win: implement Semaphore

util/synchronization/semaphore.cc

Index: util/synchronization/semaphore.cc
diff --git a/util/synchronization/semaphore.cc b/util/synchronization/semaphore.cc
index d513fa0dd43981acc72b1ff155fa2d1e77616388..789ac1e9e0f65421f7f31c550066b2d72a0a8e61 100644
--- a/util/synchronization/semaphore.cc
+++ b/util/synchronization/semaphore.cc
@@ -14,6 +14,8 @@
 
 #include "util/synchronization/semaphore.h"
 
+#include <limits>
+
 #include "base/logging.h"
 #include "base/posix/eintr_wrapper.h"

[scottmg, 2014/12/17 22:58:15]

I didn't realize before, but this guards its entire contents, so is OK to
include.

 
@@ -38,6 +40,28 @@ void Semaphore::Signal() {
   dispatch_semaphore_signal(semaphore_);
 }
 
+#elif defined(OS_WIN)
+
+Semaphore::Semaphore(int value)
+    : semaphore_(CreateSemaphore(nullptr,
+                                 value,
+                                 std::numeric_limits<LONG>::max(),
+                                 nullptr)) {
+  PCHECK(semaphore_) << "CreateSemaphore";
+}
+
+Semaphore::~Semaphore() {
+  PCHECK(CloseHandle(semaphore_));
+}
+
+void Semaphore::Wait() {
+  CHECK_EQ(WaitForSingleObject(semaphore_, INFINITE), WAIT_OBJECT_0);

[Mark Mentovai, 2014/12/18 14:38:47]

PCHECK this and ReleaseSemaphore()?

[scottmg, 2014/12/18 17:07:02]

Done.

+}
+
+void Semaphore::Signal() {
+  CHECK(ReleaseSemaphore(semaphore_, 1, nullptr));
+}
+
 #else
 
 Semaphore::Semaphore(int value) {