1/* Get frequency of the system processor. i386/Linux version.
2 Copyright (C) 2000-2019 Free Software Foundation, Inc.
3 This file is part of the GNU C Library.
4
5 The GNU C Library is free software; you can redistribute it and/or
6 modify it under the terms of the GNU Lesser General Public
7 License as published by the Free Software Foundation; either
8 version 2.1 of the License, or (at your option) any later version.
9
10 The GNU C Library is distributed in the hope that it will be useful,
11 but WITHOUT ANY WARRANTY; without even the implied warranty of
12 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
13 Lesser General Public License for more details.
14
15 You should have received a copy of the GNU Lesser General Public
16 License along with the GNU C Library; if not, see
17 <http://www.gnu.org/licenses/>. */
18
19#include <ctype.h>
20#include <fcntl.h>
21#include <string.h>
22#include <unistd.h>
23
24hp_timing_t
25__get_clockfreq (void)
26{
27 /* We read the information from the /proc filesystem. It contains at
28 least one line like
29 cpu MHz : 497.840237
30 or also
31 cpu MHz : 497.841
32 We search for this line and convert the number in an integer. */
33 static hp_timing_t result;
34 int fd;
35
36 /* If this function was called before, we know the result. */
37 if (result != 0)
38 return result;
39
40 fd = __open ("/proc/cpuinfo", O_RDONLY);
41 if (__glibc_likely (fd != -1))
42 {
43 /* XXX AFAIK the /proc filesystem can generate "files" only up
44 to a size of 4096 bytes. */
45 char buf[4096];
46 ssize_t n;
47
48 n = __read (fd, buf, sizeof buf);
49 if (__builtin_expect (n, 1) > 0)
50 {
51 char *mhz = memmem (buf, n, "cpu MHz", 7);
52
53 if (__glibc_likely (mhz != NULL))
54 {
55 char *endp = buf + n;
56 int seen_decpoint = 0;
57 int ndigits = 0;
58
59 /* Search for the beginning of the string. */
60 while (mhz < endp && (*mhz < '0' || *mhz > '9') && *mhz != '\n')
61 ++mhz;
62
63 while (mhz < endp && *mhz != '\n')
64 {
65 if (*mhz >= '0' && *mhz <= '9')
66 {
67 result *= 10;
68 result += *mhz - '0';
69 if (seen_decpoint)
70 ++ndigits;
71 }
72 else if (*mhz == '.')
73 seen_decpoint = 1;
74
75 ++mhz;
76 }
77
78 /* Compensate for missing digits at the end. */
79 while (ndigits++ < 6)
80 result *= 10;
81 }
82 }
83
84 __close (fd);
85 }
86
87 return result;
88}
89