/*
    * $HeadURL: https://svn.apache.org/repos/asf/httpcomponents/oac.hc3x/trunk/src/java/org/apache/commons/httpclient/ChunkedOutputStream.java $
    * $Revision$
    * $Date$
    *
    * ====================================================================
    *
    *  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.commons.httpclient;
  
  import java.io.IOException;
  import java.io.OutputStream;
  
  import org.apache.commons.httpclient.util.EncodingUtil;
  
  /***
   * Implements HTTP chunking support. Writes are buffered to an internal buffer (2048 default size).
   * Chunks are guaranteed to be at least as large as the buffer size (except for the last chunk).
   *
   * @author Mohammad Rezaei, Goldman, Sachs & Co.
   */
  public class ChunkedOutputStream extends OutputStream {
  
      // ------------------------------------------------------- Static Variables
      private static final byte CRLF[] = new byte[] {(byte) 13, (byte) 10};
  
      /*** End chunk */
      private static final byte ENDCHUNK[] = CRLF;
  
      /*** 0 */
      private static final byte ZERO[] = new byte[] {(byte) '0'};
  
      // ----------------------------------------------------- Instance Variables
      private OutputStream stream = null;
  
      private byte[] cache;
  
      private int cachePosition = 0;
  
      private boolean wroteLastChunk = false;
  
      // ----------------------------------------------------------- Constructors
      /***
       * Wraps a stream and chunks the output.
       * @param stream to wrap
       * @param bufferSize minimum chunk size (excluding last chunk)
       * @throws IOException
       * 
       * @since 3.0
       */
      public ChunkedOutputStream(OutputStream stream, int bufferSize) throws IOException {
          this.cache = new byte[bufferSize];
          this.stream = stream;
      }
  
      /***
       * Wraps a stream and chunks the output. The default buffer size of 2048 was chosen because
       * the chunk overhead is less than 0.5%
       * @param stream
       * @throws IOException
       */
      public ChunkedOutputStream(OutputStream stream) throws IOException {
          this(stream, 2048);
      }
  
      // ----------------------------------------------------------- Internal methods
      /***
       * Writes the cache out onto the underlying stream
       * @throws IOException
       * 
       * @since 3.0
       */
      protected void flushCache() throws IOException {
          if (cachePosition > 0) {
              byte chunkHeader[] = EncodingUtil.getAsciiBytes(
                      Integer.toHexString(cachePosition) + "\r\n");
              stream.write(chunkHeader, 0, chunkHeader.length);
             stream.write(cache, 0, cachePosition);
             stream.write(ENDCHUNK, 0, ENDCHUNK.length);
             cachePosition = 0;
         }
     }
 
     /***
      * Writes the cache and bufferToAppend to the underlying stream
      * as one large chunk
      * @param bufferToAppend
      * @param off
      * @param len
      * @throws IOException
      * 
      * @since 3.0
      */
     protected void flushCacheWithAppend(byte bufferToAppend[], int off, int len) throws IOException {
         byte chunkHeader[] = EncodingUtil.getAsciiBytes(
                 Integer.toHexString(cachePosition + len) + "\r\n");
         stream.write(chunkHeader, 0, chunkHeader.length);
         stream.write(cache, 0, cachePosition);
         stream.write(bufferToAppend, off, len);
         stream.write(ENDCHUNK, 0, ENDCHUNK.length);
         cachePosition = 0;
     }
 
     protected void writeClosingChunk() throws IOException {
         // Write the final chunk.
 
         stream.write(ZERO, 0, ZERO.length);
         stream.write(CRLF, 0, CRLF.length);
         stream.write(ENDCHUNK, 0, ENDCHUNK.length);
     }
 
     // ----------------------------------------------------------- Public Methods
     /***
      * Must be called to ensure the internal cache is flushed and the closing chunk is written.
      * @throws IOException
      * 
      * @since 3.0
      */
     public void finish() throws IOException {
         if (!wroteLastChunk) {
             flushCache();
             writeClosingChunk();
             wroteLastChunk = true;
         }
     }
 
     // -------------------------------------------- OutputStream Methods
     /***
      * Write the specified byte to our output stream.
      * 
      * Note: Avoid this method as it will cause an inefficient single byte chunk. 
      * Use write (byte[], int, int) instead.
      * 
      * @param b The byte to be written
      * @throws IOException if an input/output error occurs
      */
     public void write(int b) throws IOException {
         cache[cachePosition] = (byte) b;
         cachePosition++;
         if (cachePosition == cache.length) flushCache();
     }
 
     /***
      * Writes the array. If the array does not fit within the buffer, it is
      * not split, but rather written out as one large chunk.
      * @param b
      * @throws IOException
      * 
      * @since 3.0
      */
     public void write(byte b[]) throws IOException {
         this.write(b, 0, b.length);
     }
 
     public void write(byte src[], int off, int len) throws IOException {
         if (len >= cache.length - cachePosition) {
             flushCacheWithAppend(src, off, len);
         } else {
             System.arraycopy(src, off, cache, cachePosition, len);
             cachePosition += len;
         }
     }
 
     /***
      * Flushes the underlying stream, but leaves the internal buffer alone.
      * @throws IOException
      */
     public void flush() throws IOException {
         stream.flush();
     }
 
     /***
      * Finishes writing to the underlying stream, but does NOT close the underlying stream.
      * @throws IOException
      */
     public void close() throws IOException {
         finish();
         super.close();
     }
 }