luau/VM/src/lbitlib.cpp

245 lines
5.3 KiB
C++
Raw Normal View History

// This file is part of the Luau programming language and is licensed under MIT License; see LICENSE.txt for details
// This code is based on Lua 5.x implementation licensed under MIT License; see lua_LICENSE.txt for details
#include "lualib.h"
#include "lcommon.h"
#include "lnumutils.h"
LUAU_FASTFLAGVARIABLE(LuauBit32Count, false)
#define ALLONES ~0u
#define NBITS int(8 * sizeof(unsigned))
/* macro to trim extra bits */
#define trim(x) ((x)&ALLONES)
/* builds a number with 'n' ones (1 <= n <= NBITS) */
#define mask(n) (~((ALLONES << 1) << ((n)-1)))
typedef unsigned b_uint;
static b_uint andaux(lua_State* L)
{
int i, n = lua_gettop(L);
b_uint r = ~(b_uint)0;
for (i = 1; i <= n; i++)
r &= luaL_checkunsigned(L, i);
return trim(r);
}
static int b_and(lua_State* L)
{
b_uint r = andaux(L);
lua_pushunsigned(L, r);
return 1;
}
static int b_test(lua_State* L)
{
b_uint r = andaux(L);
lua_pushboolean(L, r != 0);
return 1;
}
static int b_or(lua_State* L)
{
int i, n = lua_gettop(L);
b_uint r = 0;
for (i = 1; i <= n; i++)
r |= luaL_checkunsigned(L, i);
lua_pushunsigned(L, trim(r));
return 1;
}
static int b_xor(lua_State* L)
{
int i, n = lua_gettop(L);
b_uint r = 0;
for (i = 1; i <= n; i++)
r ^= luaL_checkunsigned(L, i);
lua_pushunsigned(L, trim(r));
return 1;
}
static int b_not(lua_State* L)
{
b_uint r = ~luaL_checkunsigned(L, 1);
lua_pushunsigned(L, trim(r));
return 1;
}
static int b_shift(lua_State* L, b_uint r, int i)
{
if (i < 0)
{ /* shift right? */
i = -i;
r = trim(r);
if (i >= NBITS)
r = 0;
else
r >>= i;
}
else
{ /* shift left */
if (i >= NBITS)
r = 0;
else
r <<= i;
r = trim(r);
}
lua_pushunsigned(L, r);
return 1;
}
static int b_lshift(lua_State* L)
{
return b_shift(L, luaL_checkunsigned(L, 1), luaL_checkinteger(L, 2));
}
static int b_rshift(lua_State* L)
{
return b_shift(L, luaL_checkunsigned(L, 1), -luaL_checkinteger(L, 2));
}
static int b_arshift(lua_State* L)
{
b_uint r = luaL_checkunsigned(L, 1);
int i = luaL_checkinteger(L, 2);
if (i < 0 || !(r & ((b_uint)1 << (NBITS - 1))))
return b_shift(L, r, -i);
else
{ /* arithmetic shift for 'negative' number */
if (i >= NBITS)
r = ALLONES;
else
r = trim((r >> i) | ~(~(b_uint)0 >> i)); /* add signal bit */
lua_pushunsigned(L, r);
return 1;
}
}
static int b_rot(lua_State* L, int i)
{
b_uint r = luaL_checkunsigned(L, 1);
i &= (NBITS - 1); /* i = i % NBITS */
r = trim(r);
if (i != 0) /* avoid undefined shift of NBITS when i == 0 */
r = (r << i) | (r >> (NBITS - i));
lua_pushunsigned(L, trim(r));
return 1;
}
static int b_lrot(lua_State* L)
{
return b_rot(L, luaL_checkinteger(L, 2));
}
static int b_rrot(lua_State* L)
{
return b_rot(L, -luaL_checkinteger(L, 2));
}
/*
** get field and width arguments for field-manipulation functions,
** checking whether they are valid.
** ('luaL_error' called without 'return' to avoid later warnings about
** 'width' being used uninitialized.)
*/
static int fieldargs(lua_State* L, int farg, int* width)
{
int f = luaL_checkinteger(L, farg);
int w = luaL_optinteger(L, farg + 1, 1);
luaL_argcheck(L, 0 <= f, farg, "field cannot be negative");
luaL_argcheck(L, 0 < w, farg + 1, "width must be positive");
if (f + w > NBITS)
luaL_error(L, "trying to access non-existent bits");
*width = w;
return f;
}
static int b_extract(lua_State* L)
{
int w;
b_uint r = luaL_checkunsigned(L, 1);
int f = fieldargs(L, 2, &w);
r = (r >> f) & mask(w);
lua_pushunsigned(L, r);
return 1;
}
static int b_replace(lua_State* L)
{
int w;
b_uint r = luaL_checkunsigned(L, 1);
b_uint v = luaL_checkunsigned(L, 2);
int f = fieldargs(L, 3, &w);
int m = mask(w);
v &= m; /* erase bits outside given width */
r = (r & ~(m << f)) | (v << f);
lua_pushunsigned(L, r);
return 1;
}
static int b_countlz(lua_State* L)
{
if (!FFlag::LuauBit32Count)
luaL_error(L, "bit32.countlz isn't enabled");
b_uint v = luaL_checkunsigned(L, 1);
b_uint r = NBITS;
for (int i = 0; i < NBITS; ++i)
if (v & (1u << (NBITS - 1 - i)))
{
r = i;
break;
}
lua_pushunsigned(L, r);
return 1;
}
static int b_countrz(lua_State* L)
{
if (!FFlag::LuauBit32Count)
luaL_error(L, "bit32.countrz isn't enabled");
b_uint v = luaL_checkunsigned(L, 1);
b_uint r = NBITS;
for (int i = 0; i < NBITS; ++i)
if (v & (1u << i))
{
r = i;
break;
}
lua_pushunsigned(L, r);
return 1;
}
static const luaL_Reg bitlib[] = {
{"arshift", b_arshift},
{"band", b_and},
{"bnot", b_not},
{"bor", b_or},
{"bxor", b_xor},
{"btest", b_test},
{"extract", b_extract},
{"lrotate", b_lrot},
{"lshift", b_lshift},
{"replace", b_replace},
{"rrotate", b_rrot},
{"rshift", b_rshift},
{"countlz", b_countlz},
{"countrz", b_countrz},
{NULL, NULL},
};
LUALIB_API int luaopen_bit32(lua_State* L)
{
luaL_register(L, LUA_BITLIBNAME, bitlib);
return 1;
}