bring in binary search tree code.

Obtained from: NetBSD

1 files changed, 66 insertions, 0 deletions

diff --git a/lib/libc/stdlib/tdelete.c b/lib/libc/stdlib/tdelete.c
new file mode 100644
index 0000000..daf4aa7
--- /dev/null
+++ b/lib/libc/stdlib/tdelete.c
@@ -0,0 +1,66 @@
+/*	$NetBSD: tdelete.c,v 1.2 1999/09/16 11:45:37 lukem Exp $	*/
+/* $FreeBSD$ */
+
+/*
+ * Tree search generalized from Knuth (6.2.2) Algorithm T just like
+ * the AT&T man page says.
+ *
+ * The node_t structure is for internal use only, lint doesn't grok it.
+ *
+ * Written by reading the System V Interface Definition, not the code.
+ *
+ * Totally public domain.
+ */
+
+#include <sys/cdefs.h>
+#if defined(LIBC_SCCS) && !defined(lint)
+__RCSID("$NetBSD: tdelete.c,v 1.2 1999/09/16 11:45:37 lukem Exp $");
+#endif /* LIBC_SCCS and not lint */
+
+#include <assert.h>
+#define _SEARCH_PRIVATE
+#include <search.h>
+#include <stdlib.h>
+
+
+/* delete node with given key */
+void *
+tdelete(vkey, vrootp, compar)
+	const void *vkey;	/* key to be deleted */
+	void      **vrootp;	/* address of the root of tree */
+	int       (*compar) __P((const void *, const void *));
+{
+	node_t **rootp = (node_t **)vrootp;
+	node_t *p, *q, *r;
+	int  cmp;
+
+	if (rootp == NULL || (p = *rootp) == NULL)
+		return NULL;
+
+	while ((cmp = (*compar)(vkey, (*rootp)->key)) != 0) {
+		p = *rootp;
+		rootp = (cmp < 0) ?
+		    &(*rootp)->llink :		/* follow llink branch */
+		    &(*rootp)->rlink;		/* follow rlink branch */
+		if (*rootp == NULL)
+			return NULL;		/* key not found */
+	}
+	r = (*rootp)->rlink;			/* D1: */
+	if ((q = (*rootp)->llink) == NULL)	/* Left NULL? */
+		q = r;
+	else if (r != NULL) {			/* Right link is NULL? */
+		if (r->llink == NULL) {		/* D2: Find successor */
+			r->llink = q;
+			q = r;
+		} else {			/* D3: Find NULL link */
+			for (q = r->llink; q->llink != NULL; q = r->llink)
+				r = q;
+			r->llink = q->rlink;
+			q->llink = (*rootp)->llink;
+			q->rlink = (*rootp)->rlink;
+		}
+	}
+	free(*rootp);				/* D4: Free node */
+	*rootp = q;				/* link parent to new node */
+	return p;
+}