bytetocharsinglebyte.java

来自「This is a resource based on j2me embedde」· Java 代码 · 共 141 行

/*
 * @(#)ByteToCharSingleByte.java	1.20 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;

/**
 * A table driven conversion from byte to char for single byte  character sets.
 * The needed data tables will reside in a character set specific subclass.
 *
 * @author Lloyd Honomichl
 * @author Asmus Freytag
 * @version 8/28/96
 */
public abstract class ByteToCharSingleByte extends ByteToCharConverter {

    /**
     * Mapping table. Values supplied by subclass
     */
    protected String byteToCharTable;

    public String getByteToCharTable() {
	return byteToCharTable;
    }

    public int flush(char[] output, int outStart, int outEnd) {
	byteOff = charOff = 0;
	return 0;
    }

    /**
     * Converts bytes to characters according to the selected character
     * encoding.
     * Maintains internal state, so that conversions that result in
     * exceptions can be restarted by calling convert again, with
     * appropriately modified parameters.
     * Call reset before converting input that is not a continuation of
     * the previous call.
     * @return the number of characters written to output.
     * @param input byte array containing text in character set
     * @param inStart offset in input array
     * @param inEnd offset of last byte to be converted
     * @param output character array to receive conversion result
     * @param outStart starting offset
     * @param outEnd offset of last character to be written to
     * @throw MalformedInputException for any sequence of bytes that is
     * illegal for the input character set, including any partial multi-byte
     * sequence which occurs at the end of an input buffer.
     * @throw UnsupportedCharacterException for any sequence of bytes that
     * contain a character not supported in the current conversion.
     * @throw BufferFullException whenever the output buffer is full
     * before the input is exhausted.
     * @see #reset
     */
    public int convert(byte[] input, int inOff, int inEnd,
		       char[] output, int outOff, int outEnd)
        throws UnknownCharacterException,
               MalformedInputException,
               ConversionBufferFullException
    {
    	char	outputChar;
	int 	byteIndex;

        charOff = outOff;
        byteOff = inOff;

        // Loop until we hit the end of the input
        while(byteOff < inEnd) {

	    byteIndex = input[byteOff];

	    /* old source 
	     *outputChar = byteToCharTable[input[byteOff] + 128];
	     */
	    // Lookup the output character
	    outputChar = getUnicode(byteIndex);

	    // Is the output unmappable?
	    if (outputChar == '\uFFFD')	{
		if (subMode) {
		    outputChar = subChars[0];
		} else {
		    badInputLength = 1;
		    throw new UnknownCharacterException();
		}
            }

	    // If we don't have room for the output, throw an exception
	    if (charOff >= outEnd)
		throw new ConversionBufferFullException();

	    // Put the character in the output buffer
	    output[charOff]= outputChar;
	    charOff++;
	    byteOff++;
        }
	
    	// Return the length written to the output buffer
	return charOff-outOff;
    }

    protected char getUnicode(int byteIndex) {
	int n = byteIndex + 128;
	if (n >= byteToCharTable.length() || n < 0) 
	    return '\uFFFD';
	return byteToCharTable.charAt(n);
    }

    /**
     *  Resets the converter.
     *  Call this method to reset the converter to its initial state
     */
    public void reset() {
	byteOff = charOff = 0;
    }

}