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         * Constructs a new builder of {@link UnsynchronizedFilterInputStream}.
075         */
076        public Builder() {
077            // empty
078        }
079
080        /**
081         * Builds a new {@link UnsynchronizedFilterInputStream}.
082         * <p>
083         * You must set an aspect that supports {@link #getInputStream()}, otherwise, this method throws an exception.
084         * </p>
085         * <p>
086         * This builder uses the following aspects:
087         * </p>
088         * <ul>
089         * <li>{@link #getInputStream()}</li>
090         * </ul>
091         *
092         * @return a new instance.
093         * @throws IllegalStateException         if the {@code origin} is {@code null}.
094         * @throws UnsupportedOperationException if the origin cannot be converted to an {@link InputStream}.
095         * @throws IOException                   if an I/O error occurs converting to an {@link InputStream} using {@link #getInputStream()}.
096         * @see #getInputStream()
097         * @see #getUnchecked()
098         */
099        @Override
100        public UnsynchronizedFilterInputStream get() throws IOException {
101            return new UnsynchronizedFilterInputStream(getInputStream());
102        }
103
104    }
105
106    /**
107     * Constructs a new {@link Builder}.
108     *
109     * @return a new {@link Builder}.
110     */
111    public static Builder builder() {
112        return new Builder();
113    }
114
115    /**
116     * The source input stream that is filtered.
117     */
118    protected volatile InputStream inputStream;
119
120    /**
121     * Constructs a new {@code FilterInputStream} with the specified input stream as source.
122     *
123     * @param inputStream the non-null InputStream to filter reads on.
124     */
125    UnsynchronizedFilterInputStream(final InputStream inputStream) {
126        this.inputStream = inputStream;
127    }
128
129    /**
130     * Returns the number of bytes that are available before this stream will block.
131     *
132     * @return the number of bytes available before blocking.
133     * @throws IOException if an error occurs in this stream.
134     */
135    @Override
136    public int available() throws IOException {
137        return inputStream.available();
138    }
139
140    /**
141     * Closes this stream. This implementation closes the filtered stream.
142     *
143     * @throws IOException if an error occurs while closing this stream.
144     */
145    @Override
146    public void close() throws IOException {
147        inputStream.close();
148    }
149
150    /**
151     * Sets a mark position in this stream. The parameter {@code readLimit} indicates how many bytes can be read before the mark is invalidated. Sending
152     * {@code reset()} will reposition this stream back to the marked position, provided that {@code readLimit} has not been surpassed.
153     * <p>
154     * This implementation sets a mark in the filtered stream.
155     *
156     * @param readLimit the number of bytes that can be read from this stream before the mark is invalidated.
157     * @see #markSupported()
158     * @see #reset()
159     */
160    @SuppressWarnings("sync-override") // by design.
161    @Override
162    public void mark(final int readLimit) {
163        inputStream.mark(readLimit);
164    }
165
166    /**
167     * Indicates whether this stream supports {@code mark()} and {@code reset()}. This implementation returns whether or not the filtered stream supports
168     * marking.
169     *
170     * @return {@code true} if {@code mark()} and {@code reset()} are supported, {@code false} otherwise.
171     * @see #mark(int)
172     * @see #reset()
173     * @see #skip(long)
174     */
175    @Override
176    public boolean markSupported() {
177        return inputStream.markSupported();
178    }
179
180    /**
181     * 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
182     * reached.
183     *
184     * @return the byte read or -1 if the end of the filtered stream has been reached.
185     * @throws IOException if the stream is closed or another IOException occurs.
186     */
187    @Override
188    public int read() throws IOException {
189        return inputStream.read();
190    }
191
192    /**
193     * 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
194     * the end of this stream was encountered. This implementation reads bytes from the filtered stream.
195     *
196     * @param buffer the byte array in which to store the read bytes.
197     * @return the number of bytes actually read or -1 if the end of the filtered stream has been reached while reading.
198     * @throws IOException if this stream is closed or another IOException occurs.
199     */
200    @Override
201    public int read(final byte[] buffer) throws IOException {
202        return read(buffer, 0, buffer.length);
203    }
204
205    /**
206     * 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
207     * 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
208     * stream.
209     *
210     * @param buffer the byte array in which to store the bytes read.
211     * @param offset the initial position in {@code buffer} to store the bytes read from this stream.
212     * @param count  the maximum number of bytes to store in {@code buffer}.
213     * @return the number of bytes actually read or -1 if the end of the filtered stream has been reached while reading.
214     * @throws IOException if this stream is closed or another I/O error occurs.
215     */
216    @Override
217    public int read(final byte[] buffer, final int offset, final int count) throws IOException {
218        return inputStream.read(buffer, offset, count);
219    }
220
221    /**
222     * Resets this stream to the last marked location. This implementation resets the target stream.
223     *
224     * @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
225     *                     been read since setting the mark.
226     * @see #mark(int)
227     * @see #markSupported()
228     */
229    @SuppressWarnings("sync-override") // by design.
230    @Override
231    public void reset() throws IOException {
232        inputStream.reset();
233    }
234
235    /**
236     * Skips {@code count} number of bytes in this stream. Subsequent {@code read()}'s will not return these bytes unless {@code reset()} is used. This
237     * implementation skips {@code count} number of bytes in the filtered stream.
238     *
239     * @param count the number of bytes to skip.
240     * @return the number of bytes actually skipped.
241     * @throws IOException if this stream is closed or another IOException occurs.
242     * @see #mark(int)
243     * @see #reset()
244     */
245    @Override
246    public long skip(final long count) throws IOException {
247        return inputStream.skip(count);
248    }
249}