A tool to measure code performance in Swift

MeasurePerf.swift

//
// Created by Florent Pillet on 14/11/16.
// Copyright (c) 2016 Florent Pillet. All rights reserved.
//

import Foundation

/*
 * A utility struct that helps mesure the performance of sections of code. Only uses Foundation
 * (we could also use QuartzCore's CACurrentMediaTime() for similar precision)
 *
 * Usage:
 *
 * MeasurePerf("this code took: ") {
 *     // code to execute here
 * }
 *
 * Will output:
 * this code took 0.12143673s
 *
 * You can also provide a logging closure for customized logging, or use the default constructor
 * and use the time yourself:
 *
 * let perf = MeasurePerf {
 *     // code to measure here
 * }
 *
 */
public struct MeasurePerf {
	static let NANOSECONDS_IN_SECOND : UInt64 = 1_000_000_000
	static let NANOSECONDS_IN_MILLISECOND : UInt64 = 1_000_000
	static let NANOSECONDS_IN_MICROSECOND : UInt64 = 1000

	private let startTime = mach_absolute_time()

	private(set) var doubleSeconds : Double = 0.0			// a single timing result

	private(set) var seconds : UInt64 = 0					// breakdown timing results
	private(set) var milliseconds : UInt64 = 0
	private(set) var microseconds : UInt64 = 0
	private(set) var nanoseconds : UInt64 = 0

	init(code: () throws -> Void) rethrows {
		defer { computeTime() }
		try code()
	}

	@discardableResult
	init(_ message: String, code: () throws -> Void) rethrows {
		defer {
			computeTime()
			print("\(message) \(self.doubleSeconds)s")
		}
		try code()
	}

	@discardableResult
	init(_ loggingClosure: (UInt64, UInt64, UInt64, UInt64) -> Void, code: () throws -> Void) rethrows {
		defer {
			computeTime()
			loggingClosure(self.seconds, self.milliseconds, self.microseconds, self.nanoseconds)
		}
		try code()
	}

	@discardableResult
	init(_ loggingClosure: (Double) -> Void, code: () throws -> Void) rethrows {
		defer {
			computeTime()
			loggingClosure(self.doubleSeconds)
		}
		try code()
	}

	private mutating func computeTime() {
		let endTime = mach_absolute_time()
		let elapsed = endTime - startTime

		var timeBase = mach_timebase_info_data_t()
		mach_timebase_info(&timeBase)

		var nanos = elapsed * UInt64(timeBase.numer) / UInt64(timeBase.denom);

		seconds = nanos / MeasurePerf.NANOSECONDS_IN_SECOND
		nanos = nanos - (seconds * MeasurePerf.NANOSECONDS_IN_SECOND)

		milliseconds = nanos / MeasurePerf.NANOSECONDS_IN_MILLISECOND
		nanos = nanos - (milliseconds * MeasurePerf.NANOSECONDS_IN_MILLISECOND)

		microseconds = nanos / MeasurePerf.NANOSECONDS_IN_MICROSECOND
		nanoseconds = nanos - (microseconds * MeasurePerf.NANOSECONDS_IN_MICROSECOND)

		doubleSeconds = Double(nanos) / Double(MeasurePerf.NANOSECONDS_IN_SECOND)
	}
}