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