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 * Provenance: Apache Harmony and modified.
035 * </p>
036 *
037 * @see FilterInputStream
038 * @since 2.12.0
039 */
040//@NotThreadSafe
041public class UnsynchronizedFilterInputStream extends InputStream {
042
043    /**
044     * Builds a new {@link UnsynchronizedFilterInputStream} instance.
045     * <p>
046     * Using File IO:
047     * </p>
048     * <pre>{@code
049     * UnsynchronizedFilterInputStream s = UnsynchronizedFilterInputStream.builder()
050     *   .setFile(file)
051     *   .get()}
052     * </pre>
053     * <p>
054     * Using NIO Path:
055     * </p>
056     * <pre>{@code
057     * UnsynchronizedFilterInputStream s = UnsynchronizedFilterInputStream.builder()
058     *   .setPath(path)
059     *   .get()}
060     * </pre>
061     */
062    public static class Builder extends AbstractStreamBuilder<UnsynchronizedFilterInputStream, Builder> {
063
064        /**
065         * Constructs a new instance.
066         *
067         * @throws UnsupportedOperationException if the origin cannot be converted to an InputStream.
068         */
069        @SuppressWarnings("resource") // Caller closes.
070        @Override
071        public UnsynchronizedFilterInputStream get() throws IOException {
072            return new UnsynchronizedFilterInputStream(getOrigin().getInputStream());
073        }
074
075    }
076
077    /**
078     * Constructs a new {@link Builder}.
079     *
080     * @return a new {@link Builder}.
081     */
082    public static Builder builder() {
083        return new Builder();
084    }
085
086    /**
087     * The source input stream that is filtered.
088     */
089    protected volatile InputStream inputStream;
090
091    /**
092     * Constructs a new {@code FilterInputStream} with the specified input stream as source.
093     *
094     * @param inputStream the non-null InputStream to filter reads on.
095     */
096    UnsynchronizedFilterInputStream(final InputStream inputStream) {
097        this.inputStream = inputStream;
098    }
099
100    /**
101     * Returns the number of bytes that are available before this stream will block.
102     *
103     * @return the number of bytes available before blocking.
104     * @throws IOException if an error occurs in this stream.
105     */
106    @Override
107    public int available() throws IOException {
108        return inputStream.available();
109    }
110
111    /**
112     * Closes this stream. This implementation closes the filtered stream.
113     *
114     * @throws IOException if an error occurs while closing this stream.
115     */
116    @Override
117    public void close() throws IOException {
118        inputStream.close();
119    }
120
121    /**
122     * Sets a mark position in this stream. The parameter {@code readlimit} indicates how many bytes can be read before the mark is invalidated. Sending
123     * {@code reset()} will reposition this stream back to the marked position, provided that {@code readlimit} has not been surpassed.
124     * <p>
125     * This implementation sets a mark in the filtered stream.
126     *
127     * @param readlimit the number of bytes that can be read from this stream before the mark is invalidated.
128     * @see #markSupported()
129     * @see #reset()
130     */
131    @SuppressWarnings("sync-override") // by design.
132    @Override
133    public void mark(final int readlimit) {
134        inputStream.mark(readlimit);
135    }
136
137    /**
138     * Indicates whether this stream supports {@code mark()} and {@code reset()}. This implementation returns whether or not the filtered stream supports
139     * marking.
140     *
141     * @return {@code true} if {@code mark()} and {@code reset()} are supported, {@code false} otherwise.
142     * @see #mark(int)
143     * @see #reset()
144     * @see #skip(long)
145     */
146    @Override
147    public boolean markSupported() {
148        return inputStream.markSupported();
149    }
150
151    /**
152     * 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
153     * reached.
154     *
155     * @return the byte read or -1 if the end of the filtered stream has been reached.
156     * @throws IOException if the stream is closed or another IOException occurs.
157     */
158    @Override
159    public int read() throws IOException {
160        return inputStream.read();
161    }
162
163    /**
164     * 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
165     * the end of this stream was encountered. This implementation reads bytes from the filtered stream.
166     *
167     * @param buffer the byte array in which to store the read bytes.
168     * @return the number of bytes actually read or -1 if the end of the filtered stream has been reached while reading.
169     * @throws IOException if this stream is closed or another IOException occurs.
170     */
171    @Override
172    public int read(final byte[] buffer) throws IOException {
173        return read(buffer, 0, buffer.length);
174    }
175
176    /**
177     * 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
178     * 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
179     * stream.
180     *
181     * @param buffer the byte array in which to store the bytes read.
182     * @param offset the initial position in {@code buffer} to store the bytes read from this stream.
183     * @param count  the maximum number of bytes to store in {@code buffer}.
184     * @return the number of bytes actually read or -1 if the end of the filtered stream has been reached while reading.
185     * @throws IOException if this stream is closed or another I/O error occurs.
186     */
187    @Override
188    public int read(final byte[] buffer, final int offset, final int count) throws IOException {
189        return inputStream.read(buffer, offset, count);
190    }
191
192    /**
193     * Resets this stream to the last marked location. This implementation resets the target stream.
194     *
195     * @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
196     *                     been read since setting the mark.
197     * @see #mark(int)
198     * @see #markSupported()
199     */
200    @SuppressWarnings("sync-override") // by design.
201    @Override
202    public void reset() throws IOException {
203        inputStream.reset();
204    }
205
206    /**
207     * Skips {@code count} number of bytes in this stream. Subsequent {@code read()}'s will not return these bytes unless {@code reset()} is used. This
208     * implementation skips {@code count} number of bytes in the filtered stream.
209     *
210     * @param count the number of bytes to skip.
211     * @return the number of bytes actually skipped.
212     * @throws IOException if this stream is closed or another IOException occurs.
213     * @see #mark(int)
214     * @see #reset()
215     */
216    @Override
217    public long skip(final long count) throws IOException {
218        return inputStream.skip(count);
219    }
220}