net.jpountz.lz4.LZ4FastDecompressor Maven / Gradle / Ivy

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Java ports and bindings of the LZ4 compression algorithm and the xxHash hashing algorithm
There is a newer version: 1.8.0
package net.jpountz.lz4;

import java.nio.ByteBuffer;

/*
 * 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.
 */

/**
 * LZ4 decompressor that requires the size of the original input to be known.
 * Use {@link LZ4SafeDecompressor} if you only know the size of the
 * compressed stream.
 * 
 * Instances of this class are thread-safe.
 */
public abstract class LZ4FastDecompressor implements LZ4Decompressor {

  /** Decompresses src[srcOff:] into dest[destOff:destOff+destLen]
   * and returns the number of bytes read from src.
   * destLen must be exactly the size of the decompressed data.
   *
   * @param src the compressed data
   * @param srcOff the start offset in src
   * @param dest the destination buffer to store the decompressed data
   * @param destOff the start offset in dest
   * @param destLen the exact size of the original input
   * @return the number of bytes read to restore the original input
   */
  public abstract int decompress(byte[] src, int srcOff, byte[] dest, int destOff, int destLen);

  /** Decompresses src[srcOff:] into dest[destOff:destOff+destLen]
   * and returns the number of bytes read from src.
   * destLen must be exactly the size of the decompressed data.
   * The positions and limits of the {@link ByteBuffer}s remain unchanged.
   *
   * @param src the compressed data
   * @param srcOff the start offset in src
   * @param dest the destination buffer to store the decompressed data
   * @param destOff the start offset in dest
   * @param destLen the exact size of the original input
   * @return the number of bytes read to restore the original input
   */
  public abstract int decompress(ByteBuffer src, int srcOff, ByteBuffer dest, int destOff, int destLen);

  /**
   * Convenience method, equivalent to calling
   * {@link #decompress(byte[], int, byte[], int, int) decompress(src, 0, dest, 0, destLen)}.
   *
   * @param src the compressed data
   * @param dest the destination buffer to store the decompressed data
   * @param destLen the exact size of the original input
   * @return the number of bytes read to restore the original input
   */
  public final int decompress(byte[] src, byte[] dest, int destLen) {
    return decompress(src, 0, dest, 0, destLen);
  }

  /**
   * Convenience method, equivalent to calling
   * {@link #decompress(byte[], byte[], int) decompress(src, dest, dest.length)}.
   *
   * @param src the compressed data
   * @param dest the destination buffer to store the decompressed data
   * @return the number of bytes read to restore the original input
   */
  public final int decompress(byte[] src, byte[] dest) {
    return decompress(src, dest, dest.length);
  }

  /**
   * Convenience method which returns src[srcOff:?]
   * decompressed.
   * 
Warning: this method has an
   * important overhead due to the fact that it needs to allocate a buffer to
   * decompress into.
   * Here is how this method is implemented:
   *    * final byte[] decompressed = new byte[destLen];
   * decompress(src, srcOff, decompressed, 0, destLen);
   * return decompressed;
   * 
   *
   * @param src the compressed data
   * @param srcOff the start offset in src
   * @param destLen the exact size of the original input
   * @return the decompressed data
   */
  public final byte[] decompress(byte[] src, int srcOff, int destLen) {
    final byte[] decompressed = new byte[destLen];
    decompress(src, srcOff, decompressed, 0, destLen);
    return decompressed;
  }

  /**
   * Convenience method, equivalent to calling
   * {@link #decompress(byte[], int, int) decompress(src, 0, destLen)}.
   *
   * @param src the compressed data
   * @param destLen the exact size of the original input
   * @return the decompressed data
   */
  public final byte[] decompress(byte[] src, int destLen) {
    return decompress(src, 0, destLen);
  }

  /**
   * Decompresses src into dest. dest's
   * {@link ByteBuffer#remaining()} must be exactly the size of the decompressed
   * data. This method moves the positions of the buffers.
   *
   * @param src the compressed data
   * @param dest the destination buffer to store the decompressed data
   */
  public final void decompress(ByteBuffer src, ByteBuffer dest) {
    final int read = decompress(src, src.position(), dest, dest.position(), dest.remaining());
    dest.position(dest.limit());
    src.position(src.position() + read);
  }

  @Override
  public String toString() {
    return getClass().getSimpleName();
  }

}