Re: Example to minimize redundancy of two libraries. Lua - C library & plain C library?
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- Subject: Re: Example to minimize redundancy of two libraries. Lua - C library & plain C library?
- From: Sean Conner <sean@...>
- Date: 2011年8月18日 05:19:04 -0400
It was thus said that the Great Patrick Mc(avery once stated:
> Hi Everyone
>
> After many long delays I think I am ready to start writing a scientific
> instrument control library. I would like the library to be callable from
> Lua but also just from C without Lua. I am assuming that the best way to
> go about this is to write a plain C core and then a wrapper around it
> with the Lua - C API and then to write another C wrapper around the core
> for a plain C library.
I've dome something like this at work. For instance, we have a custom
data file we use for a few of our components, so I wrote a C API to
manipulate these files, with the API looking something like:
foodblib.h:
typedef struct foodb { /* ... */ } foodb__t;
typedef struct foorec { /* ... */ } foorec__t;
int foodblib_open (foodb__t *,const char *name,int mode);
int foodblib_index_i (foodb__t *,foorec__t *,size_t idx);
int foodblib_index_s (foodb__t *,foorec__t *,const char *idx);
int foodblib_add_i (foodb__t *,foorec__t *,size_t idx);
int foodblib_add_s (foodb__t *,foorec__t *,const char *idx);
int foodblib_del_i (foodb__t *,foorec__t *,size_t idx);
int foodblib_del_s (foodb__t *,foorec__t *,const char *idx);
int foodblib_close (foodb__t *);
And foodblib.c would be the implementation of the C API. The Lua interface
would be in foodblua.h/foodblua.c and is basically as thin a wrapper as I
can get, with a similar naming convention:
foodblua.h
int foodblua_open (lua_State *);
int foodblua___index (lua_State *);
int foodblua___newindex (lua_State *);
int foodblua___gc (lua_State *);
foodblua.c
/* sample implementation */
int foodblua___indexi(lua_State *L)
{
foodb__t *db = luaL_checkudate(L,1,FOODB);
foorec__t rec;
int rc;
if (lua_type(L,2) == LUA_TNUM)
rc = foodblib_index_i(db,&rec,lua_tointeger(L,2));
else if (lua_type(L,2) == LUA_TSTRING)
rc = foodblib_index_s(db,&rec,lua_tostring(L,2));
if (rc == ERROR) /* handle error */
lua_createtable(L,0,0);
/* push fields from rec into Lua table */
return 1;
}
If I'm coding in C, I use the C API (the foodblib* calls); whereas if I'm
in Lua, I indirectly use the Lua API (ultimately, the foodblua* calls). It
seems straightforward to me, and the API mapping between C and Lua is close
enough to figure out what's going on.
-spc