ba8b5c17 |
1 | /* |
2 | ** $Id: lbitlib.c,v 1.18 2013/03/19 13:19:12 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 | r = (r << i) | (r >> (LUA_NBITS - i)); |
133 | lua_pushunsigned(L, trim(r)); |
134 | return 1; |
135 | } |
136 | |
137 | |
138 | static int b_lrot (lua_State *L) { |
139 | return b_rot(L, luaL_checkint(L, 2)); |
140 | } |
141 | |
142 | |
143 | static int b_rrot (lua_State *L) { |
144 | return b_rot(L, -luaL_checkint(L, 2)); |
145 | } |
146 | |
147 | |
148 | /* |
149 | ** get field and width arguments for field-manipulation functions, |
150 | ** checking whether they are valid. |
151 | ** ('luaL_error' called without 'return' to avoid later warnings about |
152 | ** 'width' being used uninitialized.) |
153 | */ |
154 | static int fieldargs (lua_State *L, int farg, int *width) { |
155 | int f = luaL_checkint(L, farg); |
156 | int w = luaL_optint(L, farg + 1, 1); |
157 | luaL_argcheck(L, 0 <= f, farg, "field cannot be negative"); |
158 | luaL_argcheck(L, 0 < w, farg + 1, "width must be positive"); |
159 | if (f + w > LUA_NBITS) |
160 | luaL_error(L, "trying to access non-existent bits"); |
161 | *width = w; |
162 | return f; |
163 | } |
164 | |
165 | |
166 | static int b_extract (lua_State *L) { |
167 | int w; |
168 | b_uint r = luaL_checkunsigned(L, 1); |
169 | int f = fieldargs(L, 2, &w); |
170 | r = (r >> f) & mask(w); |
171 | lua_pushunsigned(L, r); |
172 | return 1; |
173 | } |
174 | |
175 | |
176 | static int b_replace (lua_State *L) { |
177 | int w; |
178 | b_uint r = luaL_checkunsigned(L, 1); |
179 | b_uint v = luaL_checkunsigned(L, 2); |
180 | int f = fieldargs(L, 3, &w); |
181 | int m = mask(w); |
182 | v &= m; /* erase bits outside given width */ |
183 | r = (r & ~(m << f)) | (v << f); |
184 | lua_pushunsigned(L, r); |
185 | return 1; |
186 | } |
187 | |
188 | |
189 | static const luaL_Reg bitlib[] = { |
190 | {"arshift", b_arshift}, |
191 | {"band", b_and}, |
192 | {"bnot", b_not}, |
193 | {"bor", b_or}, |
194 | {"bxor", b_xor}, |
195 | {"btest", b_test}, |
196 | {"extract", b_extract}, |
197 | {"lrotate", b_lrot}, |
198 | {"lshift", b_lshift}, |
199 | {"replace", b_replace}, |
200 | {"rrotate", b_rrot}, |
201 | {"rshift", b_rshift}, |
202 | {NULL, NULL} |
203 | }; |
204 | |
205 | |
206 | |
207 | LUAMOD_API int luaopen_bit32 (lua_State *L) { |
208 | luaL_newlib(L, bitlib); |
209 | return 1; |
210 | } |
211 | |