path: root/proc.c

/* See LICENSE file for copyright and license details. */
#include "common.h"


size_t
getnproc(size_t default_count)
{
	char buf[128];
	int fd, num = 0;
	size_t n = 0, off = 0, len = 0;
	size_t nums[] = {0, 0};
	ssize_t r;
	size_t last = 0;

	fd = open("/sys/devices/system/cpu/online", O_RDONLY);
	if (fd < 0)
		return default_count;

	for (;; off++) {
		if (off == len) {
			r = read(fd, buf, sizeof(buf));
			if (r <= 0) {
				if (!r)
					break;
				if (errno == EINTR)
					continue;
			error:
				n = default_count;
				goto out;
			}
			len = (size_t)r;
			off = 0;
		}

		if (buf[off] == '-') {
			if (num++ == 1)
				goto error;
		} else if (buf[off] == ',' || buf[off] == '\n') {
			if (num == 0) {
				nums[1] = nums[0];
			} else {
				num = 0;
				if (nums[1] < nums[0])
					goto error;
			}
			if (nums[0] < last)
				goto error;
			last = nums[0];
			if (nums[1] - nums[0] + 1U > SIZE_MAX - n)
				goto error;
			n += nums[1] - nums[0] + 1U;
		} else if (isdigit(buf[off])) {
			if (nums[num] > (SIZE_MAX - (size_t)(buf[off] & 15)) / 10U)
				goto error;
			nums[num] = nums[num] * 10U + (size_t)(buf[off] & 15);
		} else {
			goto error;
		}
	}

	n = n ? n : default_count;
out:
	close(fd);
	return n;
}


size_t
getautonthreads(void)
{
	size_t n = getnproc(8U);
	return n < 3U ? 1U : n - 2U;
}