Use find in files (Ctrl + Shift + F) functionality in code

 I would like to search for given string in all files programmatically. Is there way to call this functionality in code?

Closest thing I have found is to use ReferenceSearch. However, that is not good enough for me, as I need to search string and not the PsiElement, as even occurrences in different types of files (.dat, .ftl, ...) are relevant for me.