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 32typedef lua_Unsigned b_uint; 33 34 35 36static 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 45static int b_and (lua_State *L) { 46 b_uint r = andaux(L); 47 lua_pushunsigned(L, r); 48 return 1; 49} 50 51 52static int b_test (lua_State *L) { 53 b_uint r = andaux(L); 54 lua_pushboolean(L, r != 0); 55 return 1; 56} 57 58 59static 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 69static 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 79static 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 86static 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 103static int b_lshift (lua_State *L) { 104 return b_shift(L, luaL_checkunsigned(L, 1), luaL_checkint(L, 2)); 105} 106 107 108static int b_rshift (lua_State *L) { 109 return b_shift(L, luaL_checkunsigned(L, 1), -luaL_checkint(L, 2)); 110} 111 112 113static 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 128static 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 138static int b_lrot (lua_State *L) { 139 return b_rot(L, luaL_checkint(L, 2)); 140} 141 142 143static 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*/ 154static 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 166static 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 176static 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 189static 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 207LUAMOD_API int luaopen_bit32 (lua_State *L) { 208 luaL_newlib(L, bitlib); 209 return 1; 210} 211 212