C++ (Cpp) print_iovec Examples

Example #1

int
main(void)
{
	const off_t offset = 0xdefaceddeadbeefLL;
	char *buf = tail_alloc(LEN);
	struct iovec *iov = tail_alloc(sizeof(*iov));
	iov->iov_base = buf;
	iov->iov_len = LEN;

	(void) close(0);
	if (open("/dev/zero", O_RDONLY))
		perror_msg_and_fail("open");

	if (preadv(0, iov, 1, offset) != LEN)
		perror_msg_and_fail("preadv");
	printf("preadv(0, ");
	print_iovec(iov, 1);
	printf(", 1, %lld) = %u\n", (long long) offset, LEN);

	if (preadv(0, iov, 1, -1) != -1)
		perror_msg_and_fail("preadv");
	printf("preadv(0, [{iov_base=%p, iov_len=%zu}], 1, -1) = "
	       "-1 EINVAL (%m)\n", iov->iov_base, iov->iov_len);

	if (preadv(0, NULL, 1, -2) != -1)
		perror_msg_and_fail("preadv");
	printf("preadv(0, NULL, 1, -2) = -1 EINVAL (%m)\n");

	if (preadv(0, iov, 0, -3) != -1)
		perror_msg_and_fail("preadv");
	printf("preadv(0, [], 0, -3) = -1 EINVAL (%m)\n");

	static const char tmp[] = "preadv-tmpfile";
	int fd = open(tmp, O_RDWR | O_CREAT | O_TRUNC, 0600);
	if (fd < 0)
		perror_msg_and_fail("open");
	if (unlink(tmp))
		perror_msg_and_fail("unlink");

	static const char w[] = "0123456789abcde";
	if (write(fd, w, LENGTH_OF(w)) != LENGTH_OF(w))
		perror_msg_and_fail("write");

	static const char r0_c[] = "01234567";
	static const char r1_c[] = "89abcde";

	const unsigned int r_len = (LENGTH_OF(w) + 1) / 2;
	void *r0 = tail_alloc(r_len);
	const struct iovec r0_iov_[] = {
		{
			.iov_base = r0,
			.iov_len = r_len
		}
	};

Example #2

File: pwritev.c Project: tuxtobin/strace

int
main(void)
{
	(void) close(0);
	if (open("/dev/null", O_WRONLY))
		perror_msg_and_fail("open");

	char *buf = tail_alloc(LEN);
	unsigned i;
	for (i = 0; i < LEN; ++i)
		buf[i] = i;

	struct iovec *iov = tail_alloc(sizeof(*iov) * LEN);
	for (i = 0; i < LEN; ++i) {
		buf[i] = i;
		iov[i].iov_base = &buf[i];
		iov[i].iov_len = LEN - i;
	}

	const off_t offset = 0xdefaceddeadbeefLL;
	long rc;
	int written = 0;
	for (i = 0; i < LEN; ++i) {
		written += iov[i].iov_len;
		if (pwritev(0, iov, i + 1, offset + i) != written)
			perror_msg_and_fail("pwritev");
		fputs("pwritev(0, ", stdout);
		print_iovec(iov, i + 1, LEN);
		printf(", %u, %lld) = %d\n",
		       i + 1, (long long) offset + i, written);
	}

	for (i = 0; i <= LEN; ++i) {
		unsigned int n = LEN + 1 - i;
		fputs("pwritev(0, ", stdout);
		print_iovec(iov + i, n, LEN - i);
		rc = pwritev(0, iov + i, n, offset + LEN + i);
		printf(", %u, %lld) = %ld %s (%m)\n",
		       n, (long long) offset + LEN + i, rc, errno2name());
	}

	iov->iov_base = iov + LEN * 2;
	rc = pwritev(0, iov, 1, -1);
	printf("pwritev(0, [{%p, %d}], 1, -1) = %ld %s (%m)\n",
	       iov->iov_base, LEN, rc, errno2name());

	iov += LEN;
	rc = pwritev(0, iov, 42, -2);
	printf("pwritev(0, %p, 42, -2) = %ld %s (%m)\n",
	       iov, rc, errno2name());

	rc = pwritev(0, NULL, 1, -3);
	printf("pwritev(0, NULL, 1, -3) = %ld %s (%m)\n",
	       rc, errno2name());

	rc = pwritev(0, iov, 0, -4);
	printf("pwritev(0, [], 0, -4) = %ld %s (%m)\n",
	       rc, errno2name());

	puts("+++ exited with 0 +++");
	return 0;
}