    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.codec.binary;
    019
    020import static org.apache.commons.codec.binary.BaseNCodec.EOF;
    021
    022import java.io.FilterInputStream;
    023import java.io.IOException;
    024import java.io.InputStream;
    025
    026import org.apache.commons.codec.binary.BaseNCodec.Context;
    027
    028/**
    029 * Abstract superclass for Base-N input streams.
    030 *
    031 * @since 1.5
    032 * @version $Id$
    033 */
    034public class BaseNCodecInputStream extends FilterInputStream {
    035
    036    private final BaseNCodec baseNCodec;
    037
    038    private final boolean doEncode;
    039
    040    private final byte[] singleByte = new byte[1];
    041
    042    private final Context context = new Context();
    043
    044    protected BaseNCodecInputStream(final InputStream in, final BaseNCodec baseNCodec, final boolean doEncode) {
    045        super(in);
    046        this.doEncode = doEncode;
    047        this.baseNCodec = baseNCodec;
    048    }
    049
    050    /**
    051     * {@inheritDoc}
    052     *
    053     * @return <code>0</code> if the {@link InputStream} has reached <code>EOF</code>,
    054     * <code>1</code> otherwise
    055     * @since 1.7
    056     */
    057    @Override
    058    public int available() throws IOException {
    059        // Note: the logic is similar to the InflaterInputStream:
    060        //       as long as we have not reached EOF, indicate that there is more
    061        //       data available. As we do not know for sure how much data is left,
    062        //       just return 1 as a safe guess.
    063
    064        return context.eof ? 0 : 1;
    065    }
    066
    067    /**
    068     * Marks the current position in this input stream.
    069     * <p>The {@link #mark} method of {@link BaseNCodecInputStream} does nothing.</p>
    070     *
    071     * @param readLimit the maximum limit of bytes that can be read before the mark position becomes invalid.
    072     * @since 1.7
    073     */
    074    @Override
    075    public synchronized void mark(final int readLimit) {
    076    }
    077
    078    /**
    079     * {@inheritDoc}
    080     *
    081     * @return always returns <code>false</code>
    082     */
    083    @Override
    084    public boolean markSupported() {
    085        return false; // not an easy job to support marks
    086    }
    087
    088    /**
    089     * Reads one <code>byte</code> from this input stream.
    090     *
    091     * @return the byte as an integer in the range 0 to 255. Returns -1 if EOF has been reached.
    092     * @throws IOException
    093     *             if an I/O error occurs.
    094     */
    095    @Override
    096    public int read() throws IOException {
    097        int r = read(singleByte, 0, 1);
    098        while (r == 0) {
    099            r = read(singleByte, 0, 1);
    100        }
    101        if (r > 0) {
    102            final byte b = singleByte[0];
    103            return b < 0 ? 256 + b : b;
    104        }
    105        return EOF;
    106    }
    107
    108    /**
    109     * Attempts to read <code>len</code> bytes into the specified <code>b</code> array starting at <code>offset</code>
    110     * from this InputStream.
    111     *
    112     * @param b
    113     *            destination byte array
    114     * @param offset
    115     *            where to start writing the bytes
    116     * @param len
    117     *            maximum number of bytes to read
    118     *
    119     * @return number of bytes read
    120     * @throws IOException
    121     *             if an I/O error occurs.
    122     * @throws NullPointerException
    123     *             if the byte array parameter is null
    124     * @throws IndexOutOfBoundsException
    125     *             if offset, len or buffer size are invalid
    126     */
    127    @Override
    128    public int read(final byte b[], final int offset, final int len) throws IOException {
    129        if (b == null) {
    130            throw new NullPointerException();
    131        } else if (offset < 0 || len < 0) {
    132            throw new IndexOutOfBoundsException();
    133        } else if (offset > b.length || offset + len > b.length) {
    134            throw new IndexOutOfBoundsException();
    135        } else if (len == 0) {
    136            return 0;
    137        } else {
    138            int readLen = 0;
    139            /*
    140             Rationale for while-loop on (readLen == 0):
    141             -----
    142             Base32.readResults() usually returns > 0 or EOF (-1).  In the
    143             rare case where it returns 0, we just keep trying.
    144
    145             This is essentially an undocumented contract for InputStream
    146             implementors that want their code to work properly with
    147             java.io.InputStreamReader, since the latter hates it when
    148             InputStream.read(byte[]) returns a zero.  Unfortunately our
    149             readResults() call must return 0 if a large amount of the data
    150             being decoded was non-base32, so this while-loop enables proper
    151             interop with InputStreamReader for that scenario.
    152             -----
    153             This is a fix for CODEC-101
    154            */
    155            while (readLen == 0) {
    156                if (!baseNCodec.hasData(context)) {
    157                    final byte[] buf = new byte[doEncode ? 4096 : 8192];
    158                    final int c = in.read(buf);
    159                    if (doEncode) {
    160                        baseNCodec.encode(buf, 0, c, context);
    161                    } else {
    162                        baseNCodec.decode(buf, 0, c, context);
    163                    }
    164                }
    165                readLen = baseNCodec.readResults(b, offset, len, context);
    166            }
    167            return readLen;
    168        }
    169    }
    170
    171    /**
    172     * Repositions this stream to the position at the time the mark method was last called on this input stream.
    173     * <p>
    174     * The {@link #reset} method of {@link BaseNCodecInputStream} does nothing except throw an {@link IOException}.
    175     *
    176     * @throws IOException if this method is invoked
    177     * @since 1.7
    178     */
    179    @Override
    180    public synchronized void reset() throws IOException {
    181        throw new IOException("mark/reset not supported");
    182    }
    183
    184    /**
    185     * {@inheritDoc}
    186     *
    187     * @throws IllegalArgumentException if the provided skip length is negative
    188     * @since 1.7
    189     */
    190    @Override
    191    public long skip(final long n) throws IOException {
    192        if (n < 0) {
    193            throw new IllegalArgumentException("Negative skip length: " + n);
    194        }
    195
    196        // skip in chunks of 512 bytes
    197        final byte[] b = new byte[512];
    198        long todo = n;
    199
    200        while (todo > 0) {
    201            int len = (int) Math.min(b.length, todo);
    202            len = this.read(b, 0, len);
    203            if (len == EOF) {
    204                break;
    205            }
    206            todo -= len;
    207        }
    208
    209        return n - todo;
    210    }
    211}