javascript base64编码加密解密函数

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<!doctype html public "-//w3c//dtd html 4.01 transitional//en" "http://www.w3.org/tr/html4/loose.dtd">
<html>
<head>
<meta http-equiv="content-type" content="text/html; charset=gb2312">
<title>base64编码加密</title>
<script language="javascript">
var base64encodechars = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
var base64decodechars = new Array(
-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 base64encode(str) {
var out, i, len;
var c1, c2, c3;
len = str.length;
i = 0;
out = "";
while (i < len) {
c1 = str.charCodeAt(i++) & 0xff;
if (i == len) {
out += base64encodechars.charAt(c1 >> 2);
out += base64encodechars.charAt((c1 & 0x3) << 4);
out += "==";
break;
}
c2 = str.charCodeAt(i++);
if (i == len) {
out += base64encodechars.charAt(c1 >> 2);
out += base64encodechars.charAt(((c1 & 0x3) << 4) | ((c2 & 0xf0) >> 4));
out += base64encodechars.charAt((c2 & 0xf) << 2);
out += "=";
break;
}
c3 = str.charCodeAt(i++);
out += base64encodechars.charAt(c1 >> 2);
out += base64encodechars.charAt(((c1 & 0x3) << 4) | ((c2 & 0xf0) >> 4));
out += base64encodechars.charAt(((c2 & 0xf) << 2) | ((c3 & 0xc0) >> 6));
out += base64encodechars.charAt(c3 & 0x3f);
}
return out;
}
function base64decode(str) {
var c1, c2, c3, c4;
var i, len, out;
len = str.length;
i = 0;
out = "";
while (i < len) {

do {
c1 = base64decodechars[str.charCodeAt(i++) & 0xff];
} while (i < len && c1 == -1);
if (c1 == -1)
break;

do {
c2 = base64decodechars[str.charCodeAt(i++) & 0xff];
} while (i < len && c2 == -1);
if (c2 == -1)
break;
out += String.fromCharCode((c1 << 2) | ((c2 & 0x30) >> 4));

do {
c3 = str.charCodeAt(i++) & 0xff;
if (c3 == 61)
return out;
c3 = base64decodechars[c3];
} while (i < len && c3 == -1);
if (c3 == -1)
break;
out += String.fromCharCode(((c2 & 0xf) << 4) | ((c3 & 0x3c) >> 2));

do {
c4 = str.charCodeAt(i++) & 0xff;
if (c4 == 61)
return out;
c4 = base64decodechars[c4];
} while (i < len && c4 == -1);
if (c4 == -1)
break;
out += String.fromCharCode(((c3 & 0x03) << 6) | c4);
}
return out;
}
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 f = document.f
f.source.value = base64encode(utf16to8(f.source.value));
}
function doit2() {
var f = document.f
f.source.value = utf8to16(base64decode(f.source.value));
}
</script>
</head>
<body style="padding-left:50px;">
<h1 align="center">base64编码加密解密</h1>
<form name="f">
加密或解密的代码
<br>
<textarea name="source" rows=22 cols=60 wrap="soft"></textarea><br>
<input type=button value="加密" onclick="doit()"><input type=button value="解密" onclick="doit2()">
</form>
</body>
</html>

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