feat(heap): thread-safety features

include/vieter_heap.h

@@ -11,7 +11,7 @@ typedef enum vieter_heap_error {
 } vieter_heap_error;
 
 /*
- * Allocate and initalize an empty heap.
+ * Allocate and initialize an empty heap.
  */
 vieter_heap *vieter_heap_init();
 
@@ -41,4 +41,22 @@ vieter_heap_error vieter_heap_pop(void **out, vieter_heap *heap);
  */
 vieter_heap_error vieter_heap_peek(void **out, vieter_heap *heap);
 
+/*
+ * Acquire a read lock on the heap. Return value is the result of
+ * pthread_rwlock_rdlock.
+ */
+int vieter_heap_rlock(vieter_heap *heap);
+
+/*
+ * Acquire a write lock on the heap. Return value is the result of
+ * pthread_rwlock_wrlock.
+ */
+int vieter_heap_wlock(vieter_heap *heap);
+
+/*
+ * Unlock the lock after having acquired it. Return value is the result of
+ * pthread_rwlock_unlock.
+ */
+int vieter_heap_unlock(vieter_heap *heap);
+
 #endif