[PATCH 0/2] MR4431: msvcrt: Improve _mbsrev implementation.

[PATCH 1/2] msvcrt: Avoid temporary buffer allocation in _mbsrev_l.

[Piotr Caban]

From: Piotr Caban

---
 dlls/msvcrt/mbcs.c | 50 ++++++++++++++--------------------------------
 1 file changed, 15 insertions(+), 35 deletions(-)

diff --git a/dlls/msvcrt/mbcs.c b/dlls/msvcrt/mbcs.c
index e6c0e944255..2e228d77811 100644
--- a/dlls/msvcrt/mbcs.c
+++ b/dlls/msvcrt/mbcs.c
@@ -2889,9 +2889,8 @@ size_t CDECL _mbscspn(const unsigned char* str, const unsigned char* cmp)
  */
 unsigned char* CDECL _mbsrev_l(unsigned char* str, _locale_t locale)
 {
-    int i, len;
-    unsigned char *p, *temp;
     pthreadmbcinfo mbcinfo;
+    unsigned char *p, tmp;

if (!MSVCRT_CHECK_PMT(str))
         return NULL;
@@ -2904,44 +2903,25 @@ unsigned char* CDECL _mbsrev_l(unsigned char* str, _locale_t locale)
     if (!mbcinfo->ismbcodepage)
         return u__strrev(str);

-    len = _mbslen_l(str, locale);
-    temp = malloc(len * 2);
-    if (!temp)
-        return str;
-
-    /* unpack multibyte string to temp buffer */
-    p = str;
-    for (i = 0; i < len; i++)
+    for (p = str; *p; p++)
     {
         if (_ismbblead_l(*p, locale))
         {
-            temp[i * 2] = *p++;
-            temp[i * 2 + 1] = *p++;
-        }
-        else
-        {
-            temp[i * 2] = *p++;
-            temp[i * 2 + 1] = 0;
-        }
-    }
-
-    /* repack it in the reverse order */
-    p = str;
-    for (i = len - 1; i >= 0; i--)
-    {
-        if (_ismbblead_l(temp[i * 2], locale))
-        {
-            *p++ = temp[i * 2];
-            *p++ = temp[i * 2 + 1];
-        }
-        else
-        {
-            *p++ = temp[i * 2];
+            if (p[1])
+            {
+                tmp = p[0];
+                p[0] = p[1];
+                p[1] = tmp;
+                p++;
+            }
+            else
+            {
+                /* drop trailing lead char */
+                p[0] = 0;
+            }
         }
     }
-
-    free(temp);
-    return str;
+    return u__strrev(str);
 }

/*********************************************************************

[PATCH 2/2] msvcrt: Add _mbsrev tests.

[Piotr Caban]

From: Piotr Caban

---
 dlls/msvcrt/tests/string.c | 22 ++++++++++++++++++++++
 1 file changed, 22 insertions(+)

diff --git a/dlls/msvcrt/tests/string.c b/dlls/msvcrt/tests/string.c
index b63df4b846d..34338fd4a39 100644
--- a/dlls/msvcrt/tests/string.c
+++ b/dlls/msvcrt/tests/string.c
@@ -4671,6 +4671,27 @@ static void test_wcsncpy(void)
             wine_dbgstr_wn(dst, ARRAY_SIZE(dst)));
 }

+static void test_mbsrev(void)
+{
+    unsigned char buf[64], *ret;
+    int cp = _getmbcp();
+
+    _setmbcp(932);
+
+    strcpy((char *)buf, "\x36\x8c\x8e");
+    ret = _mbsrev(buf);
+    ok(ret == buf, "ret = %p, expected %p\n", ret, buf);
+    ok(!memcmp(buf, "\x8c\x8e\x36", 4), "buf = %s\n", wine_dbgstr_a((char *)buf));
+
+    /* test string that ends with leading byte */
+    strcpy((char *)buf, "\x36\x8c");
+    ret = _mbsrev(buf);
+    ok(ret == buf, "ret = %p, expected %p\n", ret, buf);
+    ok(!memcmp(buf, "\x36", 2), "buf = %s\n", wine_dbgstr_a((char *)buf));
+
+    _setmbcp(cp);
+}
+
 START_TEST(string)
 {
     char mem[100];
@@ -4831,4 +4852,5 @@ START_TEST(string)
     test_SpecialCasing();
     test__mbbtype();
     test_wcsncpy();
+    test_mbsrev();
 }