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<html>
<HTML>
<HEAD>
<TITLE>Base64</TITLE>
<script type=‘text/javascript‘>
var BASE64_ENCODE_CHARS = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
var BASE64_DECODE_CHARS = [-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, 62, -1, -1, -1, 63, 52,
53, 54, 55, 56, 57, 58, 59, 60, 61, -1, -1, -1, -1, -1, -1, -1, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12,
13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, -1, -1, -1, -1, -1, -1, 26, 27, 28, 29, 30, 31, 32, 33,
34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, -1, -1, -1, -1, -1];
function encodeBase64(str) {
var c1, c2, c3, i = 0, len = str.length, out=[];
while (i < len) {
c1 = str.charCodeAt(i++) & 0xff;
if (i == len) {
out.push(BASE64_ENCODE_CHARS.charAt(c1 >> 2));
out.push(BASE64_ENCODE_CHARS.charAt((c1 & 0x3) << 4));
out.push(‘==‘);
break;
}
c2 = str.charCodeAt(i++);
if (i == len) {
out.push(BASE64_ENCODE_CHARS.charAt(c1 >> 2));
out.push(BASE64_ENCODE_CHARS.charAt(((c1 & 0x3) << 4) | ((c2 & 0xF0) >> 4)));
out.push(BASE64_ENCODE_CHARS.charAt((c2 & 0xF) << 2));
out.push(‘=‘);
break;
}
c3 = str.charCodeAt(i++);
out.push(BASE64_ENCODE_CHARS.charAt(c1 >> 2));
out.push(BASE64_ENCODE_CHARS.charAt(((c1 & 0x3) << 4) | ((c2 & 0xF0) >> 4)));
out.push(BASE64_ENCODE_CHARS.charAt(((c2 & 0xF) << 2) | ((c3 & 0xC0) >> 6)));
out.push(BASE64_ENCODE_CHARS.charAt(c3 & 0x3F));
}
return out.join(‘‘);
}
function decodeBase64(str) {
var c1, c2, c3, c4, i = 0, len = str.length, out=[];
while (i < len) {
/* c1 */
do {
c1 = BASE64_DECODE_CHARS[str.charCodeAt(i++) & 0xff];
} while (i < len && c1 == -1);
if (c1 == -1)
break;
/* c2 */
do {
c2 = BASE64_DECODE_CHARS[str.charCodeAt(i++) & 0xff];
} while (i < len && c2 == -1);
if (c2 == -1)
break;
out.push(String.fromCharCode((c1 << 2) | ((c2 & 0x30) >> 4)));
/* c3 */
do {
c3 = str.charCodeAt(i++) & 0xff;
if (c3 == 61)
return out.join(‘‘);
c3 = BASE64_DECODE_CHARS[c3];
} while (i < len && c3 == -1);
if (c3 == -1)
break;
out.push(String.fromCharCode(((c2 & 0XF) << 4) | ((c3 & 0x3C) >> 2)));
/* c4 */
do {
c4 = str.charCodeAt(i++) & 0xff;
if (c4 == 61)
return out.join(‘‘);
c4 = BASE64_DECODE_CHARS[c4];
} while (i < len && c4 == -1);
if (c4 == -1)
break;
out.push(String.fromCharCode(((c3 & 0x03) << 6) | c4));
}
return out.join(‘‘);
}
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 += str.charAt(i);
} else if (c > 0x07FF) {
out += String.fromCharCode(0xE0 | ((c >> 12) & 0x0F));
out += String.fromCharCode(0x80 | ((c >> 6) & 0x3F));
out += String.fromCharCode(0x80 | ((c >> 0) & 0x3F));
} else {
out += String.fromCharCode(0xC0 | ((c >> 6) & 0x1F));
out += String.fromCharCode(0x80 | ((c >> 0) & 0x3F));
}
}
return out;
}
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 += str.charAt(i - 1);
break;
case 12 :
case 13 :
// 110x xxxx 10xx xxxx
char2 = str.charCodeAt(i++);
out += 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 += String.fromCharCode(((c & 0x0F) << 12) | ((char2 & 0x3F) << 6) | ((char3 & 0x3F) << 0));
break;
}
}
return out;
}
function doIt() {
var sourceValue = document.getElementById(‘source‘).value;
document.getElementById(‘output‘).value = encodeBase64(utf16to8(sourceValue));
document.getElementById(‘decode‘).value = utf8to16(decodeBase64(sourceValue));
}
</script>
<body>
Source :<br>
<textarea id="source" style=‘width:500;height:80;‘></textarea><br><br>
base64 Encode :<br>
<textarea id="output" style=‘width:500;height:80;‘></textarea><br><br>
base64 Eecode :<br>
<textarea id="decode" style=‘width:500;height:80;‘></textarea><br><br>
<input type=button value="Transcoding" onclick="doIt()">
</body>
</html>
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原文地址：http://www.cnblogs.com/wj033/p/4412975.html
