Added CanRead()

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@3474 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

diff --git a/include/wx/gifdecod.h b/include/wx/gifdecod.h
index 30fa11cfedbe7c4168ab2a29b96c8f0b10be0176..35e073fdc898490f05a1c2ab2e302c18f5751acb 100644 (file)
--- a/include/wx/gifdecod.h
+++ b/include/wx/gifdecod.h
@@ -2,8 +2,8 @@
 // Name:        gifdecod.h
 // Purpose:     wxGIFDecoder, GIF reader for wxImage and wxAnimation
 // Author:      Guillermo Rodriguez Garcia <guille@iies.es>
-// Version:     3.0
-// Last rev:    1999/08/10
+// Version:     3.02
+// Last rev:    1999/08/18
 // Copyright:   (c) Guillermo Rodriguez Garcia
 // Licence:     wxWindows licence
 /////////////////////////////////////////////////////////////////////////////
@@ -29,7 +29,7 @@ typedef struct _IMAGEN
     unsigned int left;              /* x coord (in logical screen) */
     unsigned int top;               /* y coord (in logical screen) */
     int transparent;                /* transparent color (-1 = none) */
-    int disposal;                   /* disposal method */
+    int disposal;                   /* disposal method (-1 = unspecified) */
     long delay;                     /* delay in ms (-1 = unused) */
     unsigned char *p;               /* bitmap */
     unsigned char *pal;             /* palette */
@@ -82,6 +82,7 @@ public:
     // constructor, destructor, etc.
     wxGIFDecoder(wxInputStream *s, bool anim = FALSE);
     ~wxGIFDecoder();
+    bool CanRead();
     int ReadGIF();
     void Destroy();
 

diff --git a/src/common/gifdecod.cpp b/src/common/gifdecod.cpp
index 047189cc519eafd9a20658bd4a5b311327d95cd6..32a89223c3838334d6f7f72272d0fa535999bded 100644 (file)
--- a/src/common/gifdecod.cpp
+++ b/src/common/gifdecod.cpp
@@ -2,8 +2,8 @@
 // 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:     3.02
+// Last rev:    1999/08/18
 // Copyright:   (c) Guillermo Rodriguez Garcia
 // Licence:     wxWindows licence
 /////////////////////////////////////////////////////////////////////////////
@@ -85,6 +85,9 @@ bool wxGIFDecoder::ConvertToImage(wxImage *image) const
     unsigned long i;
     int      transparent;
 
+    /* just in case... */
+    image->Destroy();
+
     /* create the image */
     image->Create(GetWidth(), GetHeight());
 
@@ -436,6 +439,20 @@ int wxGIFDecoder::dgif(IMAGEN *img, int interl, int bits)
 }
 
 
+// CanRead:
+//  Returns TRUE if the file looks like a valid GIF, FALSE otherwise.
+//
+bool wxGIFDecoder::CanRead()
+{
+    unsigned char buf[3];
+
+    m_f->SeekI(0, wxFromStart);
+    m_f->Read(buf, 3);
+
+    return (memcmp(buf, "GIF", 3) == 0);
+}
+
+
 // ReadGIF:
 //  Reads and decodes one or more GIF images, depending on whether
 //  animated GIF support is enabled. Can read GIFs with any bit
@@ -455,13 +472,14 @@ int wxGIFDecoder::ReadGIF()
     unsigned char buf[16];
     IMAGEN        **ppimg, *pimg, *pprev;
 
+    /* check GIF signature */
+    if (!CanRead())
+        return E_FORMATO;
 
-    /* check GIF signature and animated GIF support (ver. >= 89a) */
+    /* check for and animated GIF support (ver. >= 89a) */
+    m_f->SeekI(0, wxFromStart);
     m_f->Read(buf, 6);
 
-    if (memcmp(buf, "GIF", 3) != 0)
-        return E_FORMATO;
-
     if (memcmp(buf + 3, "89a", 3) < 0)
         m_anim = FALSE;