msvcrt: Optimize tolower function when locale was never changed.

dlls/msvcrt/ctype.c

@@ -458,7 +458,9 @@ int CDECL MSVCRT__tolower_l(int c, MSVCRT__locale_t locale)
  */
 int CDECL MSVCRT_tolower(int c)
 {
-        return MSVCRT__tolower_l(c, NULL);
+    if(initial_locale)
+        return c>='A' && c<='Z' ? c-'A'+'a' : c;
+    return MSVCRT__tolower_l(c, NULL);
 }
 
 /*********************************************************************

dlls/msvcrt/locale.c

@@ -48,6 +48,7 @@ int MSVCRT___lc_collate_cp = 0;
 LCID MSVCRT___lc_handle[MSVCRT_LC_MAX - MSVCRT_LC_MIN + 1] = { 0 };
 int MSVCRT___mb_cur_max = 1;
 static unsigned char charmax = CHAR_MAX;
+BOOL initial_locale = TRUE;
 
 #define MSVCRT_LEADBYTE  0x8000
 #define MSVCRT_C1_DEFINED 0x200
@@ -1780,6 +1781,9 @@ char* CDECL MSVCRT_setlocale(int category, const char* locale)
 
     _lock_locales();
 
+    if(locale[0] != 'C' || locale[1] != '\0')
+        initial_locale = FALSE;
+
     if(locinfo->lc_handle[MSVCRT_LC_COLLATE]!=newlocinfo->lc_handle[MSVCRT_LC_COLLATE]
             || locinfo->lc_id[MSVCRT_LC_COLLATE].wCodePage!=newlocinfo->lc_id[MSVCRT_LC_COLLATE].wCodePage) {
         locinfo->lc_collate_cp = newlocinfo->lc_collate_cp;

dlls/msvcrt/msvcrt.h

@@ -283,6 +283,7 @@ extern MSVCRT__locale_t MSVCRT_locale DECLSPEC_HIDDEN;
 extern unsigned int MSVCRT___lc_codepage;
 extern int MSVCRT___lc_collate_cp;
 extern WORD MSVCRT__ctype [257];
+extern BOOL initial_locale DECLSPEC_HIDDEN;
 
 void msvcrt_set_errno(int) DECLSPEC_HIDDEN;
 #if _MSVCR_VER >= 80

dlls/msvcrt/tests/string.c

@@ -2788,13 +2788,19 @@ static void test_tolower(void)
 
     errno = 0xdeadbeef;
     ret = p_tolower((char)0xF4);
-    todo_wine ok(ret == (char)0xF4, "ret = %x\n", ret);
-    todo_wine ok(errno == 0xdeadbeef, "errno = %d\n", errno);
+    ok(ret == (char)0xF4, "ret = %x\n", ret);
+    ok(errno == 0xdeadbeef, "errno = %d\n", errno);
 
     errno = 0xdeadbeef;
     ret = p_tolower((char)0xD0);
-    todo_wine ok(ret == (char)0xD0, "ret = %x\n", ret);
-    todo_wine ok(errno == 0xdeadbeef, "errno = %d\n", errno);
+    ok(ret == (char)0xD0, "ret = %x\n", ret);
+    ok(errno == 0xdeadbeef, "errno = %d\n", errno);
+
+    setlocale(LC_ALL, "C");
+    errno = 0xdeadbeef;
+    ret = p_tolower((char)0xF4);
+    ok(ret == (char)0xF4, "ret = %x\n", ret);
+    ok(errno == 0xdeadbeef, "errno = %d\n", errno);
 
     /* test C locale after setting locale */
     if(!setlocale(LC_ALL, "us")) {