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Fixed gifInfo function
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Laurence Bank authored and Laurence Bank committed Jan 2, 2022
1 parent 9889e73 commit c627564
Showing 1 changed file with 67 additions and 22 deletions.
89 changes: 67 additions & 22 deletions src/gif.inl
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Original file line number Diff line number Diff line change
Expand Up @@ -526,6 +526,8 @@ int GIF_getInfo(GIFIMAGE *pPage, GIFINFO *pInfo)
cBuf = (uint8_t *) pPage->ucFileBuf;
(*pPage->pfnSeek)(&pPage->GIFFile, 0);
iDataAvailable = (*pPage->pfnRead)(&pPage->GIFFile, cBuf, FILE_BUF_SIZE);
iDataRemaining -= iDataAvailable;
lFileOff += iDataAvailable;
iOff = 10;
c = cBuf[iOff]; // get info bits
iOff += 3; /* Skip flags, background color & aspect ratio */
Expand All @@ -539,6 +541,16 @@ int GIF_getInfo(GIFIMAGE *pPage, GIFINFO *pInfo)
bExt = 1; /* skip extension blocks */
while (bExt && iOff < iDataAvailable)
{
if ((iDataAvailable - iOff) < 258) // need to read more data first
{
memcpy(cBuf, &cBuf[iOff], (iDataAvailable-iOff)); // move existing data down
iDataAvailable -= iOff;
iOff = 0;
iReadAmount = (*pPage->pfnRead)(&pPage->GIFFile, &cBuf[iDataAvailable], FILE_BUF_SIZE-iDataAvailable);
iDataAvailable += iReadAmount;
iDataRemaining -= iReadAmount;
lFileOff += iReadAmount;
}
switch(cBuf[iOff])
{
case 0x3b: /* End of file */
Expand Down Expand Up @@ -568,10 +580,20 @@ int GIF_getInfo(GIFIMAGE *pPage, GIFINFO *pInfo)
iOff++;
// block terminator or optional sub blocks
c = cBuf[iOff++]; /* Skip any sub-blocks */
while (c && iOff < (iDataAvailable - c))
{
iOff += (int)c;
c = cBuf[iOff++];
while (c)
{
iOff += (int)c;
c = cBuf[iOff++];
if ((iDataAvailable - iOff) < (c+258)) // need to read more data first
{
memcpy(cBuf, &cBuf[iOff], (iDataAvailable-iOff)); // move existing data down
iDataAvailable -= iOff;
iOff = 0;
iReadAmount = (*pPage->pfnRead)(&pPage->GIFFile, &cBuf[iDataAvailable], FILE_BUF_SIZE-iDataAvailable);
iDataAvailable += iReadAmount;
iDataRemaining -= iReadAmount;
lFileOff += iReadAmount;
}
}
if (c != 0) // problem, we went past the end
{
Expand Down Expand Up @@ -602,28 +624,47 @@ int GIF_getInfo(GIFIMAGE *pPage, GIFINFO *pInfo)
iOff += (2<<c)*3;
}
iOff++; /* Skip LZW code size byte */
if ((iDataAvailable - iOff) < (c+258)) // need to read more data first
{
if (iOff < iDataAvailable) {
memcpy(cBuf, &cBuf[iOff], (iDataAvailable-iOff)); // move existing data down
iDataAvailable -= iOff;
iOff = 0;
} else { // already points beyond end
iOff -= iDataAvailable;
iDataAvailable = 0;
}
iReadAmount = (*pPage->pfnRead)(&pPage->GIFFile, &cBuf[iDataAvailable], FILE_BUF_SIZE-iDataAvailable);
iDataAvailable += iReadAmount;
iDataRemaining -= iReadAmount;
lFileOff += iReadAmount;
}
c = cBuf[iOff++];
while (c) /* While there are more data blocks */
{
if (iOff > (3*FILE_BUF_SIZE/4) && iDataRemaining > 0) /* Near end of buffer, re-align */
{
lFileOff += iOff; /* adjust total file pointer */
iDataRemaining -= iOff;
iReadAmount = (iDataRemaining > FILE_BUF_SIZE) ? FILE_BUF_SIZE:iDataRemaining;
(*pPage->pfnSeek)(&pPage->GIFFile, lFileOff);
iDataAvailable = (*pPage->pfnRead)(&pPage->GIFFile, cBuf, iReadAmount);
iOff = 0; /* Start at beginning of buffer */
memcpy(cBuf, &cBuf[iOff], (iDataAvailable-iOff)); // move existing data down
iDataAvailable -= iOff;
iOff = 0;
iReadAmount = (FILE_BUF_SIZE - iDataAvailable);
if (iReadAmount > iDataRemaining)
iReadAmount = iDataRemaining;
iReadAmount = (*pPage->pfnRead)(&pPage->GIFFile, &cBuf[iDataAvailable], iReadAmount);
iDataAvailable += iReadAmount;
iDataRemaining -= iReadAmount;
lFileOff += iReadAmount;
}
iOff += (int)c; /* Skip this data block */
if ((int)lFileOff + iOff > pPage->GIFFile.iSize) // past end of file, stop
{
iNumFrames--; // don't count this page
break; // last page is corrupted, don't use it
}
// if ((int)lFileOff + iOff > pPage->GIFFile.iSize) // past end of file, stop
// {
// iNumFrames--; // don't count this page
// break; // last page is corrupted, don't use it
// }
c = cBuf[iOff++]; /* Get length of next */
}
/* End of image data, check for more pages... */
if (((int)lFileOff + iOff > pPage->GIFFile.iSize) || cBuf[iOff] == 0x3b)
if (cBuf[iOff] == 0x3b || (iDataRemaining == 0 && (iDataAvailable - iOff) < 32))
{
bDone = 1; /* End of file has been reached */
}
Expand All @@ -633,12 +674,16 @@ int GIF_getInfo(GIFIMAGE *pPage, GIFINFO *pInfo)
// read new page data starting at this offset
if (pPage->GIFFile.iSize > FILE_BUF_SIZE && iDataRemaining > 0) // since we didn't read the whole file in one shot
{
lFileOff += iOff; /* adjust total file pointer */
iDataRemaining -= iOff;
iReadAmount = (iDataRemaining > FILE_BUF_SIZE) ? FILE_BUF_SIZE : iDataRemaining;
(*pPage->pfnSeek)(&pPage->GIFFile, lFileOff);
iDataAvailable = (*pPage->pfnRead)(&pPage->GIFFile, cBuf, iReadAmount);
iOff = 0; /* Start at beginning of buffer */
memcpy(cBuf, &cBuf[iOff], (iDataAvailable-iOff)); // move existing data down
iDataAvailable -= iOff;
iOff = 0;
iReadAmount = (FILE_BUF_SIZE - iDataAvailable);
if (iReadAmount > iDataRemaining)
iReadAmount = iDataRemaining;
iReadAmount = (*pPage->pfnRead)(&pPage->GIFFile, &cBuf[iDataAvailable], iReadAmount);
iDataAvailable += iReadAmount;
iDataRemaining -= iReadAmount;
lFileOff += iReadAmount;
}
}
} /* while !bDone */
Expand Down

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