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| 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 |
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