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