1/* Get frequency of the system processor. i386/Linux version.
2 Copyright (C) 2000-2016 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#include <libc-internal.h>
24
25
26hp_timing_t
27__get_clockfreq (void)
28{
29 /* We read the information from the /proc filesystem. It contains at
30 least one line like
31 cpu MHz : 497.840237
32 or also
33 cpu MHz : 497.841
34 We search for this line and convert the number in an integer. */
35 static hp_timing_t result;
36 int fd;
37
38 /* If this function was called before, we know the result. */
39 if (result != 0)
40 return result;
41
42 fd = __open ("/proc/cpuinfo", O_RDONLY);
43 if (__glibc_likely (fd != -1))
44 {
45 /* XXX AFAIK the /proc filesystem can generate "files" only up
46 to a size of 4096 bytes. */
47 char buf[4096];
48 ssize_t n;
49
50 n = __read (fd, buf, sizeof buf);
51 if (__builtin_expect (n, 1) > 0)
52 {
53 char *mhz = memmem (buf, n, "cpu MHz", 7);
54
55 if (__glibc_likely (mhz != NULL))
56 {
57 char *endp = buf + n;
58 int seen_decpoint = 0;
59 int ndigits = 0;
60
61 /* Search for the beginning of the string. */
62 while (mhz < endp && (*mhz < '0' || *mhz > '9') && *mhz != '\n')
63 ++mhz;
64
65 while (mhz < endp && *mhz != '\n')
66 {
67 if (*mhz >= '0' && *mhz <= '9')
68 {
69 result *= 10;
70 result += *mhz - '0';
71 if (seen_decpoint)
72 ++ndigits;
73 }
74 else if (*mhz == '.')
75 seen_decpoint = 1;
76
77 ++mhz;
78 }
79
80 /* Compensate for missing digits at the end. */
81 while (ndigits++ < 6)
82 result *= 10;
83 }
84 }
85
86 __close (fd);
87 }
88
89 return result;
90}
91