Add refc.h

refc.h

@@ -0,0 +1,138 @@
+#ifndef REFC_H
+#define REFC_H
+
+#include <stddef.h>
+#include <stdbool.h>
+
+// #define REFC_IMPLEMENTATION
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+typedef void (*refc_destructor_fn)(void* obj, size_t size, void* user);
+
+typedef struct refc_obj {
+  void* ptr;
+} refc_obj;
+
+refc_obj refc_make(size_t size, refc_destructor_fn dtor, void* user);
+refc_obj refc_make_zero(size_t size, refc_destructor_fn dtor, void* user);
+
+refc_obj refc_acquire(refc_obj o);
+void     refc_drop(refc_obj* o);
+
+refc_obj refc_take(refc_obj* o);
+void*    refc_ptr(refc_obj o);
+
+unsigned refc_count(refc_obj o);
+size_t   refc_size(refc_obj o);
+bool     refc_unique(refc_obj o);
+bool     refc_is_null(refc_obj o);
+
+void refc_cleanup(refc_obj* o);
+
+#if defined(__GNUC__) || defined(__clang__)
+#define REFC_SCOPED __attribute__((cleanup(refc_cleanup)))
+#else
+#define REFC_SCOPED
+#endif
+
+#ifdef __cplusplus
+}
+#endif
+
+#ifdef REFC_IMPLEMENTATION
+
+#include <stdlib.h>
+#include <string.h>
+#include <stdalign.h>
+#include <stdatomic.h>
+
+typedef struct refc_block {
+  _Alignas(max_align_t) atomic_uint ref;
+  size_t size;
+  refc_destructor_fn dtor;
+  void* user;
+  unsigned char data[];
+} refc_block;
+
+static inline refc_block* refc_blk(const void* p) {
+  return (refc_block*)((unsigned char*)p - offsetof(refc_block, data));
+}
+
+refc_obj refc_make(size_t size, refc_destructor_fn dtor, void* user) {
+  refc_obj o = {0};
+  if (size > (size_t)-1 - sizeof(refc_block)) return o;
+  refc_block* b = (refc_block*)malloc(sizeof(refc_block) + size);
+  if (!b) return o;
+  atomic_init(&b->ref, 1u);
+  b->size = size;
+  b->dtor = dtor;
+  b->user = user;
+  o.ptr = (void*)b->data;
+  return o;
+}
+
+refc_obj refc_make_zero(size_t size, refc_destructor_fn dtor, void* user) {
+  refc_obj o = refc_make(size, dtor, user);
+  if (o.ptr && size) memset(o.ptr, 0, size);
+  return o;
+}
+
+refc_obj refc_acquire(refc_obj o) {
+  if (!o.ptr) return o;
+  refc_block* b = refc_blk(o.ptr);
+  atomic_fetch_add_explicit(&b->ref, 1u, memory_order_relaxed);
+  return o;
+}
+
+void refc_drop(refc_obj* o) {
+  if (!o || !o->ptr) return;
+  refc_block* b = refc_blk(o->ptr);
+  o->ptr = NULL;
+  if (atomic_fetch_sub_explicit(&b->ref, 1u, memory_order_acq_rel) == 1u) {
+    atomic_thread_fence(memory_order_acquire);
+    if (b->dtor) b->dtor((void*)b->data, b->size, b->user);
+    free(b);
+  }
+}
+
+refc_obj refc_take(refc_obj* o) {
+  refc_obj out = {0};
+  if (!o) return out;
+  out = *o;
+  o->ptr = NULL;
+  return out;
+}
+
+void* refc_ptr(refc_obj o) {
+  return o.ptr;
+}
+
+unsigned refc_count(refc_obj o) {
+  if (!o.ptr) return 0u;
+  const refc_block* b = refc_blk(o.ptr);
+  return atomic_load_explicit(&b->ref, memory_order_relaxed);
+}
+
+size_t refc_size(refc_obj o) {
+  if (!o.ptr) return 0u;
+  const refc_block* b = refc_blk(o.ptr);
+  return b->size;
+}
+
+bool refc_unique(refc_obj o) {
+  return refc_count(o) == 1u;
+}
+
+bool refc_is_null(refc_obj o) {
+  return o.ptr == NULL;
+}
+
+void refc_cleanup(refc_obj* o) {
+  refc_drop(o);
+}
+
+#endif
+#endif