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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