[NaCl SDK] rename nacl_io demo.

native_client_sdk/src/examples/demo/nacl_io/queue.c

-/* 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 "queue.h"
-
-#include <pthread.h>
-#include <stdlib.h>
-
-#include "ppapi/c/pp_var.h"
-
-#define MAX_QUEUE_SIZE 16
-
-/** A mutex that guards |g_queue|. */
-static pthread_mutex_t g_queue_mutex;
-
-/** A condition variable that is signalled when |g_queue| is not empty. */
-static pthread_cond_t g_queue_not_empty_cond;
-
-/** A circular queue of messages from JavaScript to be handled.
- *
- * If g_queue_start < g_queue_end:
- *   all elements in the range [g_queue_start, g_queue_end) are valid.
- * If g_queue_start > g_queue_end:
- *   all elements in the ranges [0, g_queue_end) and
- *   [g_queue_start, MAX_QUEUE_SIZE) are valid.
- * If g_queue_start == g_queue_end, and g_queue_size > 0:
- *   all elements in the g_queue are valid.
- * If g_queue_start == g_queue_end, and g_queue_size == 0:
- *   No elements are valid. */
-static struct PP_Var g_queue[MAX_QUEUE_SIZE];
-
-/** The index of the head of the queue. */
-static int g_queue_start = 0;
-
-/** The index of the tail of the queue, non-inclusive. */
-static int g_queue_end = 0;
-
-/** The size of the queue. */
-static int g_queue_size = 0;
-
-/** Return whether the queue is empty.
- *
- * NOTE: this function assumes g_queue_mutex lock is held.
- * @return non-zero if the queue is empty. */
-static int IsQueueEmpty() { return g_queue_size == 0; }
-
-/** Return whether the queue is full.
- *
- * NOTE: this function assumes g_queue_mutex lock is held.
- * @return non-zero if the queue is full. */
-static int IsQueueFull() { return g_queue_size == MAX_QUEUE_SIZE; }
-
-/** Initialize the message queue. */
-void InitializeMessageQueue() {
-  pthread_mutex_init(&g_queue_mutex, NULL);
-  pthread_cond_init(&g_queue_not_empty_cond, NULL);
-}
-
-/** Enqueue a message (i.e. add to the end)
- *
- * If the queue is full, the message will be dropped.
- *
- * NOTE: this function assumes g_queue_mutex is _NOT_ held.
- * @param[in] message The message to enqueue.
- * @return non-zero if the message was added to the queue. */
-int EnqueueMessage(struct PP_Var message) {
-  pthread_mutex_lock(&g_queue_mutex);
-
-  /* We shouldn't block the main thread waiting for the queue to not be full,
-   * so just drop the message. */
-  if (IsQueueFull()) {
-    pthread_mutex_unlock(&g_queue_mutex);
-    return 0;
-  }
-
-  g_queue[g_queue_end] = message;
-  g_queue_end = (g_queue_end + 1) % MAX_QUEUE_SIZE;
-  g_queue_size++;
-
-  pthread_cond_signal(&g_queue_not_empty_cond);
-
-  pthread_mutex_unlock(&g_queue_mutex);
-
-  return 1;
-}
-
-/** Dequeue a message and return it.
- *
- * This function blocks until a message is available. It should not be called
- * on the main thread.
- *
- * NOTE: this function assumes g_queue_mutex is _NOT_ held.
- * @return The message at the head of the queue. */
-struct PP_Var DequeueMessage() {
-  struct PP_Var message;
-
-  pthread_mutex_lock(&g_queue_mutex);
-
-  while (IsQueueEmpty()) {
-    pthread_cond_wait(&g_queue_not_empty_cond, &g_queue_mutex);
-  }
-
-  message = g_queue[g_queue_start];
-  g_queue_start = (g_queue_start + 1) % MAX_QUEUE_SIZE;
-  g_queue_size--;
-
-  pthread_mutex_unlock(&g_queue_mutex);
-
-  return message;
-}