time-util.ts

/**
 * Copyright 2019, OpenCensus Authors
 *
 * 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
 *
 * 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.
 */

import {Timestamp} from '../metrics/export/types';

const MILLIS_PER_SECOND = 1e3;
const NANOS_PER_MILLI = 1e3 * 1e3;
const NANOS_PER_SECOND = 1e3 * 1e3 * 1e3;

let hrtime = process.hrtime;
let hrtimeOrigin: [number, number] = [0, 0];
let hrtimeRefSeconds = 0;
let hrtimeRefNanos = 0;

function setHrtimeReference() {
  resetHrtimeFunctionCache();
  hrtimeOrigin = hrtime();
  const refTime = Date.now();
  hrtimeRefSeconds = Math.floor(refTime / MILLIS_PER_SECOND);
  hrtimeRefNanos = (refTime % MILLIS_PER_SECOND) * NANOS_PER_MILLI;
}

/**
 * This is used to enable tests to mock process.hrtime while still allow us to
 * cache it.
 */
function resetHrtimeFunctionCache() {
  hrtime = process.hrtime;
}

/**
 * Gets the current timestamp with seconds and nanoseconds.
 *
 * @returns {Timestamp} The Timestamp.
 */
export function getTimestampWithProcessHRTime(): Timestamp {
  const [offsetSecs, offsetNanos] = hrtime(hrtimeOrigin);

  // determine drift in seconds and nanoseconds
  const seconds = hrtimeRefSeconds + offsetSecs;
  const nanos = hrtimeRefNanos + offsetNanos;

  if (nanos >= NANOS_PER_SECOND) {
    return {seconds: seconds + 1, nanos: nanos % NANOS_PER_SECOND};
  }
  return {seconds, nanos};
}

setHrtimeReference();

export const TEST_ONLY = {
  setHrtimeReference,
  resetHrtimeFunctionCache
};