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util-src/managed_pointer.h @ 12714:82bca7191f13
util.crypto: Use stack space buffers
Removes assumption that LUAL_BUFFERSIZE is known at pre-processing time,
which it is not in Lua 5.3 and 5.4, where it is a computed macro based
on sizeof.
Allocation of stack space is safer and faster, no need to worry about
luaL_prepbuffer failing to allocate memory and skipping free()
author | Kim Alvefur <zash@zash.se> |
---|---|
date | Mon, 11 Jul 2022 17:01:55 +0200 |
parent | 12692:b001b0f42512 |
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line source
/* 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; \ }