Simple JSON task using old "idiomatic" Swift

OldJson.swift

// Copyright 2017 Google LLC
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// https://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

import Foundation

var baseTs: UInt64 = 0
func ts(_ label: String) {
    let ts = mach_absolute_time()
    print(label + String(format: ": %.3f", Double(ts - baseTs) * 1e-6))
}

let data = try Data(contentsOf: URL(fileURLWithPath: "/tmp/update.json"))

func benchOldJson() throws {
    baseTs = mach_absolute_time()
    let json = try JSONSerialization.jsonObject(with: data, options: .allowFragments)
    ts("after json ser")
    let obj = json as! [String: AnyObject]
    ts("after cast")
    let params = obj["params"] as! [String: AnyObject]
    ts("after cast2")
    let update = params["update"] as! [String: AnyObject]
    ts("after cast3")
    let ops = update["ops"] as! [[String: AnyObject]]
    ts("after cast4")
    var total = 0
    var textlen = 0
    for op in ops {
        let opcode = op["op"] as! String
        total += op["n"] as! Int
        if opcode == "ins" {
            let lines = op["lines"] as! [[String: AnyObject]]
            for line in lines {
                textlen += (line["text"] as? String)?.count ?? 0
            }
        }
    }
    ts("after sum n")
    print("Old-style JSON result:", total, textlen)
}

try benchOldJson()