content: /*
   * 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.
   */
  package com.datastax.oss.driver.internal.core.time;
  
  import com.datastax.oss.driver.internal.core.os.Native;
  import org.slf4j.Logger;
  import org.slf4j.LoggerFactory;
  
  /**
   * A small abstraction around system clock that aims to provide microsecond precision with the best
   * accuracy possible.
   */
  public interface Clock {
    Logger LOG = LoggerFactory.getLogger(Clock.class);
  
    /**
     * Returns the best implementation for the current platform.
     *
     * <p>Usage with non-blocking threads: beware that this method may block the calling thread on its
     * very first invocation, because native libraries used by the driver will be loaded at that
     * moment. If that is a problem, consider invoking this method once from a thread that is allowed
     * to block. Subsequent invocations are guaranteed not to block.
     */
    static Clock getInstance(boolean forceJavaClock) {
      if (forceJavaClock) {
        LOG.info("Using Java system clock because this was explicitly required in the configuration");
        return new JavaClock();
      } else if (!Native.isCurrentTimeMicrosAvailable()) {
        LOG.info(
            "Could not access native clock (see debug logs for details), "
                + "falling back to Java system clock");
        return new JavaClock();
      } else {
        LOG.info("Using native clock for microsecond precision");
        return new NativeClock();
      }
    }
  
    /**
     * Returns the difference, measured in <b>microseconds</b>, between the current time and and the
     * Epoch (that is, midnight, January 1, 1970 UTC).
     */
    long currentTimeMicros();
  }
  