client/src/lua_bitlib.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 ** Patched to provide a compatibility layer with Lua5.3+ where
   7 ** bit32 library was removed.
   8 */
   9
  10 #include "lua_bitlib.h"
  11
  12 #include "lauxlib.h"
  13
  14 /* number of bits to consider in a number */
  15 #define LUA_BITLIB_NBITS 32
  16
  17
  18 #define ALLONES (~(((~(lua_Unsigned)0) << (LUA_BITLIB_NBITS - 1)) << 1))
  19
  20 /* macro to trim extra bits */
  21 #define trim(x) ((x) & ALLONES)
  22
  23
  24 /* builds a number with 'n' ones (1 <= n <= LUA_BITLIB_NBITS) */
  25 #define mask(n) (~((ALLONES << 1) << ((n) - 1)))
  26
  27
  28 typedef lua_Unsigned b_uint;
  29
  30
  31 static b_uint andaux(lua_State *L) {
  32     int i, n = lua_gettop(L);
  33     b_uint r = ~(b_uint)0;
  34     for (i = 1; i <= n; i++)
  35         r &= (b_uint)luaL_checkinteger(L, i);
  36     return trim(r);
  37 }
  38
  39
  40 static int b_and(lua_State *L) {
  41     b_uint r = andaux(L);
  42     lua_pushinteger(L, r);
  43     return 1;
  44 }
  45
  46
  47 static int b_test(lua_State *L) {
  48     b_uint r = andaux(L);
  49     lua_pushboolean(L, r != 0);
  50     return 1;
  51 }
  52
  53
  54 static int b_or(lua_State *L) {
  55     int i, n = lua_gettop(L);
  56     b_uint r = 0;
  57     for (i = 1; i <= n; i++)
  58         r |= (b_uint) luaL_checkinteger(L, i);
  59     lua_pushinteger(L, trim(r));
  60     return 1;
  61 }
  62
  63
  64 static int b_xor(lua_State *L) {
  65     int i, n = lua_gettop(L);
  66     b_uint r = 0;
  67     for (i = 1; i <= n; i++)
  68         r ^= (b_uint) luaL_checkinteger(L, i);
  69     lua_pushinteger(L, trim(r));
  70     return 1;
  71 }
  72
  73
  74 static int b_not(lua_State *L) {
  75     b_uint r = ~((b_uint)luaL_checkinteger(L, 1));
  76     lua_pushinteger(L, trim(r));
  77     return 1;
  78 }
  79
  80
  81 static int b_shift(lua_State *L, b_uint r, int i) {
  82     if (i < 0) {  /* shift right? */
  83         i = -i;
  84         r = trim(r);
  85         if (i >= LUA_BITLIB_NBITS) r = 0;
  86         else r >>= i;
  87     } else { /* shift left */
  88         if (i >= LUA_BITLIB_NBITS) r = 0;
  89         else r <<= i;
  90         r = trim(r);
  91     }
  92     lua_pushinteger(L, r);
  93     return 1;
  94 }
  95
  96
  97 static int b_lshift(lua_State *L) {
  98     return b_shift(L, (b_uint)luaL_checkinteger(L, 1), luaL_checkinteger(L, 2));
  99 }
 100
 101
 102 static int b_rshift(lua_State *L) {
 103     return b_shift(L, (b_uint)luaL_checkinteger(L, 1), -luaL_checkinteger(L, 2));
 104 }
 105
 106
 107 static int b_arshift(lua_State *L) {
 108     b_uint r = (b_uint)luaL_checkinteger(L, 1);
 109     int i = luaL_checkinteger(L, 2);
 110     if (i < 0 || !(r & ((b_uint)1 << (LUA_BITLIB_NBITS - 1))))
 111         return b_shift(L, r, -i);
 112     else {  /* arithmetic shift for 'negative' number */
 113         if (i >= LUA_BITLIB_NBITS) r = ALLONES;
 114         else
 115             r = trim((r >> i) | ~(~(b_uint)0 >> i));  /* add signal bit */
 116         lua_pushinteger(L, r);
 117         return 1;
 118     }
 119 }
 120
 121
 122 static int b_rot(lua_State *L, int i) {
 123     b_uint r = (b_uint)luaL_checkinteger(L, 1);
 124     i &= (LUA_BITLIB_NBITS - 1);  /* i = i % NBITS */
 125     r = trim(r);
 126     if (i != 0)  /* avoid undefined shift of LUA_BITLIB_NBITS when i == 0 */
 127         r = (r << i) | (r >> (LUA_BITLIB_NBITS - i));
 128
 129     lua_pushinteger(L, trim(r));
 130     return 1;
 131 }
 132
 133
 134 static int b_lrot(lua_State *L) {
 135     return b_rot(L, luaL_checkinteger(L, 2));
 136 }
 137
 138
 139 static int b_rrot(lua_State *L) {
 140     return b_rot(L, -luaL_checkinteger(L, 2));
 141 }
 142
 143
 144 /*
 145 ** get field and width arguments for field-manipulation functions,
 146 ** checking whether they are valid.
 147 ** ('luaL_error' called without 'return' to avoid later warnings about
 148 ** 'width' being used uninitialized.)
 149 */
 150 static int fieldargs(lua_State *L, int farg, int *width) {
 151     int f = luaL_checkinteger(L, farg);
 152     int w = luaL_optinteger(L, farg + 1, 1);
 153     luaL_argcheck(L, 0 <= f, farg, "field cannot be negative");
 154     luaL_argcheck(L, 0 < w, farg + 1, "width must be positive");
 155     if (f + w > LUA_BITLIB_NBITS)
 156         luaL_error(L, "trying to access non-existent bits");
 157     *width = w;
 158     return f;
 159 }
 160
 161
 162 static int b_extract(lua_State *L) {
 163     int w;
 164     b_uint r = (b_uint)luaL_checkinteger(L, 1);
 165     int f = fieldargs(L, 2, &w);
 166     r = (r >> f) & mask(w);
 167     lua_pushinteger(L, r);
 168     return 1;
 169 }
 170
 171
 172 static int b_replace(lua_State *L) {
 173     int w;
 174     b_uint r = (b_uint)luaL_checkinteger(L, 1);
 175     b_uint v = (b_uint)luaL_checkinteger(L, 2);
 176     int f = fieldargs(L, 3, &w);
 177     int m = mask(w);
 178     v &= m;  /* erase bits outside given width */
 179     r = (r & ~(m << f)) | (v << f);
 180     lua_pushinteger(L, r);
 181     return 1;
 182 }
 183
 184
 185 void register_bit32_lib(lua_State *L) {
 186     static const luaL_Reg bitlib[] = {
 187         {"arshift", b_arshift},
 188         {"band", b_and},
 189         {"bnot", b_not},
 190         {"bor", b_or},
 191         {"bxor", b_xor},
 192         {"btest", b_test},
 193         {"extract", b_extract},
 194         {"lrotate", b_lrot},
 195         {"lshift", b_lshift},
 196         {"replace", b_replace},
 197         {"rrotate", b_rrot},
 198         {"rshift", b_rshift},
 199         {NULL, NULL}
 200     };
 201
 202     luaL_newlib(L, bitlib);
 203     lua_setfield(L, -2, "bit32");
 204 }
 205