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 } 211 212
