jpegimagedecoder.cpp

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                m_state = (m_info.buffered_image) ? JPEG_DECOMPRESS_PROGRESSIVE : JPEG_DECOMPRESS_SEQUENTIAL;
            }
    
            case JPEG_DECOMPRESS_SEQUENTIAL:
            {
                if (m_state == JPEG_DECOMPRESS_SEQUENTIAL) {
      
                    if (!m_decoder->outputScanlines())
                        return true; /* I/O suspension */
      
                    /* If we've completed image output ... */
                    assert(m_info.output_scanline == m_info.output_height);
                    m_state = JPEG_DONE;
                }
            }

            case JPEG_DECOMPRESS_PROGRESSIVE:
            {
                if (m_state == JPEG_DECOMPRESS_PROGRESSIVE) {
                    int status;
                    do {
                        status = jpeg_consume_input(&m_info);
                    } while ((status != JPEG_SUSPENDED) &&
                             (status != JPEG_REACHED_EOI));

                    for (;;) {
                        if (m_info.output_scanline == 0) {
                            int scan = m_info.input_scan_number;

                            /* if we haven't displayed anything yet (output_scan_number==0)
                            and we have enough data for a complete scan, force output
                            of the last full scan */
                            if ((m_info.output_scan_number == 0) &&
                                (scan > 1) &&
                                (status != JPEG_REACHED_EOI))
                                scan--;

                            if (!jpeg_start_output(&m_info, scan))
                                return true; /* I/O suspension */
                        }

                        if (m_info.output_scanline == 0xffffff)
                            m_info.output_scanline = 0;

                        if (!m_decoder->outputScanlines()) {
                            if (m_info.output_scanline == 0)
                                /* didn't manage to read any lines - flag so we don't call
                                jpeg_start_output() multiple times for the same scan */
                                m_info.output_scanline = 0xffffff;
                            return true; /* I/O suspension */
                        }

                        if (m_info.output_scanline == m_info.output_height) {
                            if (!jpeg_finish_output(&m_info))
                                return true; /* I/O suspension */

                            if (jpeg_input_complete(&m_info) &&
                                (m_info.input_scan_number == m_info.output_scan_number))
                                break;

                            m_info.output_scanline = 0;
                        }
                    }

                    m_state = JPEG_DONE;
                }
            }

            case JPEG_DONE:
            {
                /* Finish decompression */
                if (!jpeg_finish_decompress(&m_info))
                    return true; /* I/O suspension */

                m_state = JPEG_SINK_NON_JPEG_TRAILER;

                /* we're done */
                break;
            }
            
            case JPEG_SINK_NON_JPEG_TRAILER:
                break;

            case JPEG_ERROR:
                break;
        }

        return true;
    }

    jpeg_decompress_struct* info() { return &m_info; }
    JSAMPARRAY samples() const { return m_samples; }
    JPEGImageDecoder* decoder() { return m_decoder; }

private:
    JPEGImageDecoder* m_decoder;
    unsigned m_bufferLength;
    int m_bytesToSkip;
    bool m_decodingSizeOnly;
    bool m_initialized;

    jpeg_decompress_struct m_info;
    decoder_error_mgr m_err;
    jstate m_state;

    JSAMPARRAY m_samples;
};

/* Override the standard error method in the IJG JPEG decoder code. */
void error_exit(j_common_ptr cinfo)
{
    /* Return control to the setjmp point. */
    decoder_error_mgr *err = (decoder_error_mgr *) cinfo->err;
    longjmp(err->setjmp_buffer, -1);
}

void init_source(j_decompress_ptr jd)
{
}

void skip_input_data(j_decompress_ptr jd, long num_bytes)
{
    decoder_source_mgr *src = (decoder_source_mgr *)jd->src;
    src->decoder->skipBytes(num_bytes);
}

boolean fill_input_buffer(j_decompress_ptr jd)
{
    // Our decode step always sets things up properly, so if this method is ever
    // called, then we have hit the end of the buffer.  A return value of FALSE indicates
    // that we have no data to supply yet.
    return false;
}

void term_source (j_decompress_ptr jd)
{
    decoder_source_mgr *src = (decoder_source_mgr *)jd->src;
    src->decoder->decoder()->jpegComplete();
}

JPEGImageDecoder::JPEGImageDecoder()
: m_reader(0)
{}

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

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

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

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

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

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

    return m_sizeAvailable;
}

RGBA32Buffer* JPEGImageDecoder::frameBufferAtIndex(size_t index)
{
    if (index)
        return 0;

    if (m_frameBufferCache.isEmpty())
        m_frameBufferCache.resize(1);

    RGBA32Buffer& frame = m_frameBufferCache[0];
    if (frame.status() != RGBA32Buffer::FrameComplete && m_reader)
        // Decode this frame.
        decode();
    return &frame;
}

// Feed data to the JPEG reader.
void JPEGImageDecoder::decode(bool sizeOnly) const
{
    if (m_failed)
        return;

    m_failed = !m_reader->decode(m_data->buffer(), sizeOnly);

    if (m_failed || (!m_frameBufferCache.isEmpty() && m_frameBufferCache[0].status() == RGBA32Buffer::FrameComplete)) {
        delete m_reader;
        m_reader = 0;
    }
}

bool JPEGImageDecoder::outputScanlines()
{
    if (m_frameBufferCache.isEmpty())
        return false;

    // Resize to the width and height of the image.
    RGBA32Buffer& buffer = m_frameBufferCache[0];
    if (buffer.status() == RGBA32Buffer::FrameEmpty) {
        // Let's resize our buffer now to the correct width/height.
        RGBA32Array& bytes = buffer.bytes();
        bytes.resize(m_size.width() * m_size.height());

        // Update our status to be partially complete.
        buffer.setStatus(RGBA32Buffer::FramePartial);

        // For JPEGs, the frame always fills the entire image.
        buffer.setRect(IntRect(0, 0, m_size.width(), m_size.height()));

        // We don't have alpha (this is the default when the buffer is constructed).
    }

    jpeg_decompress_struct* info = m_reader->info();
    JSAMPARRAY samples = m_reader->samples();

    unsigned* dst = buffer.bytes().data() + info->output_scanline * m_size.width();
   
    while (info->output_scanline < info->output_height) {
        /* Request one scanline.  Returns 0 or 1 scanlines. */
        if (jpeg_read_scanlines(info, samples, 1) != 1)
            return false;
        JSAMPLE *j1 = samples[0];
        for (unsigned i = 0; i < info->output_width; ++i) {
            unsigned r = *j1++;
            unsigned g = *j1++;
            unsigned b = *j1++;
            RGBA32Buffer::setRGBA(*dst++, r, g, b, 0xFF);
        }

        buffer.ensureHeight(info->output_scanline);
    }

    return true;
}

void JPEGImageDecoder::jpegComplete()
{
    if (m_frameBufferCache.isEmpty())
        return;

    // Hand back an appropriately sized buffer, even if the image ended up being empty.
    RGBA32Buffer& buffer = m_frameBufferCache[0];
    buffer.setStatus(RGBA32Buffer::FrameComplete);
}

}

#endif // PLATFORM(CAIRO)