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
andaux(lua_State * L)49 static 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
b_and(lua_State * L)58 static int b_and (lua_State *L) {
59 lua_Unsigned r = andaux(L);
60 pushunsigned(L, r);
61 return 1;
62 }
63
64
b_test(lua_State * L)65 static int b_test (lua_State *L) {
66 lua_Unsigned r = andaux(L);
67 lua_pushboolean(L, r != 0);
68 return 1;
69 }
70
71
b_or(lua_State * L)72 static 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
b_xor(lua_State * L)82 static 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
b_not(lua_State * L)92 static int b_not (lua_State *L) {
93 lua_Unsigned r = ~checkunsigned(L, 1);
94 pushunsigned(L, trim(r));
95 return 1;
96 }
97
98
b_shift(lua_State * L,lua_Unsigned r,lua_Integer i)99 static 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
b_lshift(lua_State * L)116 static int b_lshift (lua_State *L) {
117 return b_shift(L, checkunsigned(L, 1), luaL_checkinteger(L, 2));
118 }
119
120
b_rshift(lua_State * L)121 static int b_rshift (lua_State *L) {
122 return b_shift(L, checkunsigned(L, 1), -luaL_checkinteger(L, 2));
123 }
124
125
b_arshift(lua_State * L)126 static 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
b_rot(lua_State * L,lua_Integer d)141 static 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
b_lrot(lua_State * L)152 static int b_lrot (lua_State *L) {
153 return b_rot(L, luaL_checkinteger(L, 2));
154 }
155
156
b_rrot(lua_State * L)157 static 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 */
fieldargs(lua_State * L,int farg,int * width)168 static 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
b_extract(lua_State * L)180 static 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
b_replace(lua_State * L)190 static 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
202 static 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
luaopen_bit32(lua_State * L)220 LUAMOD_API int luaopen_bit32 (lua_State *L) {
221 luaL_newlib(L, bitlib);
222 return 1;
223 }
224
225
226 #else /* }{ */
227
228
luaopen_bit32(lua_State * L)229 LUAMOD_API int luaopen_bit32 (lua_State *L) {
230 return luaL_error(L, "library 'bit32' has been deprecated");
231 }
232
233 #endif /* } */
234