gistfile1.txt

> db.users.findOne
function (query, fields) {
    var cursor = this._mongo.find(this._fullName, this._massageObject(query) || {}, fields, -1, 0, 0, 0);
    if (!cursor.hasNext()) {
        return null;
    }
    var ret = cursor.next();
    if (cursor.hasNext()) {
        throw "findOne has more than 1 result!";
    }
    if (ret.$err) {
        throw "error " + tojson(ret);
    }
    return ret;
}