From ecb084647631dbd284998e3df9bf0ae2f131ebed Mon Sep 17 00:00:00 2001
From: YOCKOW <YOCKOW@users.noreply.github.com>
Date: Sun, 24 May 2020 13:09:57 +0900
Subject: [PATCH] Implement `static func measure(repeatCount:_:)`

---
 README.md                                         | 12 ++++--------
 Sources/TimeSpecification/TimeSpecification.swift | 15 +++++++++++++++
 2 files changed, 19 insertions(+), 8 deletions(-)

diff --git a/README.md b/README.md
index 1c5d97f..fc7a155 100644
--- a/README.md
+++ b/README.md
@@ -10,13 +10,9 @@ Its prototype is [YOCKOW's Gist](https://gist.github.com/YOCKOW/12d9607cb30f40b7
 ```Swift
 import TimeSpecification
 
-func time(_ body:() -> Void) {
-  let start = TimeSpecification(clock: .system)
-  body()
-  let end = TimeSpecification(clock: .system)
-  let duration = end - start
-  print("\(duration)")
-}
+let duration = TimeSpecification.measure(repeatCount: 100) { doIt() }
+print("It took \(duration) seconds.") // -> Processing time to execute `doIt` 100 times. 
+
 ```
 
 ### With `Date`
@@ -25,7 +21,7 @@ func time(_ body:() -> Void) {
 import TimeSpecification
 
 let now = TimeSpecification(clock: .calendar)
-let dateNow = Date(timeIntervalSince1970: now)
+let dateNow = Date(timeIntervalSince1970: now) // -> Almost same with Date(timeIntervalSince1970: Double(time(nil)))
 ```
 
 
diff --git a/Sources/TimeSpecification/TimeSpecification.swift b/Sources/TimeSpecification/TimeSpecification.swift
index d0f9e3c..05821a2 100644
--- a/Sources/TimeSpecification/TimeSpecification.swift
+++ b/Sources/TimeSpecification/TimeSpecification.swift
@@ -190,3 +190,18 @@ extension TimeSpecification {
     self.init(c_timespec)
   }
 }
+
+extension TimeSpecification {
+  /// Measure a processing time of the closure.
+  ///
+  /// - parameters:
+  ///   * repeatCount: Indicates the number of times to execute the closure. It must be greater than zero.
+  ///   * body: The target closure.
+  public static func measure(repeatCount: Int = 1, _ body: () throws -> Void) rethrows -> TimeSpecification {
+    precondition(repeatCount > 0, "\(#function): `repeatCount` must be greater than zero.")
+    let start = TimeSpecification(clock: .system)
+    for _ in 0..<repeatCount { try body() }
+    let end = TimeSpecification(clock: .system)
+    return end - start
+  }
+}