X-Git-Url: https://git.saurik.com/wxWidgets.git/blobdiff_plain/9d1c7e8474ac6501f6ed39549b91c86eca9aae23..12b5f4b4d2d8a07962da7ba3b78c8c1ec2634a67:/src/common/gifdecod.cpp

diff --git a/src/common/gifdecod.cpp b/src/common/gifdecod.cpp
index 569b3e77ae..0a2dad2724 100644
--- a/src/common/gifdecod.cpp
+++ b/src/common/gifdecod.cpp
@@ -191,7 +191,7 @@ bool wxGIFDecoder::ConvertToImage(unsigned int frame, wxImage *image) const
 
 // Get data for current frame
 
-wxSize wxGIFDecoder::GetFrameSize(unsigned int frame) const 
+wxSize wxGIFDecoder::GetFrameSize(unsigned int frame) const
 {
     return wxSize(GetFrame(frame)->w, GetFrame(frame)->h);
 }
@@ -580,7 +580,8 @@ bool wxGIFDecoder::CanRead(wxInputStream &stream) const
     if ( !stream.Read(buf, WXSIZEOF(buf)) )
         return false;
 
-    stream.SeekI(-(wxFileOffset)WXSIZEOF(buf), wxFromCurrent);
+    if (stream.SeekI(-(wxFileOffset)WXSIZEOF(buf), wxFromCurrent) == wxInvalidOffset)
+        return false;       // this happens e.g. for non-seekable streams
 
     return memcmp(buf, "GIF", WXSIZEOF(buf)) == 0;
 }
@@ -598,7 +599,7 @@ bool wxGIFDecoder::CanRead(wxInputStream &stream) const
 wxGIFErrorCode wxGIFDecoder::LoadGIF(wxInputStream& stream)
 {
     unsigned int  global_ncolors = 0;
-    int           bits, interl, transparent, i;
+    int           bits, interl, i;
     wxAnimationDisposal disposal;
     long          size;
     long          delay;
@@ -660,7 +661,7 @@ wxGIFErrorCode wxGIFDecoder::LoadGIF(wxInputStream& stream)
     }
 
     // transparent colour, disposal method and delay default to unused
-    transparent = -1;
+    int transparent = -1;
     disposal = wxANIM_UNSPECIFIED;
     delay = -1;
 
@@ -710,8 +711,7 @@ wxGIFErrorCode wxGIFDecoder::LoadGIF(wxInputStream& stream)
                 delay = 10 * (buf[2] + 256 * buf[3]);
 
                 // read transparent colour index, if used
-                if (buf[1] & 0x01)
-                    transparent = buf[4];
+                transparent = buf[1] & 0x01 ? buf[4] : -1;
 
                 // read disposal method
                 disposal = (wxAnimationDisposal)(((buf[1] & 0x1C) >> 2) - 1);
@@ -721,12 +721,12 @@ wxGIFErrorCode wxGIFDecoder::LoadGIF(wxInputStream& stream)
             {
                 while ((i = (unsigned char)stream.GetC()) != 0)
                 {
-                    if (stream.Eof() || (stream.LastRead() == 0))
+                    if (stream.Eof() || (stream.LastRead() == 0) ||
+                        stream.SeekI(i, wxFromCurrent) == wxInvalidOffset)
                     {
                         done = true;
                         break;
                     }
-                    stream.SeekI(i, wxFromCurrent);
                 }
             }
         }
@@ -757,8 +757,8 @@ wxGIFErrorCode wxGIFDecoder::LoadGIF(wxInputStream& stream)
             pimg->w = buf[4] + 256 * buf[5];
             pimg->h = buf[6] + 256 * buf[7];
 
-            if ( anim && ((pimg->w == 0) || (pimg->w > (unsigned int)m_szAnimation.GetWidth()) || 
-			     (pimg->h == 0) || (pimg->h > (unsigned int)m_szAnimation.GetHeight())) )
+            if ( anim && ((pimg->w == 0) || (pimg->w > (unsigned int)m_szAnimation.GetWidth()) ||
+                  (pimg->h == 0) || (pimg->h > (unsigned int)m_szAnimation.GetHeight())) )
                 return wxGIF_INVFORMAT;
 
             interl = ((buf[8] & 0x40)? 1 : 0);
@@ -835,12 +835,12 @@ wxGIFErrorCode wxGIFDecoder::LoadGIF(wxInputStream& stream)
             // skip all data
             while ((i = (unsigned char)stream.GetC()) != 0)
             {
-                if (stream.Eof() || (stream.LastRead() == 0))
+                if (stream.Eof() || (stream.LastRead() == 0) ||
+                    stream.SeekI(i, wxFromCurrent) == wxInvalidOffset)
                 {
                     Destroy();
                     return wxGIF_INVFORMAT;
                 }
-                stream.SeekI(i, wxFromCurrent);
             }
         }
         else if (type == 0x2C)
@@ -859,7 +859,11 @@ wxGIFErrorCode wxGIFDecoder::LoadGIF(wxInputStream& stream)
             {
                 unsigned int local_ncolors = 2 << (buf[8] & 0x07);
                 wxFileOffset numBytes = 3 * local_ncolors;
-                stream.SeekI(numBytes, wxFromCurrent);
+                if (stream.SeekI(numBytes, wxFromCurrent) == wxInvalidOffset)
+                {
+                    Destroy();
+                    return wxGIF_INVFORMAT;
+                }
             }
 
             // initial code size
@@ -873,12 +877,12 @@ wxGIFErrorCode wxGIFDecoder::LoadGIF(wxInputStream& stream)
             // skip all data
             while ((i = (unsigned char)stream.GetC()) != 0)
             {
-                if (stream.Eof() || (stream.LastRead() == 0))
+                if (stream.Eof() || (stream.LastRead() == 0) ||
+                    stream.SeekI(i, wxFromCurrent) == wxInvalidOffset)
                 {
                     Destroy();
                     return wxGIF_INVFORMAT;
                 }
-                stream.SeekI(i, wxFromCurrent);
             }
         }
         else if ((type != 0x3B) && (type != 00)) // testing