LZ4FastDecompressor.java

package info.ata4.util.lz4;

/* Partial import of https://github.com/jpountz/lz4-java, Apache 2.0 licensed. */

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 LZ4SafeDecompressor if you only know the size of the
 * compressed stream.
 * <p>
 * Instances of this class are thread-safe.
 */
public abstract class LZ4FastDecompressor {

  /** Decompress <code>src[srcOff:]</code> into <code>dest[destOff:destOff+destLen]</code>
   * and return the number of bytes read from <code>src</code>.
   * <code>destLen</code> must be exactly the size of the decompressed data.
   *
   * @param destLen the <b>exact</b> 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);

  /** Decompress <code>src[srcOff:]</code> into <code>dest[destOff:destOff+destLen]</code>
   * and return the number of bytes read from <code>src</code>.
   * <code>destLen</code> must be exactly the size of the decompressed data.
   * The positions and limits of the {@link ByteBuffer}s remain unchanged.
   *
   * @param destLen the <b>exact</b> 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)}.
   */
  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)}.
   */
  public final int decompress(byte[] src, byte[] dest) {
    return decompress(src, dest, dest.length);
  }

  /**
   * Convenience method which returns <code>src[srcOff:?]</code>
   * decompressed.
   * <p><b><span style="color:red">Warning</span></b>: this method has an
   * important overhead due to the fact that it needs to allocate a buffer to
   * decompress into.</p>
   * <p>Here is how this method is implemented:</p>
   * <pre>
   * final byte[] decompressed = new byte[destLen];
   * decompress(src, srcOff, decompressed, 0, destLen);
   * return decompressed;
   * </pre>
   */
  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)}.
   */
  public final byte[] decompress(byte[] src, int destLen) {
    return decompress(src, 0, destLen);
  }

  /**
   * Decompress <code>src</code> into <code>dest</code>. <code>dest</code>'s
   * {@link ByteBuffer#remaining()} must be exactly the size of the decompressed
   * data. This method moves the positions of the buffers.
   */
  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();
  }

}