Standard library for bitwise operations

1 files changed, 123 insertions, 0 deletions

diff --git a/lbitlib.c b/lbitlib.c
new file mode 100644
index 00000000..4f715288
--- /dev/null
+++ b/lbitlib.c
@@ -0,0 +1,123 @@
+/*
+** $Id: $
+** Standard library for bitwise operations
+** See Copyright Notice in lua.h
+*/
+
+#include "lua.h"
+
+#include "lauxlib.h"
+#include "lualib.h"
+
+
+/* number of bits considered when shifting/rotating (must be a power of 2) */
+#define NBITS   32
+
+
+typedef LUA_INT32 b_int;
+typedef unsigned LUA_INT32 b_uint;
+
+
+static b_uint getuintarg (lua_State *L, int arg) {
+  b_uint r;
+  lua_Number x = lua_tonumber(L, arg);
+  if (x == 0) luaL_checktype(L, arg, LUA_TNUMBER);
+  lua_number2uint(r, x);
+  return r;
+}
+
+
+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 &= getuintarg(L, i);
+  return r;
+}
+
+
+static int b_and (lua_State *L) {
+  b_uint r = andaux(L);
+  lua_pushnumber(L, lua_uint2number(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 |= getuintarg(L, i);
+  lua_pushnumber(L, lua_uint2number(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 ^= getuintarg(L, i);
+  lua_pushnumber(L, lua_uint2number(r));
+  return 1;
+}
+
+
+static int b_not (lua_State *L) {
+  b_uint r = ~getuintarg(L, 1);
+  lua_pushnumber(L, lua_uint2number(r));
+  return 1;
+}
+
+
+static int b_shift (lua_State *L) {
+  b_uint r = getuintarg(L, 1);
+  lua_Integer i = luaL_checkinteger(L, 2);
+  if (i < 0) {  /* shift right? */
+    i = -i;
+    if (i >= NBITS) r = 0;
+    else r >>= i;
+  }
+  else {  /* shift left */
+    if (i >= NBITS) r = 0;
+    else r <<= i;
+  }
+  lua_pushnumber(L, lua_uint2number(r));
+  return 1;
+}
+
+
+static int b_rotate (lua_State *L) {
+  b_uint r = getuintarg(L, 1);
+  lua_Integer i = luaL_checkinteger(L, 2);
+  i &= (NBITS - 1);  /* i = i % NBITS */
+  r = (r << i) | (r >> (NBITS - i));
+  lua_pushnumber(L, lua_uint2number(r));
+  return 1;
+}
+
+
+static const luaL_Reg bitlib[] = {
+  {"band", b_and},
+  {"btest", b_test},
+  {"bor", b_or},
+  {"bxor", b_xor},
+  {"bnot", b_not},
+  {"bshift", b_shift},
+  {"brotate", b_rotate},
+  {NULL, NULL}
+};
+
+
+
+LUALIB_API int luaopen_bit (lua_State *L) {
+  luaL_register(L, LUA_BITLIBNAME, bitlib);
+  return 1;
+}