1 #include <u.h>
2 #include <libc.h>
3 #include <bio.h>
4 #include <ndb.h>
5 
6 /* replace a in t with b, the line structure in b is lost, c'est la vie */
7 Ndbtuple*
8 ndbsubstitute(Ndbtuple *t, Ndbtuple *a, Ndbtuple *b)
9 {
10 	Ndbtuple *nt;
11 
12 	if(a == b)
13 		return t;
14 	if(b == nil)
15 		return ndbdiscard(t, a);
16 
17 	/* all pointers to a become pointers to b */
18 	for(nt = t; nt != nil; nt = nt->entry){
19 		if(nt->line == a)
20 			nt->line = b;
21 		if(nt->entry == a)
22 			nt->entry = b;
23 	}
24 
25 	/* end of b chain points to a's successors */
26 	for(nt = b; nt->entry; nt = nt->entry){
27 		nt->line = nt->entry;
28 	}
29 	nt->line = a->line;
30 	nt->entry = a->entry;
31 
32 	a->entry = nil;
33 	ndbfree(a);
34 
35 	if(a == t)
36 		return b;
37 	else
38 		return t;
39 }