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- /*
- * Copyright (C) 2016, Google Inc.
- * and other copyright owners as documented in the project's IP log.
- *
- * This program and the accompanying materials are made available
- * under the terms of the Eclipse Distribution License v1.0 which
- * accompanies this distribution, is reproduced below, and is
- * available at http://www.eclipse.org/org/documents/edl-v10.php
- *
- * All rights reserved.
- *
- * Redistribution and use in source and binary forms, with or
- * without modification, are permitted provided that the following
- * conditions are met:
- *
- * - Redistributions of source code must retain the above copyright
- * notice, this list of conditions and the following disclaimer.
- *
- * - Redistributions in binary form must reproduce the above
- * copyright notice, this list of conditions and the following
- * disclaimer in the documentation and/or other materials provided
- * with the distribution.
- *
- * - Neither the name of the Eclipse Foundation, Inc. nor the
- * names of its contributors may be used to endorse or promote
- * products derived from this software without specific prior
- * written permission.
- *
- * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND
- * CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES,
- * INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
- * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
- * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR
- * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
- * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
- * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
- * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
- * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
- * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
- * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
- * ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
- */
-
- package org.eclipse.jgit.util.time;
-
- import java.time.Duration;
- import java.util.concurrent.TimeUnit;
-
- /**
- * A provider of time.
- * <p>
- * Clocks should provide wall clock time, obtained from a reasonable clock
- * source, such as the local system clock.
- * <p>
- * MonotonicClocks provide the following behavior, with the assertion always
- * being true if {@link ProposedTimestamp#blockUntil(Duration)} is used:
- *
- * <pre>
- * MonotonicClock clk = ...;
- * long r1;
- * try (ProposedTimestamp t1 = clk.propose()) {
- * r1 = t1.millis();
- * t1.blockUntil(...);
- * }
- *
- * try (ProposedTimestamp t2 = clk.propose()) {
- * assert t2.millis() > r1;
- * }
- * </pre>
- *
- * @since 4.6
- */
- public interface MonotonicClock {
- /**
- * Obtain a timestamp close to "now".
- * <p>
- * Proposed times are close to "now", but may not yet be certainly in the
- * past. This allows the calling thread to interleave other useful work
- * while waiting for the clock instance to create an assurance it will never
- * in the future propose a time earlier than the returned time.
- * <p>
- * A hypothetical implementation could read the local system clock (managed
- * by NTP) and return that proposal, concurrently sending network messages
- * to closely collaborating peers in the same cluster to also ensure their
- * system clocks are ahead of this time. In such an implementation the
- * {@link ProposedTimestamp#blockUntil(Duration)} method would wait for
- * replies from the peers indicating their own system clocks have moved past
- * the proposed time.
- *
- * @return "now". The value can be immediately accessed by
- * {@link ProposedTimestamp#read(TimeUnit)} and friends, but the
- * caller must use {@link ProposedTimestamp#blockUntil(Duration)} to
- * ensure ordering holds.
- */
- ProposedTimestamp propose();
- }
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