Prevent SkBlockMemoryStream::skip from writing to low memory.

src/core/SkStream.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 "SkStream.h"
@@ skipping 676 matching lines @@
         , fSize(size) , fOffset(0), fCurrentOffset(0) { }
 
     virtual size_t read(void* buffer, size_t rawCount) SK_OVERRIDE {
         size_t count = rawCount;
         if (fOffset + count > fSize) {
             count = fSize - fOffset;
         }
         size_t bytesLeftToRead = count;
         while (fCurrent != NULL) {
             size_t bytesLeftInCurrent = fCurrent->written() - fCurrentOffset;
-            size_t bytesFromCurrent = bytesLeftToRead <= bytesLeftInCurrent
-                                    ? bytesLeftToRead  : bytesLeftInCurrent;
+            size_t bytesFromCurrent = SkTMin(bytesLeftToRead, bytesLeftInCurrent);
             if (buffer) {
                 memcpy(buffer, fCurrent->start() + fCurrentOffset, bytesFromCurrent);
+                buffer = SkTAddOffset<void>(buffer, bytesFromCurrent);
             }
             if (bytesLeftToRead <= bytesFromCurrent) {
                 fCurrentOffset += bytesFromCurrent;
                 fOffset += count;
                 return count;
             }
             bytesLeftToRead -= bytesFromCurrent;
-            buffer = SkTAddOffset<void>(buffer, bytesFromCurrent);
             fCurrent = fCurrent->fNext;
             fCurrentOffset = 0;
         }
         SkASSERT(false);
         return 0;
     }
 
     virtual bool isAtEnd() const SK_OVERRIDE {
         return fOffset == fSize;
     }
@@ skipping 117 matching lines @@
 
     // If we get here, then our attempt at using mmap failed, so try normal
     // file access.
     SkFILEStream* stream = SkNEW_ARGS(SkFILEStream, (path));
     if (!stream->isValid()) {
         stream->unref();
         stream = NULL;
     }
     return stream;
 }