Make peeking before the head of OffsetByteQueue a hard error.

media/mp4/offset_byte_queue.cc

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "media/mp4/offset_byte_queue.h"
 
 #include "base/basictypes.h"
 #include "base/logging.h"
 
 namespace media {
@@ skipping 19 matching lines @@
   *size = size_;
 }
 
 void OffsetByteQueue::Pop(int count) {
   queue_.Pop(count);
   head_ += count;
   Sync();
 }
 
 void OffsetByteQueue::PeekAt(int64 offset, const uint8** buf, int* size) {
+  DCHECK(offset >= head());
   if (offset < head() || offset >= tail()) {
     *buf = NULL;
     *size = 0;
     return;
   }
   *buf = &buf_[offset - head()];
   *size = tail() - offset;
 }
 
 bool OffsetByteQueue::Trim(int64 max_offset) {
   if (max_offset < head_) return true;
   if (max_offset > tail()) {
     Pop(size_);
     return false;
   }
   Pop(max_offset - head_);
   return true;
 }
 
 void OffsetByteQueue::Sync() {
   queue_.Peek(&buf_, &size_);
 }
 
 }  // namespace media