Util

Class that implements the methods in /AP_HAL/utility.

Utility software is system software designed to help analyze, configure, optimize or maintain the system.

In the /AP_HAL/Util.h we find Util member for string utilities, a system clock, a state of safety controller... but also we through here everything that doesn't have an specific place within the system. New modules might end up being here.

This class is divided into two files, header (Util.h) and source (Util.cpp).

Util.h

Link to the code:Util.h

The Linux::LinuxUtil class inherits from AP_HAL::Util.

In the folder AP_HAL/utility we can find some utilities that are implemented in Util.h and Util.cpp.

#ifndef __AP_HAL_LINUX_UTIL_H__
#define __AP_HAL_LINUX_UTIL_H__

#include <AP_HAL.h>
#include "AP_HAL_Linux_Namespace.h"
...

• As usual imports AP_HAL.hand also AP_HAL_Linux_Namespace.h.

...
class Linux::LinuxUtil : public AP_HAL::Util {
public:
    void init(int argc, char * const *argv) {
        saved_argc = argc;
        saved_argv = argv;
    }

    bool run_debug_shell(AP_HAL::BetterStream *stream) { return false; }

    /**
       return commandline arguments, if available
     */
    void commandline_arguments(uint8_t &argc, char * const *&argv);

private:
    int saved_argc;
    char* const *saved_argv;
};

#endif // __AP_HAL_LINUX_UTIL_H__

• The Linux::LinuxUtilclass is defined as class of AP_HAL::Util.

• The run_debug_shell takes as argument an AP_HAL::BetterStream which is a pure virtual interface.BetterStream provided some implementations for AVR based on _vprintf().

• run a debug shell on the given stream if possible. This is used to support dropping into a debug shell to run firmware upgrade commands.

• The commandline_arguments returns commandline arguments, if available. This method should be implemented in Util.cpp.

Util.cpp

Util.cpp implements the methods defined in Util.h.

#include <AP_HAL.h>
#if CONFIG_HAL_BOARD == HAL_BOARD_LINUX
#include <stdio.h>
#include <stdarg.h>
#include <unistd.h>
#include <stdlib.h>
#include <errno.h>

extern const AP_HAL::HAL& hal;

#include "Util.h"
using namespace Linux;
...

• Includes AP_HAL.h and Util.h. Defines the board.

Some functions and libraries are included:

• Deal with Input and Output operations: manage files,read and write... - (stdio.h)

• This header defines macros to access the individual arguments of a list of unnamed arguments whose number and types are not known to the called function.- (stdarg)

• This header defines miscellaneous symbolic constants and types, and declares miscellaneous functions.It is provided by POSIX(Portable Operating System Interface-calls to the OS)-compatible systems.- (unistd.h)

• This header defines several general purpose functions, including dynamic memory management, random number generation, communication with the environment, integer arithmetics, searching, sorting and converting.- (stdlib.h)

• C Header that defines the following macro: errno->Last error number (macro ); plus at least three additional macro constants: EDOM, ERANGE and EILSEQ .errnodeals with errors (see errno for more details). - (errno.h)

...

/**
   return commandline arguments, if available
*/
void LinuxUtil::commandline_arguments(uint8_t &argc, char * const *&argv)
{
    argc = saved_argc;
    argv = saved_argv;
}

#endif // CONFIG_HAL_BOARD == HAL_BOARD_LINUX

• The commandline_arguments method is implemented.This method returns the commandline arguments in the variables: argc and argv passed by reference.