1/*
2** $Id: lbitlib.c,v 1.18.1.2 2013/07/09 18:01:41 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 "lua.h"
11
12#include "lauxlib.h"
13#include "lualib.h"
14
15
16/* number of bits to consider in a number */
17#if !defined(LUA_NBITS)
18#define LUA_NBITS	32
19#endif
20
21
22#define ALLONES		(~(((~(lua_Unsigned)0) << (LUA_NBITS - 1)) << 1))
23
24/* macro to trim extra bits */
25#define trim(x)		((x) & ALLONES)
26
27
28/* builds a number with 'n' ones (1 <= n <= LUA_NBITS) */
29#define mask(n)		(~((ALLONES << 1) << ((n) - 1)))
30
31
32typedef lua_Unsigned b_uint;
33
34
35
36static b_uint andaux (lua_State *L) {
37  int i, n = lua_gettop(L);
38  b_uint r = ~(b_uint)0;
39  for (i = 1; i <= n; i++)
40    r &= luaL_checkunsigned(L, i);
41  return trim(r);
42}
43
44
45static int b_and (lua_State *L) {
46  b_uint r = andaux(L);
47  lua_pushunsigned(L, r);
48  return 1;
49}
50
51
52static int b_test (lua_State *L) {
53  b_uint r = andaux(L);
54  lua_pushboolean(L, r != 0);
55  return 1;
56}
57
58
59static int b_or (lua_State *L) {
60  int i, n = lua_gettop(L);
61  b_uint r = 0;
62  for (i = 1; i <= n; i++)
63    r |= luaL_checkunsigned(L, i);
64  lua_pushunsigned(L, trim(r));
65  return 1;
66}
67
68
69static int b_xor (lua_State *L) {
70  int i, n = lua_gettop(L);
71  b_uint r = 0;
72  for (i = 1; i <= n; i++)
73    r ^= luaL_checkunsigned(L, i);
74  lua_pushunsigned(L, trim(r));
75  return 1;
76}
77
78
79static int b_not (lua_State *L) {
80  b_uint r = ~luaL_checkunsigned(L, 1);
81  lua_pushunsigned(L, trim(r));
82  return 1;
83}
84
85
86static int b_shift (lua_State *L, b_uint r, int i) {
87  if (i < 0) {  /* shift right? */
88    i = -i;
89    r = trim(r);
90    if (i >= LUA_NBITS) r = 0;
91    else r >>= i;
92  }
93  else {  /* shift left */
94    if (i >= LUA_NBITS) r = 0;
95    else r <<= i;
96    r = trim(r);
97  }
98  lua_pushunsigned(L, r);
99  return 1;
100}
101
102
103static int b_lshift (lua_State *L) {
104  return b_shift(L, luaL_checkunsigned(L, 1), luaL_checkint(L, 2));
105}
106
107
108static int b_rshift (lua_State *L) {
109  return b_shift(L, luaL_checkunsigned(L, 1), -luaL_checkint(L, 2));
110}
111
112
113static int b_arshift (lua_State *L) {
114  b_uint r = luaL_checkunsigned(L, 1);
115  int i = luaL_checkint(L, 2);
116  if (i < 0 || !(r & ((b_uint)1 << (LUA_NBITS - 1))))
117    return b_shift(L, r, -i);
118  else {  /* arithmetic shift for 'negative' number */
119    if (i >= LUA_NBITS) r = ALLONES;
120    else
121      r = trim((r >> i) | ~(~(b_uint)0 >> i));  /* add signal bit */
122    lua_pushunsigned(L, r);
123    return 1;
124  }
125}
126
127
128static int b_rot (lua_State *L, int i) {
129  b_uint r = luaL_checkunsigned(L, 1);
130  i &= (LUA_NBITS - 1);  /* i = i % NBITS */
131  r = trim(r);
132  if (i != 0)  /* avoid undefined shift of LUA_NBITS when i == 0 */
133    r = (r << i) | (r >> (LUA_NBITS - i));
134  lua_pushunsigned(L, trim(r));
135  return 1;
136}
137
138
139static int b_lrot (lua_State *L) {
140  return b_rot(L, luaL_checkint(L, 2));
141}
142
143
144static int b_rrot (lua_State *L) {
145  return b_rot(L, -luaL_checkint(L, 2));
146}
147
148
149/*
150** get field and width arguments for field-manipulation functions,
151** checking whether they are valid.
152** ('luaL_error' called without 'return' to avoid later warnings about
153** 'width' being used uninitialized.)
154*/
155static int fieldargs (lua_State *L, int farg, int *width) {
156  int f = luaL_checkint(L, farg);
157  int w = luaL_optint(L, farg + 1, 1);
158  luaL_argcheck(L, 0 <= f, farg, "field cannot be negative");
159  luaL_argcheck(L, 0 < w, farg + 1, "width must be positive");
160  if (f + w > LUA_NBITS)
161    luaL_error(L, "trying to access non-existent bits");
162  *width = w;
163  return f;
164}
165
166
167static int b_extract (lua_State *L) {
168  int w;
169  b_uint r = luaL_checkunsigned(L, 1);
170  int f = fieldargs(L, 2, &w);
171  r = (r >> f) & mask(w);
172  lua_pushunsigned(L, r);
173  return 1;
174}
175
176
177static int b_replace (lua_State *L) {
178  int w;
179  b_uint r = luaL_checkunsigned(L, 1);
180  b_uint v = luaL_checkunsigned(L, 2);
181  int f = fieldargs(L, 3, &w);
182  int m = mask(w);
183  v &= m;  /* erase bits outside given width */
184  r = (r & ~(m << f)) | (v << f);
185  lua_pushunsigned(L, r);
186  return 1;
187}
188
189
190static const luaL_Reg bitlib[] = {
191  {"arshift", b_arshift},
192  {"band", b_and},
193  {"bnot", b_not},
194  {"bor", b_or},
195  {"bxor", b_xor},
196  {"btest", b_test},
197  {"extract", b_extract},
198  {"lrotate", b_lrot},
199  {"lshift", b_lshift},
200  {"replace", b_replace},
201  {"rrotate", b_rrot},
202  {"rshift", b_rshift},
203  {NULL, NULL}
204};
205
206
207
208LUAMOD_API int luaopen_bit32 (lua_State *L) {
209  luaL_newlib(L, bitlib);
210  return 1;
211}
212
213