/*

 * 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();

    }

}