]>
Commit | Line | Data |
---|---|---|
16a5fed6 | 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 | ||
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 | ||
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 | ||
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 | ||
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 | ||
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 | ||
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 | ||
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 | ||
103 | static int b_lshift (lua_State *L) { | |
104 | return b_shift(L, luaL_checkunsigned(L, 1), luaL_checkint(L, 2)); | |
105 | } | |
106 | ||
107 | ||
108 | static int b_rshift (lua_State *L) { | |
109 | return b_shift(L, luaL_checkunsigned(L, 1), -luaL_checkint(L, 2)); | |
110 | } | |
111 | ||
112 | ||
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 | ||
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 | ||
139 | static int b_lrot (lua_State *L) { | |
140 | return b_rot(L, luaL_checkint(L, 2)); | |
141 | } | |
142 | ||
143 | ||
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 | */ | |
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 | ||
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 | ||
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 | ||
208 | LUAMOD_API int luaopen_bit32 (lua_State *L) { | |
209 | luaL_newlib(L, bitlib); | |
210 | return 1; | |
211 | } | |
212 |