X-Git-Url: https://git.saurik.com/wxWidgets.git/blobdiff_plain/9d0e21da25f89fa7eb269aee5db8d656d2da9c7c..55c020cf641a1e9db2e21a89aa62f85f4f23bc87:/src/common/gifdecod.cpp?ds=sidebyside

diff --git a/src/common/gifdecod.cpp b/src/common/gifdecod.cpp
index 3345366d7b..78344a08c1 100644
--- a/src/common/gifdecod.cpp
+++ b/src/common/gifdecod.cpp
@@ -36,7 +36,7 @@
 
 wxGIFDecoder::wxGIFDecoder(wxInputStream *s, bool anim)
 {
-    m_f = s;
+    m_f    = s;
     m_anim = anim;
 
     m_background = -1;
@@ -57,18 +57,24 @@ wxGIFDecoder::~wxGIFDecoder()
 
 void wxGIFDecoder::Destroy()
 {
-    IMAGEN *pimg, *paux;
+    GIFImage *pimg, *paux;
 
     pimg = m_pfirst;
 
     while (pimg != NULL)
     {
-        paux = pimg->next;
-        free(pimg->p);
-        free(pimg->pal);
-        free(pimg);
-        pimg = paux;
+	paux = pimg->next;
+	free(pimg->p);
+	free(pimg->pal);
+	delete pimg;
+	pimg = paux;
     }
+
+    m_pimage  = NULL;
+    m_pfirst  = NULL;
+    m_plast   = NULL;
+    m_image   = 0;
+    m_nimages = 0;
 }
 
 
@@ -91,7 +97,7 @@ bool wxGIFDecoder::ConvertToImage(wxImage *image) const
     image->Create(GetWidth(), GetHeight());
 
     if (!image->Ok())
-        return FALSE;
+	return FALSE;
 
     pal = GetPalette();
     src = GetData();
@@ -101,31 +107,46 @@ bool wxGIFDecoder::ConvertToImage(wxImage *image) const
     /* set transparent colour mask */
     if (transparent != -1)
     {
-        for (i = 0; i < 256; i++)
-        {
-            if ((pal[3 * i + 0] == 255) &&
-                (pal[3 * i + 1] == 0) &&
-                (pal[3 * i + 2] == 255))
-            {
-                pal[3 * i + 2] = 254;
-            }
-        }
-
-        pal[3 * transparent + 0] = 255,
-        pal[3 * transparent + 1] = 0,
-        pal[3 * transparent + 2] = 255;
-
-        image->SetMaskColour(255, 0, 255);
+	for (i = 0; i < 256; i++)
+	{
+	    if ((pal[3 * i + 0] == 255) &&
+		(pal[3 * i + 1] == 0) &&
+		(pal[3 * i + 2] == 255))
+	    {
+		pal[3 * i + 2] = 254;
+	    }
+	}
+
+	pal[3 * transparent + 0] = 255,
+	pal[3 * transparent + 1] = 0,
+	pal[3 * transparent + 2] = 255;
+
+	image->SetMaskColour(255, 0, 255);
     }
     else
-        image->SetMask(FALSE);
+	image->SetMask(FALSE);
+
+    if (pal)
+    {
+	unsigned char* r = new unsigned char[256];
+	unsigned char* g = new unsigned char[256];
+	unsigned char* b = new unsigned char[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));
+	delete[] r; delete[] g; delete[] b;
+    }
 
     /* copy image data */
     for (i = 0; i < (GetWidth() * GetHeight()); i++, src++)
     {
-        *(dst++) = pal[3 * (*src) + 0];
-        *(dst++) = pal[3 * (*src) + 1];
-        *(dst++) = pal[3 * (*src) + 2];
+	*(dst++) = pal[3 * (*src) + 0];
+	*(dst++) = pal[3 * (*src) + 1];
+	*(dst++) = pal[3 * (*src) + 2];
     }
 
     return TRUE;
@@ -165,7 +186,7 @@ bool wxGIFDecoder::IsAnimation() const          { return (m_nimages > 1); }
 bool wxGIFDecoder::GoFirstFrame()
 {
     if (!IsAnimation())
-        return FALSE;
+	return FALSE;
 
     m_image = 1;
     m_pimage = m_pfirst;
@@ -175,7 +196,7 @@ bool wxGIFDecoder::GoFirstFrame()
 bool wxGIFDecoder::GoLastFrame()
 {
     if (!IsAnimation())
-        return FALSE;
+	return FALSE;
 
     m_image = m_nimages;
     m_pimage = m_plast;
@@ -185,45 +206,45 @@ bool wxGIFDecoder::GoLastFrame()
 bool wxGIFDecoder::GoNextFrame(bool cyclic)
 {
     if (!IsAnimation())
-        return FALSE;
+	return FALSE;
 
     if ((m_image < m_nimages) || (cyclic))
     {
-        m_pimage = m_pimage->next;
-        m_image++;
+	m_pimage = m_pimage->next;
+	m_image++;
 
-        if (!m_pimage)
-        {
-            m_image = 1;
-            m_pimage = m_pfirst;
-        }
+	if (!m_pimage)
+	{
+	    m_image = 1;
+	    m_pimage = m_pfirst;
+	}
 
-        return TRUE;
+	return TRUE;
     }
     else
-        return FALSE;
+	return FALSE;
 }
 
 bool wxGIFDecoder::GoPrevFrame(bool cyclic)
 {
     if (!IsAnimation())
-        return FALSE;
+	return FALSE;
 
     if ((m_image > 1) || (cyclic))
     {
-        m_pimage = m_pimage->prev;
-        m_image--;
+	m_pimage = m_pimage->prev;
+	m_image--;
 
-        if (!m_pimage)
-        {
-            m_image = m_nimages;
-            m_pimage = m_plast;
-        }
+	if (!m_pimage)
+	{
+	    m_image = m_nimages;
+	    m_pimage = m_plast;
+	}
 
-        return TRUE;
+	return TRUE;
     }
     else
-        return FALSE;
+	return FALSE;
 }
 
 bool wxGIFDecoder::GoFrame(int which)
@@ -231,19 +252,19 @@ bool wxGIFDecoder::GoFrame(int which)
     int i;
 
     if (!IsAnimation())
-        return FALSE;
+	return FALSE;
 
     if ((which >= 1) && (which <= m_nimages))
     {
-        m_pimage = m_pfirst;
+	m_pimage = m_pfirst;
 
-        for (i = 1; i < which; i++)
-            m_pimage = m_pimage->next;
+	for (i = 1; i < which; i++)
+	    m_pimage = m_pimage->next;
 
-        return TRUE;
+	return TRUE;
     }
     else
-        return FALSE;
+	return FALSE;
 }
 
 
@@ -267,31 +288,35 @@ int wxGIFDecoder::getcode(int bits, int ab_fin)
     /* keep reading new bytes while needed */
     while (bits > m_restbits)
     {
-        /* if no bytes left in this block, read the next block */
-        if (m_restbyte == 0)
-        {
-            m_restbyte = (unsigned char)m_f->GetC();
-
-            /* Some encoders are a bit broken: instead of issuing
-             * an end-of-image symbol (ab_fin) they come up with
-             * a zero-length subblock!! We catch this here so
-             * that the decoder sees an ab_fin code.
-             */
-            if (m_restbyte == 0)
-            {
-                code = ab_fin;
-                break;
-            }
-        }
-
-        /* read next byte and isolate the bits we need */
-        m_lastbyte = (unsigned char)m_f->GetC();
-        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;
+	/* if no bytes left in this block, read the next block */
+	if (m_restbyte == 0)
+	{
+	    m_restbyte = (unsigned char)m_f->GetC();
+
+	    /* Some encoders are a bit broken: instead of issuing
+	     * an end-of-image symbol (ab_fin) they come up with
+	     * a zero-length subblock!! We catch this here so
+	     * that the decoder sees an ab_fin code.
+	     */
+	    if (m_restbyte == 0)
+	    {
+		code = ab_fin;
+		break;
+	    }
+
+	    /* prefetch data */
+	    m_f->Read((void *) m_buffer, m_restbyte);
+	    m_bufp = m_buffer;
+	}
+
+	/* read next byte and isolate the bits we need */
+	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 */
@@ -305,20 +330,19 @@ int wxGIFDecoder::getcode(int bits, int ab_fin)
 //  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)
+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 */
+    int *ab_prefix = new int[4096]; /* alphabet (prefixes) */
+    int *ab_tail = new int[4096];   /* alphabet (tails) */
+    int *stack = new int[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 */
 
     int code, readcode, lastcode, abcabca;
 
@@ -335,105 +359,109 @@ int wxGIFDecoder::dgif(IMAGEN *img, int interl, int bits)
     pass     = 1;
     pos = x = y = 0;
 
-    /* reset static globals */
+    /* reset decoder vars */
     m_restbits = 0;
     m_restbyte = 0;
     m_lastbyte = 0;
 
     do
     {
-        /* get next code */
-        readcode = code = getcode(ab_bits, ab_fin);
-
-        /* end of image? */
-        if (code == ab_fin) break;
-
-        /* reset alphabet? */
-        if (code == ab_clr)
-        {
-            /* reset main variables */
-            ab_bits  = bits + 1;
-            ab_free  = (1 << bits) + 2;
-            ab_max   = (1 << ab_bits) - 1;
-            lastcode = -1;
-            abcabca  = -1;
-
-            /* skip to next code */
-            continue;
-        }
-
-        /* unknown code: special case (like in ABCABCA) */
-        if (code >= ab_free)
-        {
-            code = lastcode;            /* take last string */
-            stack[pos++] = abcabca;     /* add first character */
-        }
-
-        /* build the string for this code in the stack */
-        while (code > ab_clr)
-        {
-            stack[pos++] = ab_tail[code];
-            code         = ab_prefix[code];
-        }
-        stack[pos] = code;              /* push last code into the stack */
-        abcabca    = code;              /* save for special case */
-
-        /* make new entry in alphabet (only if NOT just cleared) */
-        if (lastcode != -1)
-        {
-            ab_prefix[ab_free] = lastcode;
-            ab_tail[ab_free]   = code;
-            ab_free++;
-
-            if ((ab_free > ab_max) && (ab_bits < 12))
-            {
-                ab_bits++;
-                ab_max = (1 << ab_bits) - 1;
-            }
-        }
-
-        /* dump stack data to the buffer */
-        while (pos >= 0)
-        {
-            (img->p)[x + (y * (img->w))] = (char)stack[pos--];
-
-            if (++x >= (img->w))
-            {
-                x = 0;
-
-                if (interl)
-                {
-                    /* support for interlaced images */
-                    switch (pass)
-                    {
-                        case 1: y += 8; break;
-                        case 2: y += 8; break;
-                        case 3: y += 4; break;
-                        case 4: y += 2; break;
-                    }
-                    if (y >= (img->h))
-                    {
-                        switch (++pass)
-                        {
-                            case 2: y = 4; break;
-                            case 3: y = 2; break;
-                            case 4: y = 1; break;
-                        }
-                    }
-                }
-                else
-                {
-                    /* non-interlaced */
-                    y++;
-                }
-            }
-        }
-
-        pos = 0;
-        lastcode = readcode;
+	/* get next code */
+	readcode = code = getcode(ab_bits, ab_fin);
+
+	/* end of image? */
+	if (code == ab_fin) break;
+
+	/* reset alphabet? */
+	if (code == ab_clr)
+	{
+	    /* reset main variables */
+	    ab_bits  = bits + 1;
+	    ab_free  = (1 << bits) + 2;
+	    ab_max   = (1 << ab_bits) - 1;
+	    lastcode = -1;
+	    abcabca  = -1;
+
+	    /* skip to next code */
+	    continue;
+	}
+
+	/* unknown code: special case (like in ABCABCA) */
+	if (code >= ab_free)
+	{
+	    code = lastcode;            /* take last string */
+	    stack[pos++] = abcabca;     /* add first character */
+	}
+
+	/* build the string for this code in the stack */
+	while (code > ab_clr)
+	{
+	    stack[pos++] = ab_tail[code];
+	    code         = ab_prefix[code];
+	}
+	stack[pos] = code;              /* push last code into the stack */
+	abcabca    = code;              /* save for special case */
+
+	/* make new entry in alphabet (only if NOT just cleared) */
+	if (lastcode != -1)
+	{
+	    ab_prefix[ab_free] = lastcode;
+	    ab_tail[ab_free]   = code;
+	    ab_free++;
+
+	    if ((ab_free > ab_max) && (ab_bits < 12))
+	    {
+		ab_bits++;
+		ab_max = (1 << ab_bits) - 1;
+	    }
+	}
+
+	/* dump stack data to the buffer */
+	while (pos >= 0)
+	{
+	    (img->p)[x + (y * (img->w))] = (char)stack[pos--];
+
+	    if (++x >= (img->w))
+	    {
+		x = 0;
+
+		if (interl)
+		{
+		    /* support for interlaced images */
+		    switch (pass)
+		    {
+			case 1: y += 8; break;
+			case 2: y += 8; break;
+			case 3: y += 4; break;
+			case 4: y += 2; break;
+		    }
+		    if (y >= (img->h))
+		    {
+			switch (++pass)
+			{
+			    case 2: y = 4; break;
+			    case 3: y = 2; break;
+			    case 4: y = 1; break;
+			}
+		    }
+		}
+		else
+		{
+		    /* non-interlaced */
+		    y++;
+		}
+	    }
+	}
+
+	pos = 0;
+	lastcode = readcode;
     }
     while (code != ab_fin);
 
+    delete [] ab_prefix ;
+    delete [] ab_tail ;
+    delete [] stack ;
+
     return 0;
 }
 
@@ -446,7 +474,7 @@ bool wxGIFDecoder::CanRead()
     unsigned char buf[3];
 
     m_f->Read(buf, 3);
-    stream.SeekI(-3, wxFromCurrent);
+    m_f->SeekI(-3, wxFromCurrent);
 
     return (memcmp(buf, "GIF", 3) == 0);
 }
@@ -457,29 +485,30 @@ bool wxGIFDecoder::CanRead()
 //  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;
     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 E_FORMATO;
+	return wxGIF_INVFORMAT;
 
-    /* check for and animated GIF support (ver. >= 89a) */
+    /* check for animated GIF support (ver. >= 89a) */
     m_f->Read(buf, 6);
 
     if (memcmp(buf + 3, "89a", 3) < 0)
-        m_anim = FALSE;
+	m_anim = FALSE;
 
     /* read logical screen descriptor block (LSDB) */
     m_f->Read(buf, 7);
@@ -489,10 +518,10 @@ int wxGIFDecoder::ReadGIF()
     /* load global color map if available */
     if ((buf[4] & 0x80) == 0x80)
     {
-        m_background = buf[5];
+	m_background = buf[5];
 
-        ncolors = 2 << (buf[4] & 0x07);
-        m_f->Read(pal, 3 * ncolors);
+	ncolors = 2 << (buf[4] & 0x07);
+	m_f->Read(pal, 3 * ncolors);
     }
 
     /* transparent colour, disposal method and delay default to unused */
@@ -505,126 +534,164 @@ int wxGIFDecoder::ReadGIF()
     pprev = NULL;
     pimg  = NULL;
 
-#if defined(__VISAGECPP__)
-// VA just can't stand while(1)
-    bool bOs2var = TRUE;
-    while(bOs2var)
-#else
-    while (1)
-#endif
+    bool done = FALSE;
+
+    while(!done)
     {
-        type = (unsigned char)m_f->GetC();
-
-        /* end of data? */
-        if (type == 0x3B)
-            break;
-
-        /* extension block? */
-        if (type == 0x21)
-        {
-            if (((unsigned char)m_f->GetC()) == 0xF9)
-            /* graphics control extension, parse it */
-            {
-                m_f->Read(buf, 6);
-
-                /* read delay and convert from 1/100 of a second to ms */
-                delay = 10 * (buf[2] + 256 * buf[3]);
-
-                /* read transparent colour index, if used */
-                if (buf[1] & 0x01)
-                    transparent = buf[4];
-
-                /* read disposal method */
-                disposal = (buf[1] & 0x1C) - 1;
-            }
-            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?
-                     * Yes. Fixed now.
-                     */
-                    // m_f->SeekI(m_f->TellI(), wxFromStart);
-
-                    m_f->SeekI(i, wxFromCurrent);
-                }
-            }
-        }
-
-        /* image descriptor block? */
-        if (type == 0x2C)
-        {
-            /* allocate memory for IMAGEN struct */
-            pimg = (*ppimg) = (IMAGEN *) malloc(sizeof(IMAGEN));
-
-            if (pimg == NULL)
-            {
-                Destroy();
-                return E_MEMORIA;
-            }
-
-            /* fill in the data */
-            m_f->Read(buf, 9);
-            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];
-            interl = ((buf[8] & 0x40)? 1 : 0);
-            size = pimg->w * pimg->h;
-
-            pimg->transparent = transparent;
-            pimg->disposal = disposal;
-            pimg->delay = delay;
-            pimg->next = NULL;
-            pimg->prev = pprev;
-            pprev = pimg;
-            ppimg = &pimg->next;
-
-            /* allocate memory for image and palette */
-            pimg->p   = (unsigned char *) malloc(size);
-            pimg->pal = (unsigned char *) malloc(768);
-
-            if ((!pimg->p) || (!pimg->pal))
-            {
-                Destroy();
-                return E_MEMORIA;
-            }
-
-            /* 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);
-            }
-            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);
-
-            m_nimages++;
-        }
-
-        /* if we have one image and no animated GIF support, exit */
-        if (m_nimages == 1 && !m_anim)
-            break;
+	type = (unsigned char)m_f->GetC();
+
+	/* end of data? */
+	if (type == 0x3B)
+	{
+	    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);
+
+		/* read delay and convert from 1/100 of a second to ms */
+		delay = 10 * (buf[2] + 256 * buf[3]);
+
+		/* read transparent colour index, if used */
+		if (buf[1] & 0x01)
+		    transparent = buf[4];
+
+		/* read disposal method */
+		disposal = (buf[1] & 0x1C) - 1;
+	    }
+	    else
+	    /* other extension, skip */
+	    {
+		while ((i = (unsigned char)m_f->GetC()) != 0)
+		{
+		    m_f->SeekI(i, wxFromCurrent);
+		}
+	    }
+	}
+	else
+	/* image descriptor block? */
+	if (type == 0x2C)
+	{
+	    /* allocate memory for IMAGEN struct */
+	    pimg = (*ppimg) = new GIFImage();
+
+	    if (pimg == NULL)
+	    {
+		Destroy();
+		return wxGIF_MEMERR;
+	    }
+
+	    /* fill in the data */
+	    m_f->Read(buf, 9);
+	    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];
+	    interl = ((buf[8] & 0x40)? 1 : 0);
+	    size = pimg->w * pimg->h;
+
+	    pimg->transparent = transparent;
+	    pimg->disposal = disposal;
+	    pimg->delay = delay;
+	    pimg->next = NULL;
+	    pimg->prev = pprev;
+	    pprev = pimg;
+	    ppimg = &pimg->next;
+
+	    /* allocate memory for image and palette */
+	    pimg->p   = (unsigned char *) malloc((size_t)size);
+	    pimg->pal = (unsigned char *) malloc(768);
+
+	    if ((!pimg->p) || (!pimg->pal))
+	    {
+		Destroy();
+		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);
+	    }
+	    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);
+	    m_nimages++;
+
+	    /* if this is not an animated GIF, exit after first image */
+	    if (!m_anim)
+		done = TRUE;
+	}
     }
 
-    /* finish successfully :-) */
+    /* setup image pointers */
     if (m_nimages != 0)
     {
-        m_image = 1;
-        m_plast = pimg;
-        m_pimage = m_pfirst;
+	m_image = 1;
+	m_plast = pimg;
+	m_pimage = m_pfirst;
+    }
+
+    /* try to read to the end of the stream */
+    while (type != 0x3B)
+    {
+	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 */
+	    m_f->Read(buf, 9);
+
+	    /* local color map */
+	    if ((buf[8] & 0x80) == 0x80)
+	    {
+		ncolors = 2 << (buf[8] & 0x07);
+		m_f->SeekI(3 * ncolors, wxFromCurrent);
+	    }
+
+	    /* 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_STREAMS && wxUSE_GIF