channel_select.cpp File Reference

#include <algorithm>
#include <iostream>
#include <fstream>
#include <regex>
#include <string>
#include <stdint.h>
#include <sys/stat.h>
#include <unistd.h>

Include dependency graph for channel_select.cpp:

Go to the source code of this file.

Functions
template<typename... Args>
string	formatString (const string &format, Args... args)
	Simple string formatter template function. More...
bool	directoryExists (string dirPath)
	Whether or not a given directory exists or not. More...
bool	parseArgs (int32_t argC, char **argV)
	Parses command-line arguments passed to the application. More...
void	enableGpio ()
	Enables a given GPIO pin. More...
void	setGpio ()
	Sets a GPIO pin on/off, depending on the desired state. More...
void	showHelp ()
	Prints the help text. More...
int	main (int32_t argC, char **argV)

Variables
static uint32_t	g_channel = 0
	The selected channel to enable and/or toggle. More...
static bool	g_state = false
	The desired state for the channel (on/off) More...
static const uint32_t	CHANNELS [8]
	A simple array representing a map to the channels on the relay board, corresponding to the GPIO pings. More...

Function Documentation

directoryExists()

bool directoryExists

(

string

dirPath

)

Whether or not a given directory exists or not.

Determines whether or not a given directory exists.

Parameters

dirPath

The path to check.

Returns

true If the directory exists.

false Otherwise.

Definition at line 99 of file channel_select.cpp.

                                     {
    struct stat _stat;
    if (stat(dirPath.c_str(), &_stat) == 0 && S_ISDIR(_stat.st_mode)) {
        return true;
    }
    return false;
}

enableGpio()

void enableGpio

(

)

Enables a given GPIO pin.

Enables use of the desired GPIO pin.

Definition at line 142 of file channel_select.cpp.

                  {
    static const string GPIO_DIR_PATH = "/sys/class/gpio/gpio";
 
    const auto gpioPath = formatString("%s%d", GPIO_DIR_PATH.c_str(), g_channel);
 
    if (directoryExists(gpioPath)) return;
 
    // Make sure Linux exports the pin
    {
        std::ofstream fileStream("/sys/class/gpio/export", std::ios::trunc);
        fileStream << g_channel << endl;
    }
 
    // Set the GPIO direction
    {
        std::ofstream fileStream(formatString("%s/direction", gpioPath.c_str()), std::ios::trunc);
        fileStream << "out" << endl;
    }
}

References g_channel.

formatString()

template<typename... Args>

string formatString	(	const string &	format,
		Args...	args
	)

Simple string formatter template function.

Template Parameters

Args	The arguments to be formatted into the string

Parameters

format	The C-style format string
args	Varargs list of arguments

Returns

string The formatted string.

Definition at line 60 of file channel_select.cpp.

                                                         {
    auto stringSize = snprintf(NULL, 0, format.c_str(), args...) + 1; // +1 for \0
    std::unique_ptr<char[]> buffer(new char[stringSize]);
 
    snprintf(buffer.get(), stringSize, format.c_str(), args...);
 
    return string(buffer.get(), buffer.get() + stringSize - 1); // std::string handles termination for us.
}

main()

int main	(	int32_t	argC,
		char **	argV
	)

Definition at line 79 of file channel_select.cpp.

                                    {
 
    if (argC <= 2) {
        showHelp();
        return -1;
    }
 
    if (!parseArgs(argC, argV)) return -1;
 
    return 0;
}

References parseArgs(), and showHelp().

parseArgs()

bool parseArgs	(	int32_t	argC,
		char **	argV
	)

Parses command-line arguments passed to the application.

Parses arguments passed to the application and sets the required parameters accordingly.

Parameters

argC	The total arg count
argV	A pointer-pointer to the arg list

Returns

true If the application should stay alive

false Otherwise

Definition at line 116 of file channel_select.cpp.

                                          {
    const static regex CHANNEL_PATTERN(R"((ch)?[0-8])");
    const static regex STATE_PATTERN(R"(on|off|true|false)");
 
    for (int32_t i = 0; i < argC; i++) {
        string arg = argV[i];
 
        // Convert arg to lower
        transform(arg.begin(), arg.end(), arg.begin(), [&](const auto c) { return tolower(c); });
 
        if (regex_search(arg, CHANNEL_PATTERN)) {
            g_channel = std::stoi(arg.substr(arg.size() - 1, 1));
        } else if (regex_search(arg, STATE_PATTERN)) {
            g_state = (arg == "on" || arg == "true");
        } else {
            showHelp();
            return false;
        }
    }
 
    return true;
}

References g_channel, g_state, and showHelp().

Referenced by main().

setGpio()

void setGpio

(

)

Sets a GPIO pin on/off, depending on the desired state.

Sets the desired GPIO pin either on or off, depending on cmd-args.

Definition at line 165 of file channel_select.cpp.

               {
    static const string GPIO_DIR_PATH = "/sys/class/gpio/gpio";
 
    const auto gpioPath = formatString("%s%d/value", GPIO_DIR_PATH.c_str(), g_channel);
 
    std::ofstream fileStream(gpioPath, std::ios::trunc);
    fileStream << static_cast<int32_t>(g_state) << endl;
}

References g_channel, and g_state.

showHelp()

void showHelp

(

)

Prints the help text.

Prints the help text to the console.

Definition at line 177 of file channel_select.cpp.

                {
    cout << R"(
Usage:

Referenced by main(), and parseArgs().

Variable Documentation

CHANNELS

const uint32_t CHANNELS[8]

static

Initial value:

{
    5, 6, 13, 16, 19, 20, 21, 26
}

A simple array representing a map to the channels on the relay board, corresponding to the GPIO pings.

E.g.: CHANNELS[0] = channel 1 = GPIO5

Definition at line 45 of file channel_select.cpp.

g_channel

uint32_t g_channel = 0

static

The selected channel to enable and/or toggle.

Definition at line 36 of file channel_select.cpp.

Referenced by enableGpio(), parseArgs(), and setGpio().

g_state

bool g_state = false

static

The desired state for the channel (on/off)

Definition at line 37 of file channel_select.cpp.

Referenced by parseArgs(), and setGpio().