Fix caching bug in JPEGImageDecoder

Source/platform/image-decoders/jpeg/JPEGImageDecoderTest.cpp

 /*
  * Copyright (C) 2013 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 222 matching lines @@
 
 TEST(JPEGImageDecoderTest, byteByByte)
 {
     testByteByByteDecode(&createDecoder, "/LayoutTests/fast/images/resources/lenna.jpg", 1u, cAnimationNone);
     // Progressive image
     testByteByByteDecode(&createDecoder, "/LayoutTests/fast/images/resources/flowchart.jpg", 1u, cAnimationNone);
     // Image with restart markers
     testByteByByteDecode(&createDecoder, "/LayoutTests/fast/images/resources/red-at-12-oclock-with-color-profile.jpg", 1u, cAnimationNone);
 }
 
+static unsigned createDecodingBaseline(SharedBuffer* data)
+{
+    OwnPtr<ImageDecoder> decoder = createDecoder();
+    decoder->setData(data, true);
+    ImageFrame* frame = decoder->frameBufferAtIndex(0);
+    return hashBitmap(frame->bitmap());
+}
+
+// This test verifies that calling SharedBuffer::mergeSegmentsIntoBuffer() does
+// not break JPEG decoding at a critical point: in between a call to decode the
+// size (when JPEGImageDecoder stops while it may still have input data to
+// read) and a call to do a full decode.
+TEST(JPEGImageDecoderTest, mergeBuffer)
+{
+    const char* jpegFile = "/LayoutTests/fast/images/resources/lenna.jpg";
+    RefPtr<SharedBuffer> data = readFile(jpegFile);
+    ASSERT_TRUE(data);
+
+    const unsigned hash = createDecodingBaseline(data.get());
+
+    // In order to do any verification, this test needs to move the data owned
+    // by the SharedBuffer. A way to guarantee that is to create a new one, and
+    // then append a string of characters greater than kSegmentSize. This
+    // results in writing the data into a segment, skipping the internal
+    // contiguous buffer.
+    RefPtr<SharedBuffer> segmentedData = SharedBuffer::create();
+    segmentedData->append(data->data(), data->size());
+
+    OwnPtr<ImageDecoder> decoder = createDecoder();
+    decoder->setData(segmentedData.get(), true);
+
+    ASSERT_TRUE(decoder->isSizeAvailable());
+
+    // This will call SharedBuffer::mergeSegmentsIntoBuffer, copying all
+    // segments into the contiguous buffer. If JPEGImageDecoder was pointing to
+    // data in a segment, its pointer would no longer be valid.
+    segmentedData->data();
+
+    ImageFrame* frame = decoder->frameBufferAtIndex(0);
+    ASSERT_FALSE(decoder->failed());
+    EXPECT_EQ(frame->status(), ImageFrame::FrameComplete);
+    EXPECT_EQ(hashBitmap(frame->bitmap()), hash);
+}
+
 } // namespace blink