#include <stdio.h>
#include <fcntl.h>
#include <string.h>
#include <stdlib.h>
#include <dirent.h>
#include <unistd.h>
#include <err.h>
#include "liburing.h"

#define CHECK_NEGERR(_expr) \
	({ typeof(_expr) _ret = (_expr); if (_ret < 0) { errno = -_ret; err(1, #_expr); } _ret; })
#define CHECK_NULL(_expr) \
	({ typeof(_expr) _ret = (_expr); if (_ret == NULL) { errx(1, #_expr " returned NULL"); } _ret; })

ssize_t readfile_uring(struct io_uring *ring, int slot,
		       const char *path, char *buf, size_t size)
{
	struct io_uring_sqe *sqe;
	struct io_uring_cqe *cqe;
	int ret, i;
	unsigned int sum = 0;

	for (i = 0; path[i]; i++)
		sum += path[i];

	sqe = io_uring_get_sqe(ring);
	io_uring_prep_openat_direct(sqe, AT_FDCWD, path, O_RDONLY, 0, slot);
	sqe->flags = IOSQE_IO_LINK | IOSQE_CQE_SKIP_SUCCESS;
	sqe->user_data = 0xdead0000 + sum;

	sqe = io_uring_get_sqe(ring);
	io_uring_prep_read(sqe, slot, buf, size, 0);
	sqe->flags = IOSQE_FIXED_FILE;
	sqe->user_data = 0xfeed0000 + sum;

	ret = CHECK_NEGERR(io_uring_submit_and_wait(ring, 1));
	if (ret < 2)
		warnx("short submit count: %i", ret);

	ret = CHECK_NEGERR(io_uring_wait_cqe(ring, &cqe));

	if ((cqe->user_data & 0xffff) != sum)
		warnx("wrong sum: %x (should be %x)",(unsigned int) cqe->user_data, sum);
	if (cqe->res >= 0 && (cqe->user_data & 0xffff0000) != 0xfeed0000)
		warnx("not skipped: %x", (unsigned int) cqe->user_data);

	ret = cqe->res;
	io_uring_cqe_seen(ring, cqe);
	if (ret < 0) {
		errno = -ret;
		warn("failed to open or read %s", path);
	}

	return ret;
}

static ssize_t readfile_plain(const char *path, char *buf, size_t size)
{
	int fd;
	ssize_t ret;

	fd = open(path, O_RDONLY);
	if (fd == -1)
		return -errno;

	ret = read(fd, buf, size);
	if (ret == -1)
		return -errno;

	close(fd);

	return ret;
}

int main(void)
{
	int fds[] = { -1, -1 };
	struct io_uring ring;
	char *name, path[4096], buf1[4096], buf2[4096];
	DIR *dp;
	struct dirent *de;
	ssize_t ret1, ret2;
	int slot = 0;
	unsigned int numslots = sizeof(fds)/sizeof(fds[0]);

	CHECK_NEGERR(io_uring_queue_init(32, &ring, 0));
	CHECK_NEGERR(io_uring_register_files(&ring, fds, numslots));

	dp = CHECK_NULL(opendir("/proc"));
	while ((de = readdir(dp))) {
		name = de->d_name;
		if (name[0] > '0' && name[0] <= '9') {
			sprintf(path, "/proc/%s/stat", name);
			ret1 = readfile_uring(&ring, slot, path, buf1, sizeof(buf1));
			ret2 = readfile_plain(path, buf2, sizeof(buf2));
			if (ret1 != ret2)
				warnx("%s: read size mismatch %zi/%zi",
				      path, ret1, ret2);
			else if (ret1 > 0 && memcmp(buf1, buf2, ret1))
				warnx("%s: data mismatch", path);
			else {
				warnx("%s: ok (%zi)", path, ret1);
			}

			slot = (slot + 1) % numslots;
		}
	}
	closedir(dp);
	return 0;
}