Fix ijar compression

Ijar was compressing with the zlib wrapper, which is incompatible with
the ZIP format. Unfortunately, the zlib wrapper is totally undocumented.

Fixes #436.

--
MOS_MIGRATED_REVID=102846162

2 files changed, 26 insertions, 1 deletions

diff --git a/third_party/ijar/test/zip_test.sh b/third_party/ijar/test/zip_test.sh
index 4b92f32c43..19fd3de72e 100755
--- a/third_party/ijar/test/zip_test.sh
+++ b/third_party/ijar/test/zip_test.sh
@@ -85,4 +85,27 @@ function test_zipper() {
   expect_not_log "path"
 }
 
+function test_zipper_compression() {
+  echo -n > ${TEST_TMPDIR}/a
+  for i in $(seq 1 1000); do
+    echo -n "a" >> ${TEST_TMPDIR}/a
+  done
+  $ZIPPER cCf ${TEST_TMPDIR}/output.zip ${TEST_TMPDIR}/a
+  local out_size=$(cat ${TEST_TMPDIR}/output.zip | wc -c | xargs)
+  local in_size=$(cat ${TEST_TMPDIR}/a | wc -c | xargs)
+  check_gt "${in_size}" "${out_size}" "Output size is greater than input size"
+
+  rm -fr ${TEST_TMPDIR}/out
+  mkdir -p ${TEST_TMPDIR}/out
+  (cd ${TEST_TMPDIR}/out && $ZIPPER x ${TEST_TMPDIR}/output.zip)
+  diff ${TEST_TMPDIR}/a ${TEST_TMPDIR}/out/a &> $TEST_log \
+      || fail "Unzip using zipper after zipper output differ"
+
+  rm -fr ${TEST_TMPDIR}/out
+  mkdir -p ${TEST_TMPDIR}/out
+  (cd ${TEST_TMPDIR}/out && $UNZIP -q ${TEST_TMPDIR}/output.zip)
+  diff ${TEST_TMPDIR}/a ${TEST_TMPDIR}/out/a &> $TEST_log \
+      || fail "Unzip after zipper output differ"
+}
+
 run_suite "zipper tests"
diff --git a/third_party/ijar/zip.cc b/third_party/ijar/zip.cc
index 51e308de7d..5a3d1a589c 100644
--- a/third_party/ijar/zip.cc
+++ b/third_party/ijar/zip.cc
@@ -887,7 +887,9 @@ size_t TryDeflate(u1 *buf, size_t length) {
   stream.next_in = buf;
   stream.next_out = outbuf;
 
-  if (deflateInit(&stream, Z_DEFAULT_COMPRESSION) != Z_OK) {
+  // deflateInit2 negative windows size prevent the zlib wrapper to be used.
+  if (deflateInit2(&stream, Z_DEFAULT_COMPRESSION, Z_DEFLATED,
+                  -MAX_WBITS, 8, Z_DEFAULT_STRATEGY) != Z_OK) {
     // Failure to compress => return the buffer uncompressed
     free(outbuf);
     return length;