//
   //  ========================================================================
   //  Copyright (c) 1995-2016 Mort Bay Consulting Pty. Ltd.
   //  ------------------------------------------------------------------------
   //  All rights reserved. This program and the accompanying materials
   //  are made available under the terms of the Eclipse Public License v1.0
   //  and Apache License v2.0 which accompanies this distribution.
   //
   //      The Eclipse Public License is available at
  //      http://www.eclipse.org/legal/epl-v10.html
  //
  //      The Apache License v2.0 is available at
  //      http://www.opensource.org/licenses/apache2.0.php
  //
  //  You may elect to redistribute this code under either of these licenses.
  //  ========================================================================
  //
  
  package org.eclipse.jetty.http2.parser;
  
  import java.nio.ByteBuffer;
  
  import org.eclipse.jetty.http.MetaData;
  import org.eclipse.jetty.http2.hpack.HpackDecoder;
  import org.eclipse.jetty.io.ByteBufferPool;
  import org.eclipse.jetty.util.BufferUtil;
  
  public class HeaderBlockParser
  {
      private final ByteBufferPool byteBufferPool;
      private final HpackDecoder hpackDecoder;
      private ByteBuffer blockBuffer;
  
      public HeaderBlockParser(ByteBufferPool byteBufferPool, HpackDecoder hpackDecoder)
      {
          this.byteBufferPool = byteBufferPool;
          this.hpackDecoder = hpackDecoder;
      }
  
      public MetaData parse(ByteBuffer buffer, int blockLength)
      {
          // We must wait for the all the bytes of the header block to arrive.
          // If they are not all available, accumulate them.
          // When all are available, decode them.
  
          int accumulated = blockBuffer == null ? 0 : blockBuffer.position();
          int remaining = blockLength - accumulated;
  
          if (buffer.remaining() < remaining)
          {
              if (blockBuffer == null)
              {
                  blockBuffer = byteBufferPool.acquire(blockLength, false);
                  BufferUtil.clearToFill(blockBuffer);
              }
              blockBuffer.put(buffer);
              return null;
          }
          else
          {
              int limit = buffer.limit();
              buffer.limit(buffer.position() + remaining);
              ByteBuffer toDecode;
              if (blockBuffer != null)
              {
                  blockBuffer.put(buffer);
                  BufferUtil.flipToFlush(blockBuffer, 0);
                  toDecode = blockBuffer;
              }
              else
              {
                  toDecode = buffer;
              }
  
              MetaData result = hpackDecoder.decode(toDecode);
  
              buffer.limit(limit);
  
              if (blockBuffer != null)
              {
                  byteBufferPool.release(blockBuffer);
                  blockBuffer = null;
              }
  
              return result;
          }
      }
  }