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authorwm4 <wm4@nowhere>2020-05-01 11:38:15 +0200
committerwm4 <wm4@nowhere>2020-05-01 11:38:15 +0200
commit994ccaea733db1c6be1d1798c4a60557d6ed226c (patch)
treef121d4ebc7542c8cd06adc7e430d43b0b854aad6
parent92db8731dd5ef700c7a7b96cf5f2f5aebc6d3d88 (diff)
downloadmpv-rc.tar.bz2
mpv-rc.tar.xz
ta: add refcount wrapperrc
-rw-r--r--ta/ta.h15
-rw-r--r--ta/ta_utils.c114
2 files changed, 129 insertions, 0 deletions
diff --git a/ta/ta.h b/ta/ta.h
index 4baac8fb40..02be182dd9 100644
--- a/ta/ta.h
+++ b/ta/ta.h
@@ -73,6 +73,17 @@ bool ta_vasprintf_append(char **str, const char *fmt, va_list ap) TA_PRF(2, 0);
bool ta_asprintf_append_buffer(char **str, const char *fmt, ...) TA_PRF(2, 3);
bool ta_vasprintf_append_buffer(char **str, const char *fmt, va_list ap) TA_PRF(2, 0);
+struct ta_refcount;
+struct ta_refcount *ta_refcount_alloc_(const char *loc, void *ta_child,
+ void (*on_free)(void *ctx, void *ta_child),
+ void *free_ctx);
+void ta_refcount_add(struct ta_refcount *rc);
+void ta_refcount_dec(struct ta_refcount *rc);
+bool ta_refcount_is_1(struct ta_refcount *rc);
+
+struct ta_refuser;
+struct ta_refuser *ta_alloc_auto_ref(void *ta_parent, struct ta_refcount *rc);
+
#define ta_new(ta_parent, type) (type *)ta_alloc_size(ta_parent, sizeof(type))
#define ta_znew(ta_parent, type) (type *)ta_zalloc_size(ta_parent, sizeof(type))
@@ -125,6 +136,8 @@ bool ta_vasprintf_append_buffer(char **str, const char *fmt, va_list ap) TA_PRF(
#define ta_xnew_ptrtype(...) ta_oom_g(ta_new_ptrtype(__VA_ARGS__))
#define ta_xnew_array_ptrtype(...) ta_oom_g(ta_new_array_ptrtype(__VA_ARGS__))
#define ta_xdup(...) ta_oom_g(ta_dup(__VA_ARGS__))
+#define ta_xrefcount_alloc(...) ta_oom_g(ta_refcount_alloc(__VA_ARGS__))
+#define ta_xalloc_auto_ref(...) ta_oom_g(ta_alloc_auto_ref(__VA_ARGS__))
#define ta_xrealloc(ta_parent, ptr, type, count) \
(type *)ta_xrealloc_size(ta_parent, ptr, ta_calc_array_size(sizeof(type), count))
@@ -142,6 +155,8 @@ void *ta_xrealloc_size(void *ta_parent, void *ptr, size_t size);
#define ta_memdup(...) ta_dbg_set_loc(ta_memdup(__VA_ARGS__), TA_LOC)
#define ta_xmemdup(...) ta_dbg_set_loc(ta_xmemdup(__VA_ARGS__), TA_LOC)
#define ta_xrealloc_size(...) ta_dbg_set_loc(ta_xrealloc_size(__VA_ARGS__), TA_LOC)
+#define ta_refcount_alloc(...) ta_refcount_alloc_(TA_LOC, __VA_ARGS__)
+#define ta_alloc_auto_ref(...) ta_dbg_set_loc(ta_alloc_auto_ref(__VA_ARGS__), TA_LOC)
#endif
void ta_oom_b(bool b);
diff --git a/ta/ta_utils.c b/ta/ta_utils.c
index 62469686db..ecba307a7a 100644
--- a/ta/ta_utils.c
+++ b/ta/ta_utils.c
@@ -17,6 +17,8 @@
#include <string.h>
#include <stdio.h>
#include <assert.h>
+
+#include "osdep/atomic.h"
#include "osdep/strnlen.h"
#define TA_NO_WRAPPERS
@@ -313,3 +315,115 @@ char *ta_xstrndup(void *ta_parent, const char *str, size_t n)
ta_oom_b(res || !str);
return res;
}
+
+struct ta_refcount {
+ atomic_ulong count;
+ void *child;
+ void (*on_free)(void *ctx, void *ta_child);
+ void *on_free_ctx;
+};
+
+// Allocate a refcount helper. The ta_child parameter is automatically freed
+// with ta_free(). The returned object has a refcount of 1. Once the refcount
+// reaches 0, ta_free(ta_child) is called.
+//
+// If on_free() is not NULL, then instead of ta_free(), on_free() is called with
+// the parameters of the same named as passed to this function.
+//
+// The ta_child pointer must not be NULL, and must not have a parent allocation.
+// Neither make any sense for this use-case, and could be hint for serious bugs
+// in the caller, so assert()s check for this.
+//
+// The return value is not a ta allocation. You use the refcount functions to
+// manage it. It is recommended to use ta_alloc_auto_unref().
+//
+// Note: normally you use the ta_refcount_alloc() macro, which lacks the loc
+// parameter.
+struct ta_refcount *ta_refcount_alloc_(const char *loc, void *ta_child,
+ void (*on_free)(void *ctx, void *ta_child),
+ void *free_ctx)
+{
+ assert(ta_child && !ta_get_parent(ta_child));
+
+ struct ta_refcount *rc = ta_new_ptrtype(NULL, rc);
+ if (!rc)
+ return NULL;
+
+ ta_dbg_set_loc(rc, loc);
+ *rc = (struct ta_refcount){
+ .count = ATOMIC_VAR_INIT(1),
+ .child = ta_child,
+ .on_free = on_free,
+ .on_free_ctx = free_ctx,
+ };
+
+ return rc + 1; // "obfuscate" the pointer
+}
+
+void ta_refcount_add(struct ta_refcount *rc)
+{
+ assert(rc);
+ rc -= 1;
+
+ unsigned long c = atomic_fetch_add(&rc->count, 1);
+ assert(c > 0); // not allowed: refcount was 0, you can't "revive" it
+}
+
+void ta_refcount_dec(struct ta_refcount *rc)
+{
+ assert(rc);
+ rc -= 1;
+
+ unsigned long c = atomic_fetch_add(&rc->count, -1);
+ assert(c != 0); // not allowed: refcount was 0
+ if (!c) {
+ if (rc->on_free) {
+ rc->on_free(rc->on_free_ctx, rc->child);
+ } else {
+ ta_free(rc->child);
+ }
+ ta_free(rc);
+ }
+}
+
+// Return whether the refcount is 1. Note that if the result is false, it could
+// become true any time in the general case, since other threads may be changing
+// the refcount. But if true is returned, it means you are the only owner of the
+// refcounted object. (If you are not an owner, it's UB to call this function.)
+bool ta_refcount_is_1(struct ta_refcount *rc)
+{
+ assert(rc);
+ rc -= 1;
+
+ return atomic_load(&rc->count) == 1;
+}
+
+struct ta_refuser {
+ struct ta_refcount *rc;
+};
+
+static void autofree_dtor(void *p)
+{
+ struct ta_refuser *ru = p;
+
+ ta_refcount_dec(ru->rc);
+}
+
+// Refcount user helper. This is a ta allocation which on creation increments
+// the refcount, and decrements it when it is free'd.
+//
+// The user must not access the contents of the allocation or resize it. Calling
+// ta_set_destructor() is not allowed. But you can freely reparent it or add
+// child allocation. ta_free_children() is also allowed and does not affect the
+// refcount.
+struct ta_refuser *ta_alloc_auto_ref(void *ta_parent, struct ta_refcount *rc)
+{
+ struct ta_refuser *ru = ta_new(ta_parent, struct ta_refuser);
+ if (!ru)
+ return NULL;
+
+ ta_set_destructor(ru, autofree_dtor);
+ ru->rc = rc;
+ ta_refcount_add(ru->rc);
+ return ru;
+}