library/src/main/java/com/datatorrent/lib/util/ReusableStringReader.java

/*
 * Copyright (c) 2014 DataTorrent, Inc. ALL Rights Reserved.
 *
 * Licensed 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 com.datatorrent.lib.util;

import java.io.IOException;
import java.io.Reader;

/**
 * <p>ReusableStringReader class.</p>
 *
 * @since 1.0.2
 */
public class ReusableStringReader extends Reader
{
  private String str;
  private int length;
  private int next = 0;

  @Override
  public int read(char[] cbuf, int off, int len) throws IOException
  {
    ensureOpen();
    if ((off < 0) || (off > cbuf.length) || (len < 0) || ((off + len) > cbuf.length) || ((off + len) < 0)) {
      throw new IndexOutOfBoundsException();
    } else if (len == 0) {
      return 0;
    }
    if (next >= length)
      return -1;
    int n = Math.min(length - next, len);
    str.getChars(next, next + n, cbuf, off);
    next += n;
    return n;
  }

  /**
   * Reads a single character.
   *
   * @return The character read, or -1 if the end of the stream has been reached
   * @throws IOException If an I/O error occurs
   */
  public int read() throws IOException
  {
    ensureOpen();
    if (next >= length)
      return -1;
    return str.charAt(next++);
  }

  public boolean ready() throws IOException
  {
    ensureOpen();
    return true;
  }

  @Override
  public void close() throws IOException
  {
    str = null;
  }

  /**
   * Check to make sure that the stream has not been closed
   */
  private void ensureOpen() throws IOException
  {
    if (str == null) {
      throw new IOException("Stream closed");
    }
  }

  public void open(String str) throws IOException
  {
    this.str = str;
    this.length = this.str.length();
    this.next = 0;
  }

}