source: MondoRescue/branches/3.0/mindi-busybox/libbb/get_cpu_count.c@ 3085

/* vi: set sw=4 ts=4: */
/*
 * Factored out of mpstat/iostat.
 *
 * Copyright (C) 2010 Marek Polacek <mmpolacek@gmail.com>
 *
 * Licensed under GPLv2, see file LICENSE in this source tree.
 */
#include "libbb.h"

/* Does str start with "cpu"? */
int FAST_FUNC starts_with_cpu(const char *str)
{
    return ((str[0] - 'c') | (str[1] - 'p') | (str[2] - 'u')) == 0;
}

/*
 * Get number of processors. Uses /proc/stat.
 * Return value 0 means one CPU and non SMP kernel.
 * Otherwise N means N processor(s) and SMP kernel.
 */
unsigned FAST_FUNC get_cpu_count(void)
{
    FILE *fp;
    char line[256];
    int proc_nr = -1;

    fp = xfopen_for_read("/proc/stat");
    while (fgets(line, sizeof(line), fp)) {
        if (!starts_with_cpu(line)) {
            if (proc_nr >= 0)
                break; /* we are past "cpuN..." lines */
            continue;
        }
        if (line[3] != ' ') { /* "cpuN" */
            int num_proc;
            if (sscanf(line + 3, "%u", &num_proc) == 1
             && num_proc > proc_nr
            ) {
                proc_nr = num_proc;
            }
        }
    }

    fclose(fp);
    return proc_nr + 1;
}