    001/*
    002 * Licensed to the Apache Software Foundation (ASF) under one or more
    003 * contributor license agreements.  See the NOTICE file distributed with
    004 * this work for additional information regarding copyright ownership.
    005 * The ASF licenses this file to You under the Apache License, Version 2.0
    006 * (the "License"); you may not use this file except in compliance with
    007 * the License.  You may obtain a copy of the License at
    008 *
    009 *      http://www.apache.org/licenses/LICENSE-2.0
    010 *
    011 * Unless required by applicable law or agreed to in writing, software
    012 * distributed under the License is distributed on an "AS IS" BASIS,
    013 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    014 * See the License for the specific language governing permissions and
    015 * limitations under the License.
    016 */
    017package org.apache.commons.io.input;
    018
    019import static org.apache.commons.io.IOUtils.EOF;
    020
    021import java.io.IOException;
    022import java.io.InputStream;
    023import java.io.PipedInputStream;
    024import java.io.PipedOutputStream;
    025import java.time.Duration;
    026import java.util.Objects;
    027import java.util.concurrent.BlockingQueue;
    028import java.util.concurrent.LinkedBlockingQueue;
    029import java.util.concurrent.TimeUnit;
    030
    031import org.apache.commons.io.build.AbstractStreamBuilder;
    032import org.apache.commons.io.output.QueueOutputStream;
    033
    034/**
    035 * Simple alternative to JDK {@link java.io.PipedInputStream}; queue input stream provides what's written in queue output stream.
    036 * <p>
    037 * To build an instance, use {@link Builder}.
    038 * </p>
    039 * <p>
    040 * Example usage:
    041 * </p>
    042 * <pre>
    043 * QueueInputStream inputStream = new QueueInputStream();
    044 * QueueOutputStream outputStream = inputStream.newQueueOutputStream();
    045 *
    046 * outputStream.write("hello world".getBytes(UTF_8));
    047 * inputStream.read();
    048 * </pre>
    049 * <p>
    050 * Unlike JDK {@link PipedInputStream} and {@link PipedOutputStream}, queue input/output streams may be used safely in a single thread or multiple threads.
    051 * Also, unlike JDK classes, no special meaning is attached to initial or current thread. Instances can be used longer after initial threads exited.
    052 * </p>
    053 * <p>
    054 * Closing a {@link QueueInputStream} has no effect. The methods in this class can be called after the stream has been closed without generating an
    055 * {@link IOException}.
    056 * </p>
    057 *
    058 * @see Builder
    059 * @see QueueOutputStream
    060 * @since 2.9.0
    061 */
    062public class QueueInputStream extends InputStream {
    063
    064    // @formatter:off
    065    /**
    066     * Builds a new {@link QueueInputStream}.
    067     *
    068     * <p>
    069     * For example:
    070     * </p>
    071     * <pre>{@code
    072     * QueueInputStream s = QueueInputStream.builder()
    073     *   .setBlockingQueue(new LinkedBlockingQueue<>())
    074     *   .setTimeout(Duration.ZERO)
    075     *   .get();}
    076     * </pre>
    077     *
    078     * @see #get()
    079     * @since 2.12.0
    080     */
    081    // @formatter:on
    082    public static class Builder extends AbstractStreamBuilder<QueueInputStream, Builder> {
    083
    084        private BlockingQueue<Integer> blockingQueue = new LinkedBlockingQueue<>();
    085        private Duration timeout = Duration.ZERO;
    086
    087        /**
    088         * Builds a new {@link QueueInputStream}.
    089         * <p>
    090         * This builder use the following aspects:
    091         * </p>
    092         * <ul>
    093         * <li>{@link #setBlockingQueue(BlockingQueue)}</li>
    094         * <li>timeout</li>
    095         * </ul>
    096         *
    097         * @return a new instance.
    098         */
    099        @Override
    100        public QueueInputStream get() {
    101            return new QueueInputStream(blockingQueue, timeout);
    102        }
    103
    104        /**
    105         * Sets backing queue for the stream.
    106         *
    107         * @param blockingQueue backing queue for the stream.
    108         * @return this
    109         */
    110        public Builder setBlockingQueue(final BlockingQueue<Integer> blockingQueue) {
    111            this.blockingQueue = blockingQueue != null ? blockingQueue : new LinkedBlockingQueue<>();
    112            return this;
    113        }
    114
    115        /**
    116         * Sets the polling timeout.
    117         *
    118         * @param timeout the polling timeout.
    119         * @return this.
    120         */
    121        public Builder setTimeout(final Duration timeout) {
    122            if (timeout != null && timeout.toNanos() < 0) {
    123                throw new IllegalArgumentException("timeout must not be negative");
    124            }
    125            this.timeout = timeout != null ? timeout : Duration.ZERO;
    126            return this;
    127        }
    128
    129    }
    130
    131    /**
    132     * Constructs a new {@link Builder}.
    133     *
    134     * @return a new {@link Builder}.
    135     * @since 2.12.0
    136     */
    137    public static Builder builder() {
    138        return new Builder();
    139    }
    140
    141    private final BlockingQueue<Integer> blockingQueue;
    142
    143    private final long timeoutNanos;
    144
    145    /**
    146     * Constructs a new instance with no limit to its internal queue size and zero timeout.
    147     */
    148    public QueueInputStream() {
    149        this(new LinkedBlockingQueue<>());
    150    }
    151
    152    /**
    153     * Constructs a new instance with given queue and zero timeout.
    154     *
    155     * @param blockingQueue backing queue for the stream.
    156     * @deprecated Use {@link #builder()}, {@link Builder}, and {@link Builder#get()}.
    157     */
    158    @Deprecated
    159    public QueueInputStream(final BlockingQueue<Integer> blockingQueue) {
    160        this(blockingQueue, Duration.ZERO);
    161    }
    162
    163    /**
    164     * Constructs a new instance with given queue and timeout.
    165     *
    166     * @param blockingQueue backing queue for the stream.
    167     * @param timeout       how long to wait before giving up when polling the queue.
    168     */
    169    private QueueInputStream(final BlockingQueue<Integer> blockingQueue, final Duration timeout) {
    170        this.blockingQueue = Objects.requireNonNull(blockingQueue, "blockingQueue");
    171        this.timeoutNanos = Objects.requireNonNull(timeout, "timeout").toNanos();
    172    }
    173
    174    /**
    175     * Gets the blocking queue.
    176     *
    177     * @return the blocking queue.
    178     */
    179    BlockingQueue<Integer> getBlockingQueue() {
    180        return blockingQueue;
    181    }
    182
    183    /**
    184     * Gets the timeout duration.
    185     *
    186     * @return the timeout duration.
    187     */
    188    Duration getTimeout() {
    189        return Duration.ofNanos(timeoutNanos);
    190    }
    191
    192    /**
    193     * Constructs a new QueueOutputStream instance connected to this. Writes to the output stream will be visible to this input stream.
    194     *
    195     * @return QueueOutputStream connected to this stream.
    196     */
    197    public QueueOutputStream newQueueOutputStream() {
    198        return new QueueOutputStream(blockingQueue);
    199    }
    200
    201    /**
    202     * Reads and returns a single byte.
    203     *
    204     * @return the byte read, or {@code -1} if a timeout occurs before a queue element is available.
    205     * @throws IllegalStateException if thread is interrupted while waiting.
    206     */
    207    @Override
    208    public int read() {
    209        try {
    210            final Integer value = blockingQueue.poll(timeoutNanos, TimeUnit.NANOSECONDS);
    211            return value == null ? EOF : 0xFF & value;
    212        } catch (final InterruptedException e) {
    213            Thread.currentThread().interrupt();
    214            // throw runtime unchecked exception to maintain signature backward-compatibility of
    215            // this read method, which does not declare IOException
    216            throw new IllegalStateException(e);
    217        }
    218    }
    219
    220}