Update core:sync/sync2 to have a generic Futex interface, and implement the calls appropriately for each platform

core/sync/sync2/futex_darwin.odin

@@ -0,0 +1,83 @@
+//+private
+//+build darwin
+package sync2
+
+import "core:c"
+import "core:time"
+
+foreign import System "System.framework"
+
+foreign System {
+	__ulock_wait  :: proc "c" (operation: u32, addr: rawptr, value: u64, timeout_ms: u32) -> c.int ---
+	__ulock_wait2 :: proc "c" (operation: u32, addr: rawptr, value: u64, timeout_ns: u64, value2: u64) -> c.int ---
+	__ulock_wake  :: proc "c" (operation: u32, addr: rawptr, wake_value: u64) -> c.int ---
+}
+
+
+UL_COMPARE_AND_WAIT :: 1
+ULF_WAKE_ALL        :: 0x00000100
+ULF_NO_ERRNO        :: 0x01000000
+
+ENOENT    :: -2
+EINTR     :: -4
+EFAULT    :: -14
+ETIMEDOUT :: -60
+
+_futex_wait :: proc(f: ^Futex, expected: u32) -> Futex_Error {
+	return _futex_wait_with_timeout(f, expected, 0)
+}
+
+_futex_wait_with_timeout :: proc(f: ^Futex, expected: u32, duration: time.Duration) -> Futex_Error {
+	timeout_ns := u64(duration)
+	timeout_overflowed := false
+	
+	s := __ulock_wait2(UL_COMPARE_AND_WAIT | ULF_NO_ERRNO, f, u64(expected), timeout_ns, 0)
+	if s >= 0 {
+		return nil
+	}
+	switch s {
+	case EINTR, EFAULT:
+		return nil
+	case ETIMEDOUT:
+		return .Timed_Out
+	case:
+		panic("futex_wait failure")
+	}
+	return nil
+
+}
+
+_futex_wake_single :: proc(f: ^Futex) {
+	loop: for {
+		s := __ulock_wake(UL_COMPARE_AND_WAIT | ULF_NO_ERRNO, f, 0)
+		if s >= 0 {
+			return
+		}
+		switch s {
+		case EINTR, EFAULT: 
+			continue loop
+		case ENOENT:
+			return
+		case:
+			panic("futex_wake_single failure")
+		}
+	}
+}
+
+_futex_wake_all :: proc(f: ^Futex) {
+	loop: for {
+		s := __ulock_wake(UL_COMPARE_AND_WAIT | ULF_NO_ERRNO | ULF_WAKE_ALL, f, 0)
+		if s >= 0 {
+			return
+		}
+		switch s {
+		case EINTR, EFAULT: 
+			continue loop
+		case ENOENT:
+			return
+		case:
+			panic("futex_wake_all failure")
+		}
+	}
+}
+