cannam@167: Previous: Wisdom String Export/Import from Fortran, Up: Accessing the wisdom API from Fortran [Contents][Index]
cannam@167:The most generic wisdom export/import functions allow you to provide
cannam@167: an arbitrary callback function to read/write one character at a time
cannam@167: in any way you want. However, your callback function must be written
cannam@167: in a special way, using the bind(C) attribute to be passed to a
cannam@167: C interface.
cannam@167:
In particular, to call the generic wisdom export function
cannam@167: fftw_export_wisdom, you would write a callback subroutine of the form:
cannam@167:
subroutine my_write_char(c, p) bind(C) cannam@167: use, intrinsic :: iso_c_binding cannam@167: character(C_CHAR), value :: c cannam@167: type(C_PTR), value :: p cannam@167: ...write c... cannam@167: end subroutine my_write_char cannam@167:
Given such a subroutine (along with the corresponding interface definition), you could then export wisdom using: cannam@167:
cannam@167: cannam@167:call fftw_export_wisdom(c_funloc(my_write_char), p) cannam@167:
The standard c_funloc intrinsic converts a Fortran
cannam@167: bind(C) subroutine into a C function pointer. The parameter
cannam@167: p is a type(C_PTR) to any arbitrary data that you want
cannam@167: to pass to my_write_char (or C_NULL_PTR if none). (Note
cannam@167: that you can get a C pointer to Fortran data using the intrinsic
cannam@167: c_loc, and convert it back to a Fortran pointer in
cannam@167: my_write_char using c_f_pointer.)
cannam@167:
Similarly, to use the generic fftw_import_wisdom, you would
cannam@167: define a callback function of the form:
cannam@167:
integer(C_INT) function my_read_char(p) bind(C) cannam@167: use, intrinsic :: iso_c_binding cannam@167: type(C_PTR), value :: p cannam@167: character :: c cannam@167: ...read a character c... cannam@167: my_read_char = ichar(c, C_INT) cannam@167: end function my_read_char cannam@167: cannam@167: .... cannam@167: cannam@167: integer(C_INT) :: ret cannam@167: ret = fftw_import_wisdom(c_funloc(my_read_char), p) cannam@167: if (ret .eq. 0) stop 'error importing wisdom' cannam@167:
Your function can return -1 if the end of the input is reached.
cannam@167: Again, p is an arbitrary type(C_PTR that is passed
cannam@167: through to your function. fftw_import_wisdom returns 0
cannam@167: if an error occurred and nonzero otherwise.
cannam@167:
cannam@167: Previous: Wisdom String Export/Import from Fortran, Up: Accessing the wisdom API from Fortran [Contents][Index]
cannam@167: