src/micro_timer.cpp

/*
  Licensed to the Apache Software Foundation (ASF) under one
  or more contributor license agreements.  See the NOTICE file
  distributed with this work for additional information
  regarding copyright ownership.  The ASF licenses this file
  to you 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

  Unless required by applicable law or agreed to in writing, software
  distributed under the License is distributed on an "AS IS" BASIS,
  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  See the License for the specific language governing permissions and
  limitations under the License.
*/

#include "micro_timer.hpp"

#ifdef HAVE_TIMERFD
#include <string.h>
#include <sys/timerfd.h>
#include <unistd.h>
#endif

using namespace datastax::internal::core;

#ifdef HAVE_TIMERFD

MicroTimer::MicroTimer()
    : handle_(NULL)
    , fd_(-1)
    , state_(CLOSED) {}

int MicroTimer::start(uv_loop_t* loop, uint64_t timeout_us, const Callback& callback) {
  int rc = 0;
  if (fd_ == -1) {
    fd_ = timerfd_create(CLOCK_MONOTONIC, TFD_NONBLOCK);
    if (fd_ == -1) return errno;
  }
  if (handle_ == NULL) {
    handle_ = new AllocatedT<uv_poll_t>();
    handle_->loop = NULL;
    handle_->data = this;
  }
  if (state_ == CLOSED) {
    rc = uv_poll_init(loop, handle_, fd_);
    if (rc != 0) return rc;
    state_ = STOPPED;
  }
  if (state_ == STOPPED) {
    rc = uv_poll_start(handle_, UV_READABLE, on_timeout);
    if (rc != 0) return rc;
    struct itimerspec ts;
    memset(&ts.it_interval, 0, sizeof(struct timespec));
    if (timeout_us > 0) {
      ts.it_value.tv_sec = timeout_us / (1000 * 1000);
      ts.it_value.tv_nsec = (timeout_us % (1000 * 1000)) * 1000;
    } else {
      // If the timeout is 0 then set the smallest possible timeout (1 ns)
      // because all zeros disables the timer.
      ts.it_value.tv_sec = 0;
      ts.it_value.tv_nsec = 1;
    }
    timerfd_settime(fd_, 0, &ts, NULL);
    state_ = STARTED;
  }
  callback_ = callback;
  return rc;
}

void MicroTimer::stop() {
  if (fd_ != -1) {
    close(fd_);
    fd_ = -1;
  }
  if (handle_ != NULL) {
    if (state_ == CLOSED) { // The handle was allocated, but initialization failed.
      delete handle_;
    } else { // If initialized or started then close the handle properly.
      uv_close(reinterpret_cast<uv_handle_t*>(handle_), on_close);
    }
    state_ = CLOSED;
    handle_ = NULL;
  }
}

bool MicroTimer::is_running() const { return state_ == STARTED; }

void MicroTimer::on_timeout(uv_poll_t* poll, int status, int events) {
  MicroTimer* timer = static_cast<MicroTimer*>(poll->data);
  timer->handle_timeout();
}

void MicroTimer::handle_timeout() {
  uint64_t count;
  int result = read(fd_, &count, sizeof(count));
  UNUSED_(result);
  state_ = STOPPED;
  uv_poll_stop(handle_);
  callback_(this);
}

void MicroTimer::on_close(uv_handle_t* handle) {
  delete reinterpret_cast<AllocatedT<uv_poll_t>*>(handle);
}
#else

MicroTimer::MicroTimer()
    : timeout_ns_(0) {}

int MicroTimer::start(uv_loop_t* loop, uint64_t timeout_us, const Callback& callback) {
  if (is_running()) {
    return 0;
  }

  uint64_t ms = timeout_us / 1000;
  uint64_t us = timeout_us - (ms * 1000);

  timeout_ns_ = uv_hrtime() + timeout_us * 1000; // Convert to nanoseconds
  callback_ = callback;

  if (us >= (1000 * CASS_PERCENT_OF_MILLSECOND_THRESHOLD) / 100) {
    // If the requested sub-millisecond part of the timeout is within a certain
    // percentage of a millisecond then round up to the next millisecond and use
    // the timer.
    return timer_.start(loop, ms + 1, bind_callback(&MicroTimer::on_timeout, this));
  } else {
    // Note: This can potentially wait for 0 milliseconds and in that case the
    // loop will busy spin until the sub-millsecond part of the timeout is
    // reached.
    return timer_.start(loop, ms, bind_callback(&MicroTimer::on_timeout, this));
  }
}

void MicroTimer::stop() { timer_.stop(); }

bool MicroTimer::is_running() const { return timer_.is_running(); }

void MicroTimer::on_timeout(Timer* timer) {
  uint64_t now = uv_hrtime();
  if (now >= timeout_ns_) {
    // The goal timeout was reached, trigger the callback.
    callback_(this);
  } else {
    // There's still a sub-millisecond part to wait for so spin the loop until
    // the timeout is reached.
    timer_.start(timer_.loop(), 0, bind_callback(&MicroTimer::on_timeout, this));
  }
}

#endif