fourcc: allow smaller than 4 chars strings in vlc_fourcc_GetCodecFromString

vlc_fourcc_GetCodecFromString() is used to turn FourCC strings into a
VLC FourCC. Some accepted string found in fourcc_list.h can have space
character padding at the end, see fourcc_list.h. We should always allow
the mapping to work.

include/vlc_fourcc.h

@@ -737,8 +737,11 @@ VLC_API vlc_fourcc_t vlc_fourcc_GetCodec( int i_cat, vlc_fourcc_t i_fourcc );
  * It returns the codec associated to a fourcc stored in a zero terminated
  * string.
  *
- * If the string is NULL or does not have exactly 4 characters, it will
- * return 0, otherwise it behaves like vlc_fourcc_GetCodec.
+ * If the string is NULL or has more than 4 characters or doesn't correspond
+ * to a string associated with a VLC_CODEC_, it will return 0, otherwise it
+ * will one of the VLC_CODEC_ defined above.
+ *
+ * You may use UNKNOWN_ES for the ES category if you don't have the information.
  *
  * Provided for convenience.
  */

src/misc/fourcc.c

@@ -117,11 +117,16 @@ vlc_fourcc_t vlc_fourcc_GetCodec(int cat, vlc_fourcc_t fourcc)
 
 vlc_fourcc_t vlc_fourcc_GetCodecFromString( int i_cat, const char *psz_fourcc )
 {
-    if( !psz_fourcc || strlen(psz_fourcc) != 4 )
+    if( psz_fourcc == NULL )
+        return 0;
+    size_t s = strlen(psz_fourcc);
+    if (s > 4)
         return 0;
     return vlc_fourcc_GetCodec( i_cat,
-                                VLC_FOURCC( psz_fourcc[0], psz_fourcc[1],
-                                            psz_fourcc[2], psz_fourcc[3] ) );
+                                VLC_FOURCC( psz_fourcc[0],
+                                             s > 1 ? psz_fourcc[1] : ' ',
+                                             s > 2 ? psz_fourcc[2] : ' ',
+                                             s > 3 ? psz_fourcc[3] : ' ') );
 }
 
 vlc_fourcc_t vlc_fourcc_GetCodecAudio( vlc_fourcc_t i_fourcc, int i_bits )