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   /*
    * Copyright 2012 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:
    *
    *   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.
   */
  package org.jboss.netty.handler.stream;
  
  import static org.jboss.netty.buffer.ChannelBuffers.*;
  
  import java.io.InputStream;
  import java.io.PushbackInputStream;
  
  /**
   * A {@link ChunkedInput} that fetches data from an {@link InputStream} chunk by
   * chunk.
   * <p>
   * Please note that the {@link InputStream} instance that feeds data into
   * {@link ChunkedStream} must implement {@link InputStream#available()} as
   * accurately as possible, rather than using the default implementation.
   * Otherwise, {@link ChunkedStream} will generate many too small chunks or
   * block unnecessarily often.
   */
  public class ChunkedStream implements ChunkedInput {
  
      static final int DEFAULT_CHUNK_SIZE = 8192;
  
      private final PushbackInputStream in;
      private final int chunkSize;
      private long offset;
  
      /**
       * Creates a new instance that fetches data from the specified stream.
       */
      public ChunkedStream(InputStream in) {
          this(in, DEFAULT_CHUNK_SIZE);
      }
  
      /**
       * Creates a new instance that fetches data from the specified stream.
       *
       * @param chunkSize the number of bytes to fetch on each
       *                  {@link #nextChunk()} call
       */
      public ChunkedStream(InputStream in, int chunkSize) {
          if (in == null) {
              throw new NullPointerException("in");
          }
          if (chunkSize <= 0) {
              throw new IllegalArgumentException(
                      "chunkSize: " + chunkSize +
                      " (expected: a positive integer)");
          }
  
          if (in instanceof PushbackInputStream) {
              this.in = (PushbackInputStream) in;
          } else {
              this.in = new PushbackInputStream(in);
          }
          this.chunkSize = chunkSize;
      }
  
      /**
       * Returns the number of transferred bytes.
       */
      public long getTransferredBytes() {
          return offset;
      }
  
      public boolean hasNextChunk() throws Exception {
          int b = in.read();
          if (b < 0) {
              return false;
          } else {
              in.unread(b);
              return true;
          }
      }
  
      public boolean isEndOfInput() throws Exception {
          return !hasNextChunk();
      }
  
      public void close() throws Exception {
          in.close();
      }
  
      public Object nextChunk() throws Exception {
          if (!hasNextChunk()) {
              return null;
         }
 
         final int availableBytes = in.available();
         final int chunkSize;
         if (availableBytes <= 0) {
             chunkSize = this.chunkSize;
         } else {
             chunkSize = Math.min(this.chunkSize, in.available());
         }
         final byte[] chunk = new byte[chunkSize];
         int readBytes = 0;
         for (;;) {
             int localReadBytes = in.read(chunk, readBytes, chunkSize - readBytes);
             if (localReadBytes < 0) {
                 break;
             }
             readBytes += localReadBytes;
             offset += localReadBytes;
 
             if (readBytes == chunkSize) {
                 break;
             }
         }
 
         return wrappedBuffer(chunk, 0, readBytes);
     }
 }