ref: 4e4f2aca32c3409a5fca3341dccd14318c18f9b1
dir: /sys/src/libc/9sys/nsec.c/
#include <u.h> #include <libc.h> #include <tos.h> static uvlong order = 0x0001020304050607ULL; static void be2vlong(vlong *to, uchar *f) { uchar *t, *o; int i; t = (uchar*)to; o = (uchar*)ℴ for(i = 0; i < sizeof order; i++) t[o[i]] = f[i]; } static int stillopen(int fd, char *name) { char buf[64]; return fd >= 0 && fd2path(fd, buf, sizeof(buf)) == 0 && strcmp(buf, name) == 0; } vlong nsec(void) { static char name[] = "/dev/bintime"; static int *pidp = nil, *fdp = nil, fd = -1; uchar b[8]; vlong t; int f; if(pidp != nil && *pidp == _tos->pid) f = *fdp; else{ Reopen: f = fd; if(fdp != nil && *fdp != f && stillopen(*fdp, name)) f = *fdp; else if(!stillopen(f, name)){ if((f = open(name, OREAD|OCEXEC)) < 0) return 0; } fd = f; if(fdp == nil){ fdp = (int*)privalloc(); pidp = (int*)privalloc(); } *fdp = f; *pidp = _tos->pid; } if(pread(f, b, sizeof b, 0) != sizeof b){ if(!stillopen(f, name)) goto Reopen; close(f); return 0; } be2vlong(&t, b); return t; }