Reading a zip file header with reify

zread.js

var fs = require('fs');
var path = require('path');
var exists = fs.existsSync || path.existsSync;

var reified = require('reified'),
    StructT = reified.StructType,
    NumT = reified.NumericType,
    Uint16 = NumT.Uint16,
    Uint32 = NumT.Uint32;

reified.defaultEndian = 'LE';

function inspect(o) { console.log(require('util').inspect(o, false, 6)); }

var ZipHeader = new StructT('ZipHeader', {
    signature: Uint32,
    thisDiskNo: Uint16,
    cdStartDiskNo: Uint16,
    cdCountThis: Uint16,
    cdCountAll: Uint16,
    cdBytes: Uint32,
    cdOffset: Uint32,
    commentLen: Uint16
});

function Zippy(buffer, filename) {
    this.filename = filename;
    this.name = filename.slice(0, -path.extname(filename).length);

    this.index = new ZipHeader(buffer);

    inspect(this.reify());
}

Zippy.prototype.reify = function reify() {
    return Object.keys(this).reduce(function (r, s) {
        r[s] = this[s].reify ? this[s].reify() : this[s];
        return r;
    }.bind(this), {});
}

Zippy.load = function load(filename) {
    var resolved = path._makeLong(path.resolve('.', filename));
    if (exists(resolved)) {
        // Zip header is last 22 bytes of file
        var filebuf = fs.readFileSync(resolved),
            hdrbuf = filebuf.slice(filebuf.length - 22, filebuf.length);
        return new Zippy(hdrbuf, filename);
    } else {
        throw new Error(resolved + ' not found');
    }
}

Zippy.load(process.argv[2]);