Fix decoding incomplete PNG images
If process_data is unable to read (and therefore process) as many bytes
as it expects, process the bytes read before returning false.
Fixes differences in Gold.
Add a test that verifies that it is okay to call png_process_data with
0 bytes. (We could special case 0, but libpng already checks for 0.)
Change-Id: Id500b9305ee3bb6a1a7e8fc70d4e723cb4742b55
Reviewed-on: https://skia-review.googlesource.com/14144
Commit-Queue: Leon Scroggins <scroggo@google.com>
Reviewed-by: Matt Sarett <msarett@google.com>
diff --git a/src/codec/SkPngCodec.cpp b/src/codec/SkPngCodec.cpp
index 6b6ac99..1f69159 100644
--- a/src/codec/SkPngCodec.cpp
+++ b/src/codec/SkPngCodec.cpp
@@ -132,10 +132,11 @@
SkStream* stream, void* buffer, size_t bufferSize, size_t length) {
while (length > 0) {
const size_t bytesToProcess = std::min(bufferSize, length);
- if (stream->read(buffer, bytesToProcess) < bytesToProcess) {
+ const size_t bytesRead = stream->read(buffer, bytesToProcess);
+ png_process_data(png_ptr, info_ptr, (png_bytep) buffer, bytesRead);
+ if (bytesRead < bytesToProcess) {
return false;
}
- png_process_data(png_ptr, info_ptr, (png_bytep) buffer, bytesToProcess);
length -= bytesToProcess;
}
return true;
diff --git a/tests/CodecPartialTest.cpp b/tests/CodecPartialTest.cpp
index c029922..13cea8a 100644
--- a/tests/CodecPartialTest.cpp
+++ b/tests/CodecPartialTest.cpp
@@ -401,3 +401,28 @@
compare_bitmaps(r, truth, bm);
}
}
+
+DEF_TEST(Codec_emptyIDAT, r) {
+ const char* name = "baby_tux.png";
+ sk_sp<SkData> file = GetResourceAsData(name);
+ if (!file) {
+ SkDebugf("REMOVE\n");
+ return;
+ }
+
+ // Truncate to the beginning of the IDAT, immediately after the IDAT tag.
+ file = SkData::MakeSubset(file.get(), 0, 80);
+
+ std::unique_ptr<SkCodec> codec(SkCodec::NewFromData(std::move(file)));
+ if (!codec) {
+ ERRORF(r, "Failed to create a codec for %s", name);
+ return;
+ }
+
+ SkBitmap bm;
+ const auto info = standardize_info(codec.get());
+ bm.allocPixels(info);
+
+ const auto result = codec->getPixels(info, bm.getPixels(), bm.rowBytes());
+ REPORTER_ASSERT(r, SkCodec::kIncompleteInput == result);
+}