//
//  ASDispatch.h
//  Texture
//
//  Copyright (c) 2014-present, Facebook, Inc.  All rights reserved.
//  This source code is licensed under the BSD-style license found in the
//  LICENSE file in the /ASDK-Licenses directory of this source tree. An additional
//  grant of patent rights can be found in the PATENTS file in the same directory.
//
//  Modifications to this file made after 4/13/2017 are: Copyright (c) 2017-present,
//  Pinterest, Inc.  Licensed under the Apache License, Version 2.0 (the "License");
//  you may not use this file except in compliance with the License.
//  You may obtain a copy of the License at
//
//      http://www.apache.org/licenses/LICENSE-2.0
//

#import <Foundation/Foundation.h>
#import <stdatomic.h>

/**
 * Like dispatch_apply, but you can set the thread count. 0 means 2*active CPUs.
 *
 * Note: The actual number of threads may be lower than threadCount, if libdispatch
 * decides the system can't handle it. In reality this rarely happens.
 */
static void ASDispatchApply(size_t iterationCount, dispatch_queue_t queue, NSUInteger threadCount, NS_NOESCAPE void(^work)(size_t i)) {
  if (threadCount == 0) {
    threadCount = NSProcessInfo.processInfo.activeProcessorCount * 2;
  }
  dispatch_group_t group = dispatch_group_create();
  // HACK: This is a workaround for mm files that include this in Clang4.0
  // Omitting ATOMIC_VAR_INIT is okay in this case because the current
  // expansion of that macro no-ops.
  // TODO: Move this implementation into a m file so it's not compiled in C++
  // See: https://github.com/TextureGroup/Texture/pull/426
  __block atomic_size_t counter = 0;
  for (NSUInteger t = 0; t < threadCount; t++) {
    dispatch_group_async(group, queue, ^{
      size_t i;
      while ((i = atomic_fetch_add(&counter, 1)) < iterationCount) {
        work(i);
      }
    });
  }
  dispatch_group_wait(group, DISPATCH_TIME_FOREVER);
};