oledb32: Fixed length calculation in conversion to DBTYPE_STR.

dlls/oledb32/convert.c

@@ -813,26 +813,27 @@ static HRESULT WINAPI convert_DataConvert(IDataConvert* iface,
         SysFreeString(b);
         return hr;
     }
+
     case DBTYPE_STR:
     {
         BSTR b;
-        DBLENGTH bstr_len;
+        DBLENGTH length;
         INT bytes_to_copy;
-        hr = IDataConvert_DataConvert(iface, src_type, DBTYPE_BSTR, src_len, &bstr_len,
+        hr = IDataConvert_DataConvert(iface, src_type, DBTYPE_BSTR, src_len, &length,
                                       src, &b, sizeof(BSTR), src_status, dst_status,
                                       precision, scale, flags);
         if(hr != S_OK) return hr;
-        bstr_len = SysStringLen(b);
-        *dst_len = bstr_len * sizeof(char); /* Doesn't include size for '\0' */
+        length = WideCharToMultiByte(CP_ACP, 0, b, SysStringLen(b), NULL, 0, NULL, NULL);
+        *dst_len = length; /* Doesn't include size for '\0' */
         *dst_status = DBSTATUS_S_OK;
-        bytes_to_copy = min(*dst_len + sizeof(char), dst_max_len);
+        bytes_to_copy = min(length + 1, dst_max_len);
         if(dst)
         {
             if(bytes_to_copy >= sizeof(char))
             {
-                WideCharToMultiByte(CP_ACP, 0, b, bytes_to_copy - sizeof(char), dst, dst_max_len, NULL, NULL);
-                *((char *)dst + bytes_to_copy / sizeof(char) - 1) = 0;
-                if(bytes_to_copy < *dst_len + sizeof(char))
+                WideCharToMultiByte(CP_ACP, 0, b, SysStringLen(b), dst, bytes_to_copy - 1, NULL, NULL);
+                *((char *)dst + bytes_to_copy - 1) = 0;
+                if(bytes_to_copy < length + 1)
                     *dst_status = DBSTATUS_S_TRUNCATED;
             }
             else