unpack lua table { ... }

tableunpack.c

// Unpack lua table create by { ... }
#define LUA_LIB

#include <lua.h>
#include <lauxlib.h>

static int
max_index(lua_State *L, int index) {
	int n = lua_rawlen(L, index);
	if (n == 0) {
		lua_pushnil(L);
	} else {
		lua_pushinteger(L, n);
	}
	while (lua_next(L, index) != 0) {
		lua_pop(L, 1);
		int key = luaL_checkinteger(L, -1);
		if (key > n) {
			n = key;
		}
	}
	return n;
}

static int
lunpack(lua_State *L) {
	luaL_checktype(L, 1, LUA_TTABLE);
	int n = max_index(L, 1);
	int i;
	luaL_checkstack(L, n, NULL);
	for (i=0;i<n;i++) {
		lua_rawgeti(L, 1, i+1);
	}
	return n;
}

LUAMOD_API int
luaopen_tableunpack(lua_State *L) {
	luaL_checkversion(L);
	luaL_Reg l[] = {
		{ "unpack", lunpack },
		{ NULL, NULL },
	};
	luaL_newlib(L, l);
	return 1;
}