/*
    * ====================================================================
    * 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.io;
  
  import java.io.IOException;
  import java.io.OutputStream;
  
  import org.apache.http.io.SessionOutputBuffer;
  
  /**
   * Implements chunked transfer coding. The content is sent in small chunks.
   * Entities transferred using this output stream can be of unlimited length.
   * Writes are buffered to an internal buffer (2048 default size).
   * <p>
   * Note that this class NEVER closes the underlying stream, even when close
   * gets called.  Instead, the stream will be marked as closed and no further
   * output will be permitted.
   *
   *
   * @since 4.0
   */
  public class ChunkedOutputStream extends OutputStream {
  
      // ----------------------------------------------------- Instance Variables
      private final SessionOutputBuffer out;
  
      private final byte[] cache;
  
      private int cachePosition = 0;
  
      private boolean wroteLastChunk = false;
  
      /** True if the stream is closed. */
      private boolean closed = false;
  
      /**
       * Wraps a session output buffer and chunk-encodes the output.
       *
       * @param out The session output buffer
       * @param bufferSize The minimum chunk size (excluding last chunk)
       * @throws IOException not thrown
       *
       * @deprecated (4.3) use {@link ChunkedOutputStream#ChunkedOutputStream(int, SessionOutputBuffer)}
       */
      @Deprecated
      public ChunkedOutputStream(final SessionOutputBuffer out, final int bufferSize)
              throws IOException {
          this(bufferSize, out);
      }
  
      /**
       * Wraps a session output buffer and chunks the output. The default buffer
       * size of 2048 was chosen because the chunk overhead is less than 0.5%
       *
       * @param out       the output buffer to wrap
       * @throws IOException not thrown
       *
       * @deprecated (4.3) use {@link ChunkedOutputStream#ChunkedOutputStream(int, SessionOutputBuffer)}
       */
      @Deprecated
      public ChunkedOutputStream(final SessionOutputBuffer out)
              throws IOException {
          this(2048, out);
      }
  
      /**
       * Wraps a session output buffer and chunk-encodes the output.
       *
       * @param bufferSize The minimum chunk size (excluding last chunk)
       * @param out The session output buffer
       */
      public ChunkedOutputStream(final int bufferSize, final SessionOutputBuffer out) {
          super();
          this.cache = new byte[bufferSize];
         this.out = out;
     }
 
     /**
      * Writes the cache out onto the underlying stream
      */
     protected void flushCache() throws IOException {
         if (this.cachePosition > 0) {
             this.out.writeLine(Integer.toHexString(this.cachePosition));
             this.out.write(this.cache, 0, this.cachePosition);
             this.out.writeLine("");
             this.cachePosition = 0;
         }
     }
 
     /**
      * Writes the cache and bufferToAppend to the underlying stream
      * as one large chunk
      */
     protected void flushCacheWithAppend(final byte bufferToAppend[], final int off, final int len) throws IOException {
         this.out.writeLine(Integer.toHexString(this.cachePosition + len));
         this.out.write(this.cache, 0, this.cachePosition);
         this.out.write(bufferToAppend, off, len);
         this.out.writeLine("");
         this.cachePosition = 0;
     }
 
     protected void writeClosingChunk() throws IOException {
         // Write the final chunk.
         this.out.writeLine("0");
         this.out.writeLine("");
     }
 
     // ----------------------------------------------------------- Public Methods
     /**
      * Must be called to ensure the internal cache is flushed and the closing
      * chunk is written.
      * @throws IOException in case of an I/O error
      */
     public void finish() throws IOException {
         if (!this.wroteLastChunk) {
             flushCache();
             writeClosingChunk();
             this.wroteLastChunk = true;
         }
     }
 
     // -------------------------------------------- OutputStream Methods
     @Override
     public void write(final int b) throws IOException {
         if (this.closed) {
             throw new IOException("Attempted write to closed stream.");
         }
         this.cache[this.cachePosition] = (byte) b;
         this.cachePosition++;
         if (this.cachePosition == this.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.
      */
     @Override
     public void write(final byte b[]) throws IOException {
         write(b, 0, b.length);
     }
 
     /**
      * Writes the array. If the array does not fit within the buffer, it is
      * not split, but rather written out as one large chunk.
      */
     @Override
     public void write(final byte src[], final int off, final int len) throws IOException {
         if (this.closed) {
             throw new IOException("Attempted write to closed stream.");
         }
         if (len >= this.cache.length - this.cachePosition) {
             flushCacheWithAppend(src, off, len);
         } else {
             System.arraycopy(src, off, cache, this.cachePosition, len);
             this.cachePosition += len;
         }
     }
 
     /**
      * Flushes the content buffer and the underlying stream.
      */
     @Override
     public void flush() throws IOException {
         flushCache();
         this.out.flush();
     }
 
     /**
      * Finishes writing to the underlying stream, but does NOT close the underlying stream.
      */
     @Override
     public void close() throws IOException {
         if (!this.closed) {
             this.closed = true;
             finish();
             this.out.flush();
         }
     }
 }