/* utf.js - UTF-8 <=> UTF-16 convertion
 *
 * Copyright (C) 1999 Masanao Izumo <iz@onicos.co.jp> & 2006 Ma Bingyao <andot@ujn.edu.cn>
 * Version: 1.1
 * LastModified: Feb 17 2006
 * This library is free.  You can redistribute it and/or modify it.
 */

/*
 * Interfaces:
 * utf8 = utf16to8(utf16);
 * utf16 = utf16to8(utf8);
 */

function utf16to8(str) {
    var out, i, len, c;

    out = [];
    len = str.length;
    for(i = 0; i < len; i++) {
	    c = str.charCodeAt(i);
	    if ((c >= 0x0001) && (c <= 0x007F)) {
	        out[i] = str.charAt(i);
	    } else if (c > 0x07FF) {
	        out[i] = String.fromCharCode(0xE0 | ((c >> 12) & 0x0F),
	                                     0x80 | ((c >>  6) & 0x3F),
	                                     0x80 | ((c >>  0) & 0x3F));
	    } else {
	        out[i] = String.fromCharCode(0xC0 | ((c >>  6) & 0x1F),
	                                     0x80 | ((c >>  0) & 0x3F));
	    }
    }
    return out.join('');
}

function utf8to16(str) {
    var out, i, len, c;
    var char2, char3;

    out = [];
    len = str.length;
    i = 0;
    while(i < len) {
	    c = str.charCodeAt(i++);
	    switch(c >> 4)
	    { 
	        case 0: case 1: case 2: case 3: case 4: case 5: case 6: case 7:
	        // 0xxxxxxx
	        out[out.length] = str.charAt(i-1);
	        break;
	        case 12: case 13:
    	    // 110x xxxx   10xx xxxx
	        char2 = str.charCodeAt(i++);
	        out[out.length] = String.fromCharCode(((c & 0x1F) << 6) | (char2 & 0x3F));
    	    break;
            case 14:
    	    // 1110 xxxx  10xx xxxx  10xx xxxx
	        char2 = str.charCodeAt(i++);
	        char3 = str.charCodeAt(i++);
    	    out[out.length] = String.fromCharCode(((c & 0x0F) << 12) |
	    	    ((char2 & 0x3F) << 6) | ((char3 & 0x3F) << 0));
	        break;
    	}
    }

    return out.join('');
}