add refcnt util

util/CMakeLists.txt

@@ -6,10 +6,12 @@ target_sources(nf7util
     array.h
     log.h
     malloc.h
+    refcnt.h
     signal.h
 )
 target_tests(nf7util
   array.test.c
+  refcnt.test.c
 )
 target_link_libraries(nf7util
   PRIVATE

util/refcnt.h

@@ -0,0 +1,42 @@
+// No copyright
+#pragma once
+
+#include <assert.h>
+#include <stdatomic.h>
+
+#include "util/malloc.h"
+
+
+#define NF7_REFCNT_DECL(ATTR, T)  \
+  ATTR void T##_ref(struct T*);  \
+  ATTR bool T##_unref(struct T*);  \
+  static_assert(true)
+
+
+#define NF7_REFCNT_IMPL(ATTR, T, DELETER)  \
+  ATTR void T##_ref(struct T* this) {  \
+    ++this->refcnt;  \
+  }  \
+  ATTR bool T##_unref(struct T* this) {  \
+    assert(0 < this->refcnt);  \
+    if (0 == --this->refcnt) {  \
+      {DELETER};  \
+      return true;  \
+    }   \
+    return false;  \
+  }  \
+  static_assert(true)
+
+#define NF7_REFCNT_IMPL_ATOMIC(ATTR, T, DELETER)  \
+  ATTR void T##_ref(struct T* this) {  \
+    atomic_fetch_add(&this->refcnt, 1);  \
+  }  \
+  ATTR bool T##_unref(struct T* this) {  \
+    assert(0 < this->refcnt);  \
+    if (1 == atomic_fetch_sub(&this->refcnt, 1)) {  \
+      {DELETER};  \
+      return true;  \
+    }   \
+    return false;  \
+  }  \
+  static_assert(true)

util/refcnt.test.c

@@ -0,0 +1,43 @@
+// No copyright
+#include "util/refcnt.h"
+
+#include <stdatomic.h>
+#include <stdint.h>
+
+#include "test/common.h"
+
+
+struct mystruct {
+  bool deleted;
+  uint64_t refcnt;
+};
+NF7_REFCNT_IMPL(static inline, mystruct, {this->deleted = true;});
+
+struct mystruct_atomic {
+  bool deleted;
+  atomic_uint_least64_t refcnt;
+};
+NF7_REFCNT_IMPL_ATOMIC(static inline, mystruct_atomic, {this->deleted = true;});
+
+
+NF7_TEST(nf7_util_refcnt_test_delete) {
+  struct mystruct sut = {0};
+  mystruct_ref(&sut);
+  mystruct_ref(&sut);
+  return
+    nf7_test_expect(!mystruct_unref(&sut)) &&
+    nf7_test_expect(!sut.deleted) &&
+    nf7_test_expect(mystruct_unref(&sut)) &&
+    nf7_test_expect(sut.deleted);
+}
+
+NF7_TEST(nf7_util_refcnt_test_atomic_delete) {
+  struct mystruct_atomic sut = {0};
+  mystruct_atomic_ref(&sut);
+  mystruct_atomic_ref(&sut);
+  return
+    nf7_test_expect(!mystruct_atomic_unref(&sut)) &&
+    nf7_test_expect(!sut.deleted) &&
+    nf7_test_expect(mystruct_atomic_unref(&sut)) &&
+    nf7_test_expect(sut.deleted);
+}