From 3e6eaa5776cbff53a13c50cbf5592e65307bd6bb Mon Sep 17 00:00:00 2001
From: pooryorick <com.digitalsmarties@pooryorick.com>
Date: Mon, 3 Apr 2023 17:12:11 +0000
Subject: Fix for [9ca87e6286262a62], sync fcopy buffers input in ReadChars().

---
 generic/tclIO.c | 12 +++++++-----
 1 file changed, 7 insertions(+), 5 deletions(-)

diff --git a/generic/tclIO.c b/generic/tclIO.c
index 287a2f2..73d787a 100644
--- a/generic/tclIO.c
+++ b/generic/tclIO.c
@@ -196,7 +196,7 @@ static void		DiscardOutputQueued(ChannelState *chanPtr);
 static Tcl_Size		DoRead(Channel *chanPtr, char *dst, Tcl_Size bytesToRead,
 			    int allowShortReads);
 static Tcl_Size		DoReadChars(Channel *chan, Tcl_Obj *objPtr, Tcl_Size toRead,
-			    int appendFlag);
+			    int allowShortReads, int appendFlag);
 static int		FilterInputBytes(Channel *chanPtr,
 			    GetsState *statePtr);
 static int		FlushChannel(Tcl_Interp *interp, Channel *chanPtr,
@@ -5899,7 +5899,7 @@ Tcl_ReadChars(
 	return TCL_INDEX_NONE;
     }
 
-    return DoReadChars(chanPtr, objPtr, toRead, appendFlag);
+    return DoReadChars(chanPtr, objPtr, toRead, 0, appendFlag);
 }
 /*
  *---------------------------------------------------------------------------
@@ -5930,6 +5930,7 @@ DoReadChars(
     Tcl_Size toRead,		/* Maximum number of characters to store, or
 				 * TCL_INDEX_NONE to read all available data (up to EOF or
 				 * when channel blocks). */
+    int allowShortReads,	/* Allow half-blocking (pipes,sockets) */
     int appendFlag)		/* If non-zero, data read from the channel
 				 * will be appended to the object. Otherwise,
 				 * the data will replace the existing contents
@@ -6070,8 +6071,8 @@ DoReadChars(
 	    if (GotFlag(statePtr, CHANNEL_EOF)) {
 		break;
 	    }
-	    if (GotFlag(statePtr, CHANNEL_NONBLOCKING|CHANNEL_BLOCKED)
-		    == (CHANNEL_NONBLOCKING|CHANNEL_BLOCKED)) {
+	    if ((GotFlag(statePtr, CHANNEL_NONBLOCKING) || allowShortReads)
+		    && GotFlag(statePtr, CHANNEL_BLOCKED)) {
 		break;
 	    }
 	    result = GetInput(chanPtr);
@@ -9762,7 +9763,8 @@ CopyData(
                               !GotFlag(inStatePtr, CHANNEL_NONBLOCKING));
 	    } else {
 		size = DoReadChars(inStatePtr->topChanPtr, bufObj, sizeb,
-			0 /* No append */);
+			!GotFlag(inStatePtr, CHANNEL_NONBLOCKING)
+			,0 /* No append */);
 	    }
 	    underflow = (size >= 0) && ((size_t)size < sizeb);	/* Input underflow */
 	}
-- 
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