/*
    * ====================================================================
    * Licensed to the Apache Software Foundation (ASF) under one
    * or more contributor license agreements.  See the NOTICE file
    * distributed with this work for additional information
    * regarding copyright ownership.  The ASF 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
   *
   *   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.
   * ====================================================================
   *
   * This software consists of voluntary contributions made by many
   * individuals on behalf of the Apache Software Foundation.  For more
   * information on the Apache Software Foundation, please see
   * <http://www.apache.org/>.
   *
   */
  
  package org.apache.http.impl.nio.codecs;
  
  import java.io.IOException;
  import java.nio.ByteBuffer;
  import java.nio.channels.FileChannel;
  import java.nio.channels.WritableByteChannel;
  
  import org.apache.http.annotation.NotThreadSafe;
  import org.apache.http.impl.io.HttpTransportMetricsImpl;
  import org.apache.http.nio.FileContentEncoder;
  import org.apache.http.nio.reactor.SessionOutputBuffer;
  
  /**
   * Content encoder that cuts off after a defined number of bytes. This class
   * is used to send content of HTTP messages where the end of the content entity
   * is determined by the value of the <code>Content-Length header</code>.
   * Entities transferred using this stream can be maximum {@link Long#MAX_VALUE}
   * long.
   * <p>
   * This decoder is optimized to transfer data directly from
   * a {@link FileChannel} to the underlying I/O session's channel whenever
   * possible avoiding intermediate buffering in the session buffer.
   *
   * @since 4.0
   */
  @NotThreadSafe
  public class LengthDelimitedEncoder extends AbstractContentEncoder
          implements FileContentEncoder {
  
      private final long contentLength;
  
      private long len;
  
      public LengthDelimitedEncoder(
              final WritableByteChannel channel,
              final SessionOutputBuffer buffer,
              final HttpTransportMetricsImpl metrics,
              long contentLength) {
          super(channel, buffer, metrics);
          if (contentLength < 0) {
              throw new IllegalArgumentException("Content length may not be negative");
          }
          this.contentLength = contentLength;
          this.len = 0;
      }
  
      public int write(final ByteBuffer src) throws IOException {
          if (src == null) {
              return 0;
          }
          assertNotCompleted();
          int chunk = (int) Math.min((this.contentLength - this.len), Integer.MAX_VALUE);
  
          int bytesWritten;
          if (src.remaining() > chunk) {
              int oldLimit = src.limit();
              int newLimit = oldLimit - (src.remaining() - chunk);
              src.limit(newLimit);
              bytesWritten = this.channel.write(src);
              src.limit(oldLimit);
          } else {
              bytesWritten = this.channel.write(src);
          }
          if (bytesWritten > 0) {
              this.metrics.incrementBytesTransferred(bytesWritten);
          }
          this.len += bytesWritten;
          if (this.len >= this.contentLength) {
              this.completed = true;
          }
          return bytesWritten;
      }
 
     public long transfer(
             final FileChannel src,
             long position,
             long count) throws IOException {
 
         if (src == null) {
             return 0;
         }
         assertNotCompleted();
         long chunk = Math.min((this.contentLength - this.len), count);
         long bytesWritten = src.transferTo(position, chunk, this.channel);
         if (bytesWritten > 0) {
             this.metrics.incrementBytesTransferred(bytesWritten);
         }
         this.len += bytesWritten;
         if (this.len >= this.contentLength) {
             this.completed = true;
         }
         return bytesWritten;
     }
 
     @Override
     public String toString() {
         StringBuilder buffer = new StringBuilder();
         buffer.append("[content length: ");
         buffer.append(this.contentLength);
         buffer.append("; pos: ");
         buffer.append(this.len);
         buffer.append("; completed: ");
         buffer.append(this.completed);
         buffer.append("]");
         return buffer.toString();
     }
 
 }