net.jpountz.lz4.LZ4CompressorWithLength Maven / Gradle / Ivy
package net.jpountz.lz4;
/*
* Licensed 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.
*/
import java.nio.ByteBuffer;
import java.util.Arrays;
/**
* Covenience class to include the length of the original decompressed data
* in the output compressed data, so that the user does not need to save
* the length at anywhere else. The compressed data must be decompressed by
* {@link LZ4DecompressorWithLength} and is NOT compatible with any other
* decompressors in lz4-java or any other lz4 tools. This class deliberately
* does not extend {@link LZ4Compressor} because they are not interchangable.
*/
public class LZ4CompressorWithLength {
private final LZ4Compressor compressor;
/**
* Creates a new compressor that includes the length of the original
* decompressed data in the output compressed data.
*
* @param compressor compressor to use
*/
public LZ4CompressorWithLength(LZ4Compressor compressor) {
this.compressor = compressor;
}
private void putOriginalLength(byte[] dest, int destOff, int originalLength) {
dest[destOff] = (byte)originalLength;
dest[destOff + 1] = (byte)(originalLength >> 8);
dest[destOff + 2] = (byte)(originalLength >> 16);
dest[destOff + 3] = (byte)(originalLength >> 24);
}
private void putOriginalLength(ByteBuffer dest, int destOff, int originalLength) {
dest.put(destOff, (byte)originalLength);
dest.put(destOff + 1, (byte)(originalLength >> 8));
dest.put(destOff + 2, (byte)(originalLength >> 16));
dest.put(destOff + 3, (byte)(originalLength >> 24));
}
/**
* Returns the maximum compressed length for an input of size length.
*
* @param length the input size in bytes
* @return the maximum compressed length in bytes
*/
public int maxCompressedLength(int length) {
return compressor.maxCompressedLength(length) + 4;
}
/**
* Convenience method, equivalent to calling
* {@link #compress(byte[], int, int) compress(src, 0, src.length)}.
*
* @param src the source data
* @return the compressed data
*/
public byte[] compress(byte[] src) {
return compress(src, 0, src.length);
}
/**
* Convenience method which returns src[srcOff:srcOff+srcLen]
* compressed.
* Warning: this method has an
* important overhead due to the fact that it needs to allocate a buffer to
* compress into, and then needs to resize this buffer to the actual
* compressed length.
* Here is how this method is implemented:
*
* final int maxCompressedLength = maxCompressedLength(srcLen);
* final byte[] compressed = new byte[maxCompressedLength];
* final int compressedLength = compress(src, srcOff, srcLen, compressed, 0);
* return Arrays.copyOf(compressed, compressedLength);
*
*
* @param src the source data
* @param srcOff the start offset in src
* @param srcLen the number of bytes to compress
* @return the compressed data
*/
public byte[] compress(byte[] src, int srcOff, int srcLen) {
final int maxCompressedLength = maxCompressedLength(srcLen);
final byte[] compressed = new byte[maxCompressedLength];
final int compressedLength = compress(src, srcOff, srcLen, compressed, 0);
return Arrays.copyOf(compressed, compressedLength);
}
/**
* Convenience method, equivalent to calling
* {@link #compress(byte[], int, int, byte[], int) compress(src, 0, src.length, dest, 0)}.
*
* @param src the source data
* @param dest the destination buffer
* @throws LZ4Exception if dest is too small
* @return the compressed size
*/
public int compress(byte[] src, byte[] dest) {
return compress(src, 0, src.length, dest, 0);
}
/**
* Convenience method, equivalent to calling
* {@link #compress(byte[], int, int, byte[], int, int) compress(src, srcOff, srcLen, dest, destOff, dest.length - destOff)}.
*
* @param src the source data
* @param srcOff the start offset in src
* @param srcLen the number of bytes to compress
* @param dest the destination buffer
* @param destOff the start offset in dest
* @throws LZ4Exception if dest is too small
* @return the compressed size
*/
public int compress(byte[] src, int srcOff, int srcLen, byte[] dest, int destOff) {
return compress(src, srcOff, srcLen, dest, destOff, dest.length - destOff);
}
/**
* Compresses src[srcOff:srcOff+srcLen] into
* dest[destOff:destOff+maxDestLen] and returns the compressed
* length.
*
* This method will throw a {@link LZ4Exception} if this compressor is unable
* to compress the input into less than maxDestLen bytes. To
* prevent this exception to be thrown, you should make sure that
* maxDestLen >= maxCompressedLength(srcLen).
*
* @param src the source data
* @param srcOff the start offset in src
* @param srcLen the number of bytes to compress
* @param dest the destination buffer
* @param destOff the start offset in dest
* @param maxDestLen the maximum number of bytes to write in dest
* @throws LZ4Exception if maxDestLen is too small
* @return the compressed size
*/
public int compress(byte[] src, int srcOff, int srcLen, byte[] dest, int destOff, int maxDestLen) {
final int compressedLength = compressor.compress(src, srcOff, srcLen, dest, destOff + 4, maxDestLen - 4);
putOriginalLength(dest, destOff, srcLen);
return compressedLength + 4;
}
/**
* Compresses src into dest. Calling this method
* will update the positions of both {@link ByteBuffer}s.
*
* @param src the source data
* @param dest the destination buffer
* @throws LZ4Exception if dest is too small
*/
public void compress(ByteBuffer src, ByteBuffer dest) {
final int compressedLength = compress(src, src.position(), src.remaining(), dest, dest.position(), dest.remaining());
src.position(src.limit());
dest.position(dest.position() + compressedLength);
}
/**
* Compresses src[srcOff:srcOff+srcLen] into
* dest[destOff:destOff+maxDestLen] and returns the compressed
* length.
*
* This method will throw a {@link LZ4Exception} if this compressor is unable
* to compress the input into less than maxDestLen bytes. To
* prevent this exception to be thrown, you should make sure that
* maxDestLen >= maxCompressedLength(srcLen).
*
* {@link ByteBuffer} positions remain unchanged.
*
* @param src the source data
* @param srcOff the start offset in src
* @param srcLen the number of bytes to compress
* @param dest the destination buffer
* @param destOff the start offset in dest
* @param maxDestLen the maximum number of bytes to write in dest
* @throws LZ4Exception if maxDestLen is too small
* @return the compressed size
*/
public int compress(ByteBuffer src, int srcOff, int srcLen, ByteBuffer dest, int destOff, int maxDestLen) {
final int compressedLength = compressor.compress(src, srcOff, srcLen, dest, destOff + 4, maxDestLen - 4);
putOriginalLength(dest, destOff, srcLen);
return compressedLength + 4;
}
}