com.github.benmanes.caffeine.IsValidSingleConsumerQueue.java Source code

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Here is the source code for com.github.benmanes.caffeine.IsValidSingleConsumerQueue.java

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/*
 * Copyright 2014 Ben Manes. All Rights Reserved.
 *
 * 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.
 */
package com.github.benmanes.caffeine;

import static com.github.benmanes.caffeine.testing.IsEmptyIterable.deeplyEmpty;
import static org.hamcrest.Matchers.hasSize;
import static org.hamcrest.Matchers.is;
import static org.hamcrest.Matchers.not;
import static org.hamcrest.Matchers.nullValue;

import java.util.Set;
import java.util.concurrent.atomic.AtomicReference;
import java.util.function.Supplier;

import org.hamcrest.Description;
import org.hamcrest.TypeSafeDiagnosingMatcher;

import com.github.benmanes.caffeine.SingleConsumerQueue.Node;
import com.github.benmanes.caffeine.testing.DescriptionBuilder;
import com.google.common.collect.Sets;

/**
 * A matcher that evaluates a {@link SingleConsumerQueue} to determine if it is in a valid state.
 *
 * @author ben.manes@gmail.com (Ben Manes)
 */
public final class IsValidSingleConsumerQueue<E> extends TypeSafeDiagnosingMatcher<SingleConsumerQueue<E>> {

    @Override
    public void describeTo(Description description) {
        description.appendText("singleConsumerQueue");
    }

    @Override
    protected boolean matchesSafely(SingleConsumerQueue<E> queue, Description description) {
        DescriptionBuilder builder = new DescriptionBuilder(description);

        if (queue.isEmpty()) {
            builder.expectThat("empty queue", queue, is(deeplyEmpty()));
            builder.expectThat("empty queue", queue.head, is(queue.tail));
            builder.expectThat("empty queue", queue.head.next, is(nullValue()));
        }
        builder.expectThat("corrupted queue node", queue.tail.next, is(nullValue()));
        checkForLoop(queue, builder);
        checkArena(queue, builder);

        return builder.matches();
    }

    void checkForLoop(SingleConsumerQueue<E> queue, DescriptionBuilder builder) {
        builder.expectThat("Expected sentinel node", queue.head.value, is(nullValue()));
        Set<Node<E>> seen = Sets.newIdentityHashSet();
        Node<E> node = queue.head.next;
        while (node != null) {
            Node<E> current = node;
            Supplier<String> errorMsg = () -> String.format("Loop detected: %s in %s", current, seen);
            builder.expectThat(errorMsg, seen.add(node), is(true));
            builder.expectThat("not tail", node, is(not(queue.head)));
            builder.expectThat("not completed", node.isDone(), is(true));
            builder.expectThat("not null value", node.value, is(not(nullValue())));
            node = node.next;
        }
        builder.expectThat("queue size", queue, hasSize(seen.size()));
    }

    void checkArena(SingleConsumerQueue<E> queue, DescriptionBuilder builder) {
        for (AtomicReference<?> slot : queue.arena) {
            builder.expectThat("not null arena slot", slot.get(), is(nullValue()));
        }
    }

    public static <E> IsValidSingleConsumerQueue<E> validate() {
        return new IsValidSingleConsumerQueue<E>();
    }
}