    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 */
    017
    018package org.apache.commons.io.input;
    019
    020import java.io.FilterInputStream;
    021import java.io.IOException;
    022import java.io.InputStream;
    023
    024import org.apache.commons.io.build.AbstractStreamBuilder;
    025
    026/**
    027 * An unsynchronized version of {@link FilterInputStream}, not thread-safe.
    028 * <p>
    029 * Wraps an existing {@link InputStream} and performs some transformation on the input data while it is being read. Transformations can be anything from a
    030 * simple byte-wise filtering input data to an on-the-fly compression or decompression of the underlying stream. Input streams that wrap another input stream
    031 * and provide some additional functionality on top of it usually inherit from this class.
    032 * </p>
    033 * <p>
    034 * To build an instance, see {@link Builder}.
    035 * </p>
    036 * <p>
    037 * Provenance: Apache Harmony and modified.
    038 * </p>
    039 *
    040 * @see FilterInputStream
    041 * @since 2.12.0
    042 */
    043//@NotThreadSafe
    044public class UnsynchronizedFilterInputStream extends InputStream {
    045
    046    /**
    047     * Builds a new {@link UnsynchronizedFilterInputStream} instance.
    048     * <p>
    049     * Using File IO:
    050     * </p>
    051     * <pre>{@code
    052     * UnsynchronizedFilterInputStream s = UnsynchronizedFilterInputStream.builder()
    053     *   .setFile(file)
    054     *   .get();}
    055     * </pre>
    056     * <p>
    057     * Using NIO Path:
    058     * </p>
    059     * <pre>{@code
    060     * UnsynchronizedFilterInputStream s = UnsynchronizedFilterInputStream.builder()
    061     *   .setPath(path)
    062     *   .get();}
    063     * </pre>
    064     */
    065    public static class Builder extends AbstractStreamBuilder<UnsynchronizedFilterInputStream, Builder> {
    066
    067        /**
    068         * Constructs a new instance.
    069         * <p>
    070         * This builder use the aspect InputStream and OpenOption[].
    071         * </p>
    072         * <p>
    073         * You must provide an origin that can be converted to an InputStream by this builder, otherwise, this call will throw an
    074         * {@link UnsupportedOperationException}.
    075         * </p>
    076         *
    077         * @return a new instance.
    078         * @throws UnsupportedOperationException if the origin cannot provide an InputStream.
    079         * @see #getInputStream()
    080         */
    081        @SuppressWarnings("resource") // Caller closes.
    082        @Override
    083        public UnsynchronizedFilterInputStream get() throws IOException {
    084            return new UnsynchronizedFilterInputStream(getInputStream());
    085        }
    086
    087    }
    088
    089    /**
    090     * Constructs a new {@link Builder}.
    091     *
    092     * @return a new {@link Builder}.
    093     */
    094    public static Builder builder() {
    095        return new Builder();
    096    }
    097
    098    /**
    099     * The source input stream that is filtered.
    100     */
    101    protected volatile InputStream inputStream;
    102
    103    /**
    104     * Constructs a new {@code FilterInputStream} with the specified input stream as source.
    105     *
    106     * @param inputStream the non-null InputStream to filter reads on.
    107     */
    108    UnsynchronizedFilterInputStream(final InputStream inputStream) {
    109        this.inputStream = inputStream;
    110    }
    111
    112    /**
    113     * Returns the number of bytes that are available before this stream will block.
    114     *
    115     * @return the number of bytes available before blocking.
    116     * @throws IOException if an error occurs in this stream.
    117     */
    118    @Override
    119    public int available() throws IOException {
    120        return inputStream.available();
    121    }
    122
    123    /**
    124     * Closes this stream. This implementation closes the filtered stream.
    125     *
    126     * @throws IOException if an error occurs while closing this stream.
    127     */
    128    @Override
    129    public void close() throws IOException {
    130        inputStream.close();
    131    }
    132
    133    /**
    134     * Sets a mark position in this stream. The parameter {@code readlimit} indicates how many bytes can be read before the mark is invalidated. Sending
    135     * {@code reset()} will reposition this stream back to the marked position, provided that {@code readlimit} has not been surpassed.
    136     * <p>
    137     * This implementation sets a mark in the filtered stream.
    138     *
    139     * @param readlimit the number of bytes that can be read from this stream before the mark is invalidated.
    140     * @see #markSupported()
    141     * @see #reset()
    142     */
    143    @SuppressWarnings("sync-override") // by design.
    144    @Override
    145    public void mark(final int readlimit) {
    146        inputStream.mark(readlimit);
    147    }
    148
    149    /**
    150     * Indicates whether this stream supports {@code mark()} and {@code reset()}. This implementation returns whether or not the filtered stream supports
    151     * marking.
    152     *
    153     * @return {@code true} if {@code mark()} and {@code reset()} are supported, {@code false} otherwise.
    154     * @see #mark(int)
    155     * @see #reset()
    156     * @see #skip(long)
    157     */
    158    @Override
    159    public boolean markSupported() {
    160        return inputStream.markSupported();
    161    }
    162
    163    /**
    164     * Reads a single byte from the filtered stream and returns it as an integer in the range from 0 to 255. Returns -1 if the end of this stream has been
    165     * reached.
    166     *
    167     * @return the byte read or -1 if the end of the filtered stream has been reached.
    168     * @throws IOException if the stream is closed or another IOException occurs.
    169     */
    170    @Override
    171    public int read() throws IOException {
    172        return inputStream.read();
    173    }
    174
    175    /**
    176     * Reads bytes from this stream and stores them in the byte array {@code buffer}. Returns the number of bytes actually read or -1 if no bytes were read and
    177     * the end of this stream was encountered. This implementation reads bytes from the filtered stream.
    178     *
    179     * @param buffer the byte array in which to store the read bytes.
    180     * @return the number of bytes actually read or -1 if the end of the filtered stream has been reached while reading.
    181     * @throws IOException if this stream is closed or another IOException occurs.
    182     */
    183    @Override
    184    public int read(final byte[] buffer) throws IOException {
    185        return read(buffer, 0, buffer.length);
    186    }
    187
    188    /**
    189     * Reads at most {@code count} bytes from this stream and stores them in the byte array {@code buffer} starting at {@code offset}. Returns the number of
    190     * bytes actually read or -1 if no bytes have been read and the end of this stream has been reached. This implementation reads bytes from the filtered
    191     * stream.
    192     *
    193     * @param buffer the byte array in which to store the bytes read.
    194     * @param offset the initial position in {@code buffer} to store the bytes read from this stream.
    195     * @param count  the maximum number of bytes to store in {@code buffer}.
    196     * @return the number of bytes actually read or -1 if the end of the filtered stream has been reached while reading.
    197     * @throws IOException if this stream is closed or another I/O error occurs.
    198     */
    199    @Override
    200    public int read(final byte[] buffer, final int offset, final int count) throws IOException {
    201        return inputStream.read(buffer, offset, count);
    202    }
    203
    204    /**
    205     * Resets this stream to the last marked location. This implementation resets the target stream.
    206     *
    207     * @throws IOException if this stream is already closed, no mark has been set or the mark is no longer valid because more than {@code readlimit} bytes have
    208     *                     been read since setting the mark.
    209     * @see #mark(int)
    210     * @see #markSupported()
    211     */
    212    @SuppressWarnings("sync-override") // by design.
    213    @Override
    214    public void reset() throws IOException {
    215        inputStream.reset();
    216    }
    217
    218    /**
    219     * Skips {@code count} number of bytes in this stream. Subsequent {@code read()}'s will not return these bytes unless {@code reset()} is used. This
    220     * implementation skips {@code count} number of bytes in the filtered stream.
    221     *
    222     * @param count the number of bytes to skip.
    223     * @return the number of bytes actually skipped.
    224     * @throws IOException if this stream is closed or another IOException occurs.
    225     * @see #mark(int)
    226     * @see #reset()
    227     */
    228    @Override
    229    public long skip(final long count) throws IOException {
    230        return inputStream.skip(count);
    231    }
    232}