| 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 | |