测试Lua table中以lightuserdata和string作key的性能

Makefile

all:
	gcc -O2 -fpic -c -o symbol.o symbol.c
	gcc -O -shared -fpic -o symbol.so symbol.o

symbol.c

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

static const char *l_sym_click = "click";

static int l_open(lua_State *L) {
  void *h = (void **)lua_newuserdata(L, sizeof(void *));
  lua_newtable(L);
  lua_setfenv(L, -2);
  return 1;
}

static int l_regsym(lua_State *L) {
  lua_getfenv(L, 1);
  lua_pushvalue(L, 2);
  lua_pushvalue(L, 3);
  lua_rawset(L, -3);
  return 1;
}

static int l_checksym(lua_State *L) {
  luaL_checktype(L, 1, LUA_TUSERDATA);
  lua_getfenv(L, 1);
  lua_pushlightuserdata(L, l_sym_click);
  lua_rawget(L, -2); 
  return 1;
}

static int l_checkstr(lua_State *L) {
  luaL_checktype(L, 1, LUA_TUSERDATA);
  lua_getfenv(L, 1);
  lua_pushstring(L, "click");
  lua_rawget(L, -2);
  return 1;
}

static luaL_Reg sym_lib[] = {
  {"handle", l_open},
  {"regsym", l_regsym},
  {"checksym", l_checksym},
  {"checkstr", l_checkstr},
  {NULL, NULL},
};

LUALIB_API int luaopen_symbol(lua_State *L) {
  luaL_openlib(L, "symbol", sym_lib, 0, 0);
  lua_pushlightuserdata(L, l_sym_click);
  lua_setfield(L, -2, l_sym_click);
  return 1;
}

test.lua

require"symbol"
os = require"os";
local clock = os.clock

local h = symbol.handle()

function cb() end

local s = os.clock()
local click = symbol.click
symbol.regsym(h, click, cb)
for i=0, 1e7 do
  symbol.checksym(h)
end
print(clock() - s)

local s = clock()
local click = 'click'
symbol.regsym(h, click, cb)
for i=0, 1e7 do
  symbol.checkstr(h)
end
print(clock() - s)

用字符串作key, 用lightuserdata (指针)作key 1e7次设置与check分别是
1.05
1.2