gifimagedecoder.cpp

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/*
 * Copyright (C) 2006 Apple Computer, 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:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY APPLE COMPUTER, INC. ``AS IS'' AND ANY
 * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
 * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL APPLE COMPUTER, INC. OR
 * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
 * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
 * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
 * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY
 * OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 
 */

#include "config.h"
#include "GIFImageDecoder.h"
#include "GIFImageReader.h"

#if PLATFORM(CAIRO) || PLATFORM(QT) || PLATFORM(WX)

namespace WebCore {

class GIFImageDecoderPrivate
{
public:
    GIFImageDecoderPrivate(GIFImageDecoder* decoder = 0)
        : m_reader(decoder)
    {
        m_readOffset = 0;
    }

    ~GIFImageDecoderPrivate()
    {
        m_reader.close();
    }

    bool decode(const Vector<char>& data, 
                GIFImageDecoder::GIFQuery query = GIFImageDecoder::GIFFullQuery,
                unsigned int haltFrame = -1)
    {
        return m_reader.read((const unsigned char*)data.data() + m_readOffset, data.size() - m_readOffset, 
                             query,
                             haltFrame);
    }

    unsigned frameCount() const { return m_reader.images_count; }
    int repetitionCount() const { return m_reader.loop_count; }

    void setReadOffset(unsigned o) { m_readOffset = o; }

    bool isTransparent() const { return m_reader.frame_reader->is_transparent; }

    void getColorMap(unsigned char*& map, unsigned& size) const {
        if (m_reader.frame_reader->is_local_colormap_defined) {
            map = m_reader.frame_reader->local_colormap;
            size = (unsigned)m_reader.frame_reader->local_colormap_size;
        } else {
            map = m_reader.global_colormap;
            size = m_reader.global_colormap_size;
        }
    }

    unsigned frameXOffset() const { return m_reader.frame_reader->x_offset; }
    unsigned frameYOffset() const { return m_reader.frame_reader->y_offset; }
    unsigned frameWidth() const { return m_reader.frame_reader->width; }
    unsigned frameHeight() const { return m_reader.frame_reader->height; }

    int transparentPixel() const { return m_reader.frame_reader->tpixel; }

    unsigned duration() const { return m_reader.frame_reader->delay_time; }

private:
    GIFImageReader m_reader;
    unsigned m_readOffset;
};

GIFImageDecoder::GIFImageDecoder()
: m_frameCountValid(true), m_repetitionCount(cAnimationLoopOnce), m_reader(0)
{}

GIFImageDecoder::~GIFImageDecoder()
{
    delete m_reader;
}

// Take the data and store it.
void GIFImageDecoder::setData(SharedBuffer* data, bool allDataReceived)
{
    if (m_failed)
        return;

    // Cache our new data.
    ImageDecoder::setData(data, allDataReceived);

    // Our frame count is now unknown.
    m_frameCountValid = false;

    // Create the GIF reader.
    if (!m_reader && !m_failed)
        m_reader = new GIFImageDecoderPrivate(this);
}

// Whether or not the size information has been decoded yet.
bool GIFImageDecoder::isSizeAvailable() const
{
    // If we have pending data to decode, send it to the GIF reader now.
    if (!m_sizeAvailable && m_reader) {
        if (m_failed)
            return false;

        // The decoder will go ahead and aggressively consume everything up until the first
        // size is encountered.
        decode(GIFSizeQuery, 0);
    }

    return m_sizeAvailable;
}

// The total number of frames for the image.  Will scan the image data for the answer
// (without necessarily decoding all of the individual frames).
int GIFImageDecoder::frameCount()
{
    // If the decoder had an earlier error, we will just return what we had decoded
    // so far.
    if (!m_frameCountValid) {
        // FIXME: Scanning all the data has O(n^2) behavior if the data were to come in really
        // slowly.  Might be interesting to try to clone our existing read session to preserve
        // state, but for now we just crawl all the data.  Note that this is no worse than what
        // ImageIO does on Mac right now (it also crawls all the data again).
        GIFImageDecoderPrivate reader;
        reader.decode(m_data->buffer(), GIFFrameCountQuery);
        m_frameCountValid = true;
        m_frameBufferCache.resize(reader.frameCount());
    }

    return m_frameBufferCache.size();
}

// The number of repetitions to perform for an animation loop.
int GIFImageDecoder::repetitionCount() const
{
    // This value can arrive at any point in the image data stream.  Most GIFs
    // in the wild declare it near the beginning of the file, so it usually is
    // set by the time we've decoded the size, but (depending on the GIF and the
    // packets sent back by the webserver) not always.  Our caller is
    // responsible for waiting until image decoding has finished to ask this if
    // it needs an authoritative answer.  In the meantime, we should default to
    // "loop once".
    if (m_reader) {
        // Added wrinkle: ImageSource::clear() may destroy the reader, making
        // the result from the reader _less_ authoritative on future calls.  To
        // detect this, the reader returns cLoopCountNotSeen (-2) instead of
        // cAnimationLoopOnce (-1) when its current incarnation hasn't actually
        // seen a loop count yet; in this case we return our previously-cached
        // value.
        const int repetitionCount = m_reader->repetitionCount();
        if (repetitionCount != cLoopCountNotSeen)
            m_repetitionCount = repetitionCount;
    }
    return m_repetitionCount;
}

RGBA32Buffer* GIFImageDecoder::frameBufferAtIndex(size_t index)
{
    if (index >= frameCount())
        return 0;

    RGBA32Buffer& frame = m_frameBufferCache[index];
    if (frame.status() != RGBA32Buffer::FrameComplete && m_reader)
        // Decode this frame.
        decode(GIFFullQuery, index+1);
    return &frame;
}

void GIFImageDecoder::clearFrameBufferCache(size_t clearBeforeFrame)
{
    // In some cases, like if the decoder was destroyed while animating, we
    // can be asked to clear more frames than we currently have.
    if (m_frameBufferCache.isEmpty())
        return; // Nothing to do.

    // The "-1" here is tricky.  It does not mean that |clearBeforeFrame| is the
    // last frame we wish to preserve, but rather that we never want to clear
    // the very last frame in the cache: it's empty (so clearing it is
    // pointless), it's partial (so we don't want to clear it anyway), or the
    // cache could be enlarged with a future setData() call and it could be
    // needed to construct the next frame (see comments below).  Callers can
    // always use ImageSource::clear(true, ...) to completely free the memory in
    // this case.
    clearBeforeFrame = std::min(clearBeforeFrame, m_frameBufferCache.size() - 1);
    const Vector<RGBA32Buffer>::iterator end(m_frameBufferCache.begin() + clearBeforeFrame);

    // We need to preserve frames such that:
    //   * We don't clear |end|
    //   * We don't clear the frame we're currently decoding
    //   * We don't clear any frame from which a future initFrameBuffer() call
    //     will copy bitmap data
    // All other frames can be cleared.  Because of the constraints on when
    // ImageSource::clear() can be called (see ImageSource.h), we're guaranteed
    // not to have non-empty frames after the frame we're currently decoding.
    // So, scan backwards from |end| as follows:
    //   * If the frame is empty, we're still past any frames we care about.
    //   * If the frame is complete, but is DisposeOverwritePrevious, we'll
    //     skip over it in future initFrameBuffer() calls.  We can clear it
    //     unless it's |end|, and keep scanning.  For any other disposal method,
    //     stop scanning, as we've found the frame initFrameBuffer() will need
    //     next.
    //   * If the frame is partial, we're decoding it, so don't clear it; if it
    //     has a disposal method other than DisposeOverwritePrevious, stop
    //     scanning, as we'll only need this frame when decoding the next one.
    Vector<RGBA32Buffer>::iterator i(end);
    for (; (i != m_frameBufferCache.begin()) && ((i->status() == RGBA32Buffer::FrameEmpty) || (i->disposalMethod() == RGBA32Buffer::DisposeOverwritePrevious)); --i) {
        if ((i->status() == RGBA32Buffer::FrameComplete) && (i != end))
            i->clear();
    }

    // Now |i| holds the last frame we need to preserve; clear prior frames.
    for (Vector<RGBA32Buffer>::iterator j(m_frameBufferCache.begin()); j != i; ++j) {
        ASSERT(j->status() != RGBA32Buffer::FramePartial);
        if (j->status() != RGBA32Buffer::FrameEmpty)
            j->clear();
    }
}

// Feed data to the GIF reader.
void GIFImageDecoder::decode(GIFQuery query, unsigned haltAtFrame) const
{
    if (m_failed)
        return;