    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 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         * Constructs a new builder of {@link QueueInputStream}.
    089         */
    090        public Builder() {
    091            // empty
    092        }
    093
    094        /**
    095         * Builds a new {@link QueueInputStream}.
    096         * <p>
    097         * This builder uses the following aspects:
    098         * </p>
    099         * <ul>
    100         * <li>{@link #setBlockingQueue(BlockingQueue)}</li>
    101         * <li>timeout</li>
    102         * </ul>
    103         *
    104         * @return a new instance.
    105         * @see #getUnchecked()
    106         */
    107        @Override
    108        public QueueInputStream get() {
    109            return new QueueInputStream(this);
    110        }
    111
    112        /**
    113         * Sets backing queue for the stream.
    114         *
    115         * @param blockingQueue backing queue for the stream, null resets to a new blocking queue instance.
    116         * @return {@code this} instance.
    117         */
    118        public Builder setBlockingQueue(final BlockingQueue<Integer> blockingQueue) {
    119            this.blockingQueue = blockingQueue != null ? blockingQueue : new LinkedBlockingQueue<>();
    120            return this;
    121        }
    122
    123        /**
    124         * Sets the polling timeout.
    125         *
    126         * @param timeout the polling timeout.
    127         * @return {@code this} instance.
    128         */
    129        public Builder setTimeout(final Duration timeout) {
    130            if (timeout != null && timeout.toNanos() < 0) {
    131                throw new IllegalArgumentException("timeout must not be negative");
    132            }
    133            this.timeout = timeout != null ? timeout : Duration.ZERO;
    134            return this;
    135        }
    136
    137    }
    138
    139    /**
    140     * Constructs a new {@link Builder}.
    141     *
    142     * @return a new {@link Builder}.
    143     * @since 2.12.0
    144     */
    145    public static Builder builder() {
    146        return new Builder();
    147    }
    148
    149    private final BlockingQueue<Integer> blockingQueue;
    150
    151    private final long timeoutNanos;
    152
    153    /**
    154     * Constructs a new instance with no limit to its internal queue size and zero timeout.
    155     */
    156    public QueueInputStream() {
    157        this(new LinkedBlockingQueue<>());
    158    }
    159
    160    /**
    161     * Constructs a new instance with given queue and zero timeout.
    162     *
    163     * @param blockingQueue backing queue for the stream, null maps to a new blocking queue instance.
    164     * @deprecated Use {@link #builder()}, {@link Builder}, and {@link Builder#get()}.
    165     */
    166    @Deprecated
    167    public QueueInputStream(final BlockingQueue<Integer> blockingQueue) {
    168        this(builder().setBlockingQueue(blockingQueue));
    169    }
    170
    171    /**
    172     * Constructs a new instance.
    173     *
    174     * @param builder The builder.
    175     */
    176    private QueueInputStream(final Builder builder) {
    177        this.blockingQueue = Objects.requireNonNull(builder.blockingQueue, "blockingQueue");
    178        this.timeoutNanos = Objects.requireNonNull(builder.timeout, "timeout").toNanos();
    179    }
    180
    181    /**
    182     * Gets the blocking queue.
    183     *
    184     * @return the blocking queue.
    185     */
    186    BlockingQueue<Integer> getBlockingQueue() {
    187        return blockingQueue;
    188    }
    189
    190    /**
    191     * Gets the timeout duration.
    192     *
    193     * @return the timeout duration.
    194     */
    195    Duration getTimeout() {
    196        return Duration.ofNanos(timeoutNanos);
    197    }
    198
    199    /**
    200     * Constructs a new QueueOutputStream instance connected to this. Writes to the output stream will be visible to this input stream.
    201     *
    202     * @return QueueOutputStream connected to this stream.
    203     */
    204    public QueueOutputStream newQueueOutputStream() {
    205        return new QueueOutputStream(blockingQueue);
    206    }
    207
    208    /**
    209     * Reads and returns a single byte.
    210     *
    211     * @return the byte read, or {@code -1} if a timeout occurs before a queue element is available.
    212     * @throws IllegalStateException if thread is interrupted while waiting.
    213     */
    214    @Override
    215    public int read() {
    216        try {
    217            final Integer value = blockingQueue.poll(timeoutNanos, TimeUnit.NANOSECONDS);
    218            return value == null ? EOF : 0xFF & value;
    219        } catch (final InterruptedException e) {
    220            Thread.currentThread().interrupt();
    221            // throw runtime unchecked exception to maintain signature backward-compatibility of
    222            // this read method, which does not declare IOException
    223            throw new IllegalStateException(e);
    224        }
    225    }
    226
    227}