Added two tests demonstrating that the tickets [8af92dfb66] (bad stream expansion) and [f70ce1fead] (multi-stream decoding without readahead limit shenanigans) are fixed.

Verified that the tests fail with commit [4eb66645d6], just before the zlib fixes.

Tweaked the zlib manpage paragraphs about -limit.
Tweaked some code comments.
Fixed typos in description of two unrelated zlib tests.

4 files changed, 73 insertions, 10 deletions

diff --git a/doc/zlib.n b/doc/zlib.n
index 994a063..3714fc1 100644
--- a/doc/zlib.n
+++ b/doc/zlib.n
@@ -193,12 +193,18 @@ How hard to compress the data. Must be an integer from 0 (uncompressed) to 9
 .TP
 \fB\-limit\fI readaheadLimit\fR
 .
-The maximum number of bytes ahead to read when decompressing. This can be set
-to 1 to find the border for multi-stream inflate or mixed data, to ensure it
-would handle correctly e. g. some operations on following streams after first
-caused to due time.
-Otherwise Tcl would try to automatically return previously read extra data
-to input stream back.
+The maximum number of bytes ahead to read when decompressing.
+.RS
+.PP
+This option has become \fBirrelevant\fR. It was originally introduced
+to prevent Tcl from reading beyond the end of a compressed stream in
+multi-stream channels to ensure that the data after was left alone for
+further reading, at the cost of speed.
+.PP
+Tcl now automatically returns any bytes it has read beyond the end of
+a compressed stream back to the channel, making them appear as unread
+to further readers.
+.RE
 .PP
 Both compressing and decompressing channel transformations add extra
 configuration options that may be accessed through \fBchan configure\fR. The
diff --git a/generic/tclZlib.c b/generic/tclZlib.c
index 68bdf92..42d7156 100644
--- a/generic/tclZlib.c
+++ b/generic/tclZlib.c
@@ -2948,8 +2948,9 @@ ZlibTransformClose(
 	(void) deflateEnd(&cd->outStream);
     } else {
 	/*
-	 * If we have rest of read input (overshot by Z_STREAM_END or on possible error),
-	 * unget this part of buffer back to the parent channel.
+	 * If we have unused bytes from the read input (overshot by
+	 * Z_STREAM_END or on possible error), unget them back to the parent
+	 * channel, so that they appear as not being read yet.
 	 */
 	if (cd->inStream.avail_in) {
 	    Tcl_Ungets (cd->parent, (char *)cd->inStream.next_in, cd->inStream.avail_in, 0);
diff --git a/tests/assets/zlib.bin b/tests/assets/zlib.bin
new file mode 100644
index 0000000..dadb639
--- /dev/null
+++ b/tests/assets/zlib.bin
diff --git a/tests/zlib.test b/tests/zlib.test
index c2f7825..e7ffcfe 100644
--- a/tests/zlib.test
+++ b/tests/zlib.test
@@ -920,7 +920,7 @@ test zlib-10.2 "bug #2818131 (mismatch gets)" -constraints {
     rename zlibRead {}
 } -result {error {invalid block type}}
 
-test zlib-11.1 "Bug #3390073: mis-appled gzip filtering" -setup {
+test zlib-11.1 "Bug #3390073: mis-applied gzip filtering" -setup {
     set file [makeFile {} test.input]
 } -constraints zlib -body {
     set f [open $file wb]
@@ -934,7 +934,7 @@ test zlib-11.1 "Bug #3390073: mis-appled gzip filtering" -setup {
 } -cleanup {
     removeFile $file
 } -result {1000 0}
-test zlib-11.2 "Bug #3390073: mis-appled gzip filtering" -setup {
+test zlib-11.2 "Bug #3390073: mis-applied gzip filtering" -setup {
     set file [makeFile {} test.input]
 } -constraints zlib -body {
     set f [open $file wb]
@@ -1005,6 +1005,62 @@ test zlib-12.2 {Patrick Dunnigan's issue} -constraints zlib -setup {
     removeFile $filesrc
     removeFile $filedst
 } -result 56
+
+test zlib-13.1 {Ticket 8af92dfb66 - zlib stream mis-expansion} -constraints zlib -setup {
+    set pathin  [file join $::tcltest::testsDirectory assets zlib.bin]
+    set chanin  [open $pathin rb]
+    set pathout [file join [pwd] zlib.deflated]
+    set chanout [open $pathout wb]
+    zlib push inflate $chanin
+    fcopy $chanin $chanout
+    close $chanin
+    close $chanout
+} -body {
+    file size $pathout    
+} -cleanup {
+    file delete $pathout
+    unset chanin pathin chanout pathout
+} -result 458752
+
+test zlib-13.2 {Ticket f70ce1fead - zlib multi-stream expansion} -constraints zlib -setup {
+    # Start from the basic asset
+    set pathin  [file join $::tcltest::testsDirectory assets zlib.bin]
+    set chanin  [open $pathin rb]
+    # Create a multi-stream by copying the asset twice into it.
+    set pathout [file join [pwd] zlib.multi]
+    set chanout [open $pathout wb]
+    fcopy $chanin $chanout
+    seek  $chanin 0 start
+    fcopy $chanin $chanout
+    close $chanin
+    close $chanout
+    # The multi-stream file shall be our input
+    set pathin $pathout
+    set chanin [open $pathin rb]
+    # And our destinations
+    set pathout1 [file join [pwd] zlib.1]
+    set pathout2 [file join [pwd] zlib.2]
+} -body {
+    # Decode first stream
+    set chanout [open $pathout1 wb]
+    zlib push inflate $chanin
+    fcopy $chanin $chanout
+    chan pop $chanin
+    close $chanout
+    # Decode second stream
+    set chanout [open $pathout2 wb]
+    zlib push inflate $chanin
+    fcopy $chanin $chanout
+    chan pop $chanin
+    close $chanout
+    #    
+    list [file size $pathout1] [file size $pathout2]
+} -cleanup {
+    close $chanin
+    file delete $pathout $pathout1 $pathout2
+    unset chanin pathin chanout pathout pathout1 pathout2
+} -result {458752 458752}
+
 
 ::tcltest::cleanupTests
 return