ctype_members.cc (do_is(mask, wchar_t)): Speed-up for the common case of mask ==…

ctype_members.cc (do_is(mask, wchar_t)): Speed-up for the common case of mask == ctype_base::space...

2005-07-18  Paolo Carlini  <pcarlini@suse.de>

	* config/locale/gnu/ctype_members.cc (do_is(mask, wchar_t)):
	Speed-up for the common case of mask == ctype_base::space;
	otherwise, exit the loop earlier if the mask is one of the
	elementary ones.

From-SVN: r102137

libstdc++-v3/ChangeLog

+2005-07-18  Paolo Carlini  <pcarlini@suse.de>
+
+	* config/locale/gnu/ctype_members.cc (do_is(mask, wchar_t)):
+	Speed-up for the common case of mask == ctype_base::space;
+	otherwise, exit the loop earlier if the mask is one of the
+	elementary ones.
+
 2005-07-14  Paolo Carlini  <pcarlini@suse.de>
 
 	PR libstdc++/21193 (float, double, long double)

libstdc++-v3/config/locale/gnu/ctype_members.cc

@@ -134,20 +134,34 @@ namespace std
   ctype<wchar_t>::
   do_is(mask __m, wchar_t __c) const
   { 
-    // Highest bitmask in ctype_base == 10, but extra in "C"
-    // library for blank.
+    // The case of __m == ctype_base::space is particularly important,
+    // due to its use in many istream functions.  Therefore we deal with
+    // it first, exploiting the knowledge that on GNU systems _M_bit[5]
+    // is the mask corresponding to ctype_base::space.  NB: an encoding
+    // change would not affect correctness!
     bool __ret = false;
-    const size_t __bitmasksize = 11; 
-    for (size_t __bitcur = 0; __bitcur <= __bitmasksize; ++__bitcur)
-      if (__m & _M_bit[__bitcur]
-	  && __iswctype_l(__c, _M_wmask[__bitcur], _M_c_locale_ctype))
-	{
-	  __ret = true;
-	  break;
-	}
+    if (__m == _M_bit[5])
+      __ret = __iswctype_l(__c, _M_wmask[5], _M_c_locale_ctype);
+    else
+      {
+	// Highest bitmask in ctype_base == 10, but extra in "C"
+	// library for blank.
+	const size_t __bitmasksize = 11;
+	for (size_t __bitcur = 0; __bitcur <= __bitmasksize; ++__bitcur)
+	  if (__m & _M_bit[__bitcur])
+	    {
+	      if (__iswctype_l(__c, _M_wmask[__bitcur], _M_c_locale_ctype))
+		{
+		  __ret = true;
+		  break;
+		}
+	      else if (__m == _M_bit[__bitcur])
+		break;
+	    }
+      }
     return __ret;    
   }
-  
+
   const wchar_t* 
   ctype<wchar_t>::
   do_is(const wchar_t* __lo, const wchar_t* __hi, mask* __vec) const