/*
    * 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 java.nio.ByteBuffer;
  
  final class CompressionUtil {
  
      private CompressionUtil() { }
  
      static void checkChecksum(ByteBufChecksum checksum, ByteBuf uncompressed, int currentChecksum) {
          checksum.reset();
          checksum.update(uncompressed,
                  uncompressed.readerIndex(), uncompressed.readableBytes());
  
          final int checksumResult = (int) checksum.getValue();
          if (checksumResult != currentChecksum) {
              throw new DecompressionException(String.format(
                      "stream corrupted: mismatching checksum: %d (expected: %d)",
                      checksumResult, currentChecksum));
          }
      }
  
      static ByteBuffer safeReadableNioBuffer(ByteBuf buffer) {
          return safeNioBuffer(buffer, buffer.readerIndex(), buffer.readableBytes());
      }
  
      static ByteBuffer safeNioBuffer(ByteBuf buffer, int index, int length) {
          return buffer.nioBufferCount() == 1 ? buffer.internalNioBuffer(index, length)
                  : buffer.nioBuffer(index, length);
      }
  }