在Fortran90 +中具有可分配組件的數據類型的二進制讀/寫

Question

什么是保存該變量的二進制快照的最好方法save它做出來的sample下面的數據類型？

program save_it

   type core
      integer, dimension(8) :: indx
   end type core 

   type sample
      integer :: a
      real*8, dimension(:), allocatable :: b
      type(core), dimension(:), allocatable :: c
   end type sample

   ! here it comes
   type(sample) :: save

   ! here we allocate all componenets of variable "save"
   !.
   !.

   ! Now, how to write/read variable "save" to/from external file?

end program save_it 

C ++中有非常直接的二進制輸入/輸出流，但是我不知道如何在Fortran 90+中做到這一點。

Answer 1

如果使用Fortran90 +表示對Fortran 2003感到滿意，則可以選擇用戶定義的派生類型IO。 這使您可以將分配所需的額外簿記包裝在write語句中。 我將示例代碼放在底部。

如果您不想使用此功能，可能是因為您沒有支持該功能的編譯器（我已經使用ifort 14進行了測試），那么您可以輕松地模仿簿記。

關鍵部分是發送並回讀大小，並在讀取之前分配變量。

編碼：

module types

   type core
      integer, dimension(8) :: indx
   end type core 

   type sample
      integer :: a
      real*8, dimension(:), allocatable :: b
      type(core), dimension(:), allocatable :: c
    contains
      procedure write_sample
      procedure read_sample
      generic :: write(unformatted) => write_sample
      generic :: read(unformatted) => read_sample
   end type sample

   contains

     ! Unformatted writing for the sample derived type
     subroutine write_sample(dtv, unit, iostat, iomsg)
       class(sample), intent(in) :: dtv
       integer, intent(in) :: unit
       integer, intent(out) :: iostat
       character(*), intent(inout) :: iomsg

       integer i

       ! Write a record giving sizes for the allocation
       write(unit, iostat=iostat, iomsg=iomsg) SIZE(dtv%b), SIZE(dtv%c)
       write(unit, iostat=iostat, iomsg=iomsg) dtv%a, dtv%b, &
                                               (dtv%c(i)%indx, i=1,SIZE(dtv%c))

     end subroutine write_sample

     ! Unformatted reading for the sample derived type
     subroutine read_sample(dtv, unit, iostat, iomsg)
       class(sample), intent(inout) :: dtv
       integer, intent(in) :: unit
       integer, intent(out) :: iostat
       character(*), intent(inout) :: iomsg

       integer i
       integer sizeb, sizec

       ! We first have a record telling us the sizes of components
       read(unit, iostat=iostat, iomsg=iomsg) sizeb, sizec
       ! So we do the allocation
       allocate(dtv%b(sizeb), dtv%c(sizec))
       ! And then finally the reading.
       read(unit, iostat=iostat, iomsg=iomsg) dtv%a, dtv%b, &
                                             (dtv%c(i)%indx, i=1,SIZE(dtv%c))

     end subroutine read_sample

end module types

program save_it
   use types

   implicit none

   integer i, unit_in, unit_out

   ! here it comes
   type(sample) :: save
   type(sample) :: save_test

   ! Define some values - using ifort don't forget to set the compile flag
   save%a = 14
   save%b = [(i*1., i=1, 10)]
   save%c = [core([(i, i=1,8)]), core([(i, i=11, 18)])]

   ! Write out the derived type
   open(newunit=unit_out, file='serial', form='unformatted', &
        status='replace', action='write')
   write(unit_out) save
   close(unit_out)

   ! Read in the derived type to a new one
   open(newunit=unit_in, file='serial', form='unformatted', &
        status='old', action='read')
   read(unit_in) save_test
   close(unit_in)

   ! Test, if we want to be certain

end program save_it

要使它變得強大，當然還有很多工作要做。