//

// STScrollPerfDiagnostics.swift

// STBaseProject

//

// Created by 寒江孤影 on 2018/06/12.

//

import os

import UIKit

// 滑动/布局等主线程性能诊断工具

// 通过 os_signpost 在 Instruments 的 Points of Interest 中标记区间

// 仅在 DEBUG 下启用，Release 下为零成本空实现

public enum STScrollPerfDiagnostics {

/// 使用 PointsOfInterest category，Instruments 选 "Points of Interest" 模板即可看到区间

private static let log = OSLog(

subsystem: Bundle.main.bundleIdentifier ?? "app",

category: "PointsOfInterest"

)

/// 超过此毫秒数打日志，便于发现主线程长任务（一帧约 16ms）

private static let thresholdMs: Double = 16

/// 是否打印超时日志（可在调试时改为 true）

private static let logSlowBlocks = true

/// 测量一段主线程耗时，并用 os_signpost 记录；超过 thresholdMs 时打日志

/// - Parameters:

/// - name: 区间名称（在 Instruments Points of Interest / os_signpost 中显示）

/// - block: 要测量的闭包

/// - Returns: block 的返回值

@inline(__always)

public static func measure<T>(name: StaticString, block: () -> T) -> T {

#if DEBUG

let start = CFAbsoluteTimeGetCurrent()

os_signpost(.begin, log: log, name: name)

defer {

os_signpost(.end, log: log, name: name)

let ms = (CFAbsoluteTimeGetCurrent() - start) * 1000

if logSlowBlocks, ms > thresholdMs {

os_log(

.default,

log: log,

"[STScrollPerf] %{public}s %.1f ms",

"\(name)",

ms

)

}

}

return block()

#else

return block()

#endif

}

/// 无返回值版本

@inline(__always)

public static func measure(name: StaticString, block: () -> Void) {

#if DEBUG

let start = CFAbsoluteTimeGetCurrent()

os_signpost(.begin, log: log, name: name)

block()

os_signpost(.end, log: log, name: name)

let ms = (CFAbsoluteTimeGetCurrent() - start) * 1000

if logSlowBlocks, ms > thresholdMs {

os_log(.default, log: log, "[STScrollPerf] %{public}s %.1f ms", "\(name)", ms)

}

#else

block()

#endif

}

}