ref: 9ca0eeaaed1dd8a9ced7e13a560d12fd9e7ac494
dir: /libc/nsec.c/
#include <u.h> #include <libc.h> static uvlong order = (uvlong) 0x0001020304050607ULL; static void be2vlong(vlong *to, uchar *f) { uchar *t, *o; int i; t = (uchar*)to; o = (uchar*)ℴ for(i = 0; i < 8; i++) t[o[i]] = f[i]; } /* * After a fork with fd's copied, both fd's are pointing to * the same Chan structure. Since the offset is kept in the Chan * structure, the seek's and read's in the two processes can * compete at moving the offset around. Hence the retry loop. * * Since the bintime version doesn't need a seek, it doesn't * have the loop. */ vlong nsec(void) { char b[12+1]; static int f = -1; static int usebintime; int retries; vlong t; if(f < 0){ usebintime = 1; f = open("/dev/bintime", OREAD|OCEXEC); if(f < 0){ usebintime = 0; f = open("/dev/nsec", OREAD|OCEXEC); if(f < 0) return 0; } } if(usebintime){ if(read(f, b, sizeof(uvlong)) < 0) goto error; be2vlong(&t, (uchar*)b); return t; } else { for(retries = 0; retries < 100; retries++){ if(seek(f, 0, 0) >= 0 && read(f, b, sizeof(b)-1) >= 0){ b[sizeof(b)-1] = 0; return strtoll(b, 0, 0); } } } error: close(f); f = -1; return 0; }