Next: Matrices and Arrays in Oct-Files, Up: Oct-Files [Contents][Index]
Oct-files are pieces of C++ code that have been compiled with the Octave API into a dynamically loadable object. They take their name from the file which contains the object which has the extension .oct.
Finding a C++ compiler, using the correct switches, adding the right include
paths for header files, etc. is a difficult task. Octave automates this by
providing the mkoctfile command with which to build oct-files. The
command is available from within Octave or at the shell command line.
The mkoctfile function compiles source code written in C, C++, or
Fortran. Depending on the options used with mkoctfile, the
compiled code can be called within Octave or can be used as a stand-alone
application.
mkoctfile can be called from the shell prompt or from the Octave
prompt. Calling it from the Octave prompt simply delegates the call to
the shell prompt. The output is stored in the output variable and
the exit status in the status variable.
mkoctfile accepts the following options, all of which are optional
except for the file name of the code you wish to compile:
Add the include directory DIR to compile commands.
Add the definition DEF to the compiler call.
Add the library LIB to the link command.
Add the library directory DIR to the link command.
Generate dependency files (.d) for C and C++ source files.
Add the run-time path to the link command.
Pass flags though the linker like "-Wl,-rpath=…". The quotes are needed since commas are interpreted as command separators.
Pass flags though the compiler like "-Wa,OPTION".
Compile but do not link.
Enable debugging options for compilers.
Output file name. Default extension is .oct (or .mex if ‘--mex’ is specified) unless linking a stand-alone executable.
Print the configuration variable VAR. Recognized variables are:
ALL_CFLAGS INCFLAGS ALL_CXXFLAGS INCLUDEDIR ALL_FFLAGS LAPACK_LIBS ALL_LDFLAGS LD_CXX AR LDFLAGS BLAS_LIBS LD_STATIC_FLAG CC LFLAGS CFLAGS LIBDIR CPICFLAG LIBOCTAVE CPPFLAGS LIBOCTINTERP CXX LIBS CXXFLAGS OCTAVE_HOME CXXPICFLAG OCTAVE_LIBS DEPEND_EXTRA_SED_PATTERN OCTAVE_LINK_DEPS DEPEND_FLAGS OCTAVE_LINK_OPTS DL_LD OCTAVE_PREFIX DL_LDFLAGS OCTINCLUDEDIR F77 OCTLIBDIR F77_INTEGER8_FLAG OCT_LINK_DEPS FFLAGS OCT_LINK_OPTS FFTW3F_LDFLAGS RANLIB FFTW3F_LIBS RDYNAMIC_FLAG FFTW3_LDFLAGS READLINE_LIBS FFTW3_LIBS SED FFTW_LIBS SPECIAL_MATH_LIB FLIBS XTRA_CFLAGS FPICFLAG XTRA_CXXFLAGS
Link a stand-alone executable file.
Assume we are creating a MEX file. Set the default output extension to ".mex".
Strip the output file.
Echo commands as they are executed.
The file to compile or link. Recognized file types are
.c C source .cc C++ source .C C++ source .cpp C++ source .f Fortran source (fixed form) .F Fortran source (fixed form) .f90 Fortran source (free form) .F90 Fortran source (free form) .o object file .a library file
Consider the following short example which introduces the basics of writing a C++ function that can be linked to Octave.
#include <octave/oct.h>
DEFUN_DLD (helloworld, args, nargout,
"Hello World Help String")
{
int nargin = args.length ();
octave_stdout << "Hello World has "
<< nargin << " input arguments and "
<< nargout << " output arguments.\n";
return octave_value_list ();
}
The first critical line is #include <octave/oct.h> which
makes available most of the definitions necessary for a C++ oct-file.
Note that octave/oct.h is a C++ header and cannot be directly
#include’ed in a C source file, nor any other language.
Included by oct.h is a definition for the macro
DEFUN_DLD which creates a dynamically loaded function. This
macro takes four arguments:
octave_value_list,
The return type of functions defined with DEFUN_DLD is always
octave_value_list.
There are a couple of important considerations in the choice of function
name. First, it must be a valid Octave function name and so must be a
sequence of letters, digits, and underscores not starting with a
digit. Second, as Octave uses the function name to define the filename
it attempts to find the function in, the function name in the
DEFUN_DLD macro must match the filename of the oct-file. Therefore,
the above function should be in a file helloworld.cc, and would be
compiled to an oct-file using the command
mkoctfile helloworld.cc
This will create a file called helloworld.oct that is the compiled
version of the function. It should be noted that it is perfectly
acceptable to have more than one DEFUN_DLD function in a source
file. However, there must either be a symbolic link to the oct-file for
each of the functions defined in the source code with the DEFUN_DLD
macro or the autoload (Function Files) function should be used.
The rest of the function shows how to find the number of input arguments, how to print through the Octave pager, and return from the function. After compiling this function as above, an example of its use is
helloworld (1, 2, 3) -| Hello World has 3 input arguments and 0 output arguments.
Subsequent sections show how to use specific classes from Octave’s core internals. Base classes like dMatrix (a matrix of double values) are found in the directory liboctave/array. The definitive reference for how to use a particular class is the header file itself. However, it is often enough just to study the examples in the manual in order to be able to use the class.
Next: Matrices and Arrays in Oct-Files, Up: Oct-Files [Contents][Index]