#include <stdio.h>
#include <errno.h>
#include <sys/mman.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <unistd.h>
#include <fcntl.h>
#include <ctype.h>
#include <linux/fb.h>

static char filename[] = "/dev/fb0";
int main(int argc, char *argv[])
{
	struct fb_var_screeninfo screeninfo;
	int fd = -1;
	int rc;
	unsigned char *fbuf;
	struct stat buf;
	int row, column;
	int i;
	int len;

	printf("Starting..[%s]\n", filename);

	fd = open(filename, O_RDWR);
	if (fd <= 0) {
		printf("Could not open; err: %d\n", errno);
		return errno;
	}
	if (stat(filename, &buf) != 0) {
		printf("Could not open; err: %d\n", errno);
		return errno;
	}

	printf("%s: len:%d\n", filename, buf.st_size);
	rc = ioctl(fd, FBIOGET_VSCREENINFO, &screeninfo);
	if (rc) {
		printf("Could not do ioctl. err: %d\n", errno);
		return errno;
	}	
	printf("%s: bits/pixel%d\n", filename, screeninfo.bits_per_pixel);
	len = screeninfo.xres * screeninfo.yres;
	fbuf = mmap(0, len, PROT_WRITE|PROT_READ, MAP_SHARED, fd, 0);
	if (fbuf == MAP_FAILED) {
		printf("Could not map: error: %d\n", errno);
		return errno;
	}
        if (argc > 1) {
		int outfd;
		outfd = open(argv[1], O_RDWR|O_CREAT, 0644);
		if (outfd != -1) {
			write(outfd, fbuf, len);
			close(outfd);
		}
	}
	printf("(%lx): Writting .. [%d:%d]\n", fbuf, screeninfo.xres,screeninfo.yres);
	i = 0;
	for (i = 0; i < len; i++) {
		fbuf[i] = (i % 255);
	}
	printf("Done!\n");
	if (munmap(fbuf, len)) {
		printf("Could not unmap: %d\n", errno);
		return errno;
	}
	close(fd);
	return 0;
}