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
32 typedef lua_Unsigned b_uint;
33
34
35
andaux(lua_State * L)36 static 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
b_and(lua_State * L)45 static int b_and (lua_State *L) {
46 b_uint r = andaux(L);
47 lua_pushunsigned(L, r);
48 return 1;
49 }
50
51
b_test(lua_State * L)52 static int b_test (lua_State *L) {
53 b_uint r = andaux(L);
54 lua_pushboolean(L, r != 0);
55 return 1;
56 }
57
58
b_or(lua_State * L)59 static 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
b_xor(lua_State * L)69 static 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
b_not(lua_State * L)79 static 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
b_shift(lua_State * L,b_uint r,int i)86 static 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
b_lshift(lua_State * L)103 static int b_lshift (lua_State *L) {
104 return b_shift(L, luaL_checkunsigned(L, 1), luaL_checkint(L, 2));
105 }
106
107
b_rshift(lua_State * L)108 static int b_rshift (lua_State *L) {
109 return b_shift(L, luaL_checkunsigned(L, 1), -luaL_checkint(L, 2));
110 }
111
112
b_arshift(lua_State * L)113 static 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
b_rot(lua_State * L,int i)128 static 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
b_lrot(lua_State * L)139 static int b_lrot (lua_State *L) {
140 return b_rot(L, luaL_checkint(L, 2));
141 }
142
143
b_rrot(lua_State * L)144 static 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 */
fieldargs(lua_State * L,int farg,int * width)155 static 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
b_extract(lua_State * L)167 static 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
b_replace(lua_State * L)177 static 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
190 static 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
luaopen_bit32(lua_State * L)208 LUAMOD_API int luaopen_bit32 (lua_State *L) {
209 luaL_newlib(L, bitlib);
210 return 1;
211 }
212
213