semaphore: Add GCD semaphore implementation. (#1677)

src/core/libraries/kernel/sync/semaphore.h

@@ -11,6 +11,8 @@
 
 #ifdef _WIN64
 #include <windows.h>
+#elif defined(__APPLE__)
+#include <dispatch/dispatch.h>
 #else
 #include <semaphore>
 #endif
@@ -21,25 +23,32 @@ template <s64 max>
 class Semaphore {
 public:
     Semaphore(s32 initialCount)
-#ifndef _WIN64
+#if !defined(_WIN64) && !defined(__APPLE__)
         : sem{initialCount}
 #endif
     {
 #ifdef _WIN64
         sem = CreateSemaphore(nullptr, initialCount, max, nullptr);
         ASSERT(sem);
+#elif defined(__APPLE__)
+        sem = dispatch_semaphore_create(initialCount);
+        ASSERT(sem);
 #endif
     }
 
     ~Semaphore() {
 #ifdef _WIN64
         CloseHandle(sem);
+#elif defined(__APPLE__)
+        dispatch_release(sem);
 #endif
     }
 
     void release() {
 #ifdef _WIN64
         ReleaseSemaphore(sem, 1, nullptr);
+#elif defined(__APPLE__)
+        dispatch_semaphore_signal(sem);
 #else
         sem.release();
 #endif
@@ -53,6 +62,13 @@ public:
                 return;
             }
         }
+#elif defined(__APPLE__)
+        for (;;) {
+            const auto res = dispatch_semaphore_wait(sem, DISPATCH_TIME_FOREVER);
+            if (res == 0) {
+                return;
+            }
+        }
 #else
         sem.acquire();
 #endif
@@ -61,6 +77,8 @@ public:
     bool try_acquire() {
 #ifdef _WIN64
         return WaitForSingleObjectEx(sem, 0, true) == WAIT_OBJECT_0;
+#elif defined(__APPLE__)
+        return dispatch_semaphore_wait(sem, DISPATCH_TIME_NOW) == 0;
 #else
         return sem.try_acquire();
 #endif
@@ -77,6 +95,10 @@ public:
         }
 
         return WaitForSingleObjectEx(sem, timeout_ms, true) == WAIT_OBJECT_0;
+#elif defined(__APPLE__)
+        const auto rel_time_ns = std::chrono::ceil<std::chrono::nanoseconds>(rel_time).count();
+        const auto timeout = dispatch_time(DISPATCH_TIME_NOW, rel_time_ns);
+        return dispatch_semaphore_wait(sem, timeout) == 0;
 #else
         return sem.try_acquire_for(rel_time);
 #endif
@@ -98,6 +120,16 @@ public:
 
         u64 res = WaitForSingleObjectEx(sem, static_cast<u64>(timeout_ms), true);
         return res == WAIT_OBJECT_0;
+#elif defined(__APPLE__)
+        auto abs_s = std::chrono::time_point_cast<std::chrono::seconds>(abs_time);
+        auto abs_ns = std::chrono::time_point_cast<std::chrono::nanoseconds>(abs_time) -
+                      std::chrono::time_point_cast<std::chrono::nanoseconds>(abs_s);
+        const timespec abs_timespec = {
+            .tv_sec = abs_s.time_since_epoch().count(),
+            .tv_nsec = abs_ns.count(),
+        };
+        const auto timeout = dispatch_walltime(&abs_timespec, 0);
+        return dispatch_semaphore_wait(sem, timeout) == 0;
 #else
         return sem.try_acquire_until(abs_time);
 #endif
@@ -106,6 +138,8 @@ public:
 private:
 #ifdef _WIN64
     HANDLE sem;
+#elif defined(__APPLE__)
+    dispatch_semaphore_t sem;
 #else
     std::counting_semaphore<max> sem;
 #endif