Enforce non-negative BitstreamBuffer id

media/filters/gpu_video_decoder.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/filters/gpu_video_decoder.h"
 
 #include "base/bind.h"
 #include "base/callback_helpers.h"
 #include "base/cpu.h"
 #include "base/message_loop.h"
@@ skipping 266 matching lines @@
     return;
   }
 
   if (!pending_reset_cb_.is_null())
     return;
 
   size_t size = buffer->GetDataSize();
   SHMBuffer* shm_buffer = GetSHM(size);
   memcpy(shm_buffer->shm->memory(), buffer->GetData(), size);
   BitstreamBuffer bitstream_buffer(
-      next_bitstream_buffer_id_++, shm_buffer->shm->handle(), size);
+      next_bitstream_buffer_id_, shm_buffer->shm->handle(), size);
+  // Mask against 30 bits, to avoid (undefined) wraparound on signed integer.
+  next_bitstream_buffer_id_ = (next_bitstream_buffer_id_ + 1) & 0x3FFFFFFF;
   bool inserted = bitstream_buffers_in_decoder_.insert(std::make_pair(
       bitstream_buffer.id(), BufferPair(shm_buffer, buffer))).second;
   DCHECK(inserted);
   RecordBufferData(bitstream_buffer, *buffer);
 
   vda_loop_proxy_->PostTask(FROM_HERE, base::Bind(
       &VideoDecodeAccelerator::Decode, weak_vda_, bitstream_buffer));
 
   if (CanMoreDecodeWorkBeDone())
     EnsureDemuxOrDecode();
@@ skipping 283 matching lines @@
 
   error_occured_ = true;
 
   if (!pending_read_cb_.is_null()) {
     base::ResetAndReturn(&pending_read_cb_).Run(kDecodeError, NULL);
     return;
   }
 }
 
 }  // namespace media