	}
 
-	/*
-	 * Loop over the current buffer, converting "\r" and "\r\n" to "\n".
-	 */
+	assert (bufPtr != NULL);
 
-	if (bytesInBuffer < space) {
-	    space = bytesInBuffer;
-	}
-	memcpy(result, RemovePoint(bufPtr), (size_t) space);
-	bufPtr->nextRemoved += space;
-	copied = space;
+	bytesRead = BytesLeft(bufPtr);
+	bytesWritten = bytesToRead;
 
-	end = result + copied;
-	dst = result;
-	for (src = result; src < end; src++) {
-	    curByte = *src;
-	    if (curByte == '\r') {
-		SetFlag(statePtr, INPUT_SAW_CR);
-		*dst = '\n';
-		dst++;
-	    } else {
-		if ((curByte != '\n') || !GotFlag(statePtr, INPUT_SAW_CR)) {
-		    *dst = (char) curByte;
-		    dst++;
-		}
-		ResetFlag(statePtr, INPUT_SAW_CR);
-	    }
-	}
-	copied = dst - result;
-	break;
-    }
-    default:
-	Tcl_Panic("unknown eol translation mode");
-    }
+	TranslateInputEOL(statePtr, p, RemovePoint(bufPtr),
+		&bytesWritten, &bytesRead);
+	bufPtr->nextRemoved += bytesRead;
+	p += bytesWritten;
+	bytesToRead -= bytesWritten;
 
-    /*
-     * If an in-stream EOF character is set for this channel, check that the
-     * input we copied so far does not contain the EOF char. If it does, copy
-     * only up to and excluding that character.
-     */
-
-    if (statePtr->inEofChar != 0) {
-	for (i = 0; i < copied; i++) {
-	    if (result[i] == (char) statePtr->inEofChar) {
-		/*
-		 * Set sticky EOF so that no further input is presented to the
-		 * caller.
-		 */
+	if (!IsBufferEmpty(bufPtr)) {
+	    /*
+	     * Buffer is not empty.  How can that be?
+	     *
+	     * 0) We stopped early because we got all the bytes
+	     *    we were seeking.  That's fine.
+	     */
 
-		SetFlag(statePtr, CHANNEL_EOF | CHANNEL_STICKY_EOF);
-		statePtr->inputEncodingFlags |= TCL_ENCODING_END;
-		copied = i;
+	    if (bytesToRead == 0) {
+		UpdateInterest(chanPtr);
 		break;
 	    }
-	}
-    }
-
-    /*
-     * If the current buffer is empty recycle it.
-     */
-
-    if (IsBufferEmpty(bufPtr)) {
-	statePtr->inQueueHead = bufPtr->nextPtr;
-	if (statePtr->inQueueHead == NULL) {
-	    statePtr->inQueueTail = NULL;
-	}
-	RecycleBuffer(statePtr, bufPtr, 0);
-    }
-
-    /*
-     * Return the number of characters copied into the result buffer. This may
-     * be different from the number of bytes consumed, because of EOL
-     * translations.
-     */
-
-    return copied;
-}
-
-/*
- *----------------------------------------------------------------------
- *
- * CopyBuffer --
- *
- *	Copy at most one buffer of input to the result space.
- *
- * Results:
- *	Number of bytes stored in the result buffer. May return zero if no
- *	input is available.
- *
- * Side effects:
- *	Consumes buffered input. May deallocate one buffer.
- *
- *----------------------------------------------------------------------
- */
-
-static int
-CopyBuffer(
-    Channel *chanPtr,		/* Channel from which to read input. */
-    char *result,		/* Where to store the copied input. */
-    int space)			/* How many bytes are available in result to
-				 * store the copied input? */
-{
-    ChannelBuffer *bufPtr;	/* The buffer from which to copy bytes. */
-    int bytesInBuffer;		/* How many bytes are available to be copied
-				 * in the current input buffer? */
-    int copied;			/* How many characters were already copied
-				 * into the destination space? */
-
-    /*
-     * If there is no input at all, return zero. The invariant is that either
-     * there is no buffer in the queue, or if the first buffer is empty, it is
-     * also the last buffer (and thus there is no input in the queue). Note
-     * also that if the buffer is empty, we don't leave it in the queue, but
-     * recycle it.
-     */
-
-    if (chanPtr->inQueueHead == NULL) {
-	return 0;
-    }
-    bufPtr = chanPtr->inQueueHead;
-    bytesInBuffer = BytesLeft(bufPtr);
-
-    copied = 0;
 
-    if (bytesInBuffer == 0) {
-	RecycleBuffer(chanPtr->state, bufPtr, 0);
-	chanPtr->inQueueHead = NULL;
-	chanPtr->inQueueTail = NULL;
-	return 0;
-    }
-
-    /*
-     * Copy the current chunk into the result buffer.
-     */
-
-    if (bytesInBuffer < space) {
-	space = bytesInBuffer;
-    }
-
-    memcpy(result, RemovePoint(bufPtr), (size_t) space);
-    bufPtr->nextRemoved += space;
-    copied = space;
-
-    /*
-     * We don't care about in-stream EOF characters here as the data read here
-     * may still flow through one or more transformations, i.e. is not in its
-     * final state yet.
-     */
-
-    /*
-     * If the current buffer is empty recycle it.
-     */
-
-    if (IsBufferEmpty(bufPtr)) {
-	chanPtr->inQueueHead = bufPtr->nextPtr;
-	if (chanPtr->inQueueHead == NULL) {
-	    chanPtr->inQueueTail = NULL;
-	}
-	RecycleBuffer(chanPtr->state, bufPtr, 0);
-    }
+	    /*
+	     * 1) We're @EOF because we saw eof char.
+	     */
 
-    /*
-     * Return the number of characters copied into the result buffer.
-     */
+	    if (GotFlag(statePtr, CHANNEL_STICKY_EOF)) {
+		UpdateInterest(chanPtr);
+		break;
+	    }
 
-    return copied;
-}
-
-/*
- *----------------------------------------------------------------------
- *
- * DoWrite --
- *
- *	Puts a sequence of characters into an output buffer, may queue the
- *	buffer for output if it gets full, and also remembers whether the
- *	current buffer is ready e.g. if it contains a newline and we are in
- *	line buffering mode.
- *
- * Results:
- *	The number of bytes written or -1 in case of error. If -1,
- *	Tcl_GetErrno will return the error code.
- *
- * Side effects:
- *	May buffer up output and may cause output to be produced on the
- *	channel.
- *
- *----------------------------------------------------------------------
- */
+	    /*
+	     * 2) The buffer holds a \r while in CRLF translation,
+	     *    followed by the end of the buffer.
+	     */
 
-static int
-DoWrite(
-    Channel *chanPtr,		/* The channel to buffer output for. */
-    const char *src,		/* Data to write. */
-    int srcLen)			/* Number of bytes to write. */
-{
-    ChannelState *statePtr = chanPtr->state;
-				/* State info for channel */
-    ChannelBuffer *outBufPtr;	/* Current output buffer. */
-    int foundNewline;		/* Did we find a newline in output? */
-    char *dPtr;
-    const char *sPtr;		/* Search variables for newline. */
-    int crsent;			/* In CRLF eol translation mode, remember the
-				 * fact that a CR was output to the channel
-				 * without its following NL. */
-    int i;			/* Loop index for newline search. */
-    int destCopied;		/* How many bytes were used in this
-				 * destination buffer to hold the output? */
-    int totalDestCopied;	/* How many bytes total were copied to the
-				 * channel buffer? */
-    int srcCopied;		/* How many bytes were copied from the source
-				 * string? */
-    char *destPtr;		/* Where in line to copy to? */
+	    assert(statePtr->inputTranslation == TCL_TRANSLATE_CRLF);
+	    assert(RemovePoint(bufPtr)[0] == '\r');
+	    assert(BytesLeft(bufPtr) == 1);
 
-    /*
-     * If we are in network (or windows) translation mode, record the fact
-     * that we have not yet sent a CR to the channel.
-     */
+	    if (bufPtr->nextPtr == NULL) {
+		/* There's no more buffered data.... */
 
-    crsent = 0;
+		if (statePtr->flags & CHANNEL_EOF) {
+		    /* ...and there never will be. */
 
-    /*
-     * Loop filling buffers and flushing them until all output has been
-     * consumed.
-     */
+		    *p++ = '\r';
+		    bytesToRead--;
+		    bufPtr->nextRemoved++;
+		} else if (statePtr->flags & CHANNEL_BLOCKED) {
+		    /* ...and we cannot get more now. */
+		    SetFlag(statePtr, CHANNEL_NEED_MORE_DATA);
+		    UpdateInterest(chanPtr);
+		    break;
+		} else {
+		    /* ... so we need to get some. */
+		    goto moreData;
+		}
+	    }
 
-    srcCopied = 0;
-    totalDestCopied = 0;
+	    if (bufPtr->nextPtr) {
+		/* There's a next buffer.  Shift orphan \r to it. */
 
-    while (srcLen > 0) {
-	/*
-	 * Make sure there is a current output buffer to accept output.
-	 */
+		ChannelBuffer *nextPtr = bufPtr->nextPtr;
 
-	if (statePtr->curOutPtr == NULL) {
-	    statePtr->curOutPtr = AllocChannelBuffer(statePtr->bufSize);
+		nextPtr->nextRemoved -= 1;
+		RemovePoint(nextPtr)[0] = '\r';
+		bufPtr->nextRemoved++;
+	    }
 	}
 
-	outBufPtr = statePtr->curOutPtr;
-
-	destCopied = SpaceLeft(outBufPtr);
-	if (destCopied > srcLen) {
-	    destCopied = srcLen;
+	if (IsBufferEmpty(bufPtr)) {
+	    statePtr->inQueueHead = bufPtr->nextPtr;
+	    if (statePtr->inQueueHead == NULL) {
+		statePtr->inQueueTail = NULL;
+	    }
+	    RecycleBuffer(statePtr, bufPtr, 0);
+	    bufPtr = statePtr->inQueueHead;
 	}
 
-	destPtr = InsertPoint(outBufPtr);
-	switch (statePtr->outputTranslation) {
-	case TCL_TRANSLATE_LF:
-	    srcCopied = destCopied;
-	    memcpy(destPtr, src, (size_t) destCopied);
+	if ((GotFlag(statePtr, CHANNEL_NONBLOCKING) || allowShortReads)
+		&& GotFlag(statePtr, CHANNEL_BLOCKED)) {
 	    break;
-	case TCL_TRANSLATE_CR:
-	    srcCopied = destCopied;
-	    memcpy(destPtr, src, (size_t) destCopied);
-	    for (dPtr = destPtr; dPtr < destPtr + destCopied; dPtr++) {
-		if (*dPtr == '\n') {
-		    *dPtr = '\r';
-		}
-	    }
-	    break;
-	case TCL_TRANSLATE_CRLF:
-	    for (srcCopied = 0, dPtr = destPtr, sPtr = src;
-		    dPtr < destPtr + destCopied;
-		    dPtr++, sPtr++, srcCopied++) {
-		if (*sPtr == '\n') {
-		    if (crsent) {
-			*dPtr = '\n';
-			crsent = 0;
-		    } else {
-			*dPtr = '\r';
-			crsent = 1;
-			sPtr--, srcCopied--;
-		    }
-		} else {
-		    *dPtr = *sPtr;
-		}
-	    }
-	    break;
-	case TCL_TRANSLATE_AUTO:
-	    Tcl_Panic("Tcl_Write: AUTO output translation mode not supported");
-	default:
-	    Tcl_Panic("Tcl_Write: unknown output translation mode");
 	}
 
 	/*
-	 * The current buffer is ready for output if it is full, or if it
-	 * contains a newline and this channel is line-buffered, or if it
-	 * contains any output and this channel is unbuffered.
+	 * When there's no buffered data to read, and we're at EOF,
+	 * escape to the caller.
 	 */
 
-	outBufPtr->nextAdded += destCopied;
-	if (!GotFlag(statePtr, BUFFER_READY)) {
-	    if (IsBufferFull(outBufPtr)) {
-		SetFlag(statePtr, BUFFER_READY);
-	    } else if (GotFlag(statePtr, CHANNEL_LINEBUFFERED)) {
-		for (sPtr = src, i = 0, foundNewline = 0;
-			(i < srcCopied) && (!foundNewline);
-			i++, sPtr++) {
-		    if (*sPtr == '\n') {
-			foundNewline = 1;
-			break;
-		    }
-		}
-		if (foundNewline) {
-		    SetFlag(statePtr, BUFFER_READY);
-		}
-	    } else if (GotFlag(statePtr, CHANNEL_UNBUFFERED)) {
-		SetFlag(statePtr, BUFFER_READY);
-	    }
-	}
-
-	totalDestCopied += srcCopied;
-	src += srcCopied;
-	srcLen -= srcCopied;
-
-	if (GotFlag(statePtr, BUFFER_READY)) {
-	    if (FlushChannel(NULL, chanPtr, 0) != 0) {
-		return -1;
-	    }
+	if (GotFlag(statePtr, CHANNEL_EOF)
+		&& (bufPtr == NULL || IsBufferEmpty(bufPtr))) {
+	    break;
 	}
-    } /* Closes "while" */
+    }
+    if (bytesToRead == 0) {
+	ResetFlag(statePtr, CHANNEL_BLOCKED);
+    }
 
-    return totalDestCopied;
+	assert(!GotFlag(statePtr, CHANNEL_EOF)
+		|| GotFlag(statePtr, CHANNEL_STICKY_EOF)
+		|| Tcl_InputBuffered((Tcl_Channel)chanPtr) == 0);
+	assert( !(GotFlag(statePtr, CHANNEL_EOF|CHANNEL_BLOCKED)
+		== (CHANNEL_EOF|CHANNEL_BLOCKED)) );
+    TclChannelRelease((Tcl_Channel)chanPtr);
+    return (int)(p - dst);
 }
 
 /*
@@ -10154,12 +9931,16 @@ StopCopy(
     CopyState *csPtr)		/* State for bg copy to stop . */
 {
     ChannelState *inStatePtr, *outStatePtr;
+    Tcl_Channel inChan, outChan;
+
     int nonBlocking;
 
     if (!csPtr) {
 	return;
     }
 
+    inChan = (Tcl_Channel) csPtr->readPtr;
+    outChan = (Tcl_Channel) csPtr->writePtr;
     inStatePtr = csPtr->readPtr->state;
     outStatePtr = csPtr->writePtr->state;
 
@@ -10184,12 +9965,12 @@ StopCopy(
 	    csPtr->writeFlags & (CHANNEL_LINEBUFFERED | CHANNEL_UNBUFFERED);
 
     if (csPtr->cmdPtr) {
-	Tcl_DeleteChannelHandler((Tcl_Channel) csPtr->readPtr, CopyEventProc,
-		csPtr);
-	if (csPtr->readPtr != csPtr->writePtr) {
-	    Tcl_DeleteChannelHandler((Tcl_Channel) csPtr->writePtr,
-		    CopyEventProc, csPtr);
+	Tcl_DeleteChannelHandler(inChan, CopyEventProc, csPtr);
+	if (inChan != outChan) {
+	    Tcl_DeleteChannelHandler(outChan, CopyEventProc, csPtr);
 	}
+	Tcl_DeleteChannelHandler(inChan, MBEvent, csPtr);
+	Tcl_DeleteChannelHandler(outChan, MBEvent, csPtr);
 	TclDecrRefCount(csPtr->cmdPtr);
     }
     inStatePtr->csPtrR = NULL;
@@ -10223,12 +10004,15 @@ StackSetBlockMode(
 {
     int result = 0;
     Tcl_DriverBlockModeProc *blockModeProc;
+    ChannelState *statePtr = chanPtr->state;
 
     /*
      * Start at the top of the channel stack
+     * TODO: Examine what can go wrong when blockModeProc calls
+     * disturb the stacking state of the channel.
      */
 
-    chanPtr = chanPtr->state->topChanPtr;
+    chanPtr = statePtr->topChanPtr;
     while (chanPtr != NULL) {
 	blockModeProc = Tcl_ChannelBlockModeProc(chanPtr->typePtr);
 	if (blockModeProc != NULL) {
@@ -11331,12 +11115,11 @@ DupChannelIntRep(
 				 * currently have an internal rep.*/
 {
     ChannelState *statePtr  = GET_CHANNELSTATE(srcPtr);
-    Interp *interpPtr = GET_CHANNELINTERP(srcPtr);
 
     SET_CHANNELSTATE(copyPtr, statePtr);
-    SET_CHANNELINTERP(copyPtr, interpPtr);
+    SET_CHANNELINTERP(copyPtr, GET_CHANNELINTERP(srcPtr));
     Tcl_Preserve(statePtr);
-    copyPtr->typePtr = &tclChannelType;
+    copyPtr->typePtr = srcPtr->typePtr;
 }
 
 /*
@@ -11362,43 +11145,30 @@ SetChannelFromAny(
     register Tcl_Obj *objPtr)	/* The object to convert. */
 {
     ChannelState *statePtr;
-    Interp *interpPtr;
 
     if (interp == NULL) {
 	return TCL_ERROR;
     }
-    if (objPtr->typePtr == &tclChannelType) {
+    if (objPtr->typePtr == &chanObjType) {
 	/*
+	 * TODO: TAINT Flag and dup'd channel values?
 	 * The channel is valid until any call to DetachChannel occurs.
 	 * Ensure consistency checks are done.
 	 */
 
 	statePtr = GET_CHANNELSTATE(objPtr);
-	interpPtr = GET_CHANNELINTERP(objPtr);
 	if (GotFlag(statePtr, CHANNEL_TAINTED|CHANNEL_CLOSED)) {
 	    ResetFlag(statePtr, CHANNEL_TAINTED);
 	    Tcl_Release(statePtr);
-	    UpdateStringOfChannel(objPtr);
 	    objPtr->typePtr = NULL;
-	} else if (interpPtr != (Interp*) interp) {
+	} else if (interp != GET_CHANNELINTERP(objPtr)) {
 	    Tcl_Release(statePtr);
-	    UpdateStringOfChannel(objPtr);
 	    objPtr->typePtr = NULL;
 	}
     }
-    if (objPtr->typePtr != &tclChannelType) {
-	Tcl_Channel chan;
+    if (objPtr->typePtr != &chanObjType) {
+	Tcl_Channel chan = Tcl_GetChannel(interp, TclGetString(objPtr), NULL);
 
-	/*
-	 * We need a valid string with which to check for a valid channel, but
-	 * make sure not to free internal rep until validated. [Bug 1847044]
-	 */
-
-	if ((objPtr->typePtr != NULL) && (objPtr->bytes == NULL)) {
-	    objPtr->typePtr->updateStringProc(objPtr);
-	}
-
-	chan = Tcl_GetChannel(interp, objPtr->bytes, NULL);
 	if (chan == NULL) {
 	    return TCL_ERROR;
 	}
@@ -11408,7 +11178,7 @@ SetChannelFromAny(
 	Tcl_Preserve(statePtr);
 	SET_CHANNELSTATE(objPtr, statePtr);
 	SET_CHANNELINTERP(objPtr, interp);
-	objPtr->typePtr = &tclChannelType;
+	objPtr->typePtr = &chanObjType;
     }
     return TCL_OK;
 }
@@ -11416,45 +11186,6 @@ SetChannelFromAny(
 /*
  *----------------------------------------------------------------------
  *
- * UpdateStringOfChannel --
- *
- *	Update the string representation for an object whose internal
- *	representation is "Channel".
- *
- * Results:
- *	None.
- *
- * Side effects:
- *	The object's string may be set by converting its Unicode represention
- *	to UTF format.
- *
- *----------------------------------------------------------------------
- */
-
-static void
-UpdateStringOfChannel(
-    Tcl_Obj *objPtr)		/* Object with string rep to update. */
-{
-    if (objPtr->bytes == NULL) {
-	ChannelState *statePtr = GET_CHANNELSTATE(objPtr);
-	const char *name = statePtr->channelName;
-
-	if (name) {
-	    size_t len = strlen(name);
-
-	    objPtr->bytes = ckalloc(len + 1);
-	    objPtr->length = len;
-	    memcpy(objPtr->bytes, name, len);
-	} else {
-	    objPtr->bytes = tclEmptyStringRep;
-	    objPtr->length = 0;
-	}
-    }
-}
-
-/*
- *----------------------------------------------------------------------
- *
  * FreeChannelIntRep --
  *
  *	Release statePtr storage.
@@ -11497,20 +11228,14 @@ DumpFlags(
     ChanFlag('n', CHANNEL_NONBLOCKING);
     ChanFlag('l', CHANNEL_LINEBUFFERED);
     ChanFlag('u', CHANNEL_UNBUFFERED);
-    ChanFlag('R', BUFFER_READY);
     ChanFlag('F', BG_FLUSH_SCHEDULED);
     ChanFlag('c', CHANNEL_CLOSED);
     ChanFlag('E', CHANNEL_EOF);
     ChanFlag('S', CHANNEL_STICKY_EOF);
     ChanFlag('B', CHANNEL_BLOCKED);
     ChanFlag('/', INPUT_SAW_CR);
-    ChanFlag('*', INPUT_NEED_NL);
     ChanFlag('D', CHANNEL_DEAD);
     ChanFlag('R', CHANNEL_RAW_MODE);
-#ifdef TCL_IO_TRACK_OS_FOR_DRIVER_WITH_BAD_BLOCKING
-    ChanFlag('T', CHANNEL_TIMER_FEV);
-    ChanFlag('H', CHANNEL_HAS_MORE_DATA);
-#endif /* TCL_IO_TRACK_OS_FOR_DRIVER_WITH_BAD_BLOCKING */
     ChanFlag('x', CHANNEL_INCLOSE);
 
     buf[i] ='\0';