66 lines
1.2 KiB
C
66 lines
1.2 KiB
C
#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*)ℴ
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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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}
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