subroutineaddpure

pure subroutine add(b, text)
    type(buffer_t), intent(inout) :: b      !! the buffer
    character(len=*), intent(in) :: text    !! the text
    character(len=:), allocatable :: grown
    integer :: capacity

    if (.not. allocated(b%s)) allocate (character(len=max(256, 2*len(text))) :: b%s)
    capacity = len(b%s)
    if (b%n + len(text) > capacity) then
        allocate (character(len=max(2*capacity, b%n + len(text))) :: grown)
        grown(1:b%n) = b%s(1:b%n)
        call move_alloc(grown, b%s)
    end if
    b%s(b%n + 1:b%n + len(text)) = text
    b%n = b%n + len(text)
end subroutine add