module iso_c_utils
   use iso_c_binding
   implicit none

   ! always use max stringlen for c arrays otherwise you have to specify lengths by hand
   integer(c_int), parameter :: MAXSTRINGLEN = 1024
contains
   ! Utility functions, move these to interop module
   ! Make functions pure so they can be used as input arguments.
   integer(c_int) pure function strlen(char_array)
      character(c_char), intent(in) :: char_array(MAXSTRINGLEN)
      integer :: i
      strlen = 0
      do i = 1, size(char_array)
         if (char_array(i) .eq. C_NULL_CHAR) then
            strlen = i-1
            exit
         end if
      end do
   end function strlen

   integer(c_int) pure function strcmp(char_array1, char_array2)
      character(c_char), intent(in) :: char_array1(MAXSTRINGLEN)
      character(c_char), intent(in) :: char_array2(MAXSTRINGLEN)

      character(len=strlen(char_array1)) :: string1
      character(len=strlen(char_array2)) :: string2

      string1 = trim(char_array_to_string(char_array1))
      string2 = trim(char_array_to_string(char_array1))
      strcmp = 0
      if (llt(string1,string2)) strcmp = -1
      if (lgt(string1,string2)) strcmp = 1

   end function strcmp



   subroutine strcpy(str1, str2)
      character(c_char), intent(in) :: str1(MAXSTRINGLEN)
      character(c_char), intent(out) :: str2(MAXSTRINGLEN)

      integer :: i
      str2 = ' '
      do i=1,(strlen(str1) + 1)
         str2(i) = str1(i)
      end do
   end subroutine strcpy

   pure function char_array_to_string(char_array) result(string)
      character(c_char),intent(in) :: char_array(MAXSTRINGLEN)
      character(len=strlen(char_array)) :: string
      integer :: i
      do i = 1, strlen(char_array)
         string(i:i) = char_array(i)
      enddo
   end function char_array_to_string

   pure function string_to_char_array(string) result(char_array)
      character(len=*), intent(in) :: string
      character(kind=c_char,len=1) :: char_array(MAXSTRINGLEN)
      integer :: i
      do i = 1, len_trim(string)
         char_array(i) = string(i:i)
      enddo
      char_array(len_trim(string)+1) = C_NULL_CHAR
   end function string_to_char_array

end module iso_c_utils