bitlib renamed to 'bit32' + new function for arithmetic shift

lbitlib.c

@@ -1,5 +1,5 @@
 /*
-** $Id: lbitlib.c,v 1.5 2010/07/02 11:38:13 roberto Exp roberto $
+** $Id: lbitlib.c,v 1.6 2010/07/02 12:01:53 roberto Exp roberto $
 ** Standard library for bitwise operations
 ** See Copyright Notice in lua.h
 */
@@ -81,8 +81,7 @@ static int b_not (lua_State *L) {
 }
 
 
-static int b_shift (lua_State *L, int i) {
-  b_uint r = getuintarg(L, 1);
+static int b_shift (lua_State *L, b_uint r, int i) {
   if (i < 0) {  /* shift right? */
     i = -i;
     if (i >= NBITS) r = 0;
@@ -98,12 +97,27 @@ static int b_shift (lua_State *L, int i) {
 
 
 static int b_lshift (lua_State *L) {
-  return b_shift(L, luaL_checkint(L, 2));
+  return b_shift(L, getuintarg(L, 1), luaL_checkint(L, 2));
 }
 
 
 static int b_rshift (lua_State *L) {
-  return b_shift(L, -luaL_checkint(L, 2));
+  return b_shift(L, getuintarg(L, 1), -luaL_checkint(L, 2));
+}
+
+
+static int b_arshift (lua_State *L) {
+  b_uint r = getuintarg(L, 1);
+  int i = luaL_checkint(L, 2);
+  if (i < 0 || !(r & 0x80000000))
+    return b_shift(L, r, -i);
+  else {  /* arithmetic shift for 'negative' number */
+    if (i >= NBITS) r = 0xffffffff;
+    else
+      r = (r >> i) | ~(~(b_uint)0 >> i);  /* add signal bit */
+    lua_pushnumber(L, lua_uint2number(r));
+    return 1;
+  }
 }
 
 
@@ -133,6 +147,7 @@ static const luaL_Reg bitlib[] = {
   {"bxor", b_xor},
   {"bnot", b_not},
   {"lshift", b_lshift},
+  {"arshift", b_arshift},
   {"rshift", b_rshift},
   {"rol", b_rol},
   {"ror", b_ror},
@@ -141,7 +156,7 @@ static const luaL_Reg bitlib[] = {
 
 
 
-LUAMOD_API int luaopen_bit (lua_State *L) {
+LUAMOD_API int luaopen_bit32 (lua_State *L) {
   luaL_newlib(L, bitlib);
   return 1;
 }

linit.c

@@ -1,5 +1,5 @@
 /*
-** $Id: linit.c,v 1.27 2010/06/30 17:40:27 roberto Exp roberto $
+** $Id: linit.c,v 1.28 2010/07/02 11:38:13 roberto Exp roberto $
 ** Initialization of libraries for lua.c and other clients        
 ** See Copyright Notice in lua.h
 */
@@ -34,7 +34,7 @@ static const luaL_Reg loadedlibs[] = {
   {LUA_IOLIBNAME, luaopen_io},
   {LUA_OSLIBNAME, luaopen_os},
   {LUA_STRLIBNAME, luaopen_string},
-  {LUA_BITLIBNAME, luaopen_bit},
+  {LUA_BITLIBNAME, luaopen_bit32},
   {LUA_MATHLIBNAME, luaopen_math},
 #if defined(LUA_COMPAT_DEBUGLIB)
   {LUA_DBLIBNAME, luaopen_debug},

lualib.h

@@ -1,5 +1,5 @@
 /*
-** $Id: lualib.h,v 1.39 2009/11/24 12:05:44 roberto Exp roberto $
+** $Id: lualib.h,v 1.40 2010/06/10 21:29:47 roberto Exp roberto $
 ** Lua standard libraries
 ** See Copyright Notice in lua.h
 */
@@ -32,8 +32,8 @@ LUAMOD_API int (luaopen_os) (lua_State *L);
 #define LUA_STRLIBNAME	"string"
 LUAMOD_API int (luaopen_string) (lua_State *L);
 
-#define LUA_BITLIBNAME	"bit"
-LUAMOD_API int (luaopen_bit) (lua_State *L);
+#define LUA_BITLIBNAME	"bit32"
+LUAMOD_API int (luaopen_bit32) (lua_State *L);
 
 #define LUA_MATHLIBNAME	"math"
 LUAMOD_API int (luaopen_math) (lua_State *L);