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1087
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1 /*
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2 ** $Id: lbitlib.c,v 1.16 2011/06/20 16:35:23 roberto Exp $
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3 ** Standard library for bitwise operations
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4 ** See Copyright Notice in lua.h
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5 */
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6
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7 #define lbitlib_c
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8 #define LUA_LIB
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9
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10 #include "lua.h"
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11
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12 #include "lauxlib.h"
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13 #include "lualib.h"
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14
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15
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16 /* number of bits to consider in a number */
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17 #if !defined(LUA_NBITS)
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18 #define LUA_NBITS 32
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19 #endif
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20
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21
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22 #define ALLONES (~(((~(lua_Unsigned)0) << (LUA_NBITS - 1)) << 1))
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23
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24 /* macro to trim extra bits */
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25 #define trim(x) ((x) & ALLONES)
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26
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27
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28 /* builds a number with 'n' ones (1 <= n <= LUA_NBITS) */
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29 #define mask(n) (~((ALLONES << 1) << ((n) - 1)))
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30
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31
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32 typedef lua_Unsigned b_uint;
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33
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34
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35
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36 static b_uint andaux (lua_State *L) {
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37 int i, n = lua_gettop(L);
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38 b_uint r = ~(b_uint)0;
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39 for (i = 1; i <= n; i++)
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40 r &= luaL_checkunsigned(L, i);
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41 return trim(r);
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42 }
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43
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44
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45 static int b_and (lua_State *L) {
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46 b_uint r = andaux(L);
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47 lua_pushunsigned(L, r);
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48 return 1;
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49 }
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50
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51
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52 static int b_test (lua_State *L) {
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53 b_uint r = andaux(L);
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54 lua_pushboolean(L, r != 0);
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55 return 1;
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56 }
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57
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58
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59 static int b_or (lua_State *L) {
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60 int i, n = lua_gettop(L);
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61 b_uint r = 0;
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62 for (i = 1; i <= n; i++)
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63 r |= luaL_checkunsigned(L, i);
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64 lua_pushunsigned(L, trim(r));
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65 return 1;
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66 }
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67
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68
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69 static int b_xor (lua_State *L) {
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70 int i, n = lua_gettop(L);
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71 b_uint r = 0;
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72 for (i = 1; i <= n; i++)
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73 r ^= luaL_checkunsigned(L, i);
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74 lua_pushunsigned(L, trim(r));
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75 return 1;
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76 }
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77
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78
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79 static int b_not (lua_State *L) {
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80 b_uint r = ~luaL_checkunsigned(L, 1);
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81 lua_pushunsigned(L, trim(r));
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82 return 1;
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83 }
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84
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85
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86 static int b_shift (lua_State *L, b_uint r, int i) {
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87 if (i < 0) { /* shift right? */
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88 i = -i;
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89 r = trim(r);
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90 if (i >= LUA_NBITS) r = 0;
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91 else r >>= i;
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92 }
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93 else { /* shift left */
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94 if (i >= LUA_NBITS) r = 0;
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95 else r <<= i;
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96 r = trim(r);
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97 }
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98 lua_pushunsigned(L, r);
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99 return 1;
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100 }
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101
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102
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103 static int b_lshift (lua_State *L) {
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104 return b_shift(L, luaL_checkunsigned(L, 1), luaL_checkint(L, 2));
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105 }
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106
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107
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108 static int b_rshift (lua_State *L) {
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109 return b_shift(L, luaL_checkunsigned(L, 1), -luaL_checkint(L, 2));
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110 }
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111
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112
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113 static int b_arshift (lua_State *L) {
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114 b_uint r = luaL_checkunsigned(L, 1);
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115 int i = luaL_checkint(L, 2);
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116 if (i < 0 || !(r & ((b_uint)1 << (LUA_NBITS - 1))))
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117 return b_shift(L, r, -i);
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118 else { /* arithmetic shift for 'negative' number */
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119 if (i >= LUA_NBITS) r = ALLONES;
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120 else
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121 r = trim((r >> i) | ~(~(b_uint)0 >> i)); /* add signal bit */
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122 lua_pushunsigned(L, r);
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123 return 1;
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124 }
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125 }
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126
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127
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128 static int b_rot (lua_State *L, int i) {
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129 b_uint r = luaL_checkunsigned(L, 1);
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130 i &= (LUA_NBITS - 1); /* i = i % NBITS */
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131 r = trim(r);
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132 r = (r << i) | (r >> (LUA_NBITS - i));
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133 lua_pushunsigned(L, trim(r));
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134 return 1;
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135 }
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136
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137
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138 static int b_lrot (lua_State *L) {
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139 return b_rot(L, luaL_checkint(L, 2));
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140 }
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141
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142
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143 static int b_rrot (lua_State *L) {
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144 return b_rot(L, -luaL_checkint(L, 2));
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145 }
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146
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147
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148 /*
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149 ** get field and width arguments for field-manipulation functions,
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150 ** checking whether they are valid
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151 */
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152 static int fieldargs (lua_State *L, int farg, int *width) {
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153 int f = luaL_checkint(L, farg);
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154 int w = luaL_optint(L, farg + 1, 1);
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155 luaL_argcheck(L, 0 <= f, farg, "field cannot be negative");
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156 luaL_argcheck(L, 0 < w, farg + 1, "width must be positive");
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157 if (f + w > LUA_NBITS)
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158 luaL_error(L, "trying to access non-existent bits");
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159 *width = w;
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160 return f;
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161 }
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162
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163
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164 static int b_extract (lua_State *L) {
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165 int w;
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166 b_uint r = luaL_checkunsigned(L, 1);
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167 int f = fieldargs(L, 2, &w);
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168 r = (r >> f) & mask(w);
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169 lua_pushunsigned(L, r);
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170 return 1;
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171 }
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172
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173
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174 static int b_replace (lua_State *L) {
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175 int w;
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176 b_uint r = luaL_checkunsigned(L, 1);
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177 b_uint v = luaL_checkunsigned(L, 2);
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178 int f = fieldargs(L, 3, &w);
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179 int m = mask(w);
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180 v &= m; /* erase bits outside given width */
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181 r = (r & ~(m << f)) | (v << f);
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182 lua_pushunsigned(L, r);
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183 return 1;
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184 }
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185
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186
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187 static const luaL_Reg bitlib[] = {
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188 {"arshift", b_arshift},
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189 {"band", b_and},
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190 {"bnot", b_not},
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191 {"bor", b_or},
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192 {"bxor", b_xor},
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193 {"btest", b_test},
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194 {"extract", b_extract},
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195 {"lrotate", b_lrot},
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196 {"lshift", b_lshift},
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197 {"replace", b_replace},
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198 {"rrotate", b_rrot},
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199 {"rshift", b_rshift},
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200 {NULL, NULL}
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201 };
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202
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203
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204
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205 LUAMOD_API int luaopen_bit32 (lua_State *L) {
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206 luaL_newlib(L, bitlib);
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207 return 1;
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208 }
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209
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