/* Perform Lempel-Ziv-Welch decoding */
bool
nsGIFDecoder2::DoLzw(const uint8_t *q)
{
if (!mGIFStruct.rows_remaining)
return true;
/* Copy all the decoder state variables into locals so the compiler
* won't worry about them being aliased. The locals will be homed
* back into the GIF decoder structure when we exit.
*/
int avail = mGIFStruct.avail;
int bits = mGIFStruct.bits;
int codesize = mGIFStruct.codesize;
int codemask = mGIFStruct.codemask;
int count = mGIFStruct.count;
int oldcode = mGIFStruct.oldcode;
const int clear_code = ClearCode();
uint8_t firstchar = mGIFStruct.firstchar;
int32_t datum = mGIFStruct.datum;
uint16_t *prefix = mGIFStruct.prefix;
uint8_t *stackp = mGIFStruct.stackp;
uint8_t *suffix = mGIFStruct.suffix;
uint8_t *stack = mGIFStruct.stack;
uint8_t *rowp = mGIFStruct.rowp;
uint32_t bpr = mGIFStruct.width;
if (!mGIFStruct.images_decoded)
bpr *= sizeof(uint32_t);
uint8_t *rowend = mImageData + (bpr * mGIFStruct.irow) + mGIFStruct.width;
#define OUTPUT_ROW() \
PR_BEGIN_MACRO \
if (!OutputRow()) \
goto END; \
rowp = mImageData + mGIFStruct.irow * bpr; \
rowend = rowp + mGIFStruct.width; \
PR_END_MACRO
for (const uint8_t* ch = q; count-- > 0; ch++)
{
/* Feed the next byte into the decoder's 32-bit input buffer. */
datum += ((int32_t) *ch) << bits;
bits += 8;
/* Check for underflow of decoder's 32-bit input buffer. */
while (bits >= codesize)
{
/* Get the leading variable-length symbol from the data stream */
int code = datum & codemask;
datum >>= codesize;
bits -= codesize;
/* Reset the dictionary to its original state, if requested */
if (code == clear_code) {
codesize = mGIFStruct.datasize + 1;
codemask = (1 << codesize) - 1;
avail = clear_code + 2;
oldcode = -1;
continue;
}
/* Check for explicit end-of-stream code */
if (code == (clear_code + 1)) {
/* end-of-stream should only appear after all image data */
return (mGIFStruct.rows_remaining == 0);
}
if (oldcode == -1) {
if (code >= MAX_BITS)
return false;
*rowp++ = suffix[code] & mColorMask; // ensure index is within colormap
if (rowp == rowend)
OUTPUT_ROW();
firstchar = oldcode = code;
continue;
}
int incode = code;
if (code >= avail) {
*stackp++ = firstchar;
code = oldcode;
if (stackp >= stack + MAX_BITS)
return false;
}
while (code >= clear_code)
{
if ((code >= MAX_BITS) || (code == prefix[code]))
return false;
*stackp++ = suffix[code];
code = prefix[code];
if (stackp == stack + MAX_BITS)
return false;
}
*stackp++ = firstchar = suffix[code];
/* Define a new codeword in the dictionary. */
if (avail < 4096) {
prefix[avail] = oldcode;
suffix[avail] = firstchar;
avail++;
/* If we've used up all the codewords of a given length
* increase the length of codewords by one bit, but don't
* exceed the specified maximum codeword size of 12 bits.
*/
if (((avail & codemask) == 0) && (avail < 4096)) {
codesize++;
codemask += avail;
}
}
oldcode = incode;
/* Copy the decoded data out to the scanline buffer. */
do {
*rowp++ = *--stackp & mColorMask; // ensure index is within colormap
if (rowp == rowend)
OUTPUT_ROW();
} while (stackp > stack);
}
}
END:
/* Home the local copies of the GIF decoder state variables */
mGIFStruct.avail = avail;
mGIFStruct.bits = bits;
mGIFStruct.codesize = codesize;
mGIFStruct.codemask = codemask;
mGIFStruct.count = count;
mGIFStruct.oldcode = oldcode;
mGIFStruct.firstchar = firstchar;
mGIFStruct.datum = datum;
mGIFStruct.stackp = stackp;
mGIFStruct.rowp = rowp;
return true;
}
void
nsGIFDecoder2::WriteInternal(const char *aBuffer, uint32_t aCount, DecodeStrategy)
{
NS_ABORT_IF_FALSE(!HasError(), "Shouldn't call WriteInternal after error!");
// These variables changed names, and 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 (IsSizeDecode()) {
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) { /* global map */
// 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;
// Some specs say 3rd bit (value 4), other specs say value 3
// Let's choose 3 (the more popular)
if (mGIFStruct.disposal_method == 4)
mGIFStruct.disposal_method = 3;
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:
{
/* 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 size decode, we're done
if (IsSizeDecode())
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);
BeginImageFrame(realDepth);
if (NeedsNewFrame()) {
// We now need a new frame from the decoder framework. We leave all our
// data in the buffer as if it wasn't consumed, copy to our hold and return
// to the decoder framework.
uint32_t size = len + mGIFStruct.bytes_to_consume + mGIFStruct.bytes_in_hold;
if (size) {
if (SetHold(q, mGIFStruct.bytes_to_consume + mGIFStruct.bytes_in_hold, buf, len)) {
// Back into the decoder infrastructure so we can get called again.
GETN(9, gif_image_header_continue);
return;
}
}
break;
} else {
// 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++;
}
if (q[8] & 0x80) /* has a local colormap? */
{
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(!IsSizeDecode(), "Size decodes shouldn't reach gif_done");
FinishInternal();
goto done;
case gif_error:
PostDataError();
return;
// We shouldn't ever get here.
default:
break;
}
}
// 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;
}
return;
}
nsresult nsGIFDecoder2::GifWrite(const PRUint8 *buf, PRUint32 len)
{
if (!buf || !len)
return NS_ERROR_FAILURE;
const PRUint8 *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
PRUint8* p = (mGIFStruct.state == gif_global_colormap) ? (PRUint8*)mGIFStruct.global_colormap :
(mGIFStruct.state == gif_image_colormap) ? (PRUint8*)mColormap :
(mGIFStruct.bytes_in_hold) ? mGIFStruct.hold : nsnull;
if (p) {
// Add what we have sofar to the block
PRUint32 l = PR_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 NS_OK;
}
// Reset hold buffer count
mGIFStruct.bytes_in_hold = 0;
// 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) {
// 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;
// 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) { /* global map */
// Get the global colormap
const PRUint32 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:
mGIFStruct.state = gif_control_extension;
break;
case GIF_APPLICATION_EXTENSION_LABEL:
mGIFStruct.state = gif_application_extension;
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;
// Some specs say 3rd bit (value 4), other specs say value 3
// Let's choose 3 (the more popular)
if (mGIFStruct.disposal_method == 4)
mGIFStruct.disposal_method = 3;
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 (!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)
GETN(*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);
/* Zero loop count is infinite animation loop request */
if (mGIFStruct.loop_count == 0)
mGIFStruct.loop_count = -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:
{
/* 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 we were doing header-only, we're done
if (mFlags & imgIDecoder::DECODER_FLAG_HEADERONLY)
return NS_OK;
}
/* 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 */
PRUint32 depth = mGIFStruct.global_colormap_depth;
if (q[8] & 0x80)
depth = (q[8]&0x07) + 1;
PRUint32 realDepth = depth;
while (mGIFStruct.tpixel >= (1 << realDepth) && (realDepth < 8)) {
realDepth++;
}
// Mask to limit the color values within the colormap
mColorMask = 0xFF >> (8 - realDepth);
nsresult rv = BeginImageFrame(realDepth);
if (NS_FAILED(rv) || !mImageData) {
mGIFStruct.state = gif_error;
break;
}
if (q[8] & 0x40) {
mGIFStruct.interlaced = PR_TRUE;
mGIFStruct.ipass = 1;
} else {
mGIFStruct.interlaced = PR_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;
/* bits per pixel is q[8]&0x07 */
if (q[8] & 0x80) /* has a local colormap? */
{
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(PRUint32) << realDepth;
if (!mGIFStruct.local_colormap) {
mGIFStruct.local_colormap = (PRUint32*)PR_MALLOC(mColormapSize);
if (!mGIFStruct.local_colormap) {
mGIFStruct.state = gif_oom;
break;
}
}
mColormap = mGIFStruct.local_colormap;
}
const PRUint32 size = 3 << depth;
if (mColormapSize > size) {
// Clear the notfilled part of the colormap
memset(((PRUint8*)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:
EndGIF(/* aSuccess = */ PR_TRUE);
return NS_OK;
break;
case gif_error:
EndGIF(/* aSuccess = */ PR_FALSE);
return NS_ERROR_FAILURE;
break;
// Handle out of memory errors
case gif_oom:
return NS_ERROR_OUT_OF_MEMORY;
// We shouldn't ever get here.
default:
break;
}
}
// if an error state is set but no data remains, code flow reaches here
if (mGIFStruct.state == gif_error) {
EndGIF(/* aSuccess = */ PR_FALSE);
return NS_ERROR_FAILURE;
}
// Copy the leftover into mGIFStruct.hold
mGIFStruct.bytes_in_hold = len;
if (len) {
// Add what we have sofar to the block
PRUint8* p = (mGIFStruct.state == gif_global_colormap) ? (PRUint8*)mGIFStruct.global_colormap :
(mGIFStruct.state == gif_image_colormap) ? (PRUint8*)mColormap :
mGIFStruct.hold;
memcpy(p, buf, len);
mGIFStruct.bytes_to_consume -= len;
}
return NS_OK;
}