A component cannot be an array if the encompassing structure is an array.

I have the following problem:

I need to create an datasets array which size is not known at first. It is an composition of different subarrays. 
For example the first subdataset has 4 elements, the second 10, and a third 8. Because this sizes are  not known at the start of the programm I can not do somethin like:

INTEGER(4), ALLOCATE :: datasets(:)

ALLOCATE(datasets(1:4+10+8))

The sizes of each subdataset is evaluated one after each other. Because there is no such thing like appending an array to an array I would have to reallocate the datasets size after each subdataset to manually expend the array. But this always involves a copy process which I definetly have to avoid.

So I tried to use an array of pointers in which every pointer points to an allocatable array. This works.

P1  | P2  | P3
1   |   2  |  3
1   |   2  |  3
1   |   2  |  3
1   |   2  |  3
    |   2  |  3
    |   2  |  3
    |   2  |  3
    |   2  |  3
    |   2  |
    |   2  |  

Its getting tricky now, because I have a subroutine  (sub1) which needs one array. Is there any possibility to pass the data inside the subroutine without copying it?

1  | 1  | 1  | 1  | 2  |  2  |  2  |  2  |  2  |  2  |  2  |  2  |  2  |  2  |  3  |  3  |  3  |  3  |  3  |  3  |  3  |  3  | 

MODULE TEST_MOD
	IMPLICIT NONE

	PRIVATE

	! Type
	TYPE :: TYPE_TESTDATA
		INTEGER(4), ALLOCATABLE :: data(:)
	END TYPE TYPE_TESTDATA

	TYPE :: TYPE_TEST_PTR
		TYPE(TYPE_TESTDATA), POINTER :: p
	END TYPE TYPE_TEST_PTR

	CONTAINS

	! Subroutines
	SUBROUTINE sub1(array)
		IMPLICIT NONE
		INTEGER(4), ALLOCATABLE, INTENT(IN) :: array( : )

		! do smth with array

	END SUBROUTINE sub1


	SUBROUTINE sub2()
		IMPLICIT NONE

		INTEGER(4)							:: size_data1, size_data2, size_data3
		INTEGER(4)							:: num_datasets
		TYPE(TYPE_TEST_PTR), ALLOCATABLE	:: datasets(:)

		num_datasets = 3
		size_data1 = 4
		size_data2 = 10
		size_data3 = 8

		! allocate
		ALLOCATE(datasets(1:num_datasets))
		ALLOCATE(datasets(1)%p%data(1:size_data1))
		ALLOCATE(datasets(2)%p%data(1:size_data2))
		ALLOCATE(datasets(3)%p%data(1:size_data3))

		datasets(1)%p%data = 1
		datasets(2)%p%data = 2
		datasets(3)%p%data = 3

		CALL sub1(datasets(:)%p%data)

	END SUBROUTINE sub2
END MODULE TEST_MOD

I hope I have described the problem quite understandably. Thanks for your help in advance.