From 4efb5c7aeb3a33fa0bbcdf2766aa8bf9ed8c91ae Mon Sep 17 00:00:00 2001
From: Yuta Koshizawa <koher@koherent.org>
Date: Sat, 14 Jan 2017 04:38:09 +0900
Subject: [PATCH] Add temporary `_sync`

---
 Sources/Async.swift | 26 ++++++++++++++++++++++++++
 1 file changed, 26 insertions(+)

diff --git a/Sources/Async.swift b/Sources/Async.swift
index 27f0540..d504639 100644
--- a/Sources/Async.swift
+++ b/Sources/Async.swift
@@ -27,6 +27,32 @@ public func sync<T, R>(operation: (@escaping (T, @escaping (() throws -> R) -> (
     }
 }
 
+public func _sync<T, R>(operation: (@escaping (T, @escaping (() throws -> R) -> ()) -> ())) -> (T) throws -> R {
+    return  { value in
+        var resultValue: R!
+        var resultError: Error?
+        
+        let semaphore = DispatchSemaphore(value: 0)
+        operation(value) { getValue in
+            defer {
+                semaphore.signal()
+            }
+            do {
+                resultValue = try getValue()
+            } catch let error {
+                resultError = error
+            }
+        }
+        semaphore.wait()
+        
+        if let error = resultError {
+            throw error
+        }
+        
+        return resultValue
+    }
+}
+
 internal func repeated<T, R>(operation: (@escaping (T, @escaping (() throws -> R) -> ()) -> ()), interval: TimeInterval? = nil) -> ([T], @escaping (() throws -> [R]) -> ()) -> () {
     return { values, callback in
         _repeat(operation: operation, for: values[0..<values.count], interval: interval, callback: callback)