void
Decoder::Init()
{
// No re-initializing
MOZ_ASSERT(!mInitialized, "Can't re-initialize a decoder!");
// It doesn't make sense to decode anything but the first frame if we can't
// store anything in the SurfaceCache, since only the last frame we decode
// will be retrievable.
MOZ_ASSERT(ShouldUseSurfaceCache() || IsFirstFrameDecode());
// Implementation-specific initialization
InitInternal();
mInitialized = true;
}
void
nsGIFDecoder2::WriteInternal(const char* aBuffer, uint32_t aCount)
{
MOZ_ASSERT(!HasError(), "Shouldn't call WriteInternal after error!");
// These variables changed names; renaming would make a much bigger patch :(
const uint8_t* buf = (const uint8_t*)aBuffer;
uint32_t len = aCount;
const uint8_t* q = buf;
// Add what we have sofar to the block
// If previous call to me left something in the hold first complete current
// block, or if we are filling the colormaps, first complete the colormap
uint8_t* p =
(mGIFStruct.state ==
gif_global_colormap) ? (uint8_t*) mGIFStruct.global_colormap :
(mGIFStruct.state == gif_image_colormap) ? (uint8_t*) mColormap :
(mGIFStruct.bytes_in_hold) ? mGIFStruct.hold : nullptr;
if (len == 0 && buf == nullptr) {
// We've just gotten the frame we asked for. Time to use the data we
// stashed away.
len = mGIFStruct.bytes_in_hold;
q = buf = p;
} else if (p) {
// Add what we have sofar to the block
uint32_t l = std::min(len, mGIFStruct.bytes_to_consume);
memcpy(p+mGIFStruct.bytes_in_hold, buf, l);
if (l < mGIFStruct.bytes_to_consume) {
// Not enough in 'buf' to complete current block, get more
mGIFStruct.bytes_in_hold += l;
mGIFStruct.bytes_to_consume -= l;
return;
}
// Point 'q' to complete block in hold (or in colormap)
q = p;
}
// Invariant:
// 'q' is start of current to be processed block (hold, colormap or buf)
// 'bytes_to_consume' is number of bytes to consume from 'buf'
// 'buf' points to the bytes to be consumed from the input buffer
// 'len' is number of bytes left in input buffer from position 'buf'.
// At entrance of the for loop will 'buf' will be moved 'bytes_to_consume'
// to point to next buffer, 'len' is adjusted accordingly.
// So that next round in for loop, q gets pointed to the next buffer.
for (;len >= mGIFStruct.bytes_to_consume; q=buf, mGIFStruct.bytes_in_hold = 0)
{
// Eat the current block from the buffer, q keeps pointed at current block
buf += mGIFStruct.bytes_to_consume;
len -= mGIFStruct.bytes_to_consume;
switch (mGIFStruct.state) {
case gif_lzw:
if (!DoLzw(q)) {
mGIFStruct.state = gif_error;
break;
}
GETN(1, gif_sub_block);
break;
case gif_lzw_start: {
// Make sure the transparent pixel is transparent in the colormap
if (mGIFStruct.is_transparent) {
// Save old value so we can restore it later
if (mColormap == mGIFStruct.global_colormap) {
mOldColor = mColormap[mGIFStruct.tpixel];
}
mColormap[mGIFStruct.tpixel] = 0;
}
// Initialize LZW parser/decoder
mGIFStruct.datasize = *q;
const int clear_code = ClearCode();
if (mGIFStruct.datasize > MAX_LZW_BITS ||
clear_code >= MAX_BITS) {
mGIFStruct.state = gif_error;
break;
}
mGIFStruct.avail = clear_code + 2;
mGIFStruct.oldcode = -1;
mGIFStruct.codesize = mGIFStruct.datasize + 1;
mGIFStruct.codemask = (1 << mGIFStruct.codesize) - 1;
mGIFStruct.datum = mGIFStruct.bits = 0;
// init the tables
for (int i = 0; i < clear_code; i++) {
mGIFStruct.suffix[i] = i;
}
mGIFStruct.stackp = mGIFStruct.stack;
GETN(1, gif_sub_block);
}
break;
// All GIF files begin with "GIF87a" or "GIF89a"
case gif_type:
if (!strncmp((char*)q, "GIF89a", 6)) {
mGIFStruct.version = 89;
} else if (!strncmp((char*)q, "GIF87a", 6)) {
mGIFStruct.version = 87;
} else {
mGIFStruct.state = gif_error;
break;
}
GETN(7, gif_global_header);
break;
case gif_global_header:
// This is the height and width of the "screen" or
// frame into which images are rendered. The
// individual images can be smaller than the
// screen size and located with an origin anywhere
// within the screen.
mGIFStruct.screen_width = GETINT16(q);
mGIFStruct.screen_height = GETINT16(q + 2);
mGIFStruct.global_colormap_depth = (q[4]&0x07) + 1;
if (IsMetadataDecode()) {
MOZ_ASSERT(!mGIFOpen, "Gif should not be open at this point");
PostSize(mGIFStruct.screen_width, mGIFStruct.screen_height);
return;
}
// screen_bgcolor is not used
//mGIFStruct.screen_bgcolor = q[5];
// q[6] = Pixel Aspect Ratio
// Not used
// float aspect = (float)((q[6] + 15) / 64.0);
if (q[4] & 0x80) {
// Get the global colormap
const uint32_t size = (3 << mGIFStruct.global_colormap_depth);
if (len < size) {
// Use 'hold' pattern to get the global colormap
GETN(size, gif_global_colormap);
break;
}
// Copy everything, go to colormap state to do CMS correction
memcpy(mGIFStruct.global_colormap, buf, size);
buf += size;
len -= size;
GETN(0, gif_global_colormap);
break;
}
GETN(1, gif_image_start);
break;
case gif_global_colormap:
// Everything is already copied into global_colormap
// Convert into Cairo colors including CMS transformation
ConvertColormap(mGIFStruct.global_colormap,
1<<mGIFStruct.global_colormap_depth);
GETN(1, gif_image_start);
break;
case gif_image_start:
switch (*q) {
case GIF_TRAILER:
mGIFStruct.state = gif_done;
break;
case GIF_EXTENSION_INTRODUCER:
GETN(2, gif_extension);
break;
case GIF_IMAGE_SEPARATOR:
GETN(9, gif_image_header);
break;
default:
// If we get anything other than GIF_IMAGE_SEPARATOR,
// GIF_EXTENSION_INTRODUCER, or GIF_TRAILER, there is extraneous data
// between blocks. The GIF87a spec tells us to keep reading
// until we find an image separator, but GIF89a says such
// a file is corrupt. We follow GIF89a and bail out.
if (mGIFStruct.images_decoded > 0) {
// The file is corrupt, but one or more images have
// been decoded correctly. In this case, we proceed
// as if the file were correctly terminated and set
// the state to gif_done, so the GIF will display.
mGIFStruct.state = gif_done;
} else {
// No images decoded, there is nothing to display.
mGIFStruct.state = gif_error;
}
}
break;
case gif_extension:
mGIFStruct.bytes_to_consume = q[1];
if (mGIFStruct.bytes_to_consume) {
switch (*q) {
case GIF_GRAPHIC_CONTROL_LABEL:
// The GIF spec mandates that the GIFControlExtension header block
// length is 4 bytes, and the parser for this block reads 4 bytes,
// so we must enforce that the buffer contains at least this many
// bytes. If the GIF specifies a different length, we allow that, so
// long as it's larger; the additional data will simply be ignored.
mGIFStruct.state = gif_control_extension;
mGIFStruct.bytes_to_consume =
std::max(mGIFStruct.bytes_to_consume, 4u);
break;
// The GIF spec also specifies the lengths of the following two
// extensions' headers (as 12 and 11 bytes, respectively). Because
// we ignore the plain text extension entirely and sanity-check the
// actual length of the application extension header before reading it,
// we allow GIFs to deviate from these values in either direction. This
// is important for real-world compatibility, as GIFs in the wild exist
// with application extension headers that are both shorter and longer
// than 11 bytes.
case GIF_APPLICATION_EXTENSION_LABEL:
mGIFStruct.state = gif_application_extension;
break;
case GIF_PLAIN_TEXT_LABEL:
mGIFStruct.state = gif_skip_block;
break;
case GIF_COMMENT_LABEL:
mGIFStruct.state = gif_consume_comment;
break;
default:
mGIFStruct.state = gif_skip_block;
}
} else {
GETN(1, gif_image_start);
}
break;
case gif_consume_block:
if (!*q) {
GETN(1, gif_image_start);
} else {
GETN(*q, gif_skip_block);
}
break;
case gif_skip_block:
GETN(1, gif_consume_block);
break;
case gif_control_extension:
mGIFStruct.is_transparent = *q & 0x1;
mGIFStruct.tpixel = q[3];
mGIFStruct.disposal_method = ((*q) >> 2) & 0x7;
if (mGIFStruct.disposal_method == 4) {
// Some specs say 3rd bit (value 4), other specs say value 3.
// Let's choose 3 (the more popular).
mGIFStruct.disposal_method = 3;
} else if (mGIFStruct.disposal_method > 4) {
// This GIF is using a disposal method which is undefined in the spec.
// Treat it as DisposalMethod::NOT_SPECIFIED.
mGIFStruct.disposal_method = 0;
}
{
DisposalMethod method = DisposalMethod(mGIFStruct.disposal_method);
if (method == DisposalMethod::CLEAR_ALL ||
method == DisposalMethod::CLEAR) {
// We may have to display the background under this image during
// animation playback, so we regard it as transparent.
PostHasTransparency();
}
}
mGIFStruct.delay_time = GETINT16(q + 1) * 10;
GETN(1, gif_consume_block);
break;
case gif_comment_extension:
if (*q) {
GETN(*q, gif_consume_comment);
} else {
GETN(1, gif_image_start);
}
break;
case gif_consume_comment:
GETN(1, gif_comment_extension);
break;
case gif_application_extension:
// Check for netscape application extension
if (mGIFStruct.bytes_to_consume == 11 &&
(!strncmp((char*)q, "NETSCAPE2.0", 11) ||
!strncmp((char*)q, "ANIMEXTS1.0", 11))) {
GETN(1, gif_netscape_extension_block);
} else {
GETN(1, gif_consume_block);
}
break;
// Netscape-specific GIF extension: animation looping
case gif_netscape_extension_block:
if (*q) {
// We might need to consume 3 bytes in
// gif_consume_netscape_extension, so make sure we have at least that.
GETN(std::max(3, static_cast<int>(*q)), gif_consume_netscape_extension);
} else {
GETN(1, gif_image_start);
}
break;
// Parse netscape-specific application extensions
case gif_consume_netscape_extension:
switch (q[0] & 7) {
case 1:
// Loop entire animation specified # of times. Only read the
// loop count during the first iteration.
mGIFStruct.loop_count = GETINT16(q + 1);
GETN(1, gif_netscape_extension_block);
break;
case 2:
// Wait for specified # of bytes to enter buffer
// Don't do this, this extension doesn't exist (isn't used at all)
// and doesn't do anything, as our streaming/buffering takes care
// of it all...
// See: http://semmix.pl/color/exgraf/eeg24.htm
GETN(1, gif_netscape_extension_block);
break;
default:
// 0,3-7 are yet to be defined netscape extension codes
mGIFStruct.state = gif_error;
}
break;
case gif_image_header: {
if (mGIFStruct.images_decoded > 0 && IsFirstFrameDecode()) {
// We're about to get a second frame, but we only want the first. Stop
// decoding now.
mGIFStruct.state = gif_done;
break;
}
// Get image offsets, with respect to the screen origin
mGIFStruct.x_offset = GETINT16(q);
mGIFStruct.y_offset = GETINT16(q + 2);
// Get image width and height.
mGIFStruct.width = GETINT16(q + 4);
mGIFStruct.height = GETINT16(q + 6);
if (!mGIFStruct.images_decoded) {
// Work around broken GIF files where the logical screen
// size has weird width or height. We assume that GIF87a
// files don't contain animations.
if ((mGIFStruct.screen_height < mGIFStruct.height) ||
(mGIFStruct.screen_width < mGIFStruct.width) ||
(mGIFStruct.version == 87)) {
mGIFStruct.screen_height = mGIFStruct.height;
mGIFStruct.screen_width = mGIFStruct.width;
mGIFStruct.x_offset = 0;
mGIFStruct.y_offset = 0;
}
// Create the image container with the right size.
BeginGIF();
if (HasError()) {
// Setting the size led to an error.
mGIFStruct.state = gif_error;
return;
}
// If we were doing a metadata decode, we're done.
if (IsMetadataDecode()) {
return;
}
}
// Work around more broken GIF files that have zero image width or height
if (!mGIFStruct.height || !mGIFStruct.width) {
mGIFStruct.height = mGIFStruct.screen_height;
mGIFStruct.width = mGIFStruct.screen_width;
if (!mGIFStruct.height || !mGIFStruct.width) {
mGIFStruct.state = gif_error;
break;
}
}
// Depth of colors is determined by colormap
// (q[8] & 0x80) indicates local colormap
// bits per pixel is (q[8]&0x07 + 1) when local colormap is set
uint32_t depth = mGIFStruct.global_colormap_depth;
if (q[8] & 0x80) {
depth = (q[8]&0x07) + 1;
}
uint32_t realDepth = depth;
while (mGIFStruct.tpixel >= (1 << realDepth) && (realDepth < 8)) {
realDepth++;
}
// Mask to limit the color values within the colormap
mColorMask = 0xFF >> (8 - realDepth);
if (NS_FAILED(BeginImageFrame(realDepth))) {
mGIFStruct.state = gif_error;
return;
}
// FALL THROUGH
}
case gif_image_header_continue: {
// While decoders can reuse frames, we unconditionally increment
// mGIFStruct.images_decoded when we're done with a frame, so we both can
// and need to zero out the colormap and image data after every new frame.
memset(mImageData, 0, mImageDataLength);
if (mColormap) {
memset(mColormap, 0, mColormapSize);
}
if (!mGIFStruct.images_decoded) {
// Send a onetime invalidation for the first frame if it has a y-axis
// offset. Otherwise, the area may never be refreshed and the
// placeholder will remain on the screen. (Bug 37589)
if (mGIFStruct.y_offset > 0) {
nsIntRect r(0, 0, mGIFStruct.screen_width, mGIFStruct.y_offset);
PostInvalidation(r);
}
}
if (q[8] & 0x40) {
mGIFStruct.interlaced = true;
mGIFStruct.ipass = 1;
} else {
mGIFStruct.interlaced = false;
mGIFStruct.ipass = 0;
}
// Only apply the Haeberli display hack on the first frame
mGIFStruct.progressive_display = (mGIFStruct.images_decoded == 0);
// Clear state from last image
mGIFStruct.irow = 0;
mGIFStruct.rows_remaining = mGIFStruct.height;
mGIFStruct.rowp = mImageData;
// Depth of colors is determined by colormap
// (q[8] & 0x80) indicates local colormap
// bits per pixel is (q[8]&0x07 + 1) when local colormap is set
uint32_t depth = mGIFStruct.global_colormap_depth;
if (q[8] & 0x80) {
depth = (q[8]&0x07) + 1;
}
uint32_t realDepth = depth;
while (mGIFStruct.tpixel >= (1 << realDepth) && (realDepth < 8)) {
realDepth++;
}
// has a local colormap?
if (q[8] & 0x80) {
mGIFStruct.local_colormap_size = 1 << depth;
if (!mGIFStruct.images_decoded) {
// First frame has local colormap, allocate space for it
// as the image frame doesn't have its own palette
mColormapSize = sizeof(uint32_t) << realDepth;
if (!mGIFStruct.local_colormap) {
mGIFStruct.local_colormap = (uint32_t*)moz_xmalloc(mColormapSize);
}
mColormap = mGIFStruct.local_colormap;
}
const uint32_t size = 3 << depth;
if (mColormapSize > size) {
// Clear the notfilled part of the colormap
memset(((uint8_t*)mColormap) + size, 0, mColormapSize - size);
}
if (len < size) {
// Use 'hold' pattern to get the image colormap
GETN(size, gif_image_colormap);
break;
}
// Copy everything, go to colormap state to do CMS correction
memcpy(mColormap, buf, size);
buf += size;
len -= size;
GETN(0, gif_image_colormap);
break;
} else {
// Switch back to the global palette
if (mGIFStruct.images_decoded) {
// Copy global colormap into the palette of current frame
memcpy(mColormap, mGIFStruct.global_colormap, mColormapSize);
} else {
mColormap = mGIFStruct.global_colormap;
}
}
GETN(1, gif_lzw_start);
}
break;
case gif_image_colormap:
// Everything is already copied into local_colormap
// Convert into Cairo colors including CMS transformation
ConvertColormap(mColormap, mGIFStruct.local_colormap_size);
GETN(1, gif_lzw_start);
break;
case gif_sub_block:
mGIFStruct.count = *q;
if (mGIFStruct.count) {
// Still working on the same image: Process next LZW data block
// Make sure there are still rows left. If the GIF data
// is corrupt, we may not get an explicit terminator.
if (!mGIFStruct.rows_remaining) {
#ifdef DONT_TOLERATE_BROKEN_GIFS
mGIFStruct.state = gif_error;
break;
#else
// This is an illegal GIF, but we remain tolerant.
GETN(1, gif_sub_block);
#endif
if (mGIFStruct.count == GIF_TRAILER) {
// Found a terminator anyway, so consider the image done
GETN(1, gif_done);
break;
}
}
GETN(mGIFStruct.count, gif_lzw);
} else {
// See if there are any more images in this sequence.
EndImageFrame();
GETN(1, gif_image_start);
}
break;
case gif_done:
MOZ_ASSERT(!IsMetadataDecode(),
"Metadata decodes shouldn't reach gif_done");
FinishInternal();
goto done;
case gif_error:
PostDataError();
return;
// We shouldn't ever get here.
default:
MOZ_ASSERT_UNREACHABLE("Unexpected mGIFStruct.state");
PostDecoderError(NS_ERROR_UNEXPECTED);
return;
}
}
// if an error state is set but no data remains, code flow reaches here
if (mGIFStruct.state == gif_error) {
PostDataError();
return;
}
// Copy the leftover into mGIFStruct.hold
if (len) {
// Add what we have sofar to the block
if (mGIFStruct.state != gif_global_colormap &&
mGIFStruct.state != gif_image_colormap) {
if (!SetHold(buf, len)) {
PostDataError();
return;
}
} else {
uint8_t* p = (mGIFStruct.state == gif_global_colormap) ?
(uint8_t*)mGIFStruct.global_colormap :
(uint8_t*)mColormap;
memcpy(p, buf, len);
mGIFStruct.bytes_in_hold = len;
}
mGIFStruct.bytes_to_consume -= len;
}
// We want to flush before returning if we're on the first frame
done:
if (!mGIFStruct.images_decoded) {
FlushImageData();
mLastFlushedRow = mCurrentRow;
mLastFlushedPass = mCurrentPass;
}
}
