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/*
** $Id: lbitlib.c,v 1.28 2014/11/02 19:19:04 roberto Exp $
** Standard library for bitwise operations
** See Copyright Notice in lua.h
*/
#define lbitlib_c
#define LUA_LIB
#include "lprefix.h"
#include "lua.h"
#include "lauxlib.h"
#include "lualib.h"
#if defined(LUA_COMPAT_BITLIB) /* { */
/* number of bits to consider in a number */
#if !defined(LUA_NBITS)
#define LUA_NBITS 32
#endif
/*
** a lua_Unsigned with its first LUA_NBITS bits equal to 1. (Shift must
** be made in two parts to avoid problems when LUA_NBITS is equal to the
** number of bits in a lua_Unsigned.)
*/
#define ALLONES (~(((~(lua_Unsigned)0) << (LUA_NBITS - 1)) << 1))
/* macro to trim extra bits */
#define trim(x) ((x) & ALLONES)
/* builds a number with 'n' ones (1 <= n <= LUA_NBITS) */
#define mask(n) (~((ALLONES << 1) << ((n) - 1)))
static lua_Unsigned andaux (lua_State *L) {
int i, n = lua_gettop(L);
lua_Unsigned r = ~(lua_Unsigned)0;
for (i = 1; i <= n; i++)
r &= luaL_checkunsigned(L, i);
return trim(r);
}
static int b_and (lua_State *L) {
lua_Unsigned r = andaux(L);
lua_pushunsigned(L, r);
return 1;
}
static int b_test (lua_State *L) {
lua_Unsigned r = andaux(L);
lua_pushboolean(L, r != 0);
return 1;
}
static int b_or (lua_State *L) {
int i, n = lua_gettop(L);
lua_Unsigned 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);
lua_Unsigned 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) {
lua_Unsigned r = ~luaL_checkunsigned(L, 1);
lua_pushunsigned(L, trim(r));
return 1;
}
static int b_shift (lua_State *L, lua_Unsigned r, lua_Integer i) {
if (i < 0) { /* shift right? */
i = -i;
r = trim(r);
if (i >= LUA_NBITS) r = 0;
else r >>= i;
}
else { /* shift left */
if (i >= LUA_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) {
lua_Unsigned r = luaL_checkunsigned(L, 1);
lua_Integer i = luaL_checkinteger(L, 2);
if (i < 0 || !(r & ((lua_Unsigned)1 << (LUA_NBITS - 1))))
return b_shift(L, r, -i);
else { /* arithmetic shift for 'negative' number */
if (i >= LUA_NBITS) r = ALLONES;
else
r = trim((r >> i) | ~(trim(~(lua_Unsigned)0) >> i)); /* add signal bit */
lua_pushunsigned(L, r);
return 1;
}
}
static int b_rot (lua_State *L, lua_Integer d) {
lua_Unsigned r = luaL_checkunsigned(L, 1);
int i = d & (LUA_NBITS - 1); /* i = d % NBITS */
r = trim(r);
if (i != 0) /* avoid undefined shift of LUA_NBITS when i == 0 */
r = (r << i) | (r >> (LUA_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) {
lua_Integer f = luaL_checkinteger(L, farg);
lua_Integer 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 > LUA_NBITS)
luaL_error(L, "trying to access non-existent bits");
*width = (int)w;
return (int)f;
}
static int b_extract (lua_State *L) {
int w;
lua_Unsigned r = trim(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;
lua_Unsigned r = trim(luaL_checkunsigned(L, 1));
lua_Unsigned 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 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},
{NULL, NULL}
};
LUAMOD_API int luaopen_bit32 (lua_State *L) {
luaL_newlib(L, bitlib);
return 1;
}
#else /* }{ */
LUAMOD_API int luaopen_bit32 (lua_State *L) {
return luaL_error(L, "library 'bit32' has been deprecated");
}
#endif /* } */
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