content: /*
   * Copyright (c) 1996, 2013, Oracle and/or its affiliates. All rights reserved.
   * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   *
   * This code is free software; you can redistribute it and/or modify it
   * under the terms of the GNU General Public License version 2 only, as
   * published by the Free Software Foundation.  Oracle designates this
   * particular file as subject to the "Classpath" exception as provided
   * by Oracle in the LICENSE file that accompanied this code.
   *
   * This code is distributed in the hope that it will be useful, but WITHOUT
   * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
   * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
   * version 2 for more details (a copy is included in the LICENSE file that
   * accompanied this code).
   *
   * You should have received a copy of the GNU General Public License version
   * 2 along with this work; if not, write to the Free Software Foundation,
   * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
   *
   * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
   * or visit www.oracle.com if you need additional information or have any
   * questions.
   */
  
  package java.io;
  
  import java.nio.charset.Charset;
  import java.nio.charset.CharsetDecoder;
  import sun.nio.cs.StreamDecoder;
  
  
  /**
   * An InputStreamReader is a bridge from byte streams to character streams: It
   * reads bytes and decodes them into characters using a specified {@link
   * Charset charset}.  The charset that it uses
   * may be specified by name or may be given explicitly, or the platform's
   * default charset may be accepted.
   *
   * <p> Each invocation of one of an InputStreamReader's read() methods may
   * cause one or more bytes to be read from the underlying byte-input stream.
   * To enable the efficient conversion of bytes to characters, more bytes may
   * be read ahead from the underlying stream than are necessary to satisfy the
   * current read operation.
   *
   * <p> For top efficiency, consider wrapping an InputStreamReader within a
   * BufferedReader.  For example:
   *
   * <pre>
   * BufferedReader in
   *   = new BufferedReader(new InputStreamReader(System.in));
   * </pre>
   *
   * @see BufferedReader
   * @see InputStream
   * @see Charset
   *
   * @author      Mark Reinhold
   * @since       JDK1.1
   */
  
  public class InputStreamReader extends Reader {
  
      private final StreamDecoder sd;
  
      /**
       * Creates an InputStreamReader that uses the default charset.
       *
       * @param  in   An InputStream
       */
      public InputStreamReader(InputStream in) {
          super(in);
          try {
              sd = StreamDecoder.forInputStreamReader(in, this, (String)null); // ## check lock object
          } catch (UnsupportedEncodingException e) {
              // The default encoding should always be available
              throw new Error(e);
          }
      }
  
      /**
       * Creates an InputStreamReader that uses the named charset.
       *
       * @param  in
       *         An InputStream
       *
       * @param  charsetName
       *         The name of a supported
       *         {@link Charset charset}
       *
       * @exception  UnsupportedEncodingException
       *             If the named charset is not supported
       */
      public InputStreamReader(InputStream in, String charsetName)
          throws UnsupportedEncodingException
      {
          super(in);
          if (charsetName == null)
              throw new NullPointerException("charsetName");
          sd = StreamDecoder.forInputStreamReader(in, this, charsetName);
      }
  
      /**
       * Creates an InputStreamReader that uses the given charset.
       *
       * @param  in       An InputStream
       * @param  cs       A charset
       *
       * @since 1.4
       * @spec JSR-51
       */
      public InputStreamReader(InputStream in, Charset cs) {
          super(in);
          if (cs == null)
              throw new NullPointerException("charset");
          sd = StreamDecoder.forInputStreamReader(in, this, cs);
      }
  
      /**
       * Creates an InputStreamReader that uses the given charset decoder.
       *
       * @param  in       An InputStream
       * @param  dec      A charset decoder
       *
       * @since 1.4
       * @spec JSR-51
       */
      public InputStreamReader(InputStream in, CharsetDecoder dec) {
          super(in);
          if (dec == null)
              throw new NullPointerException("charset decoder");
          sd = StreamDecoder.forInputStreamReader(in, this, dec);
      }
  
      /**
       * Returns the name of the character encoding being used by this stream.
       *
       * <p> If the encoding has an historical name then that name is returned;
       * otherwise the encoding's canonical name is returned.
       *
       * <p> If this instance was created with the {@link
       * #InputStreamReader(InputStream, String)} constructor then the returned
       * name, being unique for the encoding, may differ from the name passed to
       * the constructor. This method will return <code>null</code> if the
       * stream has been closed.
       * </p>
       * @return The historical name of this encoding, or
       *         <code>null</code> if the stream has been closed
       *
       * @see Charset
       *
       * @revised 1.4
       * @spec JSR-51
       */
      public String getEncoding() {
          return sd.getEncoding();
      }
  
      /**
       * Reads a single character.
       *
       * @return The character read, or -1 if the end of the stream has been
       *         reached
       *
       * @exception  IOException  If an I/O error occurs
       */
      public int read() throws IOException {
          return sd.read();
      }
  
      /**
       * Reads characters into a portion of an array.
       *
       * @param      cbuf     Destination buffer
       * @param      offset   Offset at which to start storing characters
       * @param      length   Maximum number of characters to read
       *
       * @return     The number of characters read, or -1 if the end of the
       *             stream has been reached
       *
       * @exception  IOException  If an I/O error occurs
       */
      public int read(char cbuf[], int offset, int length) throws IOException {
          return sd.read(cbuf, offset, length);
      }
  
      /**
       * Tells whether this stream is ready to be read.  An InputStreamReader is
       * ready if its input buffer is not empty, or if bytes are available to be
       * read from the underlying byte stream.
       *
       * @exception  IOException  If an I/O error occurs
       */
      public boolean ready() throws IOException {
          return sd.ready();
      }
  
      public void close() throws IOException {
          sd.close();
      }
  }
  