bitlib提供5.1版本下位操作符(c 语言实现,跨平台)

在LuaForge中提供bitlib可以在lua5.1版本中提高为操作符运算。bitlib通过c语言来实现跨平台位操作符。

Lua functions provided:

bit.bnot(a) returns the one's complement of a

bit.band(w1,...) returns the bitwise and of the w's

bit.bor(w1,...) returns the bitwise or of the w's

bit.bxor(w1,...) returns the bitwise exclusive or of the w's

bit.lshift(a,b) returns a shifted left b places

bit.rshift(a,b) returns a shifted logically right b places

bit.arshift(a,b) returns a shifted arithmetically right b places

bit.mod(a,b) returns the integer remainder of a divided by b

All function arguments should be integers.

The number of bits available for logical operations depends on the data type used to represent Lua numbers;

this is typically 8-byte IEEE floats, which give 53 bits (the size of the mantissa).

在bitlib中所有位操作的参数为整数。

位操作中有效位数依赖于LUA Number的实现。IEEE中8 btye floats 仅仅有53位有效位数。

#include "lauxlib.h"
#include "lua.h"

typedef long long Integer; 
typedef unsigned long long UInteger;

#define luaL_checkbit(L, n)  ((Integer)luaL_checknumber(L, n))  //定义可以操作的最大整数。会依赖于LUA Number
#define luaL_checkubit(L, n) ((UInteger)luaL_checkbit(L, n))    //在实现中可以操作64bit,但是最大有效位数依赖于LUA Number的实现

#define TDYADIC(name, op, checkbit1, checkbit2) \
  static int bit_ ## name(lua_State* L) { \
    lua_pushnumber(L, \
      checkbit1(L, 1) op checkbit2(L, 2)); \ //通过c语言提供的移位运算符直接移位
    return 1; \
  }

#define DYADIC(name, op) \
  TDYADIC(name, op, luaL_checkbit, luaL_checkbit)

#define MONADIC(name, op) \
  static int bit_ ## name(lua_State* L) { \
    lua_pushnumber(L, op luaL_checkbit(L, 1)); \ //直接取反位运算
    return 1; \
  }

#define VARIADIC(name, op) \
  static int bit_ ## name(lua_State *L) { \
    int n = lua_gettop(L), i; \
    Integer w = luaL_checkbit(L, 1); \
    for (i = 2; i <= n; i++) \
      w op luaL_checkbit(L, i); \ //可以实现可变参数的复合位运算&=、|=、^=
    lua_pushnumber(L, w); \
    return 1; \
  }

MONADIC(bnot,     ~)
VARIADIC(band,    &=)
VARIADIC(bor,     |=)
VARIADIC(bxor,    ^=)
TDYADIC(lshift,  <<, luaL_checkbit, luaL_checkubit)
TDYADIC(rshift,  >>, luaL_checkubit, luaL_checkubit)
TDYADIC(arshift, >>, luaL_checkbit, luaL_checkubit)
DYADIC(mod,      %)

static const struct luaL_reg bitlib[] = {
  {"bnot",    bit_bnot},
  {"band",    bit_band},
  {"bor",     bit_bor},
  {"bxor",    bit_bxor},
  {"lshift",  bit_lshift},
  {"rshift",  bit_rshift},
  {"arshift", bit_arshift},
  {"mod",     bit_mod},
  {NULL, NULL}
};

LUALIB_API int luaopen_bit (lua_State *L) {
  luaL_openlib(L, "bit", bitlib, 0);
  return 1;
}