load_file_as_stream Function

  function load_file_as_stream(filename, delimiter_start, delimiter_end, fast_read, iostat, iomsg) result(stream)
  !< Load file contents and store as single characters stream.
  character(*),           intent(in)  :: filename        !< File name.
  character(*), optional, intent(in)  :: delimiter_start !< Delimiter from which start the stream.
  character(*), optional, intent(in)  :: delimiter_end   !< Delimiter to which end the stream.
  logical,      optional, intent(in)  :: fast_read       !< Flag for activating efficient reading with one single read.
  integer(I4P), optional, intent(out) :: iostat          !< IO error.
  character(*), optional, intent(out) :: iomsg           !< IO error message.
  character(len=:), allocatable       :: stream          !< Output string containing the file data as a single stream.
  logical                             :: is_file         !< Flag for inquiring the presence of the file.
  integer(I4P)                        :: unit            !< Unit file.
  integer(I4P)                        :: iostatd         !< IO error.
  character(500)                      :: iomsgd          !< IO error message.
  character(1)                        :: c1              !< Single character.
  character(len=:), allocatable       :: string          !< Dummy string.
  logical                             :: cstart          !< Flag for stream capturing trigging.
  logical                             :: cend            !< Flag for stream capturing trigging.
  logical                             :: fast            !< Flag for activating efficient reading with one single read.
  integer(I4P)                        :: filesize        !< Size of the file for fast reading.

  fast = .false. ; if (present(fast_read)) fast = fast_read
  ! inquire file existance
  inquire(file=adjustl(trim(filename)), exist=is_file, iostat=iostatd, iomsg=iomsgd)
  if (.not.is_file) then
    if (present(iostat)) iostat = iostatd
    if (present(iomsg )) iomsg  = iomsgd
    return
  endif
  ! open file
  open(newunit=unit, file=adjustl(trim(filename)), access='STREAM', form='UNFORMATTED', iostat=iostatd, iomsg=iomsgd)
  if (iostatd/=0) then
    if (present(iostat)) iostat = iostatd
    if (present(iomsg )) iomsg  = iomsgd
    return
  endif
  ! loadg data
  stream = ''
  if (present(delimiter_start).and.present(delimiter_end)) then
    ! load only data inside delimiter_start and delimiter_end
    string = ''
    Main_Read_Loop: do
      read(unit=unit, iostat=iostatd, iomsg=iomsgd, end=10)c1
      if (c1==delimiter_start(1:1)) then
        cstart = .true.
        string = c1
        Start_Read_Loop: do while(len(string)<len(delimiter_start))
          read(unit=unit, iostat=iostatd, iomsg=iomsgd, end=10)c1
          string = string//c1
          if (.not.(index(string=delimiter_start, substring=string)>0)) then
            cstart = .false.
            exit Start_Read_Loop
          endif
        enddo Start_Read_Loop
        if (cstart) then
          cend = .false.
          stream = string
          do while(.not.cend)
            read(unit=unit, iostat=iostatd, iomsg=iomsgd, end=10)c1
            if (c1==delimiter_end(1:1)) then ! maybe the end
              string = c1
              End_Read_Loop: do while(len(string)<len(delimiter_end))
                read(unit=unit, iostat=iostatd, iomsg=iomsgd, end=10)c1
                string = string//c1
                if (.not.(index(string=delimiter_end, substring=string)>0)) then
                  stream = stream//string
                  exit End_Read_Loop
                elseif (len(string)==len(delimiter_end)) then
                  cend = .true.
                  stream = stream//string
                  exit Main_Read_Loop
                endif
              enddo End_Read_Loop
            else
              stream = stream//c1
            endif
          enddo
        endif
      endif
    enddo Main_Read_Loop
  else
    ! load all data
    if (fast) then
      ! load fast
      inquire(file=adjustl(trim(filename)), size=filesize, iostat=iostatd, iomsg=iomsgd)
      if (iostatd==0) then
        if (allocated(stream)) deallocate(stream)
        allocate(character(len=filesize):: stream)
        read(unit=unit, iostat=iostatd, iomsg=iomsgd, end=10)stream
      endif
    else
      ! load slow, one character loop
      Read_Loop: do
        read(unit=unit,iostat=iostatd,iomsg=iomsgd,end=10)c1
        stream = stream//c1
      enddo Read_Loop
    endif
  endif
  10 close(unit)
  if (present(iostat)) iostat = iostatd
  if (present(iomsg))  iomsg  = iomsgd
  endfunction load_file_as_stream