First round of dead file removal

experimental/hex/shared_queue.h

-// Copyright (c) 2011 The Native Client Authors. All rights reserved.
-// Use of this source code is governed by a BSD-style license that can be
-// found in the LICENSE file.
-
-#ifndef SHARED_QUEUE_H
-#define SHARED_QUEUE_H
-
-#include <pthread.h>
-#include <cassert>
-#include <deque>
-
-#include "thread_safe_ref_count.h"
-
-namespace  {
-
-// This file provides a queue that uses a mutex and condition variable so that
-// one thread can put pointers into the queue and another thread can pull items
-// out of the queue.
-
-const int kPthreadMutexSuccess = 0;
-
-// Specifies whether we want to wait for the queue.
-enum QueueWaitingFlag {
-  kWait = 0,
-  kDontWait
-};
-
-// Indicates if we got an item, did not wait, or if the queue was cancelled.
-enum QueueGetResult {
-  kReturnedItem = 0,
-  kDidNotWait = 1,
-  kQueueWasCancelled
-};
-
-// LockingQueue contains a collection of <T>, such as a collection of
-// objects or pointers.  The Push() method is used to add items to the
-// queue in a thread-safe manner.  The GetItem() is used to retrieve
-// items from the queue in a thread-safe manner.
-template <class T>
-class LockingQueue {
-  public:
-    LockingQueue() : quit_(false) {
-      int result = pthread_mutex_init(&queue_mutex_, NULL);
-      assert(result == 0);
-      result = pthread_cond_init(&queue_condition_var_, NULL);
-      assert(result == 0);
-    }
-    ~LockingQueue() {
-      pthread_mutex_destroy(&queue_mutex_);
-    }
-
-    // The producer (who instantiates the queue) calls this to tell the
-    // consumer that the queue is no longer being used.
-    void CancelQueue() {
-      ScopedLock scoped_mutex(&queue_mutex_);
-      quit_ = true;
-      // Signal the condition var so that if a thread is waiting in
-      // GetItem the thread will wake up and see that the queue has
-      // been cancelled.
-      pthread_cond_signal(&queue_condition_var_);
-    }
-
-    // The consumer calls this to see if the queue has been cancelled by
-    // the producer.  If so, the thread should not call GetItem and may
-    // need to terminate -- i.e. in a case where the producer created
-    // the consumer thread.
-    bool IsCancelled() {
-      ScopedLock scoped_mutex(&queue_mutex_);
-      return quit_;
-    }
-
-    // Grabs the mutex and pushes a new item to the end of the queue if the
-    // queue is not full.  Signals the condition variable so that a thread
-    // that is waiting will wake up and grab the item.
-    void Push(const T& item) {
-      ScopedLock scoped_mutex(&queue_mutex_);
-      the_queue_.push_back(item);
-      pthread_cond_signal(&queue_condition_var_);
-    }
-
-    // Tries to pop the front element from the queue; returns an enum:
-    //  kReturnedItem if an item is returned in |item_ptr|,
-    //  kDidNotWait if |wait| was kDontWait and the queue was empty,
-    //  kQueueWasCancelled if the producer called CancelQueue().
-    // If |wait| is kWait, GetItem will wait to return until the queue
-    // contains an item (unless the queue is cancelled).
-    QueueGetResult GetItem(T* item_ptr, QueueWaitingFlag wait) {
-      // Because we use both pthread_mutex_lock and pthread_cond_wait,
-      // we directly use the mutex instead of using ScopedLock.
-      ScopedLock scoped_mutex(&queue_mutex_);
-      // Use a while loop to get an item. If the user does not want to wait,
-      // we will exit from the loop anyway, unlocking the mutex.
-      // If the user does want to wait, we will wait for pthread_cond_wait,
-      // and the while loop will check is_empty_no_locking() one more
-      // time so that a spurious wake-up of pthread_cond_wait is handled.
-      // If |quit_| has been set, break out of the loop.
-      while (!quit_ && is_empty_no_locking()) {
-        // If user doesn't want to wait, return...
-        if (kDontWait == wait) {
-          return kDidNotWait;
-        }
-        // Wait for signal to occur.
-        pthread_cond_wait(&queue_condition_var_, &queue_mutex_);
-      }
-      // Check to see if quit_ woke us up
-      if (quit_) {
-        return kQueueWasCancelled;
-      }
-
-      // At this point, the queue was either not empty or, if it was empty,
-      // we called pthread_cond_wait (which released the mutex, waited for the
-      // signal to occur, and then atomically reacquired the mutex).
-      // Thus, if we are here, the queue cannot be empty because we either
-      // had the mutex and verified it was not empty, or we waited for the
-      // producer to put an item in and signal a single thread (us).
-      T& item = the_queue_.front();
-      *item_ptr = item;
-      the_queue_.pop_front();
-      return kReturnedItem;
-    }
-
-  private:
-    std::deque<T> the_queue_;
-    bool quit_;
-    pthread_mutex_t queue_mutex_;
-    pthread_cond_t queue_condition_var_;
-
-    // This is used by methods that already have the lock.
-    bool is_empty_no_locking() const {
-      return the_queue_.empty();
-    }
-};
-
-}  // end of unnamed namespace
-
-#endif  // SHARED_QUEUE_H
-