Add user callbacks to wmem. This feature is a generic way to transparently mimic

the behaviour emem has for seasonal trees, which is that the master tree
structure is not actually seasonal - it is permanent. When the seasonal memory
pool is cleared, the root node pointer in all of these permanent trees is set
to NULL, and the pool takes care of actually freeing the nodes.

Wmem can now mimic this by allocating the tree header struct in epan_scope(),
allocating any node structs in file_scope(), and registering a callback on
file_scope() that NULLs the pointer in the epan_scope() header. Yes, this is
confusing, but it seemed simpler than adding manual callback registrations to
every single dissector that currently uses seasonal trees.

The callbacks may also be useful for other things that need cleanup (I'm
thinking resource handles stored in wmem memory that need to be fclosed or
what-have-you before they the handle is lost).

As indicated by the number of caveats in README.wmem, the implementation
probably needs a bit of work to make it safer/saner/more-useful. Thoughts
(or patches!) in this direction are more than welcome.

svn path=/trunk/; revision=49205

1 files changed, 12 insertions, 3 deletions

diff --git a/epan/wmem/wmem_core.h b/epan/wmem/wmem_core.h
index 4ce51baba9..83735a7095 100644
--- a/epan/wmem/wmem_core.h
+++ b/epan/wmem/wmem_core.h
@@ -33,15 +33,19 @@
 extern "C" {
 #endif /* __cplusplus */
 
+/* Allocator structure and typedef */
+struct _wmem_allocator_t;
+typedef struct _wmem_allocator_t wmem_allocator_t;
+
+/* Different types of allocators */
 typedef enum _wmem_allocator_type_t {
     WMEM_ALLOCATOR_SIMPLE,
     WMEM_ALLOCATOR_BLOCK,
     WMEM_ALLOCATOR_STRICT
 } wmem_allocator_type_t;
 
-struct _wmem_allocator_t;
-
-typedef struct _wmem_allocator_t wmem_allocator_t;
+/* User callback type for registering cleanup routines */
+typedef void (*wmem_user_cb_t) (wmem_allocator_t *, void *);
 
 WS_DLL_PUBLIC
 void *
@@ -78,6 +82,11 @@ wmem_gc(wmem_allocator_t *allocator);
 
 WS_DLL_PUBLIC
 void
+wmem_register_cleanup_callback(wmem_allocator_t *allocator,
+        wmem_user_cb_t callback, void *user_data);
+
+WS_DLL_PUBLIC
+void
 wmem_destroy_allocator(wmem_allocator_t *allocator);
 
 WS_DLL_PUBLIC