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authorAndrew Tridgell <tridge@samba.org>2004-08-25 06:40:58 +0000
committerGerald (Jerry) Carter <jerry@samba.org>2007-10-10 12:58:21 -0500
commit4f55a7af084137822c813cbe3822fca54e64df76 (patch)
tree2355f2d9b4bb93eeda9309574aceb4331dd656fe /source4/lib
parentc4a2128db5fd36f4e616df74de8bddd9285d2728 (diff)
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r2049: talloc now has destructors and reference counts
this means you can do: talloc_set_destructor(ptr, my_destructor); and your destructor will be called with the pointer as an argument when the pointer is about to be freed. The destructor can refuse the free by returning -1. You can also increase the reference count on a pointer like this: talloc_increase_ref_count(ptr); and a talloc_free() will just reduce the reference count, only actually freeing the memory when the count reaches zero. (This used to be commit b5608d52d33a1d8be5a8a6751bc6cec162c7ed92)
Diffstat (limited to 'source4/lib')
-rw-r--r--source4/lib/talloc.c131
1 files changed, 75 insertions, 56 deletions
diff --git a/source4/lib/talloc.c b/source4/lib/talloc.c
index 4a48347832..31b6584845 100644
--- a/source4/lib/talloc.c
+++ b/source4/lib/talloc.c
@@ -27,17 +27,32 @@
#include "includes.h"
#define MAX_TALLOC_SIZE 0x10000000
-#define TALLOC_MAGIC 0x14082004
-#define TALLOC_MAGIC_FREE 0x3421abcd
+#define TALLOC_MAGIC 0xe814ec4f
+#define TALLOC_MAGIC_FREE 0x7faebef3
struct talloc_chunk {
struct talloc_chunk *next, *prev;
struct talloc_chunk *parent, *child;
size_t size;
uint_t magic;
+ uint_t ref_count;
+ int (*destructor)(void *);
char *name;
};
+/* panic if we get a bad magic value */
+static struct talloc_chunk *talloc_chunk_from_ptr(void *ptr)
+{
+ struct talloc_chunk *tc = ((struct talloc_chunk *)ptr)-1;
+ if (tc->magic != TALLOC_MAGIC) {
+ if (tc->magic == TALLOC_MAGIC_FREE) {
+ smb_panic("Bad talloc magic value - double free\n");
+ } else {
+ smb_panic("Bad talloc magic value\n");
+ }
+ }
+ return tc;
+}
/*
Allocate a bit of memory as a child of an existing pointer
@@ -57,18 +72,13 @@ void *talloc(void *context, size_t size)
tc->size = size;
tc->magic = TALLOC_MAGIC;
+ tc->ref_count = 1;
+ tc->destructor = NULL;
tc->child = NULL;
tc->name = NULL;
if (context) {
- struct talloc_chunk *parent = ((struct talloc_chunk *)context)-1;
-
- if (parent->magic != TALLOC_MAGIC) {
- DEBUG(0,("Bad magic in context - 0x%08x\n", parent->magic));
- free(tc);
- smb_panic("Bad magic in talloc context");
- return NULL;
- }
+ struct talloc_chunk *parent = talloc_chunk_from_ptr(context);
tc->parent = parent;
@@ -86,17 +96,35 @@ void *talloc(void *context, size_t size)
/*
- add a name to an existing pointer - va_list version
+ setup a destructor to be called on free of a pointer
+ the destructor should return 0 on success, or -1 on failure.
+ if the destructor fails then the free is failed, and the memory can
+ be continued to be used
*/
-static void talloc_set_name_v(void *ptr, const char *fmt, va_list ap)
+void talloc_set_destructor(void *ptr, int (*destructor)(void *))
{
- struct talloc_chunk *tc;
+ struct talloc_chunk *tc = talloc_chunk_from_ptr(ptr);
+ tc->destructor = destructor;
+}
+
+/*
+ increase the reference count on a piece of memory. To decrease the
+ reference count call talloc_free(), which will free the memory if
+ the reference count reaches zero
+*/
+void talloc_increase_ref_count(void *ptr)
+{
+ struct talloc_chunk *tc = talloc_chunk_from_ptr(ptr);
+ tc->ref_count++;
+}
- tc = ((struct talloc_chunk *)ptr)-1;
- if (tc->magic != TALLOC_MAGIC) {
- return;
- }
+/*
+ add a name to an existing pointer - va_list version
+*/
+static void talloc_set_name_v(void *ptr, const char *fmt, va_list ap)
+{
+ struct talloc_chunk *tc = talloc_chunk_from_ptr(ptr);
vasprintf(&tc->name, fmt, ap);
}
@@ -141,17 +169,14 @@ void *talloc_init(const char *fmt, ...) _PRINTF_ATTRIBUTE(1,2)
{
va_list ap;
void *ptr;
- struct talloc_chunk *tc;
ptr = talloc(NULL, 0);
if (ptr == NULL) {
return NULL;
}
- tc = ((struct talloc_chunk *)ptr)-1;
-
va_start(ap, fmt);
- vasprintf(&tc->name, fmt, ap);
+ talloc_set_name_v(ptr, fmt, ap);
va_end(ap);
return ptr;
@@ -162,23 +187,36 @@ void *talloc_init(const char *fmt, ...) _PRINTF_ATTRIBUTE(1,2)
/*
free a talloc pointer. This also frees all child pointers of this
pointer recursively
+
+ return 0 if the memory is actually freed, otherwise -1. The memory
+ will not be freed if the ref_count is > 1 or the destructor (if
+ any) returns non-zero
*/
-void talloc_free(void *ptr)
+int talloc_free(void *ptr)
{
struct talloc_chunk *tc;
- if (ptr == NULL) return;
+ if (ptr == NULL) {
+ return -1;
+ }
- tc = ((struct talloc_chunk *)ptr)-1;
+ tc = talloc_chunk_from_ptr(ptr);
- if (tc->magic != TALLOC_MAGIC) {
- DEBUG(0,("Bad talloc magic 0x%08x in talloc_free\n", tc->magic));
- smb_panic("Bad talloc magic in talloc_realloc");
- return;
+ tc->ref_count--;
+ if (tc->ref_count != 0) {
+ return -1;
+ }
+
+ if (tc->destructor && tc->destructor(ptr) == -1) {
+ tc->ref_count++;
+ return -1;
}
while (tc->child) {
- talloc_free(tc->child + 1);
+ if (talloc_free(tc->child + 1) != 0) {
+ tc->child->parent = NULL;
+ break;
+ }
}
if (tc->parent) {
@@ -195,6 +233,7 @@ void talloc_free(void *ptr)
if (tc->name) free(tc->name);
free(tc);
+ return 0;
}
@@ -218,18 +257,7 @@ void *talloc_realloc(void *ptr, size_t size)
return talloc(NULL, size);
}
- tc = ((struct talloc_chunk *)ptr)-1;
-
- if (tc->magic != TALLOC_MAGIC) {
- if (tc->magic == TALLOC_MAGIC_FREE) {
-
- DEBUG(0,("Bad talloc magic - magic 0x%08x indicates double-free in talloc_realloc\n", tc->magic));
- smb_panic("Bad talloc magic - double-free - in talloc_realloc");
- } else {
- DEBUG(0,("Bad talloc magic 0x%08x in talloc_realloc\n", tc->magic));
- smb_panic("Bad talloc magic in talloc_realloc");
- }
- }
+ tc = talloc_chunk_from_ptr(ptr);
/* by resetting magic we catch users of the old memory */
tc->magic = TALLOC_MAGIC_FREE;
@@ -270,18 +298,11 @@ void *talloc_steal(void *new_ctx, void *ptr)
return NULL;
}
- tc = ((struct talloc_chunk *)ptr)-1;
- new_tc = ((struct talloc_chunk *)new_ctx)-1;
+ tc = talloc_chunk_from_ptr(ptr);
+ new_tc = talloc_chunk_from_ptr(new_ctx);
- if (tc->magic != TALLOC_MAGIC) {
- DEBUG(0,("Bad talloc magic 0x%08x in talloc_steal\n", tc->magic));
- smb_panic("Bad talloc magic in talloc_steal");
- return NULL;
- }
- if (new_tc->magic != TALLOC_MAGIC) {
- DEBUG(0,("Bad new talloc magic 0x%08x in talloc_steal\n", new_tc->magic));
- smb_panic("Bad new talloc magic in talloc_steal");
- return NULL;
+ if (tc == new_tc) {
+ return ptr;
}
if (tc->parent) {
@@ -304,12 +325,10 @@ void *talloc_steal(void *new_ctx, void *ptr)
/*
return the total size of a talloc pool (subtree)
*/
-off_t talloc_total_size(void *p)
+off_t talloc_total_size(void *ptr)
{
off_t total = 0;
- struct talloc_chunk *c, *tc;
-
- tc = ((struct talloc_chunk *)p)-1;
+ struct talloc_chunk *c, *tc = talloc_chunk_from_ptr(ptr);
total = tc->size;
for (c=tc->child;c;c=c->next) {