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glibc/ports/sysdeps/unix/sysv/linux/ia64/get_clockfreq.c
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/* Get frequency of the system processor. IA-64/Linux version. | |
Copyright (C) 2001-2012 Free Software Foundation, Inc. | |
This file is part of the GNU C Library. | |
The GNU C Library is free software; you can redistribute it and/or | |
modify it under the terms of the GNU Lesser General Public | |
License as published by the Free Software Foundation; either | |
version 2.1 of the License, or (at your option) any later version. | |
The GNU C Library is distributed in the hope that it will be useful, | |
but WITHOUT ANY WARRANTY; without even the implied warranty of | |
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU | |
Lesser General Public License for more details. | |
You should have received a copy of the GNU Lesser General Public | |
License along with the GNU C Library; if not, see | |
<http://www.gnu.org/licenses/>. */ | |
#include <ctype.h> | |
#include <fcntl.h> | |
#include <string.h> | |
#include <unistd.h> | |
#include <libc-internal.h> | |
hp_timing_t | |
__get_clockfreq (void) | |
{ | |
/* We read the information from the /proc filesystem. It contains at | |
least one line like | |
itc MHz : 733.390988 | |
We search for this line and convert the number in an integer. */ | |
static hp_timing_t result; | |
int fd; | |
/* If this function was called before, we know the result. */ | |
if (result != 0) | |
return result; | |
fd = __open ("/proc/cpuinfo", O_RDONLY); | |
if (__builtin_expect (fd != -1, 1)) | |
{ | |
/* XXX AFAIK the /proc filesystem can generate "files" only up | |
to a size of 4096 bytes. */ | |
char buf[4096]; | |
ssize_t n; | |
n = __read (fd, buf, sizeof buf); | |
if (__builtin_expect (n, 1) > 0) | |
{ | |
char *mhz = memmem (buf, n, "itc MHz", 7); | |
if (__builtin_expect (mhz != NULL, 1)) | |
{ | |
char *endp = buf + n; | |
int seen_decpoint = 0; | |
int ndigits = 0; | |
/* Search for the beginning of the string. */ | |
while (mhz < endp && (*mhz < '0' || *mhz > '9') && *mhz != '\n') | |
++mhz; | |
while (mhz < endp && *mhz != '\n') | |
{ | |
if (*mhz >= '0' && *mhz <= '9') | |
{ | |
result *= 10; | |
result += *mhz - '0'; | |
if (seen_decpoint) | |
++ndigits; | |
} | |
else if (*mhz == '.') | |
seen_decpoint = 1; | |
++mhz; | |
} | |
/* Compensate for missing digits at the end. */ | |
while (ndigits++ < 6) | |
result *= 10; | |
} | |
} | |
__close (fd); | |
} | |
return result; | |
} |