client/deps/liblua/lbitlib.c

   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     } else { /* shift left */
  93         if (i >= LUA_NBITS) r = 0;
  94         else r <<= i;
  95         r = trim(r);
  96     }
  97     lua_pushunsigned(L, r);
  98     return 1;
  99 }
 100
 101
 102 static int b_lshift(lua_State *L) {
 103     return b_shift(L, luaL_checkunsigned(L, 1), luaL_checkint(L, 2));
 104 }
 105
 106
 107 static int b_rshift(lua_State *L) {
 108     return b_shift(L, luaL_checkunsigned(L, 1), -luaL_checkint(L, 2));
 109 }
 110
 111
 112 static int b_arshift(lua_State *L) {
 113     b_uint r = luaL_checkunsigned(L, 1);
 114     int i = luaL_checkint(L, 2);
 115     if (i < 0 || !(r & ((b_uint)1 << (LUA_NBITS - 1))))
 116         return b_shift(L, r, -i);
 117     else {  /* arithmetic shift for 'negative' number */
 118         if (i >= LUA_NBITS) r = ALLONES;
 119         else
 120             r = trim((r >> i) | ~(~(b_uint)0 >> i));  /* add signal bit */
 121         lua_pushunsigned(L, r);
 122         return 1;
 123     }
 124 }
 125
 126
 127 static int b_rot(lua_State *L, int i) {
 128     b_uint r = luaL_checkunsigned(L, 1);
 129     i &= (LUA_NBITS - 1);  /* i = i % NBITS */
 130     r = trim(r);
 131     r = (r << i) | (r >> (LUA_NBITS - i));
 132     lua_pushunsigned(L, trim(r));
 133     return 1;
 134 }
 135
 136
 137 static int b_lrot(lua_State *L) {
 138     return b_rot(L, luaL_checkint(L, 2));
 139 }
 140
 141
 142 static int b_rrot(lua_State *L) {
 143     return b_rot(L, -luaL_checkint(L, 2));
 144 }
 145
 146
 147 /*
 148 ** get field and width arguments for field-manipulation functions,
 149 ** checking whether they are valid.
 150 ** ('luaL_error' called without 'return' to avoid later warnings about
 151 ** 'width' being used uninitialized.)
 152 */
 153 static int fieldargs(lua_State *L, int farg, int *width) {
 154     int f = luaL_checkint(L, farg);
 155     int w = luaL_optint(L, farg + 1, 1);
 156     luaL_argcheck(L, 0 <= f, farg, "field cannot be negative");
 157     luaL_argcheck(L, 0 < w, farg + 1, "width must be positive");
 158     if (f + w > LUA_NBITS)
 159         luaL_error(L, "trying to access non-existent bits");
 160     *width = w;
 161     return f;
 162 }
 163
 164
 165 static int b_extract(lua_State *L) {
 166     int w;
 167     b_uint r = luaL_checkunsigned(L, 1);
 168     int f = fieldargs(L, 2, &w);
 169     r = (r >> f) & mask(w);
 170     lua_pushunsigned(L, r);
 171     return 1;
 172 }
 173
 174
 175 static int b_replace(lua_State *L) {
 176     int w;
 177     b_uint r = luaL_checkunsigned(L, 1);
 178     b_uint v = luaL_checkunsigned(L, 2);
 179     int f = fieldargs(L, 3, &w);
 180     int m = mask(w);
 181     v &= m;  /* erase bits outside given width */
 182     r = (r & ~(m << f)) | (v << f);
 183     lua_pushunsigned(L, r);
 184     return 1;
 185 }
 186
 187
 188 static const luaL_Reg bitlib[] = {
 189     {"arshift", b_arshift},
 190     {"band", b_and},
 191     {"bnot", b_not},
 192     {"bor", b_or},
 193     {"bxor", b_xor},
 194     {"btest", b_test},
 195     {"extract", b_extract},
 196     {"lrotate", b_lrot},
 197     {"lshift", b_lshift},
 198     {"replace", b_replace},
 199     {"rrotate", b_rrot},
 200     {"rshift", b_rshift},
 201     {NULL, NULL}
 202 };
 203
 204
 205
 206 LUAMOD_API int luaopen_bit32(lua_State *L) {
 207     luaL_newlib(L, bitlib);
 208     return 1;
 209 }
 210