/*

  * Copyright (c) 1996, 2005, 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;

 /**

  * An InputStreamReader is a bridge from byte streams to character streams: It

  * reads bytes and decodes them into characters using a specified {@link

  * java.nio.charset.Charset <code>charset</code>}.  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 java.nio.charset.Charset

  *

  * @author      Mark Reinhold

  * @since       JDK1.1

  */

 public class InputStreamReader extends Reader {

     /**

      * Creates an InputStreamReader that uses the default charset.

      *

      * @param  in   An InputStream

      */

     public InputStreamReader(InputStream in) {

         super(in);

     }

     /**

      * Creates an InputStreamReader that uses the named charset.

      *

      * @param  in

      *         An InputStream

      *

      * @param  charsetName

      *         The name of a supported

      *         {@link java.nio.charset.Charset </code>charset<code>}

      *

      * @exception  UnsupportedEncodingException

      *             If the named charset is not supported

      */

     public InputStreamReader(InputStream in, String charsetName)

         throws UnsupportedEncodingException

     {

         super(in);

         if (!charsetName.toUpperCase().equals("UTF-8")) {

             throw new UnsupportedEncodingException(charsetName);

         }

     }

     /**

      * Creates an InputStreamReader that uses the given charset. </p>

      *

      * @param  in       An InputStream

      * @param  cs       A charset

      *

      * @since 1.4

      * @spec JSR-51

      */

 /* XXX:

     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.  </p>

      *

      * @param  in       An InputStream

      * @param  dec      A charset decoder

      *

      * @since 1.4

      * @spec JSR-51

      */

 /* XXX:

     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 java.nio.charset.Charset

      *

      * @revised 1.4

      * @spec JSR-51

      */

     public String getEncoding() {

         return "UTF-8";

     }

     /**

      * 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 {

         final InputStream is = (InputStream)lock;

         int c = is.read();

         if (c == -1) {

             return -1;

         }

         c = (int) c & 0xff;

         switch (c >> 4) {

             case 0: case 1: case 2: case 3: case 4: case 5: case 6: case 7:

                 /* 0xxxxxxx*/

                 return c;

             case 12: case 13: {

                 /* 110x xxxx   10xx xxxx*/

                 int char2 = (int) is.read();

                 if ((char2 & 0xC0) != 0x80)

                     throw new UTFDataFormatException("malformed input");

                 return (((c & 0x1F) << 6) | (char2 & 0x3F));

             }

             case 14: {

                 /* 1110 xxxx  10xx xxxx  10xx xxxx */

                 int char2 = is.read();

                 int char3 = is.read();

                 if (((char2 & 0xC0) != 0x80) || ((char3 & 0xC0) != 0x80))

                     throw new UTFDataFormatException("malformed input");

                 return (((c    & 0x0F) << 12) |

                        ((char2 & 0x3F) << 6)  |

                        ((char3 & 0x3F) << 0));

             }

             default:

                 /* 10xx xxxx,  1111 xxxx */

                 throw new UTFDataFormatException("malformed input");

         }

     }

     /**

      * 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 {

         for (int i = 0; i < length; i++) {

             int ch = read();

             if (ch == -1) {

                 if (i == 0) return -1;

                 return i;

             }

             cbuf[offset++] = (char) ch;

         }

         return 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 ((InputStream)lock).available() > 0;

     }

     public void close() throws IOException {

         ((InputStream)lock).close();

     }

 }