    001/*
    002 * Licensed to the Apache Software Foundation (ASF) under one
    003 * or more contributor license agreements.  See the NOTICE file
    004 * distributed with this work for additional information
    005 * regarding copyright ownership.  The ASF licenses this file
    006 * to you under the Apache License, Version 2.0 (the
    007 * "License"); you may not use this file except in compliance
    008 * with the License.  You may obtain a copy of the License at
    009 *
    010 *   https://www.apache.org/licenses/LICENSE-2.0
    011 *
    012 * Unless required by applicable law or agreed to in writing,
    013 * software distributed under the License is distributed on an
    014 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
    015 * KIND, either express or implied.  See the License for the
    016 * specific language governing permissions and limitations
    017 * under the License.
    018 */
    019package org.apache.commons.compress.compressors.lz77support;
    020
    021import java.io.IOException;
    022import java.io.InputStream;
    023import java.util.Arrays;
    024
    025import org.apache.commons.compress.compressors.CompressorInputStream;
    026import org.apache.commons.compress.utils.ByteUtils;
    027import org.apache.commons.compress.utils.IOUtils;
    028import org.apache.commons.compress.utils.InputStreamStatistics;
    029import org.apache.commons.io.input.BoundedInputStream;
    030
    031/**
    032 * Encapsulates code common to LZ77 decompressors.
    033 *
    034 * <p>
    035 * Assumes the stream consists of blocks of literal data and back-references (called copies) in any order. Of course the first block must be a literal block for
    036 * the scheme to work - unless the {@link #prefill prefill} method has been used to provide initial data that is never returned by {@link #read read} but only
    037 * used for back-references.
    038 * </p>
    039 *
    040 * <p>
    041 * Subclasses must override the three-arg {@link #read read} method as the no-arg version delegates to it and the default implementation delegates to the no-arg
    042 * version, leading to infinite mutual recursion and a {@code StackOverflowError} otherwise.
    043 * </p>
    044 *
    045 * <p>
    046 * The contract for subclasses' {@code read} implementation is:
    047 * </p>
    048 * <ul>
    049 *
    050 * <li>keep track of the current state of the stream. Is it inside a literal block or a back-reference or in-between blocks?</li>
    051 *
    052 * <li>Use {@link #readOneByte} to access the underlying stream directly.</li>
    053 *
    054 * <li>If a new literal block starts, use {@link #startLiteral} to tell this class about it and read the literal data using {@link #readLiteral} until it
    055 * returns {@code 0}. {@link #hasMoreDataInBlock} will return {@code false} before the next call to {@link #readLiteral} would return {@code 0}.</li>
    056 *
    057 * <li>If a new back-reference starts, use {@link #startBackReference} to tell this class about it and read the literal data using {@link #readBackReference}
    058 * until it returns {@code 0}. {@link #hasMoreDataInBlock} will return {@code false} before the next call to {@link #readBackReference} would return
    059 * {@code 0}.</li>
    060 *
    061 * <li>If the end of the stream has been reached, return {@code -1} as this class' methods will never do so themselves.</li>
    062 *
    063 * </ul>
    064 *
    065 * <p>
    066 * {@link #readOneByte} and {@link #readLiteral} update the counter for bytes read.
    067 * </p>
    068 *
    069 * @since 1.14
    070 */
    071public abstract class AbstractLZ77CompressorInputStream extends CompressorInputStream implements InputStreamStatistics {
    072
    073    /** Size of the window - must be bigger than the biggest offset expected. */
    074    private final int windowSize;
    075
    076    /**
    077     * Buffer to write decompressed bytes to for back-references, will be three times windowSize big.
    078     *
    079     * <p>
    080     * Three times so we can slide the whole buffer a windowSize to the left once we've read twice windowSize and still have enough data inside of it to satisfy
    081     * back-references.
    082     * </p>
    083     */
    084    private final byte[] buf;
    085
    086    /** One behind the index of the last byte in the buffer that was written, i.e. the next position to write to */
    087    private int writeIndex;
    088
    089    /** Index of the next byte to be read. */
    090    private int readIndex;
    091
    092    /** The underlying stream to read compressed data from */
    093    private final BoundedInputStream in;
    094
    095    /** Number of bytes still to be read from the current literal or back-reference. */
    096    private long bytesRemaining;
    097
    098    /** Offset of the current back-reference. */
    099    private int backReferenceOffset;
    100
    101    /** Uncompressed size */
    102    private int size;
    103
    104    // used in no-arg read method
    105    private final byte[] oneByte = new byte[1];
    106
    107    /**
    108     * Supplier that delegates to {@link #readOneByte}.
    109     */
    110    protected final ByteUtils.ByteSupplier supplier = this::readOneByte;
    111
    112    /**
    113     * Creates a new LZ77 input stream.
    114     *
    115     * @param is         An InputStream to read compressed data from
    116     * @param windowSize Size of the window kept for back-references, must be bigger than the biggest offset expected.
    117     * @throws IllegalArgumentException if windowSize is not bigger than 0
    118     */
    119    public AbstractLZ77CompressorInputStream(final InputStream is, final int windowSize) {
    120        this.in = BoundedInputStream.builder().setInputStream(is).asSupplier().get();
    121        if (windowSize <= 0) {
    122            throw new IllegalArgumentException("windowSize must be bigger than 0");
    123        }
    124        this.windowSize = windowSize;
    125        buf = new byte[3 * windowSize];
    126        writeIndex = readIndex = 0;
    127        bytesRemaining = 0;
    128    }
    129
    130    /** {@inheritDoc} */
    131    @Override
    132    public int available() {
    133        return writeIndex - readIndex;
    134    }
    135
    136    /** {@inheritDoc} */
    137    @Override
    138    public void close() throws IOException {
    139        in.close();
    140    }
    141
    142    /**
    143     * @since 1.17
    144     */
    145    @Override
    146    public long getCompressedCount() {
    147        return in.getCount();
    148    }
    149
    150    /**
    151     * Gets the uncompressed size of the stream
    152     *
    153     * @return the uncompressed size
    154     */
    155    public int getSize() {
    156        return size;
    157    }
    158
    159    /**
    160     * Is there still data remaining inside the current block?
    161     *
    162     * @return true if there is still data remaining inside the current block.
    163     */
    164    protected final boolean hasMoreDataInBlock() {
    165        return bytesRemaining > 0;
    166    }
    167
    168    /**
    169     * Adds some initial data to fill the window with.
    170     *
    171     * <p>
    172     * This is used if the stream has been cut into blocks and back-references of one block may refer to data of the previous block(s). One such example is the
    173     * LZ4 frame format using block dependency.
    174     * </p>
    175     *
    176     * @param data the data to fill the window with.
    177     * @throws IllegalStateException if the stream has already started to read data
    178     */
    179    public void prefill(final byte[] data) {
    180        if (writeIndex != 0) {
    181            throw new IllegalStateException("The stream has already been read from, can't prefill anymore");
    182        }
    183        // we don't need more data than the big offset could refer to, so cap it
    184        final int len = Math.min(windowSize, data.length);
    185        // we need the last data as we are dealing with *back*-references
    186        System.arraycopy(data, data.length - len, buf, 0, len);
    187        writeIndex += len;
    188        readIndex += len;
    189    }
    190
    191    /** {@inheritDoc} */
    192    @Override
    193    public int read() throws IOException {
    194        return read(oneByte, 0, 1) == -1 ? -1 : oneByte[0] & 0xFF;
    195    }
    196
    197    /**
    198     * Reads data from the current back-reference.
    199     *
    200     * @param b   buffer to write data to
    201     * @param off offset to start writing to
    202     * @param len maximum amount of data to read
    203     * @return number of bytes read, may be 0. Will never return -1 as EOF-detection is the responsibility of the subclass
    204     * @throws NullPointerException      if {@code b} is null
    205     * @throws IndexOutOfBoundsException if {@code off} is negative, {@code len} is negative, or {@code len} is greater than {@code b.length - off}
    206     */
    207    protected final int readBackReference(final byte[] b, final int off, final int len) {
    208        final int avail = available();
    209        if (len > avail) {
    210            tryToCopy(len - avail);
    211        }
    212        return readFromBuffer(b, off, len);
    213    }
    214
    215    private int readFromBuffer(final byte[] b, final int off, final int len) {
    216        final int readable = Math.min(len, available());
    217        if (readable > 0) {
    218            System.arraycopy(buf, readIndex, b, off, readable);
    219            readIndex += readable;
    220            if (readIndex > 2 * windowSize) {
    221                slideBuffer();
    222            }
    223        }
    224        size += readable;
    225        return readable;
    226    }
    227
    228    /**
    229     * Reads data from the current literal block.
    230     *
    231     * @param b   buffer to write data to
    232     * @param off offset to start writing to
    233     * @param len maximum amount of data to read
    234     * @return number of bytes read, may be 0. Will never return -1 as EOF-detection is the responsibility of the subclass
    235     * @throws IOException               if the underlying stream throws or signals an EOF before the amount of data promised for the block have been read
    236     * @throws NullPointerException      if {@code b} is null
    237     * @throws IndexOutOfBoundsException if {@code off} is negative, {@code len} is negative, or {@code len} is greater than {@code b.length - off}
    238     */
    239    protected final int readLiteral(final byte[] b, final int off, final int len) throws IOException {
    240        final int avail = available();
    241        if (len > avail) {
    242            tryToReadLiteral(len - avail);
    243        }
    244        return readFromBuffer(b, off, len);
    245    }
    246
    247    /**
    248     * Reads a single byte from the real input stream and ensures the data is accounted for.
    249     *
    250     * @return the byte read as value between 0 and 255 or -1 if EOF has been reached.
    251     * @throws IOException if the underlying stream throws
    252     */
    253    protected final int readOneByte() throws IOException {
    254        final int b = in.read();
    255        if (b != -1) {
    256            count(1);
    257            return b & 0xFF;
    258        }
    259        return -1;
    260    }
    261
    262    private void slideBuffer() {
    263        System.arraycopy(buf, windowSize, buf, 0, windowSize * 2);
    264        writeIndex -= windowSize;
    265        readIndex -= windowSize;
    266    }
    267
    268    /**
    269     * Used by subclasses to signal the next block contains a back-reference with the given coordinates.
    270     *
    271     * @param offset the offset of the back-reference
    272     * @param length the length of the back-reference
    273     * @throws IllegalArgumentException if offset not bigger than 0 or bigger than the number of bytes available for back-references or if length is negative
    274     */
    275    protected final void startBackReference(final int offset, final long length) {
    276        if (offset <= 0 || offset > writeIndex) {
    277            throw new IllegalArgumentException("offset must be bigger than 0 but not bigger than the number of bytes available for back-references");
    278        }
    279        if (length < 0) {
    280            throw new IllegalArgumentException("length must not be negative");
    281        }
    282        backReferenceOffset = offset;
    283        bytesRemaining = length;
    284    }
    285
    286    /**
    287     * Used by subclasses to signal the next block contains the given amount of literal data.
    288     *
    289     * @param length the length of the block
    290     * @throws IllegalArgumentException if length is negative
    291     */
    292    protected final void startLiteral(final long length) {
    293        if (length < 0) {
    294            throw new IllegalArgumentException("length must not be negative");
    295        }
    296        bytesRemaining = length;
    297    }
    298
    299    private void tryToCopy(final int bytesToCopy) {
    300        // this will fit into the buffer without sliding and not
    301        // require more than is available inside the back-reference
    302        final int copy = Math.min((int) Math.min(bytesToCopy, bytesRemaining), buf.length - writeIndex);
    303        if (copy == 0) {
    304            // NOP
    305        } else if (backReferenceOffset == 1) { // pretty common special case
    306            final byte last = buf[writeIndex - 1];
    307            Arrays.fill(buf, writeIndex, writeIndex + copy, last);
    308            writeIndex += copy;
    309        } else if (copy < backReferenceOffset) {
    310            System.arraycopy(buf, writeIndex - backReferenceOffset, buf, writeIndex, copy);
    311            writeIndex += copy;
    312        } else {
    313            // back-reference overlaps with the bytes created from it
    314            // like go back two bytes and then copy six (by copying
    315            // the last two bytes three time).
    316            final int fullRots = copy / backReferenceOffset;
    317            for (int i = 0; i < fullRots; i++) {
    318                System.arraycopy(buf, writeIndex - backReferenceOffset, buf, writeIndex, backReferenceOffset);
    319                writeIndex += backReferenceOffset;
    320            }
    321
    322            final int pad = copy - backReferenceOffset * fullRots;
    323            if (pad > 0) {
    324                System.arraycopy(buf, writeIndex - backReferenceOffset, buf, writeIndex, pad);
    325                writeIndex += pad;
    326            }
    327        }
    328        bytesRemaining -= copy;
    329    }
    330
    331    private void tryToReadLiteral(final int bytesToRead) throws IOException {
    332        // min of "what is still inside the literal", "what does the user want" and "how much can fit into the buffer"
    333        final int reallyTryToRead = Math.min((int) Math.min(bytesToRead, bytesRemaining), buf.length - writeIndex);
    334        final int bytesRead = reallyTryToRead > 0 ? IOUtils.readFully(in, buf, writeIndex, reallyTryToRead) : 0 /* happens for bytesRemaining == 0 */;
    335        count(bytesRead);
    336        if (reallyTryToRead != bytesRead) {
    337            throw new IOException("Premature end of stream reading literal");
    338        }
    339        writeIndex += reallyTryToRead;
    340        bytesRemaining -= reallyTryToRead;
    341    }
    342}