external/mit/lua/dist/src/lbitlib.c

   1 /*
   2 ** $Id: lbitlib.c,v 1.2 2015/02/02 14:03:05 lneto 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 "lprefix.h"
  11
  12
  13 #include "lua.h"
  14
  15 #include "lauxlib.h"
  16 #include "lualib.h"
  17
  18
  19 #if defined(LUA_COMPAT_BITLIB)          /* { */
  20
  21
  22 /* number of bits to consider in a number */
  23 #if !defined(LUA_NBITS)
  24 #define LUA_NBITS       32
  25 #endif
  26
  27
  28 /*
  29 ** a lua_Unsigned with its first LUA_NBITS bits equal to 1. (Shift must
  30 ** be made in two parts to avoid problems when LUA_NBITS is equal to the
  31 ** number of bits in a lua_Unsigned.)
  32 */
  33 #define ALLONES         (~(((~(lua_Unsigned)0) << (LUA_NBITS - 1)) << 1))
  34
  35
  36 /* macro to trim extra bits */
  37 #define trim(x)         ((x) & ALLONES)
  38
  39
  40 /* builds a number with 'n' ones (1 <= n <= LUA_NBITS) */
  41 #define mask(n)         (~((ALLONES << 1) << ((n) - 1)))
  42
  43
  44
  45 static lua_Unsigned andaux (lua_State *L) {
  46   int i, n = lua_gettop(L);
  47   lua_Unsigned r = ~(lua_Unsigned)0;
  48   for (i = 1; i <= n; i++)
  49     r &= luaL_checkunsigned(L, i);
  50   return trim(r);
  51 }
  52
  53
  54 static int b_and (lua_State *L) {
  55   lua_Unsigned r = andaux(L);
  56   lua_pushunsigned(L, r);
  57   return 1;
  58 }
  59
  60
  61 static int b_test (lua_State *L) {
  62   lua_Unsigned r = andaux(L);
  63   lua_pushboolean(L, r != 0);
  64   return 1;
  65 }
  66
  67
  68 static int b_or (lua_State *L) {
  69   int i, n = lua_gettop(L);
  70   lua_Unsigned r = 0;
  71   for (i = 1; i <= n; i++)
  72     r |= luaL_checkunsigned(L, i);
  73   lua_pushunsigned(L, trim(r));
  74   return 1;
  75 }
  76
  77
  78 static int b_xor (lua_State *L) {
  79   int i, n = lua_gettop(L);
  80   lua_Unsigned r = 0;
  81   for (i = 1; i <= n; i++)
  82     r ^= luaL_checkunsigned(L, i);
  83   lua_pushunsigned(L, trim(r));
  84   return 1;
  85 }
  86
  87
  88 static int b_not (lua_State *L) {
  89   lua_Unsigned r = ~luaL_checkunsigned(L, 1);
  90   lua_pushunsigned(L, trim(r));
  91   return 1;
  92 }
  93
  94
  95 static int b_shift (lua_State *L, lua_Unsigned r, lua_Integer i) {
  96   if (i < 0) {  /* shift right? */
  97     i = -i;
  98     r = trim(r);
  99     if (i >= LUA_NBITS) r = 0;
 100     else r >>= i;
 101   }
 102   else {  /* shift left */
 103     if (i >= LUA_NBITS) r = 0;
 104     else r <<= i;
 105     r = trim(r);
 106   }
 107   lua_pushunsigned(L, r);
 108   return 1;
 109 }
 110
 111
 112 static int b_lshift (lua_State *L) {
 113   return b_shift(L, luaL_checkunsigned(L, 1), luaL_checkinteger(L, 2));
 114 }
 115
 116
 117 static int b_rshift (lua_State *L) {
 118   return b_shift(L, luaL_checkunsigned(L, 1), -luaL_checkinteger(L, 2));
 119 }
 120
 121
 122 static int b_arshift (lua_State *L) {
 123   lua_Unsigned r = luaL_checkunsigned(L, 1);
 124   lua_Integer i = luaL_checkinteger(L, 2);
 125   if (i < 0 || !(r & ((lua_Unsigned)1 << (LUA_NBITS - 1))))
 126     return b_shift(L, r, -i);
 127   else {  /* arithmetic shift for 'negative' number */
 128     if (i >= LUA_NBITS) r = ALLONES;
 129     else
 130       r = trim((r >> i) | ~(trim(~(lua_Unsigned)0) >> i));  /* add signal bit */
 131     lua_pushunsigned(L, r);
 132     return 1;
 133   }
 134 }
 135
 136
 137 static int b_rot (lua_State *L, lua_Integer d) {
 138   lua_Unsigned r = luaL_checkunsigned(L, 1);
 139   int i = d & (LUA_NBITS - 1);  /* i = d % NBITS */
 140   r = trim(r);
 141   if (i != 0)  /* avoid undefined shift of LUA_NBITS when i == 0 */
 142     r = (r << i) | (r >> (LUA_NBITS - i));
 143   lua_pushunsigned(L, trim(r));
 144   return 1;
 145 }
 146
 147
 148 static int b_lrot (lua_State *L) {
 149   return b_rot(L, luaL_checkinteger(L, 2));
 150 }
 151
 152
 153 static int b_rrot (lua_State *L) {
 154   return b_rot(L, -luaL_checkinteger(L, 2));
 155 }
 156
 157
 158 /*
 159 ** get field and width arguments for field-manipulation functions,
 160 ** checking whether they are valid.
 161 ** ('luaL_error' called without 'return' to avoid later warnings about
 162 ** 'width' being used uninitialized.)
 163 */
 164 static int fieldargs (lua_State *L, int farg, int *width) {
 165   lua_Integer f = luaL_checkinteger(L, farg);
 166   lua_Integer w = luaL_optinteger(L, farg + 1, 1);
 167   luaL_argcheck(L, 0 <= f, farg, "field cannot be negative");
 168   luaL_argcheck(L, 0 < w, farg + 1, "width must be positive");
 169   if (f + w > LUA_NBITS)
 170     luaL_error(L, "trying to access non-existent bits");
 171   *width = (int)w;
 172   return (int)f;
 173 }
 174
 175
 176 static int b_extract (lua_State *L) {
 177   int w;
 178   lua_Unsigned r = trim(luaL_checkunsigned(L, 1));
 179   int f = fieldargs(L, 2, &w);
 180   r = (r >> f) & mask(w);
 181   lua_pushunsigned(L, r);
 182   return 1;
 183 }
 184
 185
 186 static int b_replace (lua_State *L) {
 187   int w;
 188   lua_Unsigned r = trim(luaL_checkunsigned(L, 1));
 189   lua_Unsigned v = luaL_checkunsigned(L, 2);
 190   int f = fieldargs(L, 3, &w);
 191   int m = mask(w);
 192   v &= m;  /* erase bits outside given width */
 193   r = (r & ~(m << f)) | (v << f);
 194   lua_pushunsigned(L, r);
 195   return 1;
 196 }
 197
 198
 199 static const luaL_Reg bitlib[] = {
 200   {"arshift", b_arshift},
 201   {"band", b_and},
 202   {"bnot", b_not},
 203   {"bor", b_or},
 204   {"bxor", b_xor},
 205   {"btest", b_test},
 206   {"extract", b_extract},
 207   {"lrotate", b_lrot},
 208   {"lshift", b_lshift},
 209   {"replace", b_replace},
 210   {"rrotate", b_rrot},
 211   {"rshift", b_rshift},
 212   {NULL, NULL}
 213 };
 214
 215
 216
 217 LUAMOD_API int luaopen_bit32 (lua_State *L) {
 218   luaL_newlib(L, bitlib);
 219   return 1;
 220 }
 221
 222
 223 #else                                   /* }{ */
 224
 225
 226 LUAMOD_API int luaopen_bit32 (lua_State *L) {
 227   return luaL_error(L, "library 'bit32' has been deprecated");
 228 }
 229
 230 #endif                                  /* } */