Java ByteBuffer to UTF readUTF(ByteBuffer bb)

Description

Reads from the bytebuffer bb a representation of a Unicode character string encoded in modified UTF-8 format; this string of characters is then returned as a String.

License

Open Source License

Parameter

Parameter	Description
bb	a byte buffer.

Return

a Unicode string.

Declaration

public static String readUTF(ByteBuffer bb) throws BufferUnderflowException, UTFDataFormatException

Method Source Code

//package com.java2s;
/**/*w w w. java 2s. com*/
 * Copyright 2009 DFKI GmbH.
 * All Rights Reserved.  Use is subject to license terms.
 *
 * This file is part of MARY TTS.
 *
 * MARY TTS is free software: you can redistribute it and/or modify
 * it under the terms of the GNU Lesser General Public License as published by
 * the Free Software Foundation, version 3 of the License.
 *
 * This program 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 Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
 *
 */

import java.io.UTFDataFormatException;
import java.nio.BufferUnderflowException;
import java.nio.ByteBuffer;

public class Main {
    /**
     * Reads from the bytebuffer <code>bb</code> a representation of a Unicode character string encoded in <a
     * href="DataInput.html#modified-utf-8">modified UTF-8</a> format; this string of characters is then returned as a
     * <code>String</code>. The details of the modified UTF-8 representation are exactly the same as for the <code>readUTF</code>
     * method of <code>DataInput</code>.
     * 
     * @param bb
     *            a byte buffer.
     * @return a Unicode string.
     * @exception BufferUnderflowException
     *                if the input stream reaches the end before all the bytes.
     * @exception UTFDataFormatException
     *                if the bytes do not represent a valid modified UTF-8 encoding of a Unicode string.
     * @see java.io.DataInputStream#readUnsignedShort()
     */
    public static String readUTF(ByteBuffer bb) throws BufferUnderflowException, UTFDataFormatException {
        int utflen = readUnsignedShort(bb);
        byte[] bytearr = new byte[utflen];
        char[] chararr = new char[utflen];

        int c, char2, char3;
        int count = 0;
        int chararr_count = 0;

        bb.get(bytearr);

        while (count < utflen) {
            c = (int) bytearr[count] & 0xff;
            if (c > 127)
                break;
            count++;
            chararr[chararr_count++] = (char) c;
        }

        while (count < utflen) {
            c = (int) bytearr[count] & 0xff;
            switch (c >> 4) {
            case 0:
            case 1:
            case 2:
            case 3:
            case 4:
            case 5:
            case 6:
            case 7:
                /* 0xxxxxxx */
                count++;
                chararr[chararr_count++] = (char) c;
                break;
            case 12:
            case 13:
                /* 110x xxxx 10xx xxxx */
                count += 2;
                if (count > utflen)
                    throw new UTFDataFormatException("malformed input: partial character at end");
                char2 = (int) bytearr[count - 1];
                if ((char2 & 0xC0) != 0x80)
                    throw new UTFDataFormatException("malformed input around byte " + count);
                chararr[chararr_count++] = (char) (((c & 0x1F) << 6) | (char2 & 0x3F));
                break;
            case 14:
                /* 1110 xxxx 10xx xxxx 10xx xxxx */
                count += 3;
                if (count > utflen)
                    throw new UTFDataFormatException("malformed input: partial character at end");
                char2 = (int) bytearr[count - 2];
                char3 = (int) bytearr[count - 1];
                if (((char2 & 0xC0) != 0x80) || ((char3 & 0xC0) != 0x80))
                    throw new UTFDataFormatException("malformed input around byte " + (count - 1));
                chararr[chararr_count++] = (char) (((c & 0x0F) << 12) | ((char2 & 0x3F) << 6)
                        | ((char3 & 0x3F) << 0));
                break;
            default:
                /* 10xx xxxx, 1111 xxxx */
                throw new UTFDataFormatException("malformed input around byte " + count);
            }
        }
        // The number of chars produced may be less than utflen
        return new String(chararr, 0, chararr_count);
    }

    /**
     * See the general contract of the <code>readUnsignedShort</code> method of <code>DataInput</code>.
     * <p>
     * Bytes for this operation are read from the given byte buffer
     * 
     * @param bb
     *            bb
     * @return the next two bytes of this input stream, interpreted as an unsigned 16-bit integer.
     * @exception BufferUnderflowException
     *                if this input stream reaches the end before reading two bytes.
     * @see java.io.FilterInputStream#in
     */
    public static int readUnsignedShort(ByteBuffer bb) throws BufferUnderflowException {
        int ch1 = bb.get() & 0xFF; // convert byte to unsigned byte
        int ch2 = bb.get() & 0xFF; // convert byte to unsigned byte
        return (ch1 << 8) + (ch2 << 0);
    }
}