extendarray.f90

module class_ExtendArray
  implicit none
  private

  type, public :: ExtendArray
    integer(8) :: capacity
    integer(8) :: length
    real(8), pointer :: data(:)
    real(8), pointer :: buffer(:)
  contains
    procedure :: init => ea_init
    procedure :: append => ea_append
    final :: ea_deallocate
  end type ExtendArray

contains

  subroutine ea_init(this, capacity)
    class(ExtendArray) :: this
    integer(8), optional  :: capacity

    if (.not. present(capacity) ) capacity = 32
    ! allocate buffer
    allocate(this%buffer(capacity))
    this%capacity = capacity
    this%length = 0
    this%data => this%buffer(1:1)
  end subroutine ea_init

  subroutine ea_append(this, val)
    class(ExtendArray) :: this
    real(8), intent(in) :: val
    integer(8) :: new_length
    real(8), pointer :: newbuffer(:)
    integer(8) :: new_capacity

    new_length = this%length + 1
    if( new_length .gt. this%capacity ) then
      ! reallocate and copy
      new_capacity = 2*this%capacity
      allocate(newbuffer(new_capacity))
      newbuffer(1:this%capacity) = this%buffer
      deallocate(this%buffer)
      this%buffer => newbuffer
      this%capacity = new_capacity
    endif

    this%data => this%buffer(1:new_length)
    this%length = new_length
    this%data(new_length) = val
  end subroutine ea_append

  subroutine ea_deallocate(this)
    type(ExtendArray) :: this

    nullify(this%data)
    deallocate(this%buffer)
  end subroutine ea_deallocate

end module class_ExtendArray