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 } 212 213
