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