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/*
 * 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.
 */
package org.apache.thrift.transport;

import org.apache.thrift.TConfiguration;

/**
 * TTransport for writing to an AutoExpandingBuffer.
 */
public final class AutoExpandingBufferWriteTransport extends TEndpointTransport {

  private final AutoExpandingBuffer buf;
  private int pos;
  private int res;

  /**
   * Constructor.
   * @param config the configuration to use. Currently used for defining the maximum message size.
   * @param initialCapacity the initial capacity of the buffer
   * @param frontReserve space, if any, to reserve at the beginning such
   *                     that the first write is after this reserve.
   *                     This allows framed transport to reserve space
   *                     for the frame buffer length.
   * @throws IllegalArgumentException if initialCapacity is less than one
   * @throws IllegalArgumentException if frontReserve is less than zero
   * @throws IllegalArgumentException if frontReserve is greater than initialCapacity
   */
  public AutoExpandingBufferWriteTransport(TConfiguration config, int initialCapacity, int frontReserve) throws TTransportException {
    super(config);
    if (initialCapacity < 1) {
      throw new IllegalArgumentException("initialCapacity");
    }
    if (frontReserve < 0 || initialCapacity < frontReserve) {
      throw new IllegalArgumentException("frontReserve");
    }
    this.buf = new AutoExpandingBuffer(initialCapacity);
    this.pos = frontReserve;
    this.res = frontReserve;
  }

  @Override
  public void close() {}

  @Override
  public boolean isOpen() {return true;}

  @Override
  public void open() throws TTransportException {}

  @Override
  public int read(byte[] buf, int off, int len) throws TTransportException {
    throw new UnsupportedOperationException();
  }

  @Override
  public void write(byte[] toWrite, int off, int len) throws TTransportException {
    buf.resizeIfNecessary(pos + len);
    System.arraycopy(toWrite, off, buf.array(), pos, len);
    pos += len;
  }

  public AutoExpandingBuffer getBuf() {
    return buf;
  }

  /**
   * @return length of the buffer, including any front reserve
   */
  public int getLength() {
    return pos;
  }

  public void reset() {
    pos = res;
  }
}