Fortran: Difference between revisions
Jump to navigation
Jump to search
m (→C++ function: Fix syntax highlight.) |
(→C++ function: Use file template.) |
||
| Line 8: | Line 8: | ||
=== C++ function === | === C++ function === | ||
{{ | {{File|octave_file_io.cc|C++ function to load a single matrix, stored in ASCII format, from a data file.|<syntaxhighlight lang="C++"> | ||
// Octave header | // Octave header | ||
#include <octave/oct.h> | #include <octave/oct.h> | ||
Revision as of 04:58, 13 July 2020
This page describes an example of how to call liboctave functions from a Fortran program. In the example we will load an Octave array from a file in Octave's native ASCII format, it consists of two steps:
- write a C++ function with a C compatible interface and C linkage that reads a variable from an Octave ASCII file
- write Fortran code using the "iso_c_binding" intrinsic module to call the C++ function
C++ function
File: octave_file_io.cc
C++ function to load a single matrix, stored in ASCII format, from a data file.Header file
| Code: octave_file_io.h: header file with C interface to octave_file_io.cc |
#ifndef OCTAVE_FILE_IO_H
#define OCTAVE_FILE_IO_H
#ifdef __cplusplus
extern "C" {
#endif
int octave_load (const char* filename, const char* varname, double** data, int* numel);
#ifdef __cplusplus
}
#endif
#endif
|
Fortran Code
| Code: octave_file_io_example.f90 |
program octave_file_io_example
use iso_c_binding
implicit none
interface
function octave_load (filename, varname, data, numel) bind(c, name="octave_load")
use iso_c_binding
implicit none
integer(c_int) :: octave_load
character(kind=c_char), intent(in) :: filename(*)
character(kind=c_char), intent(in) :: varname(*)
type(c_ptr), intent(out) :: data
integer(c_int), intent(out) :: numel
end function octave_load
end interface
integer(c_int) :: res
type(c_ptr) :: data
real(c_double), pointer :: fdata(:)
integer(c_int) :: numel
res = octave_load (c_char_'pippo.octxt' // c_null_char, c_char_'A' // c_null_char, data, numel)
call c_f_pointer (data, fdata, (/numel/))
write (*,*) fdata
end program octave_file_io_example
|
Compiling the code
mkoctfile -I. octave_file_io.cc mkoctfile -I. --mkoctfile --link-stand-alone octave_file_io_example.f90 octave_file_io.o -o octave_file_io_example