databuffer.js

function DataBuffer(data) {
    this.data  = data;
    this.index = 0;
}

DataBuffer.prototype.check = function(n) {
    return this.data.length >= this.index + n;
}

DataBuffer.prototype.readByte = function() {
    if(!this.check(1))
        return null;
    
    rv = this.data.charCodeAt(this.index) & 0xff;
    this.index++;
    return rv;
}

DataBuffer.prototype.readShort = function() {
    if(!this.check(2))
        return null;

    hi = (this.data.charCodeAt(this.index) << 8) & 0xff00;
    lo = this.data.charCodeAt(this.index+1) & 0xff;

    this.index += 2;

    return hi|lo;
}

DataBuffer.prototype.readWord = function() {
    if(!this.check(4))
        return null;

    hihi = (this.data.charCodeAt(this.index) << 24) & 0xff000000;
    hilo = (this.data.charCodeAt(this.index+1) << 16) & 0x00ff0000;
 
    lohi = (this.data.charCodeAt(this.index+2) << 8) & 0x0000ff00;
    lolo = this.data.charCodeAt(this.index+3) & 0x000000ff;

    this.index += 4;

    return hihi|hilo|lohi|lolo;
}

DataBuffer.prototype.dump = function() {
    return dump(this.data.substr(this.index));
}