[Bug 3603553]: Ensure that data gets written to the underlying stream by

compressing transforms when the amount of data to be written is one
buffer's-worth; problem was particularly likely to occur when compressing
large quantities of not-very-compressible data.

Many thanks to Piera Poggio (vampiera) for reporting.

1 files changed, 19 insertions, 0 deletions

diff --git a/tests/zlib.test b/tests/zlib.test
index 891dba0..96914ca 100644
--- a/tests/zlib.test
+++ b/tests/zlib.test
@@ -366,6 +366,25 @@ test zlib-8.15 {transformtion and fconfigure} -setup {
     catch {close $inSide}
     catch {$strm close}
 } -result {358 358}
+test zlib-8.16 {Bug 3603553: buffer transfer with large writes} -setup {
+    # Actual data isn't very important; needs to be substantially larger than
+    # the internal buffer (8kB) and incompressible.
+    set largeData {}
+    for {set i 0;expr srand(1)} {$i < 100000} {incr i} {
+	append largeData [lindex "a b c d e f g h i j k l m n o p" \
+		[expr {int(16*rand())}]]
+    }
+    set file [makeFile {} test.gz]
+} -constraints zlib -body {
+    set f [open $file wb]
+    fconfigure $f -buffering none
+    zlib push gzip $f
+    puts -nonewline $f $largeData
+    close $f
+    file size $file
+} -cleanup {
+    removeFile $file
+} -result 57647
 
 test zlib-9.1 "check fcopy with push" -constraints zlib -setup {
     set sfile [makeFile {} testsrc.gz]