chartobytesinglebyte.java

来自「This is a resource based on j2me embedde」· Java 代码 · 共 226 行

/*
 * @(#)CharToByteSingleByte.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;

/**
 * A table driven conversion from char to byte for single byte
 * character sets.  Tables will reside in the class CharToByteYYYYY,
 * where YYYYY is a unique character set identifier

 < TBD: Tables are of the form... >

 *
 * @author Lloyd Honomichl
 * @author Asmus Freytag
 * @version 8/28/96
 */

public abstract class CharToByteSingleByte extends CharToByteConverter {
    /*
     * 1st level index, provided by subclass
     */
    protected short index1[];
    /*
     * 2nd level index, provided by subclass
     */
    protected String  index2;
    /*
     * Mask to isolate bits for 1st level index, from subclass
     */
    protected int   mask1;
    /*
     * Mask to isolate bits for 2nd level index, from subclass
     */
    protected int   mask2;
    /*
     * Shift to isolate bits for 1st level index, from subclass
     */
    protected int   shift;
    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;
    }

    /**
     * Converts characters to sequences of bytes.
     * Conversions that result in Exceptions can be restarted by calling
     * convert again, with appropriately modified parameters.
     * @return the characters written to output.
     * @param input char array containing text in Unicode
     * @param inStart offset in input array
     * @param inEnd offset of last byte to be converted
     * @param output byte array to receive conversion result
     * @param outStart starting offset
     * @param outEnd offset of last byte to be written to
     * @throw MalformedInputException for any sequence of chars that is
     * illegal in Unicode (principally unpaired surrogates
     * and \uFFFF or \uFFFE), including any partial surrogate pair
     * which occurs at the end of an input buffer.
     * @throw UnsupportedCharacterException for any character that
     * that cannot be converted to the external character set.
     */
    public int convert(char[] input, int inOff, int inEnd,
        byte[] output, int outOff, int outEnd)
        throws MalformedInputException,
            UnknownCharacterException,
            ConversionBufferFullException {
        char    inputChar;          // Input character to be converted
        byte[]  outputByte;         // Output byte written to output
        int     inputSize;          // Size of input
        int	outputSize;	    // Size of output
        byte[]  tmpArray = new byte[1];
        // Record beginning offsets
        charOff = inOff;
        byteOff = outOff;
        if (highHalfZoneCode != 0) {
            inputChar = highHalfZoneCode;
            highHalfZoneCode = 0;
            if (input[inOff] >= 0xdc00 && input[inOff] <= 0xdfff) {
                // This is legal UTF16 sequence.
                badInputLength = 1;
                throw new UnknownCharacterException();
            } else {
                // This is illegal UTF16 sequence.
                badInputLength = 0;
                throw new MalformedInputException();
            }
        }
        // Loop until we hit the end of the input
        while (charOff < inEnd) {
            outputByte = tmpArray;
            // Get the input character
            inputChar = input[charOff];
            // Default output size
            outputSize = 1;
            // Assume this is a simple character
            inputSize = 1;
            // Is this a high surrogate?
            if (inputChar >= '\uD800' && inputChar <= '\uDBFF') {
                // Is this the last character in the input?
                if (charOff + 1 >= inEnd) {
                    highHalfZoneCode = inputChar;
                    break;
                }
                // Is there a low surrogate following?
                inputChar = input[charOff + 1];
                if (inputChar >= '\uDC00' && inputChar <= '\uDFFF') {
                    // We have a valid surrogate pair.  Too bad we don't map
                    //  surrogates.  Is substitution enabled?
                    if (subMode) {
                        outputByte = subBytes;
                        outputSize = subBytes.length;
                        inputSize = 2;
                    } else {
                        badInputLength = 2;
                        throw new UnknownCharacterException();
                    }
                } else {
                    // We have a malformed surrogate pair
                    badInputLength = 1;
                    throw new MalformedInputException();
                }
            } // Is this an unaccompanied low surrogate?
            else if (inputChar >= '\uDC00' && inputChar <= '\uDFFF') {
                badInputLength = 1;
                throw new MalformedInputException();
            } // Not part of a surrogate, so look it up
            else {
                // Get output using two level lookup
                outputByte[0] = getNative(inputChar);
                // Might this character be unmappable?
                if (outputByte[0] == 0) {
                    // If outputByte is zero because the input was zero
                    //  then this character is actually mappable
                    if (input[charOff] != '\u0000') {
                        // We have an unmappable character
                        // Is substitution enabled?
                        if (subMode) {
                            outputByte = subBytes;
                            outputSize = subBytes.length;
                        } else {
                            badInputLength = 1;
                            throw new UnknownCharacterException();
                        }
                    }
                }
            }
            // If we don't have room for the output, throw an exception
            if (byteOff + outputSize > outEnd)
                throw new ConversionBufferFullException();
                // Put the byte in the output buffer
            for (int i = 0; i < outputSize; i++) {
                output[byteOff++] = outputByte[i];
            }
            charOff += inputSize;
        }
        // Return the length written to the output buffer
        return byteOff - outOff;
    }

    /**
     * the maximum number of bytes needed to hold a converted char
     * @returns the maximum number of bytes needed for a converted char
     */
    public int getMaxBytesPerChar() {
        return 1;
    }

    public byte getNative(char inputChar) {
        return (byte) index2.charAt(index1[(inputChar & mask1) >> shift] 
                + (inputChar & mask2));
    }

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

    /**
     * Return whether a character is mappable or not
     * @return true if a character is mappable
     */
    public boolean canConvert(char ch) {
        // Look it up in the table
        if (index2.charAt(index1[((ch & mask1) >> shift)] + (ch & mask2)) != '\u0000')
            return true;
            // Nulls are always mappable
        return (ch == '\u0000');
    }
}