Paul Hollands

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March 09, 2006

JavaScript code for base64 encoding and decoding mailto URLs

//First things first, set up our array that we are going to use.
var keyStr = "ABCDEFGHIJKLMNOPQRSTUVWXYZ" + //all caps
"abcdefghijklmnopqrstuvwxyz" + //all lowercase
"0123456789+/="; // all numbers plus +/=
//Heres the encode function
function base64_encode(inp)
{
var out = ""; //This is the output
var chr1, chr2, chr3 = ""; //These are the 3 bytes to be encoded
var enc1, enc2, enc3, enc4 = ""; //These are the 4 encoded bytes
var i = 0; //Position counter
do { //Set up the loop here
chr1 = inp.charCodeAt(i++); //Grab the first byte
chr2 = inp.charCodeAt(i++); //Grab the second byte
chr3 = inp.charCodeAt(i++); //Grab the third byte
//Here is the actual base64 encode part.
//There really is only one way to do it.
enc1 = chr1 >> 2;
enc2 = ((chr1 & 3) << 4) | (chr2 >> 4);
enc3 = ((chr2 & 15) << 2) | (chr3 >> 6);
enc4 = chr3 & 63;

if (isNaN(chr2)) {
enc3 = enc4 = 64;
} else if (isNaN(chr3)) {
enc4 = 64;
}
//Lets spit out the 4 encoded bytes
out = out + keyStr.charAt(enc1) + keyStr.charAt(enc2) + keyStr.charAt(enc3) +
keyStr.charAt(enc4);
// OK, now clean out the variables used.
chr1 = chr2 = chr3 = "";
enc1 = enc2 = enc3 = enc4 = "";
} while (i < inp.length); //And finish off the loop
//Now return the encoded values.
return out;
}
//Heres the decode function
function base64_decode(inp)
{
var out = ""; //This is the output
var chr1, chr2, chr3 = ""; //These are the 3 decoded bytes
var enc1, enc2, enc3, enc4 = ""; //These are the 4 bytes to be decoded
var i = 0; //Position counter
// remove all characters that are not A-Z, a-z, 0-9, +, /, or =
var base64test = /[^A-Za-z0-9\+\/\=]/g;
if (base64test.exec(inp)) { //Do some error checking
alert("There were invalid base64 characters in the input text.\n" +
"Valid base64 characters are A-Z, a-z, 0-9, ?+?, ?/?, and ?=?\n" +
"Expect errors in decoding.");
}
inp = inp.replace(/[^A-Za-z0-9\+\/\=]/g, "");
do { //Here’s the decode loop.
//Grab 4 bytes of encoded content.
enc1 = keyStr.indexOf(inp.charAt(i++));
enc2 = keyStr.indexOf(inp.charAt(i++));
enc3 = keyStr.indexOf(inp.charAt(i++));
enc4 = keyStr.indexOf(inp.charAt(i++));
//Heres the decode part. There’s really only one way to do it.
chr1 = (enc1 << 2) | (enc2 >> 4);
chr2 = ((enc2 & 15) << 4) | (enc3 >> 2);
chr3 = ((enc3 & 3) << 6) | enc4;
//Start to output decoded content
out = out + String.fromCharCode(chr1);
if (enc3 != 64) {
out = out + String.fromCharCode(chr2);
}
if (enc4 != 64) {
out = out + String.fromCharCode(chr3);
}
//now clean out the variables used
chr1 = chr2 = chr3 = "";
enc1 = enc2 = enc3 = enc4 = "";
} while (i < inp.length); //finish off the loop
//Now return the decoded values.
return out;
}
function encode(text){
    document.write(base64_encode(text));
    }
function decode(text){
    document.write(base64_decode(text));
    }
function decode_mailto(text){
    dato = new Date();
    email = base64_decode(text);
    email2 = email.replace('@',"@");
    email3 = email2.replace('.',".");
    //alert(email3);
    document.write('' + email3 + '');
    }
function decode_link_mailto(text){
    dato = new Date();
    email = base64_decode(text);
    email2 = email.replace('@',"@");
    email3 = email2.replace('.',".");
    //alert(email3);
    document.write('<a href="mailto:' + email +'">' + email3 + '</a>');
    }

Tags: JavaScript

Posted by pj at March 9, 2006 10:22 AM