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.IOException;
022import java.io.InputStream;
023import java.util.Objects;
024
025import org.apache.commons.io.IOUtils;
026
027/**
028 * Implements a buffered input stream, which is internally based on a {@link CircularByteBuffer}. Unlike the
029 * {@link java.io.BufferedInputStream}, this one doesn't need to reallocate byte arrays internally.
030 */
031public class CircularBufferInputStream extends InputStream {
032
033    /** What we are streaming, used to fill the internal buffer. */
034    protected final InputStream in;
035
036    /** Internal buffer. */
037    protected final CircularByteBuffer buffer;
038
039    /** Internal buffer size. */
040    protected final int bufferSize;
041
042    /** Whether we've see the input stream EOF. */
043    private boolean eof;
044
045    /**
046     * Creates a new instance, which filters the given input stream, and uses the given buffer size.
047     *
048     * @param inputStream The input stream, which is being buffered.
049     * @param bufferSize The size of the {@link CircularByteBuffer}, which is used internally.
050     */
051    public CircularBufferInputStream(final InputStream inputStream, final int bufferSize) {
052        if (bufferSize <= 0) {
053            throw new IllegalArgumentException("Invalid bufferSize: " + bufferSize);
054        }
055        this.in = Objects.requireNonNull(inputStream, "inputStream");
056        this.buffer = new CircularByteBuffer(bufferSize);
057        this.bufferSize = bufferSize;
058        this.eof = false;
059    }
060
061    /**
062     * Creates a new instance, which filters the given input stream, and uses a reasonable default buffer size
063     * ({@link IOUtils#DEFAULT_BUFFER_SIZE}).
064     *
065     * @param inputStream The input stream, which is being buffered.
066     */
067    public CircularBufferInputStream(final InputStream inputStream) {
068        this(inputStream, IOUtils.DEFAULT_BUFFER_SIZE);
069    }
070
071    /**
072     * Fills the buffer with the contents of the input stream.
073     *
074     * @throws IOException in case of an error while reading from the input stream.
075     */
076    protected void fillBuffer() throws IOException {
077        if (eof) {
078            return;
079        }
080        int space = buffer.getSpace();
081        final byte[] buf = IOUtils.byteArray(space);
082        while (space > 0) {
083            final int res = in.read(buf, 0, space);
084            if (res == EOF) {
085                eof = true;
086                return;
087            }
088            if (res > 0) {
089                buffer.add(buf, 0, res);
090                space -= res;
091            }
092        }
093    }
094
095    /**
096     * Fills the buffer from the input stream until the given number of bytes have been added to the buffer.
097     *
098     * @param count number of byte to fill into the buffer
099     * @return true if the buffer has bytes
100     * @throws IOException in case of an error while reading from the input stream.
101     */
102    protected boolean haveBytes(final int count) throws IOException {
103        if (buffer.getCurrentNumberOfBytes() < count) {
104            fillBuffer();
105        }
106        return buffer.hasBytes();
107    }
108
109    @Override
110    public int read() throws IOException {
111        if (!haveBytes(1)) {
112            return EOF;
113        }
114        return buffer.read() & 0xFF; // return unsigned byte
115    }
116
117    @Override
118    public int read(final byte[] buffer) throws IOException {
119        return read(buffer, 0, buffer.length);
120    }
121
122    @Override
123    public int read(final byte[] targetBuffer, final int offset, final int length) throws IOException {
124        Objects.requireNonNull(targetBuffer, "targetBuffer");
125        if (offset < 0) {
126            throw new IllegalArgumentException("Offset must not be negative");
127        }
128        if (length < 0) {
129            throw new IllegalArgumentException("Length must not be negative");
130        }
131        if (!haveBytes(length)) {
132            return EOF;
133        }
134        final int result = Math.min(length, buffer.getCurrentNumberOfBytes());
135        for (int i = 0; i < result; i++) {
136            targetBuffer[offset + i] = buffer.read();
137        }
138        return result;
139    }
140
141    @Override
142    public void close() throws IOException {
143        in.close();
144        eof = true;
145        buffer.clear();
146    }
147}