diff options
Diffstat (limited to 'util-src')
| -rw-r--r-- | util-src/managed_pointer.h | 61 |
1 files changed, 61 insertions, 0 deletions
diff --git a/util-src/managed_pointer.h b/util-src/managed_pointer.h new file mode 100644 index 00000000..213b5fd7 --- /dev/null +++ b/util-src/managed_pointer.h @@ -0,0 +1,61 @@ +/* managed_pointer.h + +These macros allow wrapping an allocator/deallocator into an object that is +owned and managed by the Lua garbage collector. + +Why? It is too easy to leak objects that need to be manually released, especially +when dealing with the Lua API which can throw errors from many operations. + +USAGE +----- + +For example, given an object that can be created or released with the following +functions: + + fancy_buffer* new_buffer(); + void free_buffer(fancy_buffer* p_buffer) + +You could declare a managed version like so: + + MANAGED_POINTER_ALLOCATOR(new_managed_buffer, fancy_buffer*, new_buffer, free_buffer) + +And then, when you need to create a new fancy_buffer in your code: + + fancy_buffer *my_buffer = new_managed_buffer(L); + +NOTES +----- + +Managed objects MUST NOT be freed manually. They will automatically be +freed during the next GC sweep after your function exits (even if via an error). + +The managed object is pushed onto the stack, but should generally be ignored, +but you'll need to bear this in mind when creating managed pointers in the +middle of a sequence of stack operations. +*/ + +#define MANAGED_POINTER_MT(wrapped_type) #wrapped_type "_managedptr_mt" + +#define MANAGED_POINTER_ALLOCATOR(name, wrapped_type, wrapped_alloc, wrapped_free) \ + static int _release_ ## name(lua_State *L) { \ + wrapped_type *p = (wrapped_type*)lua_topointer(L, 1); \ + if(*p != NULL) { \ + wrapped_free(*p); \ + } \ + return 0; \ + } \ + static wrapped_type name(lua_State *L) { \ + wrapped_type *p = (wrapped_type*)lua_newuserdata(L, sizeof(wrapped_type)); \ + if(luaL_newmetatable(L, MANAGED_POINTER_MT(wrapped_type)) != 0) { \ + lua_pushcfunction(L, _release_ ## name); \ + lua_setfield(L, -2, "__gc"); \ + } \ + lua_setmetatable(L, -2); \ + *p = wrapped_alloc(); \ + if(*p == NULL) { \ + lua_pushliteral(L, "not enough memory"); \ + lua_error(L); \ + } \ + return *p; \ + } + |