Struct for Javascript, based on Python struct. (In development)

Struct.js

            var struct = new (function(){
                var dLen = {
                    /*"Type": [Size, Read, Write]*/
                    /*pad byte          */"x": [1, "getUint8", "setUint8"],
                    /*char              */"c": [1, "getUint8", "setUint8"],
                    /*signed char       */"b": [1, "getInt8", "setInt8"],
                    /*unsigned char     */"B": [1, "getUint8", "setUint8"],
                    /*_Bool             */"?": [1, "getUint8", "setUint8"],
                    /*short             */"h": [2, "getInt16", "getInt16"],
                    /*unsigned short    */"H": [2, "getUint16", "getUint16"],
                    /*int               */"i": [4, "getInt32", "getInt32"],
                    /*unsigned int      */"I": [4, "getUint32", "getUint32"],
                    /*long              */"l": [4, "getInt32", "getInt32"],
                    /*unsigned long     */"L": [4, "getUint32", "getUint32"],
                    /*long long         */"q": [8, "", ""],
                    /*unsigned long long*/"Q": [8, "", ""],
                    /*ssize_t           */"n": [8, "", ""],
                    /*size_t            */"N": [8, "", ""],
                    /*float             */"f": [4, "getFloat32", "setFloat32"],
                    /*double            */"d": [8, "getFloat64", "setFloat64"],
                    /*char[]            */"s": [1, "", ""],
                    /*char[]            */"p": [1, "", ""],
                    /*void *            */"P": [8, "", ""],
                                          ">": [0, "", ""],
                                          "<": [0, "", ""],
                                          "!": [0, "", ""],
                                          "@": [0, "", ""]
                };
                function getDataView(blah){
                    if(blah.constructor === DataView)
                        return blah;
                    if(typeof(blah) === "string"){
                        var a = new TextEncoder("utf-8").encode("asdf")
                        var b = new DataView(new ArrayBuffer(a.length));
                        for(var i=0,l=a.length;i<l;i++){
                            b.setUint8(i, a[i])
                        }
                        return b;
                    }
                    if(Array.isArray(blah)){
                        var b = new DataView(new ArrayBuffer(blah.length));
                        for(var i=0,l=blah.length;i<l;i++){
                            b.setUint8(i, blah[i])
                        }
                        return b;
                    }
                }
                this.calcsize = function(fmt){
                    var size = 0, calcdsize = 0;
                    for(var i=0,l=fmt.length;i<l;i++){
                        if(!isNaN(parseInt(fmt[i]))){
                            if(size == 0){
                                size = parseInt(fmt[i]);
                            }else{
                                size = (size*10)+parseInt(fmt[i]);
                            }
                        }else{
                            if(size == 0)size = 1;
                            if(fmt[i] in dLen){
                                calcdsize += dLen[fmt[i]][0]*size;
                            }else{
                                throw "bad char in struct format";
                            }
                            size = 0;
                        }
                    }
                    return calcdsize;
                };
                /*fmt, v1, v2, ...*/
                this.pack = function(){
                    if(arguments.length == 0)
                        throw "bad char in struct format";
                    var fmt = arguments[0], size = 0;
                    var result = new DataView(new ArrayBuffer(self.calcsize(fmt)));
                    for(var i=0,l=fmt.length;i<l;i++){
                        if(!isNaN(parseInt(fmt[i]))){
                            if(size == 0) size = parseInt(fmt[i]);
                            else size = (size*10)+parseInt(fmt[i]);
                        }else{
                            if(size == 0)size = 1;
                            if(fmt[i] == ""){
                            }else if(fmt[i] in dLen){
                                calcdsize += dLen[fmt[i]][0]*size;
                            }else{
                                throw "bad char in struct format";
                            }
                            size = 0;
                        }
                    }
                    return calcdsize;
                };
            });
            var a = new TextEncoder("utf-8").encode("asdf")
            var b = new DataView(new ArrayBuffer(a.length));
            for(var i=0,l=a.length;i<l;i++){
                b.setUint8(i, a[i])
            }