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91 lines
2.4 KiB
C
91 lines
2.4 KiB
C
/* Get frequency of the system processor. i386/Linux version.
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Copyright (C) 2000-2016 Free Software Foundation, Inc.
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This file is part of the GNU C Library.
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The GNU C Library is free software; you can redistribute it and/or
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modify it under the terms of the GNU Lesser General Public
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License as published by the Free Software Foundation; either
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version 2.1 of the License, or (at your option) any later version.
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The GNU C Library is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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Lesser General Public License for more details.
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You should have received a copy of the GNU Lesser General Public
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License along with the GNU C Library; if not, see
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<http://www.gnu.org/licenses/>. */
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#include <ctype.h>
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#include <fcntl.h>
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#include <string.h>
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#include <unistd.h>
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#include <libc-internal.h>
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hp_timing_t
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__get_clockfreq (void)
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{
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/* We read the information from the /proc filesystem. It contains at
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least one line like
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cpu MHz : 497.840237
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or also
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cpu MHz : 497.841
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We search for this line and convert the number in an integer. */
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static hp_timing_t result;
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int fd;
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/* If this function was called before, we know the result. */
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if (result != 0)
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return result;
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fd = __open ("/proc/cpuinfo", O_RDONLY);
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if (__glibc_likely (fd != -1))
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{
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/* XXX AFAIK the /proc filesystem can generate "files" only up
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to a size of 4096 bytes. */
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char buf[4096];
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ssize_t n;
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n = __read (fd, buf, sizeof buf);
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if (__builtin_expect (n, 1) > 0)
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{
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char *mhz = memmem (buf, n, "cpu MHz", 7);
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if (__glibc_likely (mhz != NULL))
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{
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char *endp = buf + n;
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int seen_decpoint = 0;
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int ndigits = 0;
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/* Search for the beginning of the string. */
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while (mhz < endp && (*mhz < '0' || *mhz > '9') && *mhz != '\n')
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++mhz;
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while (mhz < endp && *mhz != '\n')
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{
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if (*mhz >= '0' && *mhz <= '9')
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{
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result *= 10;
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result += *mhz - '0';
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if (seen_decpoint)
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++ndigits;
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}
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else if (*mhz == '.')
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seen_decpoint = 1;
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++mhz;
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}
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/* Compensate for missing digits at the end. */
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while (ndigits++ < 6)
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result *= 10;
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}
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}
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__close (fd);
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}
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return result;
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}
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