gpio.h

#pragma once
#include "die.h"
#include <stdio.h>
#include <unistd.h>
#include <fcntl.h>


class Gpio {
	int fd = -1;
	char *path = NULL;

	Gpio() = delete;
	Gpio( Gpio const & ) = delete;

protected:
	Gpio( const char *name, int mode )
	{
		if( asprintf( &path, "/dev/gpio/%s/value", name ) < 0 ) {
			path = NULL;
			sysdie( "asprintf" );
		}
		fd = open( path, mode | O_CLOEXEC );
		if( fd < 0 )
			sysdie( "open %s", path );
	}

public:
	~Gpio()
	{
		if( fd >= 0 )
			close( fd );
		free( path );
	}

	operator bool () const
	{
		char c;
		auto res = pread( fd, &c, 1, 0 );
		if( res < 0 )
			sysdie( "pread %s", path );
		if( res == 0 )
			die( "pread %s: no data", path );
		return c & 1;
	}
};


class GpIn : public Gpio {
	GpIn( const char *name ) : Gpio( name, O_RDONLY ) {}
};

class GpOut : public Gpio {

	GpOut( const char *name ) : Gpio( name, O_RDWR ) {}

	bool operator = ( bool value ) &
	{
		char c = '0' + value;
		auto res = pwrite( fd, &c, 1, 0 );
		if( res < 0 )
			sysdie( "pwrite %s", path );
		return value;
	}
};