Chris@19: Next: Wisdom Generic Export/Import from Fortran, Chris@19: Previous: Wisdom File Export/Import from Fortran, Chris@19: Up: Accessing the wisdom API from Fortran Chris@19:
Dealing with FFTW's C string export/import is a bit more painful. In
Chris@19: particular, the fftw_export_wisdom_to_string function requires
Chris@19: you to deal with a dynamically allocated C string. To get its length,
Chris@19: you must define an interface to the C strlen function, and to
Chris@19: deallocate it you must define an interface to C free:
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use, intrinsic :: iso_c_binding Chris@19: interface Chris@19: integer(C_INT) function strlen(s) bind(C, name='strlen') Chris@19: import Chris@19: type(C_PTR), value :: s Chris@19: end function strlen Chris@19: subroutine free(p) bind(C, name='free') Chris@19: import Chris@19: type(C_PTR), value :: p Chris@19: end subroutine free Chris@19: end interface Chris@19:Chris@19:
Given these definitions, you can then export wisdom to a Fortran Chris@19: character array: Chris@19: Chris@19:
character(C_CHAR), pointer :: s(:) Chris@19: integer(C_SIZE_T) :: slen Chris@19: type(C_PTR) :: p Chris@19: p = fftw_export_wisdom_to_string() Chris@19: if (.not. c_associated(p)) stop 'error exporting wisdom' Chris@19: slen = strlen(p) Chris@19: call c_f_pointer(p, s, [slen+1]) Chris@19: ... Chris@19: call free(p) Chris@19:Chris@19:
Chris@19: Note that slen is the length of the C string, but the length of
Chris@19: the array is slen+1 because it includes the terminating null
Chris@19: character. (You can omit the ‘+1’ if you don't want Fortran to
Chris@19: know about the null character.) The standard c_associated function
Chris@19: checks whether p is a null pointer, which is returned by
Chris@19: fftw_export_wisdom_to_string if there was an error.
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To import wisdom from a string, use
Chris@19: fftw_import_wisdom_from_string as usual; note that the argument
Chris@19: of this function must be a character(C_CHAR) that is terminated
Chris@19: by the C_NULL_CHAR character, like the s array above.
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