Disabling and enabling formating in clang-format

I have text file with c++ code fragments and I want to format only these fragments. I'm trying to use clang-format on/off for these purposes. Example of text file:

// clang-format on
for(const auto& element: elements){if(element > 0){element++;}}
// clang-format off
some text
// clang-format on
for(const auto& element: elements){if(element > 0){element++;}}
// clang-format off
some text

and after clang-format i have:

// clang-format on
for(const auto& element: elements)
{
    if(element > 0)
    {
        element++;
    }
}
// clang-format off
some text
    // clang-format on                 <---------------
    for(const auto& element: elements) <---------------
{
    if(element > 0)
    {
        element++;
    }
}
// clang-format off
some text   

     

if there is no any text before '// clang-format on' formatting is good, but if there is some text before - first lines have additional shift to the right.

How can I resolve this issue?