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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.TByteArrayOutputStream;
import org.apache.thrift.TConfiguration;

import java.nio.charset.Charset;

/**
 * Memory buffer-based implementation of the TTransport interface.
 */
public class TMemoryBuffer extends TEndpointTransport {
  /**
   * Create a TMemoryBuffer with an initial buffer size of size. The
   * internal buffer will grow as necessary to accommodate the size of the data
   * being written to it.
   *
   * @param size the initial size of the buffer
   * @throws TTransportException on error initializing the underlying transport.
   */
  public TMemoryBuffer(int size) throws TTransportException {
    super(new TConfiguration());
    arr_ = new TByteArrayOutputStream(size);
    updateKnownMessageSize(size);
  }

  /**
   * Create a TMemoryBuffer with an initial buffer size of size. The
   * internal buffer will grow as necessary to accommodate the size of the data
   * being written to it.
   *
   * @param config the configuration to use.
   * @param size the initial size of the buffer
   * @throws TTransportException on error initializing the underlying transport.
   */
  public TMemoryBuffer(TConfiguration config, int size) throws TTransportException {
    super(config);
    arr_ = new TByteArrayOutputStream(size);
    updateKnownMessageSize(size);
  }

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

  @Override
  public void open() {
    /* Do nothing */
  }

  @Override
  public void close() {
    /* Do nothing */
  }

  @Override
  public int read(byte[] buf, int off, int len) throws TTransportException {
    checkReadBytesAvailable(len);
    byte[] src = arr_.get();
    int amtToRead = (len > arr_.len() - pos_ ? arr_.len() - pos_ : len);

    if (amtToRead > 0) {
      System.arraycopy(src, pos_, buf, off, amtToRead);
      pos_ += amtToRead;
    }
    return amtToRead;
  }

  @Override
  public void write(byte[] buf, int off, int len) {
    arr_.write(buf, off, len);
  }

  /**
   * Output the contents of the memory buffer as a String, using the supplied
   * encoding
   * @param charset the encoding to use
   * @return the contents of the memory buffer as a String
   */
  public String toString(Charset charset) {
    return arr_.toString(charset);
  }

  public String inspect() {
    StringBuilder buf = new StringBuilder();
    byte[] bytes = arr_.toByteArray();
    for (int i = 0; i < bytes.length; i++) {
      buf.append(pos_ == i ? "==>" : "" ).append(Integer.toHexString(bytes[i] & 0xff)).append(" ");
    }
    return buf.toString();
  }

  // The contents of the buffer
  private TByteArrayOutputStream arr_;

  // Position to read next byte from
  private int pos_;

  public int length() {
    return arr_.size();
  }

  public byte[] getArray() {
    return arr_.get();
  }
}