1 files changed, 211 insertions, 0 deletions

diff --git a/lbitlib.c b/lbitlib.c
new file mode 100644
index 00000000..9637532e
--- /dev/null
+++ b/lbitlib.c
@@ -0,0 +1,211 @@
+/*
+** $Id: lbitlib.c,v 1.18 2013/03/19 13:19:12 roberto Exp $
+** Standard library for bitwise operations
+** See Copyright Notice in lua.h
+*/
+
+#define lbitlib_c
+#define LUA_LIB
+
+#include "lua.h"
+
+#include "lauxlib.h"
+#include "lualib.h"
+
+
+/* number of bits to consider in a number */
+#if !defined(LUA_NBITS)
+#define LUA_NBITS       32
+#endif
+
+
+#define ALLONES         (~(((~(lua_Unsigned)0) << (LUA_NBITS - 1)) << 1))
+
+/* macro to trim extra bits */
+#define trim(x)         ((x) & ALLONES)
+
+
+/* builds a number with 'n' ones (1 <= n <= LUA_NBITS) */
+#define mask(n)         (~((ALLONES << 1) << ((n) - 1)))
+
+
+typedef lua_Unsigned b_uint;
+
+
+
+static b_uint andaux (lua_State *L) {
+  int i, n = lua_gettop(L);
+  b_uint r = ~(b_uint)0;
+  for (i = 1; i <= n; i++)
+    r &= luaL_checkunsigned(L, i);
+  return trim(r);
+}
+
+
+static int b_and (lua_State *L) {
+  b_uint r = andaux(L);
+  lua_pushunsigned(L, r);
+  return 1;
+}
+
+
+static int b_test (lua_State *L) {
+  b_uint r = andaux(L);
+  lua_pushboolean(L, r != 0);
+  return 1;
+}
+
+
+static int b_or (lua_State *L) {
+  int i, n = lua_gettop(L);
+  b_uint r = 0;
+  for (i = 1; i <= n; i++)
+    r |= luaL_checkunsigned(L, i);
+  lua_pushunsigned(L, trim(r));
+  return 1;
+}
+
+
+static int b_xor (lua_State *L) {
+  int i, n = lua_gettop(L);
+  b_uint r = 0;
+  for (i = 1; i <= n; i++)
+    r ^= luaL_checkunsigned(L, i);
+  lua_pushunsigned(L, trim(r));
+  return 1;
+}
+
+
+static int b_not (lua_State *L) {
+  b_uint r = ~luaL_checkunsigned(L, 1);
+  lua_pushunsigned(L, trim(r));
+  return 1;
+}
+
+
+static int b_shift (lua_State *L, b_uint r, int i) {
+  if (i < 0) {  /* shift right? */
+    i = -i;
+    r = trim(r);
+    if (i >= LUA_NBITS) r = 0;
+    else r >>= i;
+  }
+  else {  /* shift left */
+    if (i >= LUA_NBITS) r = 0;
+    else r <<= i;
+    r = trim(r);
+  }
+  lua_pushunsigned(L, r);
+  return 1;
+}
+
+
+static int b_lshift (lua_State *L) {
+  return b_shift(L, luaL_checkunsigned(L, 1), luaL_checkint(L, 2));
+}
+
+
+static int b_rshift (lua_State *L) {
+  return b_shift(L, luaL_checkunsigned(L, 1), -luaL_checkint(L, 2));
+}
+
+
+static int b_arshift (lua_State *L) {
+  b_uint r = luaL_checkunsigned(L, 1);
+  int i = luaL_checkint(L, 2);
+  if (i < 0 || !(r & ((b_uint)1 << (LUA_NBITS - 1))))
+    return b_shift(L, r, -i);
+  else {  /* arithmetic shift for 'negative' number */
+    if (i >= LUA_NBITS) r = ALLONES;
+    else
+      r = trim((r >> i) | ~(~(b_uint)0 >> i));  /* add signal bit */
+    lua_pushunsigned(L, r);
+    return 1;
+  }
+}
+
+
+static int b_rot (lua_State *L, int i) {
+  b_uint r = luaL_checkunsigned(L, 1);
+  i &= (LUA_NBITS - 1);  /* i = i % NBITS */
+  r = trim(r);
+  r = (r << i) | (r >> (LUA_NBITS - i));
+  lua_pushunsigned(L, trim(r));
+  return 1;
+}
+
+
+static int b_lrot (lua_State *L) {
+  return b_rot(L, luaL_checkint(L, 2));
+}
+
+
+static int b_rrot (lua_State *L) {
+  return b_rot(L, -luaL_checkint(L, 2));
+}
+
+
+/*
+** get field and width arguments for field-manipulation functions,
+** checking whether they are valid.
+** ('luaL_error' called without 'return' to avoid later warnings about
+** 'width' being used uninitialized.)
+*/
+static int fieldargs (lua_State *L, int farg, int *width) {
+  int f = luaL_checkint(L, farg);
+  int w = luaL_optint(L, farg + 1, 1);
+  luaL_argcheck(L, 0 <= f, farg, "field cannot be negative");
+  luaL_argcheck(L, 0 < w, farg + 1, "width must be positive");
+  if (f + w > LUA_NBITS)
+    luaL_error(L, "trying to access non-existent bits");
+  *width = w;
+  return f;
+}
+
+
+static int b_extract (lua_State *L) {
+  int w;
+  b_uint r = luaL_checkunsigned(L, 1);
+  int f = fieldargs(L, 2, &w);
+  r = (r >> f) & mask(w);
+  lua_pushunsigned(L, r);
+  return 1;
+}
+
+
+static int b_replace (lua_State *L) {
+  int w;
+  b_uint r = luaL_checkunsigned(L, 1);
+  b_uint v = luaL_checkunsigned(L, 2);
+  int f = fieldargs(L, 3, &w);
+  int m = mask(w);
+  v &= m;  /* erase bits outside given width */
+  r = (r & ~(m << f)) | (v << f);
+  lua_pushunsigned(L, r);
+  return 1;
+}
+
+
+static const luaL_Reg bitlib[] = {
+  {"arshift", b_arshift},
+  {"band", b_and},
+  {"bnot", b_not},
+  {"bor", b_or},
+  {"bxor", b_xor},
+  {"btest", b_test},
+  {"extract", b_extract},
+  {"lrotate", b_lrot},
+  {"lshift", b_lshift},
+  {"replace", b_replace},
+  {"rrotate", b_rrot},
+  {"rshift", b_rshift},
+  {NULL, NULL}
+};
+
+
+
+LUAMOD_API int luaopen_bit32 (lua_State *L) {
+  luaL_newlib(L, bitlib);
+  return 1;
+}
+