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