new

src/libndb/ndbreorder.c

@@ -0,0 +1,53 @@
+#include <u.h>
+#include <libc.h>
+#include <bio.h>
+#include <ndb.h>
+
+/*
+ *  reorder the tuple to put x's line first in the entry and x fitst in its line
+ */
+Ndbtuple*
+ndbreorder(Ndbtuple *t, Ndbtuple *x)
+{
+	Ndbtuple *nt;
+	Ndbtuple *last, *prev;
+
+	/* if x is first, we're done */
+	if(x == t)
+		return t;
+
+	/* find end of x's line */
+	for(last = x; last->line == last->entry; last = last->line)
+		;
+
+	/* rotate to make this line first */
+	if(last->line != t){
+
+		/* detach this line and everything after it from the entry */
+		for(nt = t; nt->entry != last->line; nt = nt->entry)
+			;
+		nt->entry = nil;
+	
+		/* switch */
+		for(nt = last; nt->entry != nil; nt = nt->entry)
+			;
+		nt->entry = t;
+	}
+
+	/* rotate line to make x first */
+	if(x != last->line){
+
+		/* find entry before x */
+		for(prev = last; prev->line != x; prev = prev->line);
+			;
+
+		/* detach line */
+		nt = last->entry;
+		last->entry = last->line;
+
+		/* reattach */
+		prev->entry = nt;
+	}
+
+	return x;
+}