/*
    * Copyright 2016 The Netty Project
    *
    * The Netty Project 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:
    *
    *   https://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 io.netty.handler.codec.compression;
  
  import io.netty.buffer.ByteBuf;
  import io.netty.util.ByteProcessor;
  import io.netty.util.internal.ObjectUtil;
  
  import java.nio.ByteBuffer;
  import java.util.zip.Adler32;
  import java.util.zip.CRC32;
  import java.util.zip.Checksum;
  
  /**
   * {@link Checksum} implementation which can directly act on a {@link ByteBuf}.
   * <p>
   * Implementations may optimize access patterns depending on if the {@link ByteBuf} is backed by a
   * byte array ({@link ByteBuf#hasArray()} is {@code true}) or not.
   */
  abstract class ByteBufChecksum implements Checksum {
      private final ByteProcessor updateProcessor = new ByteProcessor() {
          @Override
          public boolean process(byte value) throws Exception {
              update(value);
              return true;
          }
      };
  
      static ByteBufChecksum wrapChecksum(Checksum checksum) {
          ObjectUtil.checkNotNull(checksum, "checksum");
          if (checksum instanceof ByteBufChecksum) {
              return (ByteBufChecksum) checksum;
          }
          return new JdkByteBufChecksum(checksum);
      }
  
      /**
       * @see #update(byte[], int, int)
       */
      public void update(ByteBuf b, int off, int len) {
          if (b.hasArray()) {
              update(b.array(), b.arrayOffset() + off, len);
          } else {
              b.forEachByte(off, len, updateProcessor);
          }
      }
  
      private static class JdkByteBufChecksum extends ByteBufChecksum {
          protected final Checksum checksum;
  
          JdkByteBufChecksum(Checksum checksum) {
              this.checksum = checksum;
          }
  
          @Override
          public void update(int b) {
              checksum.update(b);
          }
  
          @Override
          public void update(ByteBuf b, int off, int len) {
              if (b.hasArray()) {
                  update(b.array(), b.arrayOffset() + off, len);
              } else if (checksum instanceof CRC32) {
                  ByteBuffer byteBuffer = CompressionUtil.safeNioBuffer(b, off, len);
                  ((CRC32) checksum).update(byteBuffer);
              } else if (checksum instanceof Adler32) {
                  ByteBuffer byteBuffer = CompressionUtil.safeNioBuffer(b, off, len);
                  ((Adler32) checksum).update(byteBuffer);
              } else {
                  super.update(b, off, len);
              }
          }
  
          @Override
          public void update(byte[] b, int off, int len) {
              checksum.update(b, off, len);
          }
  
          @Override
          public long getValue() {
              return checksum.getValue();
          }
  
          @Override
          public void reset() {
             checksum.reset();
         }
     }
 }