    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 *
    037 * <p>
    038 * Example usage:
    039 * </p>
    040 *
    041 * <pre>
    042 * QueueInputStream inputStream = new QueueInputStream();
    043 * QueueOutputStream outputStream = inputStream.newQueueOutputStream();
    044 *
    045 * outputStream.write("hello world".getBytes(UTF_8));
    046 * inputStream.read();
    047 * </pre>
    048 * <p>
    049 * Unlike JDK {@link PipedInputStream} and {@link PipedOutputStream}, queue input/output streams may be used safely in a single thread or multiple threads.
    050 * Also, unlike JDK classes, no special meaning is attached to initial or current thread. Instances can be used longer after initial threads exited.
    051 * </p>
    052 * <p>
    053 * Closing a {@link QueueInputStream} has no effect. The methods in this class can be called after the stream has been closed without generating an
    054 * {@link IOException}.
    055 * </p>
    056 *
    057 * @see QueueOutputStream
    058 * @since 2.9.0
    059 */
    060public class QueueInputStream extends InputStream {
    061
    062    /**
    063     * Builds a new {@link QueueInputStream} instance.
    064     * <p>
    065     * For example:
    066     * </p>
    067     *
    068     * <pre>{@code
    069     * QueueInputStream s = QueueInputStream.builder()
    070     *   .setBlockingQueue(new LinkedBlockingQueue<>())
    071     *   .setTimeout(Duration.ZERO)
    072     *   .get()}
    073     * </pre>
    074     * <p>
    075     *
    076     * @since 2.12.0
    077     */
    078    public static class Builder extends AbstractStreamBuilder<QueueInputStream, Builder> {
    079
    080        private BlockingQueue<Integer> blockingQueue = new LinkedBlockingQueue<>();
    081        private Duration timeout = Duration.ZERO;
    082
    083        @Override
    084        public QueueInputStream get() {
    085            return new QueueInputStream(blockingQueue, timeout);
    086        }
    087
    088        /**
    089         * Sets backing queue for the stream.
    090         *
    091         * @param blockingQueue backing queue for the stream.
    092         * @return this
    093         */
    094        public Builder setBlockingQueue(final BlockingQueue<Integer> blockingQueue) {
    095            this.blockingQueue = blockingQueue != null ? blockingQueue : new LinkedBlockingQueue<>();
    096            return this;
    097        }
    098
    099        /**
    100         * Sets the polling timeout.
    101         *
    102         * @param timeout the polling timeout.
    103         * @return this.
    104         */
    105        public Builder setTimeout(final Duration timeout) {
    106            if (timeout != null && timeout.toNanos() < 0) {
    107                throw new IllegalArgumentException("timeout must not be negative");
    108            }
    109            this.timeout = timeout != null ? timeout : Duration.ZERO;
    110            return this;
    111        }
    112
    113    }
    114
    115    /**
    116     * Constructs a new {@link Builder}.
    117     *
    118     * @return a new {@link Builder}.
    119     * @since 2.12.0
    120     */
    121    public static Builder builder() {
    122        return new Builder();
    123    }
    124
    125    private final BlockingQueue<Integer> blockingQueue;
    126
    127    private final long timeoutNanos;
    128
    129    /**
    130     * Constructs a new instance with no limit to its internal queue size and zero timeout.
    131     */
    132    public QueueInputStream() {
    133        this(new LinkedBlockingQueue<>());
    134    }
    135
    136    /**
    137     * Constructs a new instance with given queue and zero timeout.
    138     *
    139     * @param blockingQueue backing queue for the stream.
    140     * @deprecated Use {@link #builder()}.
    141     */
    142    @Deprecated
    143    public QueueInputStream(final BlockingQueue<Integer> blockingQueue) {
    144        this(blockingQueue, Duration.ZERO);
    145    }
    146
    147    /**
    148     * Constructs a new instance with given queue and timeout.
    149     *
    150     * @param blockingQueue backing queue for the stream.
    151     * @param timeout       how long to wait before giving up when polling the queue.
    152     */
    153    private QueueInputStream(final BlockingQueue<Integer> blockingQueue, final Duration timeout) {
    154        this.blockingQueue = Objects.requireNonNull(blockingQueue, "blockingQueue");
    155        this.timeoutNanos = Objects.requireNonNull(timeout, "timeout").toNanos();
    156    }
    157
    158    /**
    159     * Gets the blocking queue.
    160     *
    161     * @return the blocking queue.
    162     */
    163    BlockingQueue<Integer> getBlockingQueue() {
    164        return blockingQueue;
    165    }
    166
    167    /**
    168     * Gets the timeout duration.
    169     *
    170     * @return the timeout duration.
    171     */
    172    Duration getTimeout() {
    173        return Duration.ofNanos(timeoutNanos);
    174    }
    175
    176    /**
    177     * Creates a new QueueOutputStream instance connected to this. Writes to the output stream will be visible to this input stream.
    178     *
    179     * @return QueueOutputStream connected to this stream.
    180     */
    181    public QueueOutputStream newQueueOutputStream() {
    182        return new QueueOutputStream(blockingQueue);
    183    }
    184
    185    /**
    186     * Reads and returns a single byte.
    187     *
    188     * @return the byte read, or {@code -1} if a timeout occurs before a queue element is available.
    189     * @throws IllegalStateException if thread is interrupted while waiting.
    190     */
    191    @Override
    192    public int read() {
    193        try {
    194            final Integer value = blockingQueue.poll(timeoutNanos, TimeUnit.NANOSECONDS);
    195            return value == null ? EOF : 0xFF & value;
    196        } catch (final InterruptedException e) {
    197            Thread.currentThread().interrupt();
    198            // throw runtime unchecked exception to maintain signature backward-compatibilty of
    199            // this read method, which does not declare IOException
    200            throw new IllegalStateException(e);
    201        }
    202    }
    203
    204}