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6689a188 | 1 | /* Get frequency of the system processor. i386/Linux version. |
f7a9f785 | 2 | Copyright (C) 2000-2016 Free Software Foundation, Inc. |
6689a188 UD |
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 | |
41bdb6e2 AJ |
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. | |
6689a188 UD |
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 | |
41bdb6e2 | 13 | Lesser General Public License for more details. |
6689a188 | 14 | |
41bdb6e2 | 15 | You should have received a copy of the GNU Lesser General Public |
59ba27a6 PE |
16 | License along with the GNU C Library; if not, see |
17 | <http://www.gnu.org/licenses/>. */ | |
6689a188 UD |
18 | |
19 | #include <ctype.h> | |
20 | #include <fcntl.h> | |
4a199526 | 21 | #include <string.h> |
6689a188 | 22 | #include <unistd.h> |
66539a73 | 23 | #include <libc-internal.h> |
6689a188 UD |
24 | |
25 | ||
3b5c1b57 | 26 | hp_timing_t |
6689a188 UD |
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 | |
01608292 UD |
32 | or also |
33 | cpu MHz : 497.841 | |
6689a188 | 34 | We search for this line and convert the number in an integer. */ |
3b5c1b57 | 35 | static hp_timing_t result; |
6689a188 UD |
36 | int fd; |
37 | ||
e7c036b3 UD |
38 | /* If this function was called before, we know the result. */ |
39 | if (result != 0) | |
40 | return result; | |
41 | ||
6e6249d0 | 42 | fd = __open ("/proc/cpuinfo", O_RDONLY); |
a1ffb40e | 43 | if (__glibc_likely (fd != -1)) |
6689a188 UD |
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 | ||
6e6249d0 | 50 | n = __read (fd, buf, sizeof buf); |
6689a188 UD |
51 | if (__builtin_expect (n, 1) > 0) |
52 | { | |
53 | char *mhz = memmem (buf, n, "cpu MHz", 7); | |
54 | ||
a1ffb40e | 55 | if (__glibc_likely (mhz != NULL)) |
6689a188 UD |
56 | { |
57 | char *endp = buf + n; | |
01608292 UD |
58 | int seen_decpoint = 0; |
59 | int ndigits = 0; | |
6689a188 UD |
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'; | |
01608292 UD |
71 | if (seen_decpoint) |
72 | ++ndigits; | |
6689a188 | 73 | } |
01608292 UD |
74 | else if (*mhz == '.') |
75 | seen_decpoint = 1; | |
6689a188 UD |
76 | |
77 | ++mhz; | |
78 | } | |
01608292 UD |
79 | |
80 | /* Compensate for missing digits at the end. */ | |
81 | while (ndigits++ < 6) | |
82 | result *= 10; | |
6689a188 UD |
83 | } |
84 | } | |
85 | ||
6e6249d0 | 86 | __close (fd); |
6689a188 UD |
87 | } |
88 | ||
89 | return result; | |
90 | } |