text: /*
   * Copyright (C) 2006 Apple 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 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 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"
  #include <limits>
  
  namespace WebCore {
  
  GIFImageDecoder::GIFImageDecoder(AlphaOption alphaOption, GammaAndColorProfileOption gammaAndColorProfileOption)
      : ScalableImageDecoder(alphaOption, gammaAndColorProfileOption)
  {
  }
  
  GIFImageDecoder::~GIFImageDecoder() = default;
  
  void GIFImageDecoder::setData(SharedBuffer& data, bool allDataReceived)
  {
      if (failed())
          return;
  
      ScalableImageDecoder::setData(data, allDataReceived);
      if (m_reader)
          m_reader->setData(&data);
  }
  
  bool GIFImageDecoder::setSize(const IntSize& size)
  {
      if (ScalableImageDecoder::encodedDataStatus() >= EncodedDataStatus::SizeAvailable && this->size() == size)
          return true;
  
      if (!ScalableImageDecoder::setSize(size))
          return false;
  
      prepareScaleDataIfNecessary();
      return true;
  }
  
  size_t GIFImageDecoder::frameCount() const
  {
      const_cast<GIFImageDecoder*>(this)->decode(std::numeric_limits<unsigned>::max(), GIFFrameCountQuery, isAllDataReceived());
      return m_frameBufferCache.size();
  }
  
  RepetitionCount 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.  If the reader hasn't
      // seen a loop count yet, it will return cLoopCountNotSeen, in which case we
      // should default to looping once (the initial value for
      // |m_repetitionCount|).
      //
      // There are some additional wrinkles here. First, ImageSource::clear()
      // may destroy the reader, making the result from the reader _less_
      // authoritative on future calls if the recreated reader hasn't seen the
      // loop count.  We don't need to special-case this because in this case the
      // new reader will once again return cLoopCountNotSeen, and we won't
      // overwrite the cached correct value.
      //
      // Second, a GIF might never set a loop count at all, in which case we
      // should continue to treat it as a "loop once" animation.  We don't need
      // special code here either, because in this case we'll never change
      // |m_repetitionCount| from its default value.
      //
      // Third, we use the same GIFImageReader for counting frames and we might
      // see the loop count and then encounter a decoding error which happens
      // later in the stream. It is also possible that no frames are in the
      // stream. In these cases we should just loop once.
      if (failed() || (m_reader && (!m_reader->imagesCount())))
          m_repetitionCount = RepetitionCountOnce;
      else if (m_reader && m_reader->loopCount() != cLoopCountNotSeen)
          m_repetitionCount = m_reader->loopCount();
      return m_repetitionCount;
  }
  
  size_t GIFImageDecoder::findFirstRequiredFrameToDecode(size_t frameIndex)
  {
      // The first frame doesn't depend on any other.
      if (!frameIndex)
          return 0;
  
      for (size_t i = frameIndex; i > 0; --i) {
          ImageFrame& frame = m_frameBufferCache[i - 1];
  
          // Frames with disposal method RestoreToPrevious are useless, skip them.
          if (frame.disposalMethod() == ImageFrame::DisposalMethod::RestoreToPrevious)
              continue;
  
          // At this point the disposal method can be Unspecified, DoNotDispose or RestoreToBackground.
          // In every case, if the frame is complete we can start decoding the next one.
          if (frame.isComplete())
              return i;
  
          // If the disposal method of this frame is RestoreToBackground and it fills the whole area,
          // the next frame's backing store is initialized to transparent, so we start decoding with it.
          if (frame.disposalMethod() == ImageFrame::DisposalMethod::RestoreToBackground) {
              // We cannot use frame.backingStore()->frameRect() here, because it has been cleared
              // when the frame was removed from the cache. We need to get the values from the
              // reader context.
              const auto* frameContext = m_reader->frameContext(i - 1);
              ASSERT(frameContext);
              IntRect frameRect(frameContext->xOffset, frameContext->yOffset, frameContext->width, frameContext->height);
              // We would need to scale frameRect and check whether it fills the whole scaledSize(). But
              // can check whether the original frameRect fills size() instead. If the frame fills the
              // whole area then it can be decoded without dependencies.
              if (frameRect.contains({ { }, size() }))
                  return i;
          }
      }
  
      return 0;
  }
  
  ImageFrame* GIFImageDecoder::frameBufferAtIndex(size_t index)
  {
      if (index >= frameCount())
          return 0;
  
      ImageFrame& frame = m_frameBufferCache[index];
      if (!frame.isComplete()) {
          for (auto i = findFirstRequiredFrameToDecode(index); i <= index; i++)
              decode(i + 1, GIFFullQuery, isAllDataReceived());
      }
  
      return &frame;
  }
  
  bool GIFImageDecoder::setFailed()
  {
      m_reader = nullptr;
      return ScalableImageDecoder::setFailed();
  }
  
  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<ImageFrame>::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 DisposalMethod::RestoreToPrevious, 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 DisposalMethod::RestoreToPrevious, stop
      //     scanning, as we'll only need this frame when decoding the next one.
      Vector<ImageFrame>::iterator i(end);
      for (; (i != m_frameBufferCache.begin()) && (i->isInvalid() || (i->disposalMethod() == ImageFrame::DisposalMethod::RestoreToPrevious)); --i) {
          if (i->isComplete() && (i != end))
              i->clear();
      }
  
      // Now |i| holds the last frame we need to preserve; clear prior frames.
      for (Vector<ImageFrame>::iterator j(m_frameBufferCache.begin()); j != i; ++j) {
          ASSERT(!j->isPartial());
          if (!j->isInvalid())
              j->clear();
      }
  }
  
  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();
      // 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
      // that width == (size().width() - frameContext->xOffset), so
      // we must ensure we don't run off the end of either the source data or the
      // row's X-coordinates.
      int xBegin = upperBoundScaledX(frameContext->xOffset);
      int yBegin = upperBoundScaledY(frameContext->yOffset + rowNumber);
      int xEnd = lowerBoundScaledX(std::min(static_cast<int>(frameContext->xOffset + width), size().width()) - 1, xBegin + 1) + 1;
      int yEnd = lowerBoundScaledY(std::min(static_cast<int>(frameContext->yOffset + rowNumber + repeatCount), size().height()) - 1, yBegin + 1) + 1;
      if (rowBuffer.isEmpty() || (xBegin < 0) || (yBegin < 0) || (xEnd <= xBegin) || (yEnd <= yBegin))
          return true;
  
      // Get the colormap.
      const unsigned char* colorMap;
      unsigned colorMapSize;
      if (frameContext->isLocalColormapDefined) {
          colorMap = m_reader->localColormap(frameContext);
          colorMapSize = m_reader->localColormapSize(frameContext);
      } else {
          colorMap = m_reader->globalColormap();
          colorMapSize = m_reader->globalColormapSize();
      }
      if (!colorMap)
          return true;
  
      // Initialize the frame if necessary.
      ImageFrame& buffer = m_frameBufferCache[frameIndex];
      if ((buffer.isInvalid() && !initFrameBuffer(frameIndex)) || !buffer.hasBackingStore())
          return false;
  
      RGBA32* currentAddress = buffer.backingStore()->pixelAt(xBegin, yBegin);
      // Write one row's worth of data into the frame.  
      for (int x = xBegin; x < xEnd; ++x) {
          const unsigned char sourceValue = rowBuffer[(m_scaled ? m_scaledColumns[x] : x) - frameContext->xOffset];
          if ((!frameContext->isTransparent || (sourceValue != frameContext->tpixel)) && (sourceValue < colorMapSize)) {
              const size_t colorIndex = static_cast<size_t>(sourceValue) * 3;
              buffer.backingStore()->setPixel(currentAddress, colorMap[colorIndex], colorMap[colorIndex + 1], colorMap[colorIndex + 2], 255);
          } else {
              m_currentBufferSawAlpha = true;
              // We may or may not need to write transparent pixels to the buffer.
              // If we're compositing against a previous image, it's wrong, and if
              // we're writing atop a cleared, fully transparent buffer, it's
              // unnecessary; but if we're decoding an interlaced gif and
              // displaying it "Haeberli"-style, we must write these for passes
              // beyond the first, or the initial passes will "show through" the
              // later ones.
              if (writeTransparentPixels)
                  buffer.backingStore()->setPixel(currentAddress, 0, 0, 0, 0);
          }
          ++currentAddress;
      }
  
      // Tell the frame to copy the row data if need be.
      if (repeatCount > 1)
          buffer.backingStore()->repeatFirstRow(IntRect(xBegin, yBegin, xEnd - xBegin , yEnd - yBegin));
  
      return true;
  }
  
  bool GIFImageDecoder::frameComplete(unsigned frameIndex, unsigned frameDuration, ImageFrame::DisposalMethod disposalMethod)
  {
      // Initialize the frame if necessary.  Some GIFs insert do-nothing frames,
      // in which case we never reach haveDecodedRow() before getting here.
      ImageFrame& buffer = m_frameBufferCache[frameIndex];
      if (buffer.isInvalid() && !initFrameBuffer(frameIndex))
          return false; // initFrameBuffer() has already called setFailed().
  
      buffer.setDecodingStatus(DecodingStatus::Complete);
      buffer.setDuration(Seconds::fromMilliseconds(frameDuration));
      buffer.setDisposalMethod(disposalMethod);
  
      if (!m_currentBufferSawAlpha) {
          IntRect rect = buffer.backingStore()->frameRect();
          
          // The whole frame was non-transparent, so it's possible that the entire
          // resulting buffer was non-transparent, and we can setHasAlpha(false).
          if (rect.contains(IntRect(IntPoint(), scaledSize())))
              buffer.setHasAlpha(false);
          else if (frameIndex) {
              // Tricky case.  This frame does not have alpha only if everywhere
              // outside its rect doesn't have alpha.  To know whether this is
              // true, we check the start state of the frame -- if it doesn't have
              // alpha, we're safe.
              //
              // First skip over prior DisposalMethod::RestoreToPrevious frames (since they
              // don't affect the start state of this frame) the same way we do in
              // initFrameBuffer().
              const ImageFrame* prevBuffer = &m_frameBufferCache[--frameIndex];
              while (frameIndex && (prevBuffer->disposalMethod() == ImageFrame::DisposalMethod::RestoreToPrevious))
                  prevBuffer = &m_frameBufferCache[--frameIndex];
  
              // Now, if we're at a DisposalMethod::Unspecified or DisposalMethod::DoNotDispose frame, then
              // we can say we have no alpha if that frame had no alpha.  But
              // since in initFrameBuffer() we already copied that frame's alpha
              // state into the current frame's, we need do nothing at all here.
              //
              // The only remaining case is a DisposalMethod::RestoreToBackground frame. If
              // it had no alpha, and its rect is contained in the current frame's
              // rect, we know the current frame has no alpha.
              IntRect prevRect = prevBuffer->backingStore()->frameRect();
              if ((prevBuffer->disposalMethod() == ImageFrame::DisposalMethod::RestoreToBackground) && !prevBuffer->hasAlpha() && rect.contains(prevRect))
                  buffer.setHasAlpha(false);
          }
      }
  
      return true;
  }
  
  void GIFImageDecoder::gifComplete()
  {
      // Cache the repetition count, which is now as authoritative as it's ever
      // going to be.
      repetitionCount();
  
      m_reader = nullptr;
  }
  
  void GIFImageDecoder::decode(unsigned haltAtFrame, GIFQuery query, bool allDataReceived)
  {
      if (failed())
          return;
  
      if (!m_reader) {
          m_reader = std::make_unique<GIFImageReader>(this);
          m_reader->setData(m_data.get());
      }
  
      if (query == GIFSizeQuery) {
          if (!m_reader->decode(GIFSizeQuery, haltAtFrame))
              setFailed();
          return;
      }
  
      if (!m_reader->decode(GIFFrameCountQuery, haltAtFrame)) {
          setFailed();
          return;
      }
  
      m_frameBufferCache.resize(m_reader->imagesCount());
  
      if (query == GIFFrameCountQuery)
          return;
  
      if (!m_reader->decode(GIFFullQuery, haltAtFrame)) {
          setFailed();
          return;
      }
  
      // It is also a fatal error if all data is received but we failed to decode
      // all frames completely.
      if (allDataReceived && haltAtFrame >= m_frameBufferCache.size() && m_reader)
          setFailed();
  }
  
  bool GIFImageDecoder::initFrameBuffer(unsigned frameIndex)
  {
      // Initialize the frame rect in our buffer.
      const GIFFrameContext* frameContext = m_reader->frameContext();
      IntRect frameRect(frameContext->xOffset, frameContext->yOffset, frameContext->width, frameContext->height);
      ImageFrame* const buffer = &m_frameBufferCache[frameIndex];
  
      if (!frameIndex) {
          // This is the first frame, so we're not relying on any previous data.
          if (!buffer->initialize(scaledSize(), m_premultiplyAlpha))
              return setFailed();
      } else {
          // The starting state for this frame depends on the previous frame's
          // disposal method.
          //
          // Frames that use the DisposalMethod::RestoreToPrevious method are effectively
          // no-ops in terms of changing the starting state of a frame compared to
          // the starting state of the previous frame, so skip over them.  (If the
          // first frame specifies this method, it will get treated like
          // DisposalMethod::RestoreToBackground below and reset to a completely empty image.)
          const ImageFrame* prevBuffer = &m_frameBufferCache[--frameIndex];
          ImageFrame::DisposalMethod prevMethod = prevBuffer->disposalMethod();
          while (frameIndex && (prevMethod == ImageFrame::DisposalMethod::RestoreToPrevious)) {
              prevBuffer = &m_frameBufferCache[--frameIndex];
              prevMethod = prevBuffer->disposalMethod();
          }
  
          ASSERT(prevBuffer->isComplete());
  
          if ((prevMethod == ImageFrame::DisposalMethod::Unspecified) || (prevMethod == ImageFrame::DisposalMethod::DoNotDispose)) {
              // Preserve the last frame as the starting state for this frame.
              if (!prevBuffer->backingStore() || !buffer->initialize(*prevBuffer->backingStore()))
                  return setFailed();
          } else {
              // We want to clear the previous frame to transparent, without
              // affecting pixels in the image outside of the frame.
              IntRect prevRect = prevBuffer->backingStore()->frameRect();
              const IntSize& bufferSize = scaledSize();
              if (!frameIndex || prevRect.contains(IntRect(IntPoint(), scaledSize()))) {
                  // Clearing the first frame, or a frame the size of the whole
                  // image, results in a completely empty image.
                  if (!buffer->initialize(bufferSize, m_premultiplyAlpha))
                      return setFailed();
              } else {
                  // Copy the whole previous buffer, then clear just its frame.
                  if (!prevBuffer->backingStore() || !buffer->initialize(*prevBuffer->backingStore()))
                      return setFailed();
                  buffer->backingStore()->clearRect(prevRect);
                  buffer->setHasAlpha(true);
              }
          }
      }
  
      // Make sure the frameRect doesn't extend outside the buffer.
      if (frameRect.maxX() > size().width())
          frameRect.setWidth(size().width() - frameContext->xOffset);
      if (frameRect.maxY() > size().height())
          frameRect.setHeight(size().height() - frameContext->yOffset);
  
      int left = upperBoundScaledX(frameRect.x());
      int right = lowerBoundScaledX(frameRect.maxX(), left);
      int top = upperBoundScaledY(frameRect.y());
      int bottom = lowerBoundScaledY(frameRect.maxY(), top);
      buffer->backingStore()->setFrameRect(IntRect(left, top, right - left, bottom - top));
  
      // Update our status to be partially complete.
      buffer->setDecodingStatus(DecodingStatus::Partial);
  
      // Reset the alpha pixel tracker for this frame.
      m_currentBufferSawAlpha = false;
      return true;
  }
  
  } // namespace WebCore
  