sys/src/libc/9sys/nsec.c

   1 #include <u.h>
   2 #include <libc.h>
   3 #include <tos.h>
   4
   5 static uvlong order = 0x0001020304050607ULL;
   6
   7 static void
   8 be2vlong(vlong *to, uchar *f)
   9 {
  10         uchar *t, *o;
  11         int i;
  12
  13         t = (uchar*)to;
  14         o = (uchar*)&order;
  15         for(i = 0; i < sizeof order; i++)
  16                 t[o[i]] = f[i];
  17 }
  18
  19 static int
  20 stillopen(int fd, char *name)
  21 {
  22         char buf[64];
  23
  24         return fd >= 0 && fd2path(fd, buf, sizeof(buf)) == 0 && strcmp(buf, name) == 0;
  25 }
  26
  27 vlong
  28 nsec(void)
  29 {
  30         static char name[] = "/dev/bintime";
  31         static int *pidp = nil, *fdp = nil, fd = -1;
  32         uchar b[8];
  33         vlong t;
  34         int f;
  35
  36         if(pidp != nil && *pidp == _tos->pid)
  37                 f = *fdp;
  38         else{
  39 Reopen:
  40                 f = fd;
  41                 if(fdp != nil && *fdp != f && stillopen(*fdp, name))
  42                         f = *fdp;
  43                 else if(!stillopen(f, name)){
  44                         if((f = open(name, OREAD|OCEXEC)) < 0)
  45                                 return 0;
  46                 }
  47                 fd = f;
  48                 if(fdp == nil){
  49                         fdp = (int*)privalloc();
  50                         pidp = (int*)privalloc();
  51                 }
  52                 *fdp = f;
  53                 *pidp = _tos->pid;
  54         }
  55         if(pread(f, b, sizeof b, 0) != sizeof b){
  56                 if(!stillopen(f, name))
  57                         goto Reopen;
  58                 close(f);
  59                 return 0;
  60         }
  61         be2vlong(&t, b);
  62         return t;
  63 }