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/*
* Copyright (c) 2020 Josef 'Jeff' Sipek <jeffpc@josefsipek.net>
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
* in the Software without restriction, including without limitation the rights
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in
* all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
* SOFTWARE.
*/
#ifndef DLUA_WRAPPER_H
#define DLUA_WRAPPER_H
/*
* The following macro generates everything necessary to wrap a C structure
* and easily push it onto Lua stacks as well as check that a value on the
* stack is of this type.
*
* To generate the necessary API, simply use the macro in your .c file. The
* arguments consist of:
*
* <typename> = the name for the structure to use in generated symbols
* <type> = the exposed structure's C type
* <putref> = the function to remove a reference from the C structure,
* called from the automatically generated __gc metamethod
* <extra_fxns_arg> = a C array of luaL_Reg structs passed to luaL_setfuncs
* to add Lua methods to the type
*
* For example, to expose struct timespec with a tostring method, one would
* use the following in a .c file:
*
* // struct timespec isn't refcounted
* static inline void timespec_putref(struct timespec *ts)
* {
* }
*
* static int timespec_tostring(lua_State *L);
*
* static const luaL_Reg timespec_fxns[] = {
* { "__tostring", timespec_tostring },
* { NULL, NULL },
* };
*
* DLUA_WRAP_C_DATA(timespec, struct timespec, timespec_putref, timespec_fxns)
*
* static int timespec_tostring(lua_State *L)
* {
* struct timespec *ts;
*
* ts = xlua_timespec_getptr(L, -1, NULL);
*
* lua_pushfstring(L, "%d.%09ld", ts->tv_sec, ts->tv_nsec);
*
* return 1;
* }
*
*
* The two functions making up the exposed structure API are:
*
* static void xlua_push<typename>(lua_State *, <type> *, bool);
* static inline <type> *xlua_<typename>_getptr(lua_State *, int, bool *);
*
* The first pushes the supplied pointer onto the Lua stack, while the
* second returns the previously pushed C pointer (or generates a Lua error
* if there is a type mismatch).
*
* The push function tracks the passed in bool argument alongside the C
* pointer itself. The getptr function fills in the bool pointer (if not
* NULL) with the pushed bool value. While this bool isn't used directly by
* the generated code and therefore it can be used for anything, the
* intention is to allow the API consumers to mark certain pointers as
* "read-only" to prevent Lua scripts from attempting to mutate them. This
* allows one to push const pointers while "notifying" the methods that
* mutation of any of the members is undefined behavior.
*
* Also note that the functions are static. That is, they are intended to
* only be used in the file where they are generated since they are somewhat
* low-level functions. If some public form of a push/get function is
* desired, it is up to the API consumer to write wrappers around these and
* expose them to the rest of the codebase.
*
* Revisiting the struct timespec example above, the generated API would
* be:
*
* static void xlua_pushtimespec(lua_State *, struct timespec *, bool);
* static inline struct timespec *xlua_timespec_getptr(lua_State *, int,
* bool *);
*/
#define DLUA_WRAP_C_DATA(typename, type, putref, extra_fxns_arg) \
struct lua_wrapper_##typename { \
type *ptr; \
bool ro; \
}; \
\
static inline type *xlua_##typename##_getptr(lua_State *state, int idx, \
bool *ro_r) \
{ \
struct lua_wrapper_##typename *wrapper; \
\
wrapper = luaL_checkudata(state, idx, #type); \
\
if (ro_r != NULL) \
*ro_r = wrapper->ro; \
\
return wrapper->ptr; \
} \
\
static int xlua_wrapper_##typename##_gc(lua_State *state) \
{ \
putref(xlua_##typename##_getptr(state, -1, NULL)); \
\
return 0; \
} \
\
static const luaL_Reg provided_##typename##_fxns[] = { \
{ "__gc", xlua_wrapper_##typename##_gc }, \
{ NULL, NULL }, \
}; \
\
/* push [-0,+1,e] */ \
static void xlua_push##typename(lua_State *state, type *ptr, bool ro) \
{ \
struct lua_wrapper_##typename *wrapper; \
\
if (ptr == NULL) { \
lua_pushnil(state); \
return; \
} \
\
wrapper = lua_newuserdata(state, sizeof(struct lua_wrapper_##typename)); \
i_assert(wrapper != NULL); \
\
wrapper->ptr = (ptr); \
wrapper->ro = ro; \
\
/* get the current metatable */ \
luaL_getmetatable(state, #type); \
if (lua_type(state, -1) != LUA_TTABLE) { \
/* initialize a new metatable */ \
const luaL_Reg *extra_fxns = (extra_fxns_arg); \
lua_CFunction index; \
\
lua_pop(state, 1); \
luaL_newmetatable(state, #type); \
luaL_setfuncs(state, provided_##typename##_fxns, 0); \
\
index = NULL; \
if (extra_fxns != NULL) { \
unsigned i; \
\
luaL_setfuncs(state, extra_fxns, 0); \
\
for (i = 0; extra_fxns[i].name != NULL; i++) { \
if (strcmp(extra_fxns[i].name, \
"__index") == 0) { \
index = extra_fxns[i].func; \
break; \
} \
} \
} \
\
if (index == NULL) { \
/* set __index == metatable */ \
lua_pushliteral(state, "__index"); \
lua_pushvalue(state, -2); /* dup the table */ \
lua_settable(state, -3); \
} \
} \
\
/* set the metatable */ \
lua_setmetatable(state, -2); \
}
#endif
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