#include <stdio.h>
#include <stdlib.h>
#include <errno.h>
#include <unistd.h>
#include <fcntl.h>
#include <string.h>

#define GPIO_DIR_IN	1
#define GPIO_DIR_OUT	0

int gpio_export(unsigned gpio)
{
 	int fd, len;
 	char buf[11];

 	fd = open("/sys/class/gpio/export", O_WRONLY);
 	if (fd < 0) {
 		perror("gpio/export");
 		return fd;
 	}

 	len = snprintf(buf, sizeof(buf), "%d", gpio);
 	write(fd, buf, len);
 	close(fd);

	return 0;
}

int gpio_unexport(unsigned gpio)
{
 	int fd, len;
 	char buf[11];

 	fd = open("/sys/class/gpio/unexport", O_WRONLY);
 	if (fd < 0) {
 		perror("gpio/export");
 		return fd;
	}

 	len = snprintf(buf, sizeof(buf), "%d", gpio);
 	write(fd, buf, len);
 	close(fd);
 	return 0;
}

int gpio_dir(unsigned gpio, unsigned dir)
{
	int fd, len;
	char buf[60];

	len = snprintf(buf, sizeof(buf), "/sys/class/gpio/gpio%d/direction", gpio);

	fd = open(buf, O_WRONLY);
	if (fd < 0) {
		perror("gpio/direction");
		return fd;
	}

	if (dir == GPIO_DIR_OUT)
 		write(fd, "out", 4);
	else
		write(fd, "in", 3);

	close(fd);
	return 0;
}

int gpio_dir_out(unsigned gpio)
{
	return gpio_dir(gpio, GPIO_DIR_OUT);
}

int gpio_dir_in(unsigned gpio)
{
	return gpio_dir(gpio, GPIO_DIR_IN);
}

int set_gpio_value(unsigned gpio, unsigned value)
{
 	int fd, len;
	char buf[60];

	len = snprintf(buf, sizeof(buf), "/sys/class/gpio/gpio%d/value", gpio);

	fd = open(buf, O_WRONLY);
	if (fd < 0) {
		perror("gpio/value");
		return fd;
	}

	if (value)
		write(fd, "1", 2);
	else
		write(fd, "0", 2);

	close(fd);
	return 0;
}

int get_gpio_value(unsigned gpio)
{
	FILE *fp;
	int c, d, len;
	char buf[60];
	len = snprintf(buf, sizeof(buf), "/sys/class/gpio/gpio%d/value", gpio);
	//fp = fopen("/sys/class/gpio/gpio54/value", "r");
	fp = fopen(buf, "r");
	while((c = fgetc(fp)) != EOF){
		if (c == '0'){
			d = 0;
		}
		if (c == '1'){
			d = 1;
		}
	}
	fclose(fp);
	return d;
}