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, use {@link Builder}.
035 * </p>
036 * <p>
037 * Provenance: Apache Harmony and modified.
038 * </p>
039 *
040 * @see Builder
041 * @see FilterInputStream
042 * @since 2.12.0
043 */
044//@NotThreadSafe
045public class UnsynchronizedFilterInputStream extends InputStream {
046
047    // @formatter:off
048    /**
049     * Builds a new {@link UnsynchronizedFilterInputStream}.
050     *
051     * <p>
052     * Using File IO:
053     * </p>
054     * <pre>{@code
055     * UnsynchronizedFilterInputStream s = UnsynchronizedFilterInputStream.builder()
056     *   .setFile(file)
057     *   .get();}
058     * </pre>
059     * <p>
060     * Using NIO Path:
061     * </p>
062     * <pre>{@code
063     * UnsynchronizedFilterInputStream s = UnsynchronizedFilterInputStream.builder()
064     *   .setPath(path)
065     *   .get();}
066     * </pre>
067     *
068     * @see #get()
069     */
070    // @formatter:on
071    public static class Builder extends AbstractStreamBuilder<UnsynchronizedFilterInputStream, Builder> {
072
073        /**
074         * Builds a new {@link UnsynchronizedFilterInputStream}.
075         * <p>
076         * You must set input that supports {@link #getInputStream()}, otherwise, this method throws an exception.
077         * </p>
078         * <p>
079         * This builder use the following aspects:
080         * </p>
081         * <ul>
082         * <li>{@link #getInputStream()}</li>
083         * </ul>
084         *
085         * @return a new instance.
086         * @throws IllegalStateException         if the {@code origin} is {@code null}.
087         * @throws UnsupportedOperationException if the origin cannot be converted to an {@link InputStream}.
088         * @throws IOException                   if an I/O error occurs.
089         * @see #getInputStream()
090         */
091        @SuppressWarnings("resource") // Caller closes.
092        @Override
093        public UnsynchronizedFilterInputStream get() throws IOException {
094            return new UnsynchronizedFilterInputStream(getInputStream());
095        }
096
097    }
098
099    /**
100     * Constructs a new {@link Builder}.
101     *
102     * @return a new {@link Builder}.
103     */
104    public static Builder builder() {
105        return new Builder();
106    }
107
108    /**
109     * The source input stream that is filtered.
110     */
111    protected volatile InputStream inputStream;
112
113    /**
114     * Constructs a new {@code FilterInputStream} with the specified input stream as source.
115     *
116     * @param inputStream the non-null InputStream to filter reads on.
117     */
118    UnsynchronizedFilterInputStream(final InputStream inputStream) {
119        this.inputStream = inputStream;
120    }
121
122    /**
123     * Returns the number of bytes that are available before this stream will block.
124     *
125     * @return the number of bytes available before blocking.
126     * @throws IOException if an error occurs in this stream.
127     */
128    @Override
129    public int available() throws IOException {
130        return inputStream.available();
131    }
132
133    /**
134     * Closes this stream. This implementation closes the filtered stream.
135     *
136     * @throws IOException if an error occurs while closing this stream.
137     */
138    @Override
139    public void close() throws IOException {
140        inputStream.close();
141    }
142
143    /**
144     * Sets a mark position in this stream. The parameter {@code readLimit} indicates how many bytes can be read before the mark is invalidated. Sending
145     * {@code reset()} will reposition this stream back to the marked position, provided that {@code readLimit} has not been surpassed.
146     * <p>
147     * This implementation sets a mark in the filtered stream.
148     *
149     * @param readLimit the number of bytes that can be read from this stream before the mark is invalidated.
150     * @see #markSupported()
151     * @see #reset()
152     */
153    @SuppressWarnings("sync-override") // by design.
154    @Override
155    public void mark(final int readLimit) {
156        inputStream.mark(readLimit);
157    }
158
159    /**
160     * Indicates whether this stream supports {@code mark()} and {@code reset()}. This implementation returns whether or not the filtered stream supports
161     * marking.
162     *
163     * @return {@code true} if {@code mark()} and {@code reset()} are supported, {@code false} otherwise.
164     * @see #mark(int)
165     * @see #reset()
166     * @see #skip(long)
167     */
168    @Override
169    public boolean markSupported() {
170        return inputStream.markSupported();
171    }
172
173    /**
174     * 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
175     * reached.
176     *
177     * @return the byte read or -1 if the end of the filtered stream has been reached.
178     * @throws IOException if the stream is closed or another IOException occurs.
179     */
180    @Override
181    public int read() throws IOException {
182        return inputStream.read();
183    }
184
185    /**
186     * 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
187     * the end of this stream was encountered. This implementation reads bytes from the filtered stream.
188     *
189     * @param buffer the byte array in which to store the read bytes.
190     * @return the number of bytes actually read or -1 if the end of the filtered stream has been reached while reading.
191     * @throws IOException if this stream is closed or another IOException occurs.
192     */
193    @Override
194    public int read(final byte[] buffer) throws IOException {
195        return read(buffer, 0, buffer.length);
196    }
197
198    /**
199     * 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
200     * 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
201     * stream.
202     *
203     * @param buffer the byte array in which to store the bytes read.
204     * @param offset the initial position in {@code buffer} to store the bytes read from this stream.
205     * @param count  the maximum number of bytes to store in {@code buffer}.
206     * @return the number of bytes actually read or -1 if the end of the filtered stream has been reached while reading.
207     * @throws IOException if this stream is closed or another I/O error occurs.
208     */
209    @Override
210    public int read(final byte[] buffer, final int offset, final int count) throws IOException {
211        return inputStream.read(buffer, offset, count);
212    }
213
214    /**
215     * Resets this stream to the last marked location. This implementation resets the target stream.
216     *
217     * @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
218     *                     been read since setting the mark.
219     * @see #mark(int)
220     * @see #markSupported()
221     */
222    @SuppressWarnings("sync-override") // by design.
223    @Override
224    public void reset() throws IOException {
225        inputStream.reset();
226    }
227
228    /**
229     * Skips {@code count} number of bytes in this stream. Subsequent {@code read()}'s will not return these bytes unless {@code reset()} is used. This
230     * implementation skips {@code count} number of bytes in the filtered stream.
231     *
232     * @param count the number of bytes to skip.
233     * @return the number of bytes actually skipped.
234     * @throws IOException if this stream is closed or another IOException occurs.
235     * @see #mark(int)
236     * @see #reset()
237     */
238    @Override
239    public long skip(final long count) throws IOException {
240        return inputStream.skip(count);
241    }
242}