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[/] [openrisc/] [trunk/] [gnu-src/] [newlib-1.18.0/] [newlib/] [libc/] [sys/] [linux/] [machine/] [i386/] [get_clockfreq.c] - Blame information for rev 207

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Line No. Rev Author Line
1 207 jeremybenn
/* Get frequency of the system processor.  i386/Linux version.
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   Copyright (C) 2000, 2001 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, write to the Free
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   Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
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   02111-1307 USA.  */
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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 (__builtin_expect (fd != -1, 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 (__builtin_expect (mhz != NULL, 1))
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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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