Convert deflate image chunks to raw if the raw data is smaller

The imgpatch will fail on empty deflates because the bspatch won't call
the sink function if the target length is zero.

Instead of compressing an empty string, it's cleaner to not generate such
empty deflate chunks in the patch. Therefore, we can just convert the
chunk type to raw if the target length is smaller than the patch data.

Also adjust some unit tests and add the testdata gzipped_source &
gzipped_target. These two files are ~1K each and are generated by
gzipping two slightly different regular files.

Bug: 79265132
Test: unit tests pass, imgpatch applys successfully on the given src/tgt
Change-Id: I6bfff3251918137f6762a6f9e9551642371a1124

3 files changed, 5 insertions, 3 deletions

diff --git a/applypatch/imgdiff.cpp b/applypatch/imgdiff.cpp
index 674cc2b1..415d95f1 100644
--- a/applypatch/imgdiff.cpp
+++ b/applypatch/imgdiff.cpp
@@ -462,12 +462,12 @@ PatchChunk::PatchChunk(const ImageChunk& tgt)
       target_len_(tgt.GetRawDataLength()),
       target_uncompressed_len_(tgt.DataLengthForPatch()),
       target_compress_level_(tgt.GetCompressLevel()),
-      data_(tgt.DataForPatch(), tgt.DataForPatch() + tgt.DataLengthForPatch()) {}
+      data_(tgt.GetRawData(), tgt.GetRawData() + tgt.GetRawDataLength()) {}
 
 // Return true if raw data is smaller than the patch size.
 bool PatchChunk::RawDataIsSmaller(const ImageChunk& tgt, size_t patch_size) {
   size_t target_len = tgt.GetRawDataLength();
-  return (tgt.GetType() == CHUNK_NORMAL && (target_len <= 160 || target_len < patch_size));
+  return target_len < patch_size || (tgt.GetType() == CHUNK_NORMAL && target_len <= 160);
 }
 
 void PatchChunk::UpdateSourceOffset(const SortedRangeSet& src_range) {
diff --git a/applypatch/imgpatch.cpp b/applypatch/imgpatch.cpp
index c4c2707f..2f8f4851 100644
--- a/applypatch/imgpatch.cpp
+++ b/applypatch/imgpatch.cpp
@@ -54,6 +54,7 @@ static bool ApplyBSDiffPatchAndStreamOutput(const uint8_t* src_data, size_t src_
                                             const Value& patch, size_t patch_offset,
                                             const char* deflate_header, SinkFn sink) {
   size_t expected_target_length = static_cast<size_t>(Read8(deflate_header + 32));
+  CHECK_GT(expected_target_length, 0);
   int level = Read4(deflate_header + 40);
   int method = Read4(deflate_header + 44);
   int window_bits = Read4(deflate_header + 48);
diff --git a/applypatch/include/applypatch/imgdiff_image.h b/applypatch/include/applypatch/imgdiff_image.h
index 08480723..67160516 100644
--- a/applypatch/include/applypatch/imgdiff_image.h
+++ b/applypatch/include/applypatch/imgdiff_image.h
@@ -44,6 +44,8 @@ class ImageChunk {
   int GetType() const {
     return type_;
   }
+
+  const uint8_t* GetRawData() const;
   size_t GetRawDataLength() const {
     return raw_data_len_;
   }
@@ -99,7 +101,6 @@ class ImageChunk {
                         bsdiff::SuffixArrayIndexInterface** bsdiff_cache);
 
  private:
-  const uint8_t* GetRawData() const;
   bool TryReconstruction(int level);
 
   int type_;                                    // CHUNK_NORMAL, CHUNK_DEFLATE, CHUNK_RAW