/*

 * Copyright (c) 1996, 2019, 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

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 */

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

 * java.nio.charset.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 java.nio.charset.Charset

 *

 * @author      Mark Reinhold

 * @since       1.1

 */

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 java.nio.charset.Charset charset}

     *

     * @throws     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} if the

     * stream has been closed.

     * </p>

     * @return The historical name of this encoding, or

     *         {@code null} if the stream has been closed

     *

     * @see java.nio.charset.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

     *

     * @throws     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

     *

     * @throws     IOException  If an I/O error occurs

     * @throws     IndexOutOfBoundsException {@inheritDoc}

     */

    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.

     *

     * @throws     IOException  If an I/O error occurs

     */

    public boolean ready() throws IOException {

        return sd.ready();

    }

    public void close() throws IOException {

        sd.close();

    }

}