base/apple/dispatch_source_mach.cc

// Copyright 2014 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#include "base/apple/dispatch_source_mach.h"

#include "base/apple/scoped_dispatch_object.h"

namespace base::apple {

struct DispatchSourceMach::Storage {
  // The dispatch queue used to service the source_.
  ScopedDispatchObject<dispatch_queue_t> queue;

  // A MACH_RECV dispatch source.
  ScopedDispatchObject<dispatch_source_t> source;

  // Semaphore used to wait on the |source_|'s cancellation in the destructor.
  ScopedDispatchObject<dispatch_semaphore_t> source_canceled;
};

DispatchSourceMach::DispatchSourceMach(const char* name,
                                       mach_port_t port,
                                       void (^event_handler)())
    : DispatchSourceMach(dispatch_queue_create(name, DISPATCH_QUEUE_SERIAL),
                         port,
                         event_handler) {
  // Since the queue was created above in the delegated constructor, and it was
  // subsequently retained, release it here.
  dispatch_release(storage_->queue.get());
}

DispatchSourceMach::DispatchSourceMach(dispatch_queue_t queue,
                                       mach_port_t port,
                                       void (^event_handler)())
    : storage_(std::make_unique<Storage>()) {
  storage_->queue.reset(queue, base::scoped_policy::RETAIN);
  storage_->source.reset(dispatch_source_create(
      DISPATCH_SOURCE_TYPE_MACH_RECV, port, 0, storage_->queue.get()));
  storage_->source_canceled.reset(dispatch_semaphore_create(0));

  dispatch_source_set_event_handler(storage_->source.get(), event_handler);
  dispatch_source_set_cancel_handler(storage_->source.get(), ^{
    dispatch_semaphore_signal(storage_->source_canceled.get());
  });
}

DispatchSourceMach::~DispatchSourceMach() {
  // Cancel the source and wait for the semaphore to be signaled. This will
  // ensure the source managed by this class is not used after it is freed.
  dispatch_source_cancel(storage_->source.get());
  storage_->source.reset();

  dispatch_semaphore_wait(storage_->source_canceled.get(),
                          DISPATCH_TIME_FOREVER);
}

void DispatchSourceMach::Resume() {
  dispatch_resume(storage_->source.get());
}

dispatch_queue_t DispatchSourceMach::Queue() const {
  return storage_->queue.get();
}

}  // namespace base::apple