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/* Get frequency of the system processor. i386/Linux version.
Copyright (C) 2000-2017 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>
hp_timing_t
__get_clockfreq (void)
{
/* We read the information from the /proc filesystem. It contains at
least one line like
cpu MHz : 497.840237
or also
cpu MHz : 497.841
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 (__glibc_likely (fd != -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, "cpu MHz", 7);
if (__glibc_likely (mhz != NULL))
{
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;
}
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