How to get size of a DataView type (eg. Uint32=4, Float64=8) to advance the offset?

Question

I'm parsing a serialized object with a DataView and want to be able to increment an offset variable depending on data sizes. I'd rather not redefine variables for simple things like BYTES_PER_UINT16

...
var dv = new DataView(payload);
var offset = 0;
anObject.field1 = dv.getUint8(offset);
offset += BYTES_PER_UINT8;
anObject.field2 = dv.getUint32(offset, true);
offset += BYTES_PER_UINT32;
...

Answer 1

You need to wrap them in an object which does this for you.

For example:

function DataViewExt(o) {
    this.view = new DataView(o);
    this.pos = 0;
}

DataViewExt.prototype = {
    getUint8: function() {
        return this.view.getUint8(this.pos++);
    },

    getUint16: function() {
        var v = this.view.getUint16(this.pos);
        this.pos += 2;
        return v
    },
    // etc...
};

Now you can create an instance:

var dv = new DataViewExt(payload);
var uint8 = dv.getUint8();       // advances 1 byte
var uint16 = dv.getUint16();     // advances 2 bytes
...
console.log("Current position:", dv.pos);

Modify to fit your scenario.