zircon/system/ulib/async/wait.cc

// Copyright 2017 The Fuchsia 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 <lib/async/cpp/wait.h>

#include <utility>

#include <zircon/assert.h>

namespace async {

WaitBase::WaitBase(zx_handle_t object, zx_signals_t trigger, uint32_t options,
                   async_wait_handler_t* handler)
    : wait_{{ASYNC_STATE_INIT}, handler, object, trigger, options} {}

WaitBase::~WaitBase() {
  if (dispatcher_) {
    // Failure to cancel here may result in a dangling pointer...
    zx_status_t status = async_cancel_wait(dispatcher_, &wait_);
    ZX_ASSERT_MSG(status == ZX_OK, "status=%d", status);
  }
}

zx_status_t WaitBase::Begin(async_dispatcher_t* dispatcher) {
  if (dispatcher_)
    return ZX_ERR_ALREADY_EXISTS;

  dispatcher_ = dispatcher;
  zx_status_t status = async_begin_wait(dispatcher, &wait_);
  if (status != ZX_OK) {
    dispatcher_ = nullptr;
  }
  return status;
}

zx_status_t WaitBase::Cancel() {
  if (!dispatcher_)
    return ZX_ERR_NOT_FOUND;

  async_dispatcher_t* dispatcher = dispatcher_;
  dispatcher_ = nullptr;

  zx_status_t status = async_cancel_wait(dispatcher, &wait_);
  // |dispatcher| is required to be single-threaded, Cancel() is
  // only supposed to be called on |dispatcher|'s thread, and
  // we verified that the wait was pending before calling
  // async_cancel_wait(). Assuming that |dispatcher| never queues
  // a wait, |wait_| must have been pending with |dispatcher|.
  ZX_DEBUG_ASSERT(status != ZX_ERR_NOT_FOUND);
  return status;
}

Wait::Wait(zx_handle_t object, zx_signals_t trigger, uint32_t options, Handler handler)
    : WaitBase(object, trigger, options, &Wait::CallHandler), handler_(std::move(handler)) {}

Wait::~Wait() = default;

void Wait::CallHandler(async_dispatcher_t* dispatcher, async_wait_t* wait, zx_status_t status,
                       const zx_packet_signal_t* signal) {
  auto self = Dispatch<Wait>(wait);
  self->handler_(dispatcher, self, status, signal);
}

}  // namespace async