Add tsearch and friends, and a test program

tsearch is missing from windows. use the netbsd version as it's
license-compatible.

lib/roken/tsearch.c

@@ -0,0 +1,180 @@
+/*
+ * 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.
+ *
+ * $NetBSD: tsearch.c,v 1.3 1999/09/16 11:45:37 lukem Exp $
+ * $NetBSD: twalk.c,v 1.1 1999/02/22 10:33:16 christos Exp $
+ * $NetBSD: tdelete.c,v 1.2 1999/09/16 11:45:37 lukem Exp $
+ * $NetBSD: tfind.c,v 1.2 1999/09/16 11:45:37 lukem Exp $
+ */
+
+#include <config.h>
+#include "roken.h"
+#include "search.h"
+#include <stdlib.h>
+
+typedef struct node {
+  char         *key;
+  struct node  *llink, *rlink;
+} node_t;
+
+#ifndef __DECONST
+#define __DECONST(type, var)    ((type)(uintptr_t)(const void *)(var))
+#endif
+
+/*
+ * find or insert datum into search tree
+ *
+ * Parameters:
+ *	vkey:	key to be located
+ *	vrootp:	address of tree root
+ */
+
+ROKEN_LIB_FUNCTION void *
+rk_tsearch(const void *vkey, void **vrootp,
+	int (*compar)(const void *, const void *))
+{
+	node_t *q;
+	node_t **rootp = (node_t **)vrootp;
+
+	if (rootp == NULL)
+		return NULL;
+
+	while (*rootp != NULL) {	/* Knuth's T1: */
+		int r;
+
+		if ((r = (*compar)(vkey, (*rootp)->key)) == 0)	/* T2: */
+			return *rootp;		/* we found it! */
+
+		rootp = (r < 0) ?
+		    &(*rootp)->llink :		/* T3: follow left branch */
+		    &(*rootp)->rlink;		/* T4: follow right branch */
+	}
+
+	q = malloc(sizeof(node_t));		/* T5: key not found */
+	if (q != 0) {				/* make new node */
+		*rootp = q;			/* link new node to old */
+		/* LINTED const castaway ok */
+		q->key = __DECONST(void *, vkey); /* initialize new node */
+		q->llink = q->rlink = NULL;
+	}
+	return q;
+}
+
+/*
+ * Walk the nodes of a tree
+ *
+ * Parameters:
+ *	root:	Root of the tree to be walked
+ */
+static void
+trecurse(const node_t *root, void (*action)(const void *, VISIT, int),
+	 int level)
+{
+
+	if (root->llink == NULL && root->rlink == NULL)
+		(*action)(root, leaf, level);
+	else {
+		(*action)(root, preorder, level);
+		if (root->llink != NULL)
+			trecurse(root->llink, action, level + 1);
+		(*action)(root, postorder, level);
+		if (root->rlink != NULL)
+			trecurse(root->rlink, action, level + 1);
+		(*action)(root, endorder, level);
+	}
+}
+
+/*
+ * Walk the nodes of a tree
+ *
+ * Parameters:
+ *	vroot:	Root of the tree to be walked
+ */
+ROKEN_LIB_FUNCTION void
+rk_twalk(const void *vroot,
+      void (*action)(const void *, VISIT, int))
+{
+	if (vroot != NULL && action != NULL)
+		trecurse(vroot, action, 0);
+}
+
+/*
+ * delete node with given key
+ *
+ * vkey:   key to be deleted
+ * vrootp: address of the root of the tree
+ * compar: function to carry out node comparisons
+ */
+ROKEN_LIB_FUNCTION void *
+rk_tdelete(const void * __restrict vkey, void ** __restrict vrootp,
+	int (*compar)(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;
+}
+
+/*
+ * find a node, or return 0
+ *
+ * Parameters:
+ *	vkey:	key to be found
+ *	vrootp:	address of the tree root
+ */
+ROKEN_LIB_FUNCTION void *
+rk_tfind(const void *vkey, void * const *vrootp,
+      int (*compar)(const void *, const void *))
+{
+	node_t **rootp = (node_t **)vrootp;
+
+	if (rootp == NULL)
+		return NULL;
+
+	while (*rootp != NULL) {		/* T1: */
+		int r;
+
+		if ((r = (*compar)(vkey, (*rootp)->key)) == 0)	/* T2: */
+			return *rootp;		/* key found */
+		rootp = (r < 0) ?
+		    &(*rootp)->llink :		/* T3: follow left branch */
+		    &(*rootp)->rlink;		/* T4: follow right branch */
+	}
+	return NULL;
+}