[PATCH 1/1] ucrtbase: Fix mbstowcs on UTF8 strings.

[Piotr Caban]

From: Piotr Caban

Wine-Bug: https://bugs.winehq.org/show_bug.cgi?id=56994
---
 dlls/msvcrt/mbcs.c           | 16 +++++++++++++++-
 dlls/ucrtbase/tests/string.c | 23 +++++++++++++++++++++++
 2 files changed, 38 insertions(+), 1 deletion(-)

diff --git a/dlls/msvcrt/mbcs.c b/dlls/msvcrt/mbcs.c
index 0bac4c9f8d9..5f5cd3e8cda 100644
--- a/dlls/msvcrt/mbcs.c
+++ b/dlls/msvcrt/mbcs.c
@@ -3266,6 +3266,17 @@ size_t CDECL mbrtowc(wchar_t *dst, const char *str,
     return len;
 }

+static inline int get_utf8_char_len(char ch)
+{
+    if((ch&0xf8) == 0xf0)
+        return 4;
+    else if((ch&0xf0) == 0xe0)
+        return 3;
+    else if((ch&0xe0) == 0xc0)
+        return 2;
+    return 1;
+}
+
 /*********************************************************************
  *		_mbstowcs_l(MSVCRT.@)
  */
@@ -3311,7 +3322,10 @@ size_t CDECL _mbstowcs_l(wchar_t *wcstr, const char *mbstr,
         if(mbstr[size] == '\0')
             break;

-        size += (_isleadbyte_l((unsigned char)mbstr[size], locale) ? 2 : 1);
+        if (locinfo->lc_codepage == CP_UTF8)
+            size += get_utf8_char_len(mbstr[size]);
+        else
+            size += (_isleadbyte_l((unsigned char)mbstr[size], locale) ? 2 : 1);
     }

if(size) {
diff --git a/dlls/ucrtbase/tests/string.c b/dlls/ucrtbase/tests/string.c
index 5714d384b05..d6085650e98 100644
--- a/dlls/ucrtbase/tests/string.c
+++ b/dlls/ucrtbase/tests/string.c
@@ -815,6 +815,28 @@ static void test__mbsncpy_s(void)
     _setmbcp(oldcp);
 }

+static void test_mbstowcs(void)
+{
+    static const char mbs[] = { 0xc3, 0xa9 };
+    WCHAR wcs[2];
+    size_t ret;
+
+    if (!setlocale(LC_ALL, "en_US.UTF-8"))
+    {
+        win_skip("skipping UTF8 mbstowcs tests\n");
+        return;
+    }
+
+    ret = mbstowcs(NULL, mbs, 0);
+    ok(ret == 1, "mbstowcs returned %Id\n", ret);
+    memset(wcs, 0xfe, sizeof(wcs));
+    ret = mbstowcs(wcs, mbs, 1);
+    ok(ret == 1, "mbstowcs returned %Id\n", ret);
+    ok(wcs[0] == 0xe9, "wcsstring[0] = %x\n", wcs[0]);
+    ok(wcs[1] == 0xfefe, "wcsstring[1] = %x\n", wcs[1]);
+    setlocale(LC_ALL, "C");
+}
+
 START_TEST(string)
 {
     ok(_set_invalid_parameter_handler(test_invalid_parameter_handler) == NULL,
@@ -834,4 +856,5 @@ START_TEST(string)
     test__mbbtype_l();
     test_strcmp();
     test__mbsncpy_s();
+    test_mbstowcs();
 }