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 fd = -1;
  20 static struct {
  21         int     pid;
  22         int     fd;
  23 } fds[64];
  24
  25 vlong
  26 nsec(void)
  27 {
  28         uchar b[8];
  29         vlong t;
  30         int pid, i, f, tries;
  31
  32         /*
  33          * Threaded programs may have multiple procs
  34          * with different fd tables, so we may need to open
  35          * /dev/bintime on a per-pid basis
  36          */
  37
  38         /* First, look if we've opened it for this particular pid */
  39         pid = _tos->pid;
  40         do{
  41                 f = -1;
  42                 for(i = 0; i < nelem(fds); i++)
  43                         if(fds[i].pid == pid){
  44                                 f = fds[i].fd;
  45                                 break;
  46                         }
  47                 tries = 0;
  48                 if(f < 0){
  49                         /* If it's not open for this pid, try the global pid */
  50                         if(fd >= 0)
  51                                 f = fd;
  52                         else{
  53                                 /* must open */
  54                                 if((f = open("/dev/bintime", OREAD|OCEXEC)) < 0)
  55                                         return 0;
  56                                 fd = f;
  57                                 for(i = 0; i < nelem(fds); i++)
  58                                         if(fds[i].pid == pid || fds[i].pid == 0){
  59                                                 fds[i].pid = pid;
  60                                                 fds[i].fd = f;
  61                                                 break;
  62                                         }
  63                         }
  64                 }
  65                 if(pread(f, b, sizeof b, 0) == sizeof b){
  66                         be2vlong(&t, b);
  67                         return t;
  68                 }
  69                 close(f);
  70                 if(i < nelem(fds))
  71                         fds[i].fd = -1;
  72         }while(tries++ == 0);   /* retry once */
  73         USED(tries);
  74         return 0;
  75 }