From f6becd63de09f3ad007bb2e1543cd21230242479 Mon Sep 17 00:00:00 2001
From: dgp <dgp@users.sourceforge.net>
Date: Sat, 17 May 2014 03:32:27 +0000
Subject: Simplify the inputProc of [testchannel transform].

---
 generic/tclIOGT.c | 39 ++++++++++++++++++---------------------
 1 file changed, 18 insertions(+), 21 deletions(-)

diff --git a/generic/tclIOGT.c b/generic/tclIOGT.c
index c5372b1..fe0a880 100644
--- a/generic/tclIOGT.c
+++ b/generic/tclIOGT.c
@@ -683,38 +683,35 @@ TransformInputProc(
 
 	read = Tcl_ReadRaw(downChan, buf, toRead);
 	if (read < 0) {
-	    /*
-	     * Report errors to caller. EAGAIN is a special situation. If we
-	     * had some data before we report that instead of the request to
-	     * re-try.
-	     */
 
-	    if ((Tcl_GetErrno() == EAGAIN) && (gotBytes > 0)) {
+	    if (Tcl_InputBlocked(downChan) && (gotBytes > 0)) {
+		/*
+		 * Zero bytes available from downChan because blocked.
+		 * But nonzero bytes already copied, so total is a
+		 * valid blocked short read. Return to caller.
+		 */
+
 		break;
 	    }
 
+	    /*
+	     * Either downChan is not blocked (there's a real error).
+	     * or it is and there are no bytes copied yet.  In either
+	     * case we want to pass the "error" along to the caller,
+	     * either to report an error, or to signal to the caller
+	     * that zero bytes are available because blocked.
+	     */
+
 	    *errorCodePtr = Tcl_GetErrno();
 	    gotBytes = -1;
 	    break;
 	} else if (read == 0) {
+
 	    /*
-	     * Check wether we hit on EOF in the underlying channel or not. If
-	     * not differentiate between blocking and non-blocking modes. In
-	     * non-blocking mode we ran temporarily out of data. Signal this
-	     * to the caller via EWOULDBLOCK and error return (-1). In the
-	     * other cases we simply return what we got and let the caller
-	     * wait for more. On the other hand, if we got an EOF we have to
-	     * convert and flush all waiting partial data.
+	     * Zero returned from Tcl_ReadRaw() always indicates EOF
+	     * on the down channel.
 	     */
 
-	    if (!Tcl_Eof(downChan)) {
-		if ((gotBytes == 0) && (dataPtr->flags & CHANNEL_ASYNC)) {
-		    *errorCodePtr = EWOULDBLOCK;
-		    gotBytes = -1;
-		}
-		break;
-	    }
-
 	    if (dataPtr->readIsFlushed) {
 		/*
 		 * Already flushed, nothing to do anymore.
-- 
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