ppapi_simple

native_client_sdk/src/libraries/ppapi_main/ppapi_queue.cc

-// Copyright (c) 2013 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 <assert.h>
-#include <stdlib.h>
-#include <string.h>
-
-#include "ppapi_main/ppapi_queue.h"
-
-PPAPIQueue::PPAPIQueue()
-  : read_(0),
-    write_(0),
-    freed_(0),
-    size_(0),
-    array_(NULL) { }
-
-PPAPIQueue::~PPAPIQueue() {
-  // Messages may be leaked if the queue is not empty.
-  assert(read_ == write_);
-
-  delete[] array_;
-}
-
-bool PPAPIQueue::SetSize(uint32_t queue_size) {
-  assert(queue_size > 0);
-
-  if (array_) return false;
-
-  array_ = new void*[queue_size];
-  size_ = queue_size;
-
-  memset(array_, 0, sizeof(void*) * queue_size);
-  return true;
-}
-
-bool PPAPIQueue::AddNewMessage(void* msg) {
-  // Writing a NULL message is illegal
-  assert(array_ != NULL);
-  assert(msg != NULL);
-
-  // If the slot not empty, the queue must be full.  Calling RemoveStaleMessage
-  // may create space by freeing messages that have already been read.
-  if (array_[write_] != NULL) return false;
-
-  // Write to the spot
-  array_[write_] = msg;
-
-  // Fence to make sure the payload and payload pointer are visible.
-  // Since Win32 is x86 which provides ordered writes, we don't need to
-  // synchronize in that case.
-#ifndef WIN32
-  __sync_synchronize();
-#endif
-
-  // Increment the write pointer, to signal it's readable.
-  write_ = (write_ + 1) % size_;
-  return true;
-}
-
-void* PPAPIQueue::RemoveStaleMessage() {
-  assert(array_ != NULL);
-
-  // If freed and read pointer are equal, this hasn't been read yet
-  if (freed_ == read_) return NULL;
-
-  assert(array_[freed_] != NULL);
-
-  void* ret = array_[freed_];
-  array_[freed_] = NULL;
-
-  freed_ = (freed_ + 1) % size_;
-  return ret;
-}
-
-void* PPAPIQueue::AcquireTopMessage() {
-  // Assert that we aren't already reading a message.
-  assert(last_msg_ == NULL);
-
-  // If read and write pointers are equal, the queue is empty.
-  if (read_ == write_) return NULL;
-
-  // Track the last message to look for illegal API use.
-  last_msg_ = array_[read_];
-  return last_msg_;
-}
-
-void PPAPIQueue::ReleaseTopMessage(void* msg) {
-  // Verify we currently acquire message.
-  assert(msg != NULL);
-  assert(msg == last_msg_);
-
-  last_msg_ = NULL;
-
-  // Signal that the message can be freed.
-  read_ = (read_ + 1) % size_;
-}