Checking if frame is complete and access duration doesn't need a decode

Source/core/platform/image-decoders/gif/GIFImageDecoder.cpp

Index: Source/core/platform/image-decoders/gif/GIFImageDecoder.cpp
diff --git a/Source/core/platform/image-decoders/gif/GIFImageDecoder.cpp b/Source/core/platform/image-decoders/gif/GIFImageDecoder.cpp
index 8186836744e475eca8dfb52e889356b9924b5817..56da95a676759dddc2e8bac24e8c875a2168b93a 100644
--- a/Source/core/platform/image-decoders/gif/GIFImageDecoder.cpp
+++ b/Source/core/platform/image-decoders/gif/GIFImageDecoder.cpp
@@ -127,6 +127,18 @@ ImageFrame* GIFImageDecoder::frameBufferAtIndex(size_t index)
     return &frame;
 }
 
+bool GIFImageDecoder::frameIsCompleteAtIndex(size_t index) const
+{
+    return m_reader && (index < m_reader->imagesCount()) && m_reader->frameContext(index)->isComplete();
+}
+
+float GIFImageDecoder::frameDurationAtIndex(size_t index) const
+{
+    return (m_reader && (index < m_reader->imagesCount()) &&
+        m_reader->frameContext(index)->isHeaderDefined()) ?
+        m_reader->frameContext(index)->delayTime : 0;
+}
+
 bool GIFImageDecoder::setFailed()
 {
     m_reader.clear();
@@ -185,7 +197,7 @@ void GIFImageDecoder::clearFrameBufferCache(size_t clearBeforeFrame)
 
 bool GIFImageDecoder::haveDecodedRow(unsigned frameIndex, const Vector<unsigned char>& rowBuffer, size_t width, size_t rowNumber, unsigned repeatCount, bool writeTransparentPixels)
 {
-    const GIFFrameContext* frameContext = m_reader->frameContext();
+    const GIFFrameContext* frameContext = m_reader->frameContext(frameIndex);
     // The pixel data and coordinates supplied to us are relative to the frame's
     // origin within the entire image size, i.e.
     // (frameContext->xOffset, frameContext->yOffset). There is no guarantee
@@ -297,8 +309,6 @@ void GIFImageDecoder::gifComplete()
     // Cache the repetition count, which is now as authoritative as it's ever
     // going to be.
     repetitionCount();
-
-    m_reader.clear();
 }
 
 void GIFImageDecoder::decode(unsigned haltAtFrame, GIFQuery query)
@@ -335,16 +345,16 @@ void GIFImageDecoder::decode(unsigned haltAtFrame, GIFQuery query)
         return;
     }
 
-    // It is also a fatal error if all data is received but we failed to decode
-    // all frames completely.
-    if (isAllDataReceived() && haltAtFrame >= m_frameBufferCache.size() && m_reader)
+    // It is also a fatal error if all data is received and we have decoded all
+    // frames available but the file is truncated.
+    if (haltAtFrame >= m_frameBufferCache.size() && truncated())
         setFailed();
 }
 
 bool GIFImageDecoder::initFrameBuffer(unsigned frameIndex)
 {
     // Initialize the frame rect in our buffer.
-    const GIFFrameContext* frameContext = m_reader->frameContext();
+    const GIFFrameContext* frameContext = m_reader->frameContext(frameIndex);
     IntRect frameRect(frameContext->xOffset, frameContext->yOffset, frameContext->width, frameContext->height);
 
     // Make sure the frameRect doesn't extend outside the buffer.
@@ -417,4 +427,9 @@ bool GIFImageDecoder::initFrameBuffer(unsigned frameIndex)
     return true;
 }
 
+bool GIFImageDecoder::truncated() const
+{
+    return isAllDataReceived() && m_reader && !m_reader->parseCompleted();

[Peter Kasting, 2013/05/03 22:03:19]

This is only going to be accurate if we've asked to decode the whole file,
though, right?  Wouldn't it be true that if we got all the data and then only
asked for an early frame, then someone could call this function and it would
erroneously return true?

Maybe for that reason, we should keep this inlined into decode() where it was
before.

[Alpha Left Google, 2013/05/06 17:43:24]

Yes you're right. Changed it back to before so we don't make mistake in the
future.

+}
+
 } // namespace WebCore