org.apache.commons.compress.archivers.zip.ExplodingInputStream Maven / Gradle / Ivy
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/*
* Licensed to the Apache Software Foundation (ASF) under one
* or more contributor license agreements. See the NOTICE file
* distributed with this work for additional information
* regarding copyright ownership. The ASF licenses this file
* to you under the Apache License, Version 2.0 (the
* "License"); you may not use this file except in compliance
* with the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing,
* software distributed under the License is distributed on an
* "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
* KIND, either express or implied. See the License for the
* specific language governing permissions and limitations
* under the License.
*/
package org.apache.commons.compress.archivers.zip;
import java.io.IOException;
import java.io.InputStream;
import org.apache.commons.compress.utils.CloseShieldFilterInputStream;
import org.apache.commons.compress.utils.CountingInputStream;
import org.apache.commons.compress.utils.ExactMath;
import org.apache.commons.compress.utils.InputStreamStatistics;
/**
* The implode compression method was added to PKZIP 1.01 released in 1989.
* It was then dropped from PKZIP 2.0 released in 1993 in favor of the deflate
* method.
*
* The algorithm is described in the ZIP File Format Specification.
*
* @see ZIP File Format Specification
*
* @since 1.7
*/
class ExplodingInputStream extends InputStream implements InputStreamStatistics {
/** The underlying stream containing the compressed data */
private final InputStream in;
/** The stream of bits read from the input stream */
private BitStream bits;
/** The size of the sliding dictionary (4K or 8K) */
private final int dictionarySize;
/** The number of Shannon-Fano trees (2 or 3) */
private final int numberOfTrees;
private final int minimumMatchLength;
/** The binary tree containing the 256 encoded literals (null when only two trees are used) */
private BinaryTree literalTree;
/** The binary tree containing the 64 encoded lengths */
private BinaryTree lengthTree;
/** The binary tree containing the 64 encoded distances */
private BinaryTree distanceTree;
/** Output buffer holding the decompressed data */
private final CircularBuffer buffer = new CircularBuffer(32 * 1024);
private long uncompressedCount;
private long treeSizes;
/**
* Create a new stream decompressing the content of the specified stream
* using the explode algorithm.
*
* @param dictionarySize the size of the sliding dictionary (4096 or 8192)
* @param numberOfTrees the number of trees (2 or 3)
* @param in the compressed data stream
*/
public ExplodingInputStream(final int dictionarySize, final int numberOfTrees, final InputStream in) {
if (dictionarySize != 4096 && dictionarySize != 8192) {
throw new IllegalArgumentException("The dictionary size must be 4096 or 8192");
}
if (numberOfTrees != 2 && numberOfTrees != 3) {
throw new IllegalArgumentException("The number of trees must be 2 or 3");
}
this.dictionarySize = dictionarySize;
this.numberOfTrees = numberOfTrees;
this.minimumMatchLength = numberOfTrees;
this.in = in;
}
/**
* @since 1.17
*/
@Override
public void close() throws IOException {
in.close();
}
/**
* Fill the sliding dictionary with more data.
* @throws IOException on error.
*/
private void fillBuffer() throws IOException {
init();
final int bit = bits.nextBit();
if (bit == -1) {
// EOF
return;
}
if (bit == 1) {
// literal value
final int literal;
if (literalTree != null) {
literal = literalTree.read(bits);
} else {
literal = bits.nextByte();
}
if (literal == -1) {
// end of stream reached, nothing left to decode
return;
}
buffer.put(literal);
} else {
// back reference
final int distanceLowSize = dictionarySize == 4096 ? 6 : 7;
final int distanceLow = (int) bits.nextBits(distanceLowSize);
final int distanceHigh = distanceTree.read(bits);
if (distanceHigh == -1 && distanceLow <= 0) {
// end of stream reached, nothing left to decode
return;
}
final int distance = distanceHigh << distanceLowSize | distanceLow;
int length = lengthTree.read(bits);
if (length == 63) {
final long nextByte = bits.nextBits(8);
if (nextByte == -1) {
// EOF
return;
}
length = ExactMath.add(length, nextByte);
}
length += minimumMatchLength;
buffer.copy(distance + 1, length);
}
}
/**
* @since 1.17
*/
@Override
public long getCompressedCount() {
return bits.getBytesRead() + treeSizes;
}
/**
* @since 1.17
*/
@Override
public long getUncompressedCount() {
return uncompressedCount;
}
/**
* Reads the encoded binary trees and prepares the bit stream.
*
* @throws IOException
*/
private void init() throws IOException {
if (bits == null) {
// we do not want to close in
try (CountingInputStream i = new CountingInputStream(new CloseShieldFilterInputStream(in))) {
if (numberOfTrees == 3) {
literalTree = BinaryTree.decode(i, 256);
}
lengthTree = BinaryTree.decode(i, 64);
distanceTree = BinaryTree.decode(i, 64);
treeSizes += i.getBytesRead();
}
bits = new BitStream(in);
}
}
@Override
public int read() throws IOException {
if (!buffer.available()) {
try {
fillBuffer();
} catch (final IllegalArgumentException ex) {
throw new IOException("bad IMPLODE stream", ex);
}
}
final int ret = buffer.get();
if (ret > -1) {
uncompressedCount++;
}
return ret;
}
}