chartobyteutf8.java

来自「This is a resource based on j2me embedde」· Java 代码 · 共 162 行

/*
 * @(#)CharToByteUTF8.java	1.19 06/10/10
 *
 * Copyright  1990-2008 Sun Microsystems, Inc. All Rights Reserved.  
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER  
 *   
 * This program 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.   
 *   
 * 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  
 * General Public License version 2 for more details (a copy is  
 * included at /legal/license.txt).   
 *   
 * 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 Sun Microsystems, Inc., 4150 Network Circle, Santa  
 * Clara, CA 95054 or visit www.sun.com if you need additional  
 * information or have any questions. 
 *
 */
package sun.io;


/**
 * UCS2 (UTF16) -> UCS Transformation Format 8 (UTF-8) converter
 * It's represented like below.
 *
 * # Bits   Bit pattern
 * 1    7   0xxxxxxx
 * 2   11   110xxxxx 10xxxxxx
 * 3   16   1110xxxx 10xxxxxx 10xxxxxx
 * 4   21   11110xxx 10xxxxxx 10xxxxxx 10xxxxxx
 * 5   26   111110xx 10xxxxxx 10xxxxxx 10xxxxxx 10xxxxxx
 * 6   31   1111110x 10xxxxxx 10xxxxxx 10xxxxxx 10xxxxxx 10xxxxxx
 *
 *     UCS2 uses 1-3 / UTF16 uses 1-4 / UCS4 uses 1-6
 */

public class CharToByteUTF8 extends CharToByteConverter {

    private char highHalfZoneCode;
    
    public int flush(byte[] output, int outStart, int outEnd)
	throws MalformedInputException
    {
	if (highHalfZoneCode != 0) {
	    highHalfZoneCode = 0;
	    badInputLength = 0;
	    throw new MalformedInputException();
	}
	byteOff = charOff = 0;
	return 0;
    }

    /**
     * Character conversion
     */
    public int convert(char[] input, int inOff, int inEnd,
		       byte[] output, int outOff, int outEnd)
	throws ConversionBufferFullException, MalformedInputException
    {
	char inputChar;
	byte[] outputByte = new byte[6];
	int inputSize;
	int outputSize;

	charOff = inOff;
	byteOff = outOff;

	if (highHalfZoneCode != 0) {
	    inputChar = highHalfZoneCode;
	    highHalfZoneCode = 0;
	    if (input[inOff] >= 0xdc00 && input[inOff] <= 0xdfff) {
		// This is legal UTF16 sequence.
		int ucs4 = (highHalfZoneCode - 0xd800) * 0x400
		    + (input[inOff] - 0xdc00) + 0x10000;
		output[0] = (byte)(0xf0 | ((ucs4 >> 18)) & 0x07);
		output[1] = (byte)(0x80 | ((ucs4 >> 12) & 0x3f));
		output[2] = (byte)(0x80 | ((ucs4 >> 6) & 0x3f));
		output[3] = (byte)(0x80 | (ucs4 & 0x3f));
		charOff++;
		highHalfZoneCode = 0;
	    } else {
		// This is illegal UTF16 sequence.
		badInputLength = 0;
		throw new MalformedInputException();
	    }
	}

	while(charOff < inEnd) {
	    inputChar = input[charOff];
	    if (inputChar < 0x80) {
		outputByte[0] = (byte)inputChar;
		inputSize = 1;
		outputSize = 1;
	    } else if (inputChar < 0x800) {
		outputByte[0] = (byte)(0xc0 | ((inputChar >> 6) & 0x1f));
		outputByte[1] = (byte)(0x80 | (inputChar & 0x3f));
		inputSize = 1;
		outputSize = 2;
	    } else if (inputChar >= 0xd800 && inputChar <= 0xdbff) {
		// this is <high-half zone code> in UTF-16
		if (charOff + 1 >= inEnd) {
		    highHalfZoneCode = inputChar;
		    break;
		}
		// check next char is valid <low-half zone code>
		char lowChar = input[charOff + 1];
		if (lowChar < 0xdc00 || lowChar > 0xdfff) {
		    badInputLength = 1;
		    throw new MalformedInputException();
		}
		int ucs4 = (inputChar - 0xd800) * 0x400 + (lowChar - 0xdc00)
		    + 0x10000;
		outputByte[0] = (byte)(0xf0 | ((ucs4 >> 18)) & 0x07);
		outputByte[1] = (byte)(0x80 | ((ucs4 >> 12) & 0x3f));
		outputByte[2] = (byte)(0x80 | ((ucs4 >> 6) & 0x3f));
		outputByte[3] = (byte)(0x80 | (ucs4 & 0x3f));
		outputSize = 4;
		inputSize = 2;
	    } else {
		outputByte[0] = (byte)(0xe0 | ((inputChar >> 12)) & 0x0f);
		outputByte[1] = (byte)(0x80 | ((inputChar >> 6) & 0x3f));
		outputByte[2] = (byte)(0x80 | (inputChar & 0x3f));
		inputSize = 1;
		outputSize = 3;
	    } 
	    if (byteOff + outputSize > outEnd) {
		throw new ConversionBufferFullException();
	    }
	    for (int i = 0; i < outputSize; i++) {
		output[byteOff++] = outputByte[i];
	    }
	    charOff += inputSize;
	}
	return byteOff - outOff;
    }

    public boolean canConvert(char ch) {
	return true;
    }

    public int getMaxBytesPerChar() {
	return 3;
    }

    public void reset() {
	byteOff = charOff = 0;
	highHalfZoneCode = 0;
    }

    public String getCharacterEncoding() {
	return "UTF8";
    }
}