added test for ReadWriteLock

Author: tgymnich

Sources/TSCBasic/Lock.swift

@@ -41,15 +41,27 @@ public class ReadWriteLock {
         pthread_rwlock_init(&lock, nil)
     }
 
+    func readLock() {
+        pthread_rwlock_rdlock(&lock)
+    }
+
+    func writeLock() {
+        pthread_rwlock_wrlock(&lock)
+    }
+
+    func unlock() {
+        pthread_rwlock_unlock(&lock)
+    }
+
     /// Execute the given block while holding the lock.
     public func withLock<T>(type lockType: LockType = .exclusive, _ body: () throws -> T) rethrows -> T {
         switch lockType {
         case .shared:
-            pthread_rwlock_rdlock(&lock)
+            readLock()
         case .exclusive:
-            pthread_rwlock_wrlock(&lock)
+            writeLock()
         }
-        defer { pthread_rwlock_unlock(&lock) }
+        defer { unlock() }
         return try body()
     }
 

Tests/TSCBasicTests/LockTests.swift

@@ -48,4 +48,37 @@ class LockTests: XCTestCase {
             }
         }
     }
+
+    func testReadWriteLock() throws {
+        var a = 0
+        var b = 0
+
+        let lock = ReadWriteLock()
+
+        let writerThreads = (0..<100).map { _ in
+           return Thread {
+                lock.withLock(type: .exclusive) {
+                    a+=1
+                    sched_yield()
+                    b+=1
+                }
+            }
+        }
+
+        let readerThreads = (0..<20).map { _ in
+            return Thread {
+                lock.withLock(type: .shared) {
+                    XCTAssertEqual(a,b)
+                    sched_yield()
+                    XCTAssertEqual(a,b)
+                }
+            }
+        }
+
+        writerThreads.forEach { $0.start() }
+        readerThreads.forEach { $0.start() }
+        writerThreads.forEach { $0.join() }
+        readerThreads.forEach { $0.join() }
+    }
+
 }