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 | |
26 | hp_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 | |