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.buffer;
018
019import static org.apache.commons.io.IOUtils.EOF;
020
021import java.io.BufferedInputStream;
022import java.io.FilterInputStream;
023import java.io.IOException;
024import java.io.InputStream;
025import java.util.Objects;
026
027import org.apache.commons.io.IOUtils;
028
029/**
030 * Implements a buffered input stream, which is internally based on a {@link CircularByteBuffer}. Unlike the
031 * {@link BufferedInputStream}, this one doesn't need to reallocate byte arrays internally.
032 *
033 * @since 2.7
034 */
035public class CircularBufferInputStream extends FilterInputStream {
036
037    /** Internal buffer. */
038    protected final CircularByteBuffer buffer;
039
040    /** Internal buffer size. */
041    protected final int bufferSize;
042
043    /** Whether we've seen the input stream EOF. */
044    private boolean eof;
045
046    /**
047     * Constructs a new instance, which filters the given input stream, and uses a reasonable default buffer size
048     * ({@link IOUtils#DEFAULT_BUFFER_SIZE}).
049     *
050     * @param inputStream The input stream, which is being buffered.
051     */
052    public CircularBufferInputStream(final InputStream inputStream) {
053        this(inputStream, IOUtils.DEFAULT_BUFFER_SIZE);
054    }
055
056    /**
057     * Constructs a new instance, which filters the given input stream, and uses the given buffer size.
058     *
059     * @param inputStream The input stream, which is being buffered.
060     * @param bufferSize The size of the {@link CircularByteBuffer}, which is used internally.
061     */
062    @SuppressWarnings("resource") // Caller closes InputStream
063    public CircularBufferInputStream(final InputStream inputStream, final int bufferSize) {
064        super(Objects.requireNonNull(inputStream, "inputStream"));
065        if (bufferSize <= 0) {
066            throw new IllegalArgumentException("Illegal bufferSize: " + bufferSize);
067        }
068        this.buffer = new CircularByteBuffer(bufferSize);
069        this.bufferSize = bufferSize;
070        this.eof = false;
071    }
072
073    @Override
074    public void close() throws IOException {
075        super.close();
076        eof = true;
077        buffer.clear();
078    }
079
080    /**
081     * Fills the buffer with the contents of the input stream.
082     *
083     * @throws IOException in case of an error while reading from the input stream.
084     */
085    protected void fillBuffer() throws IOException {
086        if (eof) {
087            return;
088        }
089        int space = buffer.getSpace();
090        final byte[] buf = IOUtils.byteArray(space);
091        while (space > 0) {
092            final int res = in.read(buf, 0, space);
093            if (res == EOF) {
094                eof = true;
095                return;
096            }
097            if (res > 0) {
098                buffer.add(buf, 0, res);
099                space -= res;
100            }
101        }
102    }
103
104    /**
105     * Fills the buffer from the input stream until the given number of bytes have been added to the buffer.
106     *
107     * @param count number of byte to fill into the buffer
108     * @return true if the buffer has bytes
109     * @throws IOException in case of an error while reading from the input stream.
110     */
111    protected boolean haveBytes(final int count) throws IOException {
112        if (buffer.getCurrentNumberOfBytes() < count) {
113            fillBuffer();
114        }
115        return buffer.hasBytes();
116    }
117
118    @Override
119    public int read() throws IOException {
120        if (!haveBytes(1)) {
121            return EOF;
122        }
123        return buffer.read() & 0xFF; // return unsigned byte
124    }
125
126    @Override
127    public int read(final byte[] targetBuffer, final int offset, final int length) throws IOException {
128        Objects.requireNonNull(targetBuffer, "targetBuffer");
129        if (offset < 0) {
130            throw new IllegalArgumentException("Offset must not be negative");
131        }
132        if (length < 0) {
133            throw new IllegalArgumentException("Length must not be negative");
134        }
135        if (!haveBytes(length)) {
136            return EOF;
137        }
138        final int result = Math.min(length, buffer.getCurrentNumberOfBytes());
139        for (int i = 0; i < result; i++) {
140            targetBuffer[offset + i] = buffer.read();
141        }
142        return result;
143    }
144}