1/* SPDX-License-Identifier: GPL-2.0 */
 2/*
 3 * Copyright (c) 2024 Meta Platforms, Inc. and affiliates.
 4 * Copyright (c) 2024 David Vernet <dvernet@meta.com>
 5 */
 6#include <errno.h>
 7#include <fcntl.h>
 8#include <stdio.h>
 9#include <stdlib.h>
10#include <string.h>
11#include <unistd.h>
12
13/* Returns read len on success, or -errno on failure. */
14static ssize_t read_text(const char *path, char *buf, size_t max_len)
15{
16	ssize_t len;
17	int fd;
18
19	fd = open(path, O_RDONLY);
20	if (fd < 0)
21		return -errno;
22
23	len = read(fd, buf, max_len - 1);
24
25	if (len >= 0)
26		buf[len] = 0;
27
28	close(fd);
29	return len < 0 ? -errno : len;
30}
31
32/* Returns written len on success, or -errno on failure. */
33static ssize_t write_text(const char *path, char *buf, ssize_t len)
34{
35	int fd;
36	ssize_t written;
37
38	fd = open(path, O_WRONLY | O_APPEND);
39	if (fd < 0)
40		return -errno;
41
42	written = write(fd, buf, len);
43	close(fd);
44	return written < 0 ? -errno : written;
45}
46
47long file_read_long(const char *path)
48{
49	char buf[128];
50
51
52	if (read_text(path, buf, sizeof(buf)) <= 0)
53		return -1;
54
55	return atol(buf);
56}
57
58int file_write_long(const char *path, long val)
59{
60	char buf[64];
61	int ret;
62
63	ret = sprintf(buf, "%lu", val);
64	if (ret < 0)
65		return ret;
66
67	if (write_text(path, buf, sizeof(buf)) <= 0)
68		return -1;
69
70	return 0;
71}