gecko-dev/image/decoders/nsIconDecoder.cpp

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 *   Bobby Holley <bobbyholley@gmail.com>
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#include "nsIconDecoder.h"
#include "nsIInputStream.h"
#include "RasterImage.h"
#include "imgIContainerObserver.h"
#include "nspr.h"
#include "nsRect.h"

#include "ImageErrors.h"

namespace mozilla {
namespace image {

nsIconDecoder::nsIconDecoder(RasterImage &aImage, imgIDecoderObserver* aObserver)
 : Decoder(aImage, aObserver),
   mWidth(-1),
   mHeight(-1),
   mPixBytesRead(0),
   mPixBytesTotal(0),
   mImageData(nsnull),
   mState(iconStateStart)
{
  // Nothing to do
}

nsIconDecoder::~nsIconDecoder()
{ }

void
nsIconDecoder::WriteInternal(const char *aBuffer, PRUint32 aCount)
{
  NS_ABORT_IF_FALSE(!HasError(), "Shouldn't call WriteInternal after error!");

  // We put this here to avoid errors about crossing initialization with case
  // jumps on linux.
  PRUint32 bytesToRead = 0;
  nsresult rv;

  // Performance isn't critical here, so our update rectangle is 
  // always the full icon
  nsIntRect r(0, 0, mWidth, mHeight);

  // Loop until the input data is gone
  while (aCount > 0) {
    switch (mState) {
      case iconStateStart:

        // Grab the width
        mWidth = (PRUint8)*aBuffer;

        // Book Keeping
        aBuffer++;
        aCount--;
        mState = iconStateHaveHeight;
        break;

      case iconStateHaveHeight:

        // Grab the Height
        mHeight = (PRUint8)*aBuffer;

        // Post our size to the superclass
        PostSize(mWidth, mHeight);
        if (HasError()) {
          // Setting the size lead to an error; this can happen when for example
          // a multipart channel sends an image of a different size.
          mState = iconStateFinished;
          return;
        }

        // If We're doing a size decode, we're done
        if (IsSizeDecode()) {
          mState = iconStateFinished;
          break;
        }

        // Add the frame and signal
        rv = mImage.EnsureFrame(0, 0, 0, mWidth, mHeight,
                                gfxASurface::ImageFormatARGB32,
                                &mImageData, &mPixBytesTotal);
        if (NS_FAILED(rv)) {
          PostDecoderError(rv);
          return;
        }

        // Tell the superclass we're starting a frame
        PostFrameStart();

        // Book Keeping
        aBuffer++;
        aCount--;
        mState = iconStateReadPixels;
        break;

      case iconStateReadPixels:

        // How many bytes are we reading?
        bytesToRead = NS_MIN(aCount, mPixBytesTotal - mPixBytesRead);

        // Copy the bytes
        memcpy(mImageData + mPixBytesRead, aBuffer, bytesToRead);

        // Invalidate
        PostInvalidation(r);

        // Book Keeping
        aBuffer += bytesToRead;
        aCount -= bytesToRead;
        mPixBytesRead += bytesToRead;

        // If we've got all the pixel bytes, we're finished
        if (mPixBytesRead == mPixBytesTotal) {
          PostFrameStop();
          PostDecodeDone();
          mState = iconStateFinished;
        }
        break;

      case iconStateFinished:

        // Consume all excess data silently
        aCount = 0;

        break;
    }
  }
}

} // namespace image
} // namespace mozilla