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#include <u.h>
#include <libc.h>
#include <bio.h>
#include <ndb.h>
/* replace a in t with b, the line structure in b is lost, c'est la vie */
Ndbtuple*
ndbsubstitute(Ndbtuple *t, Ndbtuple *a, Ndbtuple *b)
{
Ndbtuple *nt;
if(a == b)
return t;
if(b == nil)
return ndbdiscard(t, a);
/* all pointers to a become pointers to b */
for(nt = t; nt != nil; nt = nt->entry){
if(nt->line == a)
nt->line = b;
if(nt->entry == a)
nt->entry = b;
}
/* end of b chain points to a's successors */
for(nt = b; nt->entry; nt = nt->entry){
nt->line = nt->entry;
}
nt->line = a->line;
nt->entry = a->entry;
a->entry = nil;
ndbfree(a);
if(a == t)
return b;
else
return t;
}
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