sync: channel implementation (#6074)

vlib/sync/sync_nix.c.v

@@ -26,11 +26,13 @@ struct RwMutexAttr {
 
 /* MacOSX has no unnamed semaphores and no `timed_wait()` at all
    so we emulate the behaviour with other devices */
+[ref_only]
 struct MacOSX_Semaphore {
 	mtx C.pthread_mutex_t
 	cond C.pthread_cond_t
+	attr C.pthread_condattr_t
 mut:
-	count int
+	count u32
 }
 
 [ref_only]
@@ -38,19 +40,8 @@ struct PosixSemaphore {
 	sem C.sem_t
 }
 
-[ref_only]
-struct CondAttr {
-	attr C.pthread_condattr_t
-}
-
 pub struct Semaphore {
-	/*
-	$if macos {
-		sem &MacOSX_Semaphore
-	} $else {
-		sem &PosixSemaphore
-	}
-	*/
+mut:
 	sem voidptr // since the above does not work, yet
 }
 
@@ -99,22 +90,26 @@ pub fn (mut m RwMutex) w_unlock() {
 	C.pthread_rwlock_unlock(&m.mutex)
 }
 
+[inline]
 pub fn new_semaphore() Semaphore {
+	return new_semaphore_init(0)
+}
+
+pub fn new_semaphore_init(n u32) Semaphore {
 	$if macos {
 		s := Semaphore{
-			sem: &MacOSX_Semaphore{count: 0}
+			sem: &MacOSX_Semaphore{count: n}
 		}
 		C.pthread_mutex_init(&&MacOSX_Semaphore(s.sem).mtx, C.NULL)
-		a := &CondAttr{}
-		C.pthread_condattr_init(&a.attr)
-		C.pthread_condattr_setpshared(&a.attr, C.PTHREAD_PROCESS_PRIVATE)
-		C.pthread_cond_init(&&MacOSX_Semaphore(s.sem).cond, &a.attr)
+		C.pthread_condattr_init(&&MacOSX_Semaphore(s.sem).attr)
+		C.pthread_condattr_setpshared(&&MacOSX_Semaphore(s.sem).attr, C.PTHREAD_PROCESS_PRIVATE)
+		C.pthread_cond_init(&&MacOSX_Semaphore(s.sem).cond, &&MacOSX_Semaphore(s.sem).attr)
 		return s
 	} $else {
 		s := Semaphore{
 			sem: &PosixSemaphore{}
 		}
-		unsafe { C.sem_init(&&PosixSemaphore(s.sem).sem, 0, 0) }
+		unsafe { C.sem_init(&&PosixSemaphore(s.sem).sem, 0, n) }
 		return s
 	}
 }
@@ -186,3 +181,13 @@ pub fn (s Semaphore) timed_wait(timeout time.Duration) bool {
 		return unsafe { C.sem_timedwait(&&PosixSemaphore(s.sem).sem, &t_spec) == 0 }
 	}
 }
+
+pub fn (s Semaphore) destroy() bool {
+	$if macos {
+		return C.pthread_cond_destroy(&&MacOSX_Semaphore(s.sem).cond) == 0 &&
+			C.pthread_condattr_destroy(&&MacOSX_Semaphore(s.sem).attr) == 0 &&
+			C.pthread_mutex_destroy(&&MacOSX_Semaphore(s.sem).mtx) == 0
+	} $else {
+		return unsafe { C.sem_destroy(&&PosixSemaphore(s.sem).sem) == 0 }
+	}
+}