#include "wx/gifdecod.h"
+//---------------------------------------------------------------------------
+// GIFImage constructor
+//---------------------------------------------------------------------------
+GIFImage::GIFImage()
+{
+ w = 0;
+ h = 0;
+ left = 0;
+ top = 0;
+ transparent = 0;
+ disposal = 0;
+ delay = -1;
+ p = (unsigned char *) NULL;
+ pal = (unsigned char *) NULL;
+ next = (GIFImage *) NULL;
+ prev = (GIFImage *) NULL;
+}
+
//---------------------------------------------------------------------------
// wxGIFDecoder constructor and destructor
//---------------------------------------------------------------------------
/* prefetch data */
m_f->Read((void *) m_buffer, m_restbyte);
+ if (m_f->LastRead() != m_restbyte)
+ {
+ code = ab_fin;
+ return code;
+ }
m_bufp = m_buffer;
}
// dgif:
// GIF decoding function. The initial code size (aka root size)
// is 'bits'. Supports interlaced images (interl == 1).
-//
+// Returns wxGIF_OK (== 0) on success, or an error code if something
+// fails (see header file for details)
int wxGIFDecoder::dgif(GIFImage *img, int interl, int bits)
{
- int *ab_prefix = new int[4096]; /* alphabet (prefixes) */
- int *ab_tail = new int[4096]; /* alphabet (tails) */
- int *stack = new int[4096]; /* decompression stack */
+ static const int allocSize = 4096 + 1;
+ int *ab_prefix = new int[allocSize]; /* alphabet (prefixes) */
+ if (ab_prefix == NULL)
+ {
+ return wxGIF_MEMERR;
+ }
+
+ int *ab_tail = new int[allocSize]; /* alphabet (tails) */
+ if (ab_tail == NULL)
+ {
+ delete[] ab_prefix;
+ return wxGIF_MEMERR;
+ }
+
+ int *stack = new int[allocSize]; /* decompression stack */
+ if (stack == NULL)
+ {
+ delete[] ab_prefix;
+ delete[] ab_tail;
+ return wxGIF_MEMERR;
+ }
+
int ab_clr; /* clear code */
int ab_fin; /* end of info code */
int ab_bits; /* actual symbol width, in bits */
{
stack[pos++] = ab_tail[code];
code = ab_prefix[code];
+
+ // Don't overflow. This shouldn't happen with normal
+ // GIF files, the allocSize of 4096+1 is enough. This
+ // will only happen with badly formed GIFs.
+ if (pos >= allocSize)
+ {
+ delete[] ab_prefix;
+ delete[] ab_tail;
+ delete[] stack;
+ return wxGIF_INVFORMAT;
+ }
}
+
+ if (pos >= allocSize)
+ {
+ delete[] ab_prefix;
+ delete[] ab_tail;
+ delete[] stack;
+ return wxGIF_INVFORMAT;
+ }
+
stack[pos] = code; /* push last code into the stack */
abcabca = code; /* save for special case */
}
}
- /* dump stack data to the buffer */
+ /* dump stack data to the image buffer */
while (pos >= 0)
{
- (img->p)[x + (y * (img->w))] = (char)stack[pos--];
+ (img->p)[x + (y * (img->w))] = (char) stack[pos];
+ pos--;
if (++x >= (img->w))
{
case 3: y += 4; break;
case 4: y += 2; break;
}
- if (y >= (img->h))
+
+ /* loop until a valid y coordinate has been
+ found, Or if the maximum number of passes has
+ been reached, exit the loop, and stop image
+ decoding (At this point the image is succesfully
+ decoded).
+ If we don't loop, but merely set y to some other
+ value, that new value might still be invalid depending
+ on the height of the image. This would cause out of
+ bounds writing.
+ */
+ while (y >= (img->h))
{
switch (++pass)
{
case 2: y = 4; break;
case 3: y = 2; break;
case 4: y = 1; break;
+
+ default:
+ /*
+ It's possible we arrive here. For example this
+ happens when the image is interlaced, and the
+ height is 1. Looking at the above cases, the
+ lowest possible y is 1. While the only valid
+ one would be 0 for an image of height 1. So
+ 'eventually' the loop will arrive here.
+ This case makes sure this while loop is
+ exited, as well as the 2 other ones.
+ */
+
+ // Set y to a valid coordinate so the local
+ // while loop will be exited. (y = 0 always
+ // is >= img->h since if img->h == 0 the
+ // image is never decoded)
+ y = 0;
+
+ // This will exit the other outer while loop
+ pos = -1;
+
+ // This will halt image decoding.
+ code = ab_fin;
+
+ break;
}
}
}
{
/* non-interlaced */
y++;
+/*
+Normally image decoding is finished when an End of Information code is
+encountered (code == ab_fin) however some broken encoders write wrong
+"block byte counts" (The first byte value after the "code size" byte),
+being one value too high. It might very well be possible other variants
+of this problem occur as well. The only sensible solution seems to
+be to check for clipping.
+Example of wrong encoding:
+(1 * 1 B/W image, raster data stream follows in hex bytes)
+
+02 << B/W images have a code size of 2
+02 << Block byte count
+44 << LZW packed
+00 << Zero byte count (terminates data stream)
+
+Because the block byte count is 2, the zero byte count is used in the
+decoding process, and decoding is continued after this byte. (While it
+should signal an end of image)
+
+It should be:
+02
+02
+44
+01 << When decoded this correctly includes the End of Information code
+00
+
+Or (Worse solution):
+02
+01
+44
+00
+(The 44 doesn't include an End of Information code, but at least the
+decoder correctly skips to 00 now after decoding, and signals this
+as an End of Information itself)
+*/
+ if (y >= img->h)
+ {
+ code = ab_fin;
+ break;
+ }
}
}
}
delete [] ab_tail ;
delete [] stack ;
- return 0;
+ return wxGIF_OK;
}
//
int wxGIFDecoder::ReadGIF()
{
- int ncolors, bits, interl, transparent, disposal, i;
+ unsigned int ncolors;
+ int bits, interl, transparent, disposal, i;
long size;
long delay;
unsigned char type = 0;
unsigned char pal[768];
unsigned char buf[16];
GIFImage **ppimg;
- GIFImage *pimg, *pprev;
+ GIFImage *pimg, *pprev;
/* check GIF signature */
if (!CanRead())
return wxGIF_INVFORMAT;
/* check for animated GIF support (ver. >= 89a) */
- m_f->Read(buf, 6);
+
+ static const size_t headerSize = (3 + 3);
+ m_f->Read(buf, headerSize);
+ if (m_f->LastRead() != headerSize)
+ {
+ return wxGIF_INVFORMAT;
+ }
if (memcmp(buf + 3, "89a", 3) < 0)
+ {
m_anim = FALSE;
+ }
/* read logical screen descriptor block (LSDB) */
- m_f->Read(buf, 7);
+ static const size_t lsdbSize = (2 + 2 + 1 + 1 + 1);
+ m_f->Read(buf, lsdbSize);
+ if (m_f->LastRead() != lsdbSize)
+ {
+ return wxGIF_INVFORMAT;
+ }
+
m_screenw = buf[0] + 256 * buf[1];
m_screenh = buf[2] + 256 * buf[3];
m_background = buf[5];
ncolors = 2 << (buf[4] & 0x07);
- m_f->Read(pal, 3 * ncolors);
+ size_t numBytes = 3 * ncolors;
+ m_f->Read(pal, numBytes);
+ if (m_f->LastRead() != numBytes)
+ {
+ return wxGIF_INVFORMAT;
+ }
}
/* transparent colour, disposal method and delay default to unused */
{
type = (unsigned char)m_f->GetC();
+ /*
+ If the end of file has been reached (or an error) and a ";"
+ (0x3B) hasn't been encountered yet, exit the loop. (Without this
+ check the while loop would loop endlessly.) Later on, in the next while
+ loop, the file will be treated as being truncated (But still
+ be decoded as far as possible). returning wxGIF_TRUNCATED is not
+ possible here since some init code is done after this loop.
+ */
+ if (m_f->Eof())// || !m_f->IsOk())
+ {
+ /*
+ type is set to some bogus value, so there's no
+ need to continue evaluating it.
+ */
+ break; // Alternative : "return wxGIF_INVFORMAT;"
+ }
+
/* end of data? */
if (type == 0x3B)
{
if (((unsigned char)m_f->GetC()) == 0xF9)
/* graphics control extension, parse it */
{
- m_f->Read(buf, 6);
+ static const size_t gceSize = 6;
+ m_f->Read(buf, gceSize);
+ if (m_f->LastRead() != gceSize)
+ {
+ Destroy();
+ return wxGIF_INVFORMAT;
+ }
/* read delay and convert from 1/100 of a second to ms */
delay = 10 * (buf[2] + 256 * buf[3]);
while ((i = (unsigned char)m_f->GetC()) != 0)
{
m_f->SeekI(i, wxFromCurrent);
+ if (m_f->Eof())
+ {
+ done = TRUE;
+ break;
+ }
}
}
}
}
/* fill in the data */
- m_f->Read(buf, 9);
+ static const size_t idbSize = (2 + 2 + 2 + 2 + 1);
+ m_f->Read(buf, idbSize);
+ if (m_f->LastRead() != idbSize)
+ {
+ Destroy();
+ return wxGIF_INVFORMAT;
+ }
+
pimg->left = buf[0] + 256 * buf[1];
pimg->top = buf[2] + 256 * buf[3];
/*
*/
pimg->w = buf[4] + 256 * buf[5];
pimg->h = buf[6] + 256 * buf[7];
+
+ if (pimg->w == 0 || pimg->h == 0)
+ {
+ Destroy();
+ return wxGIF_INVFORMAT;
+ }
+
interl = ((buf[8] & 0x40)? 1 : 0);
size = pimg->w * pimg->h;
if ((buf[8] & 0x80) == 0x80)
{
ncolors = 2 << (buf[8] & 0x07);
- m_f->Read(pimg->pal, 3 * ncolors);
+ size_t numBytes = 3 * ncolors;
+ m_f->Read(pimg->pal, numBytes);
+ if (m_f->LastRead() != numBytes)
+ {
+ Destroy();
+ return wxGIF_INVFORMAT;
+ }
}
else
+ {
memcpy(pimg->pal, pal, 768);
+ }
/* get initial code size from first byte in raster data */
bits = (unsigned char)m_f->GetC();
/* decode image */
- dgif(pimg, interl, bits);
+ int result = dgif(pimg, interl, bits);
+ if (result != wxGIF_OK)
+ {
+ Destroy();
+ return result;
+ }
m_nimages++;
/* if this is not an animated GIF, exit after first image */
}
}
- /* setup image pointers */
- if (m_nimages != 0)
+ if (m_nimages == 0)
{
- m_image = 1;
- m_plast = pimg;
- m_pimage = m_pfirst;
+ Destroy();
+ return wxGIF_INVFORMAT;
}
+ /* setup image pointers */
+ m_image = 1;
+ m_plast = pimg;
+ m_pimage = m_pfirst;
+
/* try to read to the end of the stream */
while (type != 0x3B)
{
if (!m_f->IsOk())
return wxGIF_TRUNCATED;
-
+
type = (unsigned char)m_f->GetC();
if (type == 0x21)
else if (type == 0x2C)
{
/* image descriptor block */
- m_f->Read(buf, 9);
+ static const size_t idbSize = (2 + 2 + 2 + 2 + 1);
+ m_f->Read(buf, idbSize);
+ if (m_f->LastRead() != idbSize)
+ {
+ Destroy();
+ return wxGIF_INVFORMAT;
+ }
/* local color map */
if ((buf[8] & 0x80) == 0x80)
{
ncolors = 2 << (buf[8] & 0x07);
- m_f->SeekI(3 * ncolors, wxFromCurrent);
+ off_t pos = m_f->TellI();
+ off_t numBytes = 3 * ncolors;
+ m_f->SeekI(numBytes, wxFromCurrent);
+ if (m_f->TellI() != (pos + numBytes))
+ {
+ Destroy();
+ return wxGIF_INVFORMAT;
+ }
}
/* initial code size */
projects / wxWidgets.git / blobdiff