lbitlib.c revision 344220 
1/*
2** $Id: lbitlib.c,v 1.30.1.1 2017/04/19 17:20:42 roberto Exp $
3** Standard library for bitwise operations
4** See Copyright Notice in lua.h
5*/
6
7#define lbitlib_c
8#define LUA_LIB
9
10#include "lprefix.h"
11
12
13#include "lua.h"
14
15#include "lauxlib.h"
16#include "lualib.h"
17
18
19#if defined(LUA_COMPAT_BITLIB)		/* { */
20
21
22#define pushunsigned(L,n)	lua_pushinteger(L, (lua_Integer)(n))
23#define checkunsigned(L,i)	((lua_Unsigned)luaL_checkinteger(L,i))
24
25
26/* number of bits to consider in a number */
27#if !defined(LUA_NBITS)
28#define LUA_NBITS	32
29#endif
30
31
32/*
33** a lua_Unsigned with its first LUA_NBITS bits equal to 1. (Shift must
34** be made in two parts to avoid problems when LUA_NBITS is equal to the
35** number of bits in a lua_Unsigned.)
36*/
37#define ALLONES		(~(((~(lua_Unsigned)0) << (LUA_NBITS - 1)) << 1))
38
39
40/* macro to trim extra bits */
41#define trim(x)		((x) & ALLONES)
42
43
44/* builds a number with 'n' ones (1 <= n <= LUA_NBITS) */
45#define mask(n)		(~((ALLONES << 1) << ((n) - 1)))
46
47
48
49static lua_Unsigned andaux (lua_State *L) {
50  int i, n = lua_gettop(L);
51  lua_Unsigned r = ~(lua_Unsigned)0;
52  for (i = 1; i <= n; i++)
53    r &= checkunsigned(L, i);
54  return trim(r);
55}
56
57
58static int b_and (lua_State *L) {
59  lua_Unsigned r = andaux(L);
60  pushunsigned(L, r);
61  return 1;
62}
63
64
65static int b_test (lua_State *L) {
66  lua_Unsigned r = andaux(L);
67  lua_pushboolean(L, r != 0);
68  return 1;
69}
70
71
72static int b_or (lua_State *L) {
73  int i, n = lua_gettop(L);
74  lua_Unsigned r = 0;
75  for (i = 1; i <= n; i++)
76    r |= checkunsigned(L, i);
77  pushunsigned(L, trim(r));
78  return 1;
79}
80
81
82static int b_xor (lua_State *L) {
83  int i, n = lua_gettop(L);
84  lua_Unsigned r = 0;
85  for (i = 1; i <= n; i++)
86    r ^= checkunsigned(L, i);
87  pushunsigned(L, trim(r));
88  return 1;
89}
90
91
92static int b_not (lua_State *L) {
93  lua_Unsigned r = ~checkunsigned(L, 1);
94  pushunsigned(L, trim(r));
95  return 1;
96}
97
98
99static int b_shift (lua_State *L, lua_Unsigned r, lua_Integer i) {
100  if (i < 0) {  /* shift right? */
101    i = -i;
102    r = trim(r);
103    if (i >= LUA_NBITS) r = 0;
104    else r >>= i;
105  }
106  else {  /* shift left */
107    if (i >= LUA_NBITS) r = 0;
108    else r <<= i;
109    r = trim(r);
110  }
111  pushunsigned(L, r);
112  return 1;
113}
114
115
116static int b_lshift (lua_State *L) {
117  return b_shift(L, checkunsigned(L, 1), luaL_checkinteger(L, 2));
118}
119
120
121static int b_rshift (lua_State *L) {
122  return b_shift(L, checkunsigned(L, 1), -luaL_checkinteger(L, 2));
123}
124
125
126static int b_arshift (lua_State *L) {
127  lua_Unsigned r = checkunsigned(L, 1);
128  lua_Integer i = luaL_checkinteger(L, 2);
129  if (i < 0 || !(r & ((lua_Unsigned)1 << (LUA_NBITS - 1))))
130    return b_shift(L, r, -i);
131  else {  /* arithmetic shift for 'negative' number */
132    if (i >= LUA_NBITS) r = ALLONES;
133    else
134      r = trim((r >> i) | ~(trim(~(lua_Unsigned)0) >> i));  /* add signal bit */
135    pushunsigned(L, r);
136    return 1;
137  }
138}
139
140
141static int b_rot (lua_State *L, lua_Integer d) {
142  lua_Unsigned r = checkunsigned(L, 1);
143  int i = d & (LUA_NBITS - 1);  /* i = d % NBITS */
144  r = trim(r);
145  if (i != 0)  /* avoid undefined shift of LUA_NBITS when i == 0 */
146    r = (r << i) | (r >> (LUA_NBITS - i));
147  pushunsigned(L, trim(r));
148  return 1;
149}
150
151
152static int b_lrot (lua_State *L) {
153  return b_rot(L, luaL_checkinteger(L, 2));
154}
155
156
157static int b_rrot (lua_State *L) {
158  return b_rot(L, -luaL_checkinteger(L, 2));
159}
160
161
162/*
163** get field and width arguments for field-manipulation functions,
164** checking whether they are valid.
165** ('luaL_error' called without 'return' to avoid later warnings about
166** 'width' being used uninitialized.)
167*/
168static int fieldargs (lua_State *L, int farg, int *width) {
169  lua_Integer f = luaL_checkinteger(L, farg);
170  lua_Integer w = luaL_optinteger(L, farg + 1, 1);
171  luaL_argcheck(L, 0 <= f, farg, "field cannot be negative");
172  luaL_argcheck(L, 0 < w, farg + 1, "width must be positive");
173  if (f + w > LUA_NBITS)
174    luaL_error(L, "trying to access non-existent bits");
175  *width = (int)w;
176  return (int)f;
177}
178
179
180static int b_extract (lua_State *L) {
181  int w;
182  lua_Unsigned r = trim(checkunsigned(L, 1));
183  int f = fieldargs(L, 2, &w);
184  r = (r >> f) & mask(w);
185  pushunsigned(L, r);
186  return 1;
187}
188
189
190static int b_replace (lua_State *L) {
191  int w;
192  lua_Unsigned r = trim(checkunsigned(L, 1));
193  lua_Unsigned v = trim(checkunsigned(L, 2));
194  int f = fieldargs(L, 3, &w);
195  lua_Unsigned m = mask(w);
196  r = (r & ~(m << f)) | ((v & m) << f);
197  pushunsigned(L, r);
198  return 1;
199}
200
201
202static const luaL_Reg bitlib[] = {
203  {"arshift", b_arshift},
204  {"band", b_and},
205  {"bnot", b_not},
206  {"bor", b_or},
207  {"bxor", b_xor},
208  {"btest", b_test},
209  {"extract", b_extract},
210  {"lrotate", b_lrot},
211  {"lshift", b_lshift},
212  {"replace", b_replace},
213  {"rrotate", b_rrot},
214  {"rshift", b_rshift},
215  {NULL, NULL}
216};
217
218
219
220LUAMOD_API int luaopen_bit32 (lua_State *L) {
221  luaL_newlib(L, bitlib);
222  return 1;
223}
224
225
226#else					/* }{ */
227
228
229LUAMOD_API int luaopen_bit32 (lua_State *L) {
230  return luaL_error(L, "library 'bit32' has been deprecated");
231}
232
233#endif					/* } */
234