source: Dev/trunk/src/client/dojox/encoding/ascii85.js

define(["dojo/_base/lang"], function(lang) {

        var ascii85 = lang.getObject("dojox.encoding.ascii85", true);

        var c = function(input, length, result){
                var i, j, n, b = [0, 0, 0, 0, 0];
                for(i = 0; i < length; i += 4){
                        n = ((input[i] * 256 + input[i+1]) * 256 + input[i+2]) * 256 + input[i+3];
                        if(!n){
                                result.push("z");
                        }else{
                                for(j = 0; j < 5; b[j++] = n % 85 + 33, n = Math.floor(n / 85));
                        }
                        result.push(String.fromCharCode(b[4], b[3], b[2], b[1], b[0]));
                }
        };

        ascii85.encode = function(input){
                // summary:
                //              encodes input data in ascii85 string
                // input: Array
                //              an array of numbers (0-255) to encode
                var result = [], reminder = input.length % 4, length = input.length - reminder;
                c(input, length, result);
                if(reminder){
                        var t = input.slice(length);
                        while(t.length < 4){ t.push(0); }
                        c(t, 4, result);
                        var x = result.pop();
                        if(x == "z"){ x = "!!!!!"; }
                        result.push(x.substr(0, reminder + 1));
                }
                return result.join(""); // String
        };

        ascii85.decode = function(input){
                // summary:
                //              decodes the input string back to array of numbers
                // input: String
                //              the input string to decode
                var n = input.length, r = [], b = [0, 0, 0, 0, 0], i, j, t, x, y, d;
                for(i = 0; i < n; ++i){
                        if(input.charAt(i) == "z"){
                                r.push(0, 0, 0, 0);
                                continue;
                        }
                        for(j = 0; j < 5; ++j){ b[j] = input.charCodeAt(i + j) - 33; }
                        d = n - i;
                        if(d < 5){
                                for(j = d; j < 4; b[++j] = 0);
                                b[d] = 85;
                        }
                        t = (((b[0] * 85 + b[1]) * 85 + b[2]) * 85 + b[3]) * 85 + b[4];
                        x = t & 255;
                        t >>>= 8;
                        y = t & 255;
                        t >>>= 8;
                        r.push(t >>> 8, t & 255, y, x);
                        for(j = d; j < 5; ++j, r.pop());
                        i += 4;
                }
                return r;
        };

        return ascii85;
});