Fail to return a codec if the provided stream does not support rewind.

src/images/SkImageDecoder_Factory.cpp

 
 /*
  * Copyright 2006 The Android Open Source Project
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 
 #include "SkImageDecoder.h"
 #include "SkMovie.h"
 #include "SkStream.h"
 #include "SkTRegistry.h"
 
 typedef SkTRegistry<SkImageDecoder*, SkStream*> DecodeReg;
 
 // N.B. You can't use "DecodeReg::gHead here" due to complex C++
 // corner cases.
 template DecodeReg* SkTRegistry<SkImageDecoder*, SkStream*>::gHead;
 
 SkImageDecoder* SkImageDecoder::Factory(SkStream* stream) {
     SkImageDecoder* codec = NULL;
     const DecodeReg* curr = DecodeReg::Head();
     while (curr) {
         codec = curr->factory()(stream);
         // we rewind here, because we promise later when we call "decode", that
         // the stream will be at its beginning.
-        stream->rewind();
+        bool rewindSuceeded = stream->rewind();
+
+        // our image decoder's require that rewind is supported so we fail early
+        // if we are given a stream that does not support rewinding.
+        if (!rewindSuceeded) {
+            SkDEBUGF(("Unable to rewind the image stream."));
+            SkDELETE(codec);
+            return NULL;
+        }
+
         if (codec) {
             return codec;
         }
         curr = curr->next();
     }
     return NULL;
 }
 
 /////////////////////////////////////////////////////////////////////////
 
 typedef SkTRegistry<SkMovie*, SkStream*> MovieReg;
 
 SkMovie* SkMovie::DecodeStream(SkStream* stream) {
     const MovieReg* curr = MovieReg::Head();
     while (curr) {
         SkMovie* movie = curr->factory()(stream);
         if (movie) {
             return movie;
         }
         // we must rewind only if we got NULL, since we gave the stream to the
         // movie, who may have already started reading from it
         stream->rewind();
         curr = curr->next();
     }
     return NULL;
 }