Editing Fortran
Jump to navigation
Jump to search
The edit can be undone. Please check the comparison below to verify that this is what you want to do, and then publish the changes below to finish undoing the edit.
Latest revision | Your text | ||
Line 1: | Line 1: | ||
This page describes an example of how to call liboctave functions from a Fortran program. | This page describes an example of how to call liboctave functions from a Fortran program. | ||
In the example we will load a | 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 === | ||
{{ | {{Code|octave_file_io.cc: C++ function to load a matrix from an ASCII file in Octave native format|<syntaxhighlight lang="C" style="font-size:13px"> | ||
#include <octave_file_io.h> | |||
#include <octave/oct.h> | #include <octave/oct.h> | ||
#include <octave/ls- | #include <octave/ov.h> | ||
#include <fstream> | |||
#include <ls-oct-ascii.h> | |||
#include <octave/octave.h> | |||
#include <octave/parse.h> | |||
#include <octave/toplev.h> | |||
#include <octave/load-save.h> | |||
#include <octave/oct-map.h> | |||
#include <cstring> | |||
int octave_load (const char* filename, const char* varname, double** data, int* numel) | |||
{ | |||
string_vector argv (1); | |||
load_save_format format = LS_ASCII; | |||
install_types (); | |||
argv(0) = varname; | |||
std::ios::openmode mode = std::ios::in | std::ios::binary; | |||
std::string fname (filename); | |||
std::ifstream file (fname.c_str (), mode); | |||
octave_scalar_map m = do_load (file, fname, format, oct_mach_info::flt_fmt_unknown, | |||
false, false, true, argv, 0, 1, 1).scalar_map_value (); | |||
file.close (); | |||
Array<double> M = m.contents (varname).array_value (); | |||
if (error_state) | |||
return -1; | |||
*data = (double*) malloc (M.numel () * sizeof (double)); | |||
*numel = | *numel = M.numel (); | ||
memcpy (*data, M.fortran_vec (), *numel * sizeof (double)); | |||
return 0; | |||
return 0; | |||
} | } | ||
</syntaxhighlight>}} | </syntaxhighlight>}} | ||
=== Header file === | === Header file === | ||
{{Code|octave_file_io.h: header file with C interface to octave_file_io.cc|<syntaxhighlight lang="C" style="font-size:13px"> | |||
#ifndef OCTAVE_FILE_IO_H | #ifndef OCTAVE_FILE_IO_H | ||
#define OCTAVE_FILE_IO_H | #define OCTAVE_FILE_IO_H | ||
Line 79: | Line 66: | ||
#endif | #endif | ||
int octave_load (const char* filename, double** data, int* numel); | int octave_load (const char* filename, const char* varname, double** data, int* numel); | ||
#ifdef __cplusplus | #ifdef __cplusplus | ||
Line 87: | Line 74: | ||
#endif | #endif | ||
</syntaxhighlight>}} | </syntaxhighlight>}} | ||
=== Fortran Code === | === Fortran Code === | ||
{{Code|octave_file_io.cc: C++ function to load a matrix from an ASCII file in Octave native format|<syntaxhighlight lang="fortran" style="font-size:13px"> | |||
program octave_file_io_example | program octave_file_io_example | ||
use iso_c_binding | use iso_c_binding | ||
implicit none | implicit none | ||
interface | interface | ||
function octave_load (filename, data, numel) bind(c, name="octave_load") | function octave_load (filename, varname, data, numel) bind(c, name="octave_load") | ||
use iso_c_binding | use iso_c_binding | ||
implicit none | implicit none | ||
integer(c_int) :: octave_load | integer(c_int) :: octave_load | ||
character(kind=c_char), intent(in) :: filename(*) | character(kind=c_char), intent(in) :: filename(*) | ||
character(kind=c_char), intent(in) :: varname(*) | |||
type(c_ptr), intent(out) :: data | type(c_ptr), intent(out) :: data | ||
integer(c_int), intent(out) :: numel | integer(c_int), intent(out) :: numel | ||
end function octave_load | end function octave_load | ||
end interface | end interface | ||
integer(c_int) :: res | integer(c_int) :: res | ||
type(c_ptr) :: data | type(c_ptr) :: data | ||
real(c_double), pointer :: fdata(:) | real(c_double), pointer :: fdata(:) | ||
integer(c_int) :: numel | integer(c_int) :: numel | ||
res = octave_load (c_char_' | 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/)) | call c_f_pointer (data, fdata, (/numel/)) | ||
write (*,*) fdata | write (*,*) fdata | ||
Line 129: | Line 116: | ||
</syntaxhighlight>}} | </syntaxhighlight>}} | ||
=== 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 |