// Name: gifdecod.cpp
// Purpose: wxGIFDecoder, GIF reader for wxImage and wxAnimation
// Author: Guillermo Rodriguez Garcia <guille@iies.es>
-// Version: 3.01
-// Last rev: 1999/08/14
+// Version: 3.04
+// RCS-ID: $Id$
// Copyright: (c) Guillermo Rodriguez Garcia
// Licence: wxWindows licence
/////////////////////////////////////////////////////////////////////////////
#endif
#ifndef WX_PRECOMP
-# include "wx/setup.h"
+# include "wx/defs.h"
#endif
-#if wxUSE_STREAMS
+#if wxUSE_STREAMS && wxUSE_GIF
#include <stdlib.h>
#include <string.h>
-#include "wx/defs.h"
#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
wxGIFDecoder::wxGIFDecoder(wxInputStream *s, bool anim)
{
- m_f = s;
+ m_f = s;
m_anim = anim;
m_background = -1;
void wxGIFDecoder::Destroy()
{
- IMAGEN *pimg, *paux;
+ GIFImage *pimg, *paux;
pimg = m_pfirst;
paux = pimg->next;
free(pimg->p);
free(pimg->pal);
- free(pimg);
+ delete pimg;
pimg = paux;
}
+
+ m_pimage = NULL;
+ m_pfirst = NULL;
+ m_plast = NULL;
+ m_image = 0;
+ m_nimages = 0;
}
unsigned long i;
int transparent;
+ /* just in case... */
+ image->Destroy();
+
/* create the image */
image->Create(GetWidth(), GetHeight());
else
image->SetMask(FALSE);
+#if wxUSE_PALETTE
+ if (pal)
+ {
+ unsigned char r[256];
+ unsigned char g[256];
+ unsigned char b[256];
+
+ for (i = 0; i < 256; i++)
+ {
+ r[i] = pal[3*i + 0];
+ g[i] = pal[3*i + 1];
+ b[i] = pal[3*i + 2];
+ }
+
+ image->SetPalette(wxPalette(256, r, g, b));
+ }
+#endif // wxUSE_PALETTE
+
/* copy image data */
for (i = 0; i < (GetWidth() * GetHeight()); i++, src++)
{
return TRUE;
}
-
+
//---------------------------------------------------------------------------
// Data accessors
//---------------------------------------------------------------------------
}
else
return FALSE;
-}
+}
bool wxGIFDecoder::GoPrevFrame(bool cyclic)
{
code = ab_fin;
break;
}
+
+ /* 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;
}
/* read next byte and isolate the bits we need */
- m_lastbyte = (unsigned char)m_f->GetC();
+ m_lastbyte = (unsigned char) (*m_bufp++);
mask = (1 << (bits - m_restbits)) - 1;
code = code + ((m_lastbyte & mask) << m_restbits);
m_restbyte--;
/* adjust total number of bits extracted from the buffer */
m_restbits = m_restbits + 8;
}
-
+
/* find number of bits remaining for next code */
m_restbits = (m_restbits - bits);
// dgif:
// GIF decoding function. The initial code size (aka root size)
// is 'bits'. Supports interlaced images (interl == 1).
-//
-int wxGIFDecoder::dgif(IMAGEN *img, int interl, int bits)
+// 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[4096]; /* alphabet (prefixes) */
- int ab_tail[4096]; /* alphabet (tails) */
- int stack[4096]; /* decompression stack */
-
- int ab_clr; /* clear code */
- int ab_fin; /* end of info code */
- int ab_bits; /* actual symbol width, in bits */
- int ab_free; /* first free position in alphabet */
- int ab_max; /* last possible character in alphabet */
- int pass; /* pass number in interlaced images */
- int pos; /* index into decompresion stack */
- unsigned int x, y; /* position in image buffer */
+ 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 */
+ int ab_free; /* first free position in alphabet */
+ int ab_max; /* last possible character in alphabet */
+ int pass; /* pass number in interlaced images */
+ int pos; /* index into decompresion stack */
+ unsigned int x, y; /* position in image buffer */
int code, readcode, lastcode, abcabca;
pass = 1;
pos = x = y = 0;
- /* reset static globals */
+ /* reset decoder vars */
m_restbits = 0;
m_restbyte = 0;
m_lastbyte = 0;
{
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;
+ }
}
}
}
}
while (code != ab_fin);
- return 0;
+ delete [] ab_prefix ;
+ delete [] ab_tail ;
+ delete [] stack ;
+
+ return wxGIF_OK;
+}
+
+
+// CanRead:
+// Returns TRUE if the file looks like a valid GIF, FALSE otherwise.
+//
+bool wxGIFDecoder::CanRead()
+{
+ unsigned char buf[3];
+
+ m_f->Read(buf, 3);
+ m_f->SeekI(-3, wxFromCurrent);
+
+ return (memcmp(buf, "GIF", 3) == 0);
}
// animated GIF support is enabled. Can read GIFs with any bit
// size (color depth), but the output images are always expanded
// to 8 bits per pixel. Also, the image palettes always contain
-// 256 colors, although some of them may be unused. Returns E_OK
-// (== 0) on success, or an error code if something fails. Error
-// codes are E_ARCHIVO, E_FORMATO, E_MEMORIA (see header file).
+// 256 colors, although some of them may be unused. Returns wxGIF_OK
+// (== 0) on success, or an error code if something fails (see
+// header file for details)
//
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;
+ unsigned char type = 0;
unsigned char pal[768];
unsigned char buf[16];
- IMAGEN **ppimg, *pimg, *pprev;
+ GIFImage **ppimg;
+ GIFImage *pimg, *pprev;
+ /* check GIF signature */
+ if (!CanRead())
+ return wxGIF_INVFORMAT;
- /* check GIF signature and animated GIF support (ver. >= 89a) */
- m_f->Read(buf, 6);
+ /* check for animated GIF support (ver. >= 89a) */
- if (memcmp(buf, "GIF", 3) != 0)
- return E_FORMATO;
+ 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 */
pprev = NULL;
pimg = NULL;
- while (1)
+ bool done = FALSE;
+
+ while(!done)
{
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)
- break;
-
+ {
+ done = TRUE;
+ }
+ else
/* extension block? */
if (type == 0x21)
{
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]);
}
else
/* other extension, skip */
- {
+ {
while ((i = (unsigned char)m_f->GetC()) != 0)
{
- /* This line should not be neccessary!
- * Some images are not loaded correctly
- * without it. A bug in wxStream?
- */
- // m_f->SeekI(m_f->TellI(), wxFromStart);
m_f->SeekI(i, wxFromCurrent);
+ if (m_f->Eof())
+ {
+ done = TRUE;
+ break;
+ }
}
}
}
-
+ else
/* image descriptor block? */
if (type == 0x2C)
{
/* allocate memory for IMAGEN struct */
- pimg = (*ppimg) = (IMAGEN *) malloc(sizeof(IMAGEN));
+ pimg = (*ppimg) = new GIFImage();
if (pimg == NULL)
{
Destroy();
- return E_MEMORIA;
+ return wxGIF_MEMERR;
}
/* 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->left = buf[4] + 256 * buf[5];
pimg->top = buf[4] + 256 * buf[5];
+*/
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;
ppimg = &pimg->next;
/* allocate memory for image and palette */
- pimg->p = (unsigned char *) malloc(size);
+ pimg->p = (unsigned char *) malloc((size_t)size);
pimg->pal = (unsigned char *) malloc(768);
if ((!pimg->p) || (!pimg->pal))
{
Destroy();
- return E_MEMORIA;
+ return wxGIF_MEMERR;
}
/* load local color map if available, else use global map */
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 */
+ if (!m_anim)
+ done = TRUE;
}
+ }
- /* if we have one image and no animated GIF support, exit */
- if (m_nimages == 1 && !m_anim)
- break;
+ if (m_nimages == 0)
+ {
+ Destroy();
+ return wxGIF_INVFORMAT;
}
- /* finish successfully :-) */
- if (m_nimages != 0)
+ /* 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)
{
- m_image = 1;
- m_plast = pimg;
- m_pimage = m_pfirst;
+ if (!m_f->IsOk())
+ return wxGIF_TRUNCATED;
+
+ type = (unsigned char)m_f->GetC();
+
+ if (type == 0x21)
+ {
+ /* extension type */
+ (void) m_f->GetC();
+
+ /* skip all data */
+ while ((i = (unsigned char)m_f->GetC()) != 0)
+ {
+ m_f->SeekI(i, wxFromCurrent);
+ }
+ }
+ else if (type == 0x2C)
+ {
+ /* image descriptor block */
+ 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);
+ 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 */
+ (void) m_f->GetC();
+
+ /* skip all data */
+ while ((i = (unsigned char)m_f->GetC()) != 0)
+ {
+ m_f->SeekI(i, wxFromCurrent);
+ }
+ }
+ else if ((type != 0x3B) && (type != 00)) /* testing */
+ {
+ /* images are OK, but couldn't read to the end of the stream */
+ return wxGIF_TRUNCATED;
+ }
}
- return E_OK;
+ return wxGIF_OK;
}
-#endif // wxUSE_STREAM
+#endif // wxUSE_STREAMS && wxUSE_GIF
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