[radix-tree] alternative radix-tree implementation.

Sacrifices performance for simplicity, meant only for verification of
the real adaptive implementation.

base/Makefile

@@ -10,6 +10,9 @@
 # along with this program; if not, write to the Free Software Foundation,
 # Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
 
+# Uncomment this to build the simple radix tree.  You'll need to make clean too.
+# base/data-struct/radix-tree.o: CFLAGS += -DSIMPLE_RADIX_TREE
+
 BASE_SOURCE=\
 	base/data-struct/radix-tree.c \
 	base/data-struct/hash.c \

base/data-struct/radix-tree-simple.c

@@ -0,0 +1,256 @@
+// Copyright (C) 2018 Red Hat, Inc. All rights reserved.
+// 
+// This file is part of LVM2.
+//
+// This copyrighted material is made available to anyone wishing to use,
+// modify, copy, or redistribute it subject to the terms and conditions
+// of the GNU Lesser General Public License v.2.1.
+//
+// You should have received a copy of the GNU Lesser General Public License
+// along with this program; if not, write to the Free Software Foundation,
+// Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+
+#include "radix-tree.h"
+
+#include "base/memory/container_of.h"
+#include "base/memory/zalloc.h"
+
+#include <assert.h>
+#include <stdlib.h>
+#include <stdio.h>
+
+//----------------------------------------------------------------
+// This implementation is based around nested binary trees.  Very
+// simple (and hopefully correct).
+
+struct node {
+	struct node *left;
+	struct node *right;
+
+	uint8_t key;
+	struct node *center;
+
+	bool has_value;
+	union radix_value value;
+};
+
+struct radix_tree {
+	radix_value_dtr dtr;
+	void *dtr_context;
+
+	struct node *root;
+};
+
+struct radix_tree *
+radix_tree_create(radix_value_dtr dtr, void *dtr_context)
+{
+	struct radix_tree *rt = zalloc(sizeof(*rt));
+
+	if (rt) {
+		rt->dtr = dtr;
+		rt->dtr_context = dtr_context;
+	}
+
+	return rt;
+}
+
+// Returns the number of entries in the tree
+static unsigned _destroy_tree(struct node *n, radix_value_dtr dtr, void *context)
+{
+	unsigned r;
+
+	if (!n)
+		return 0;
+
+	r = _destroy_tree(n->left, dtr, context);
+	r += _destroy_tree(n->right, dtr, context);
+	r += _destroy_tree(n->center, dtr, context);
+
+	if (n->has_value) {
+		if (dtr)
+			dtr(context, n->value);
+		r++;
+	}
+
+	free(n);
+
+	return r;
+}
+
+void radix_tree_destroy(struct radix_tree *rt)
+{
+	_destroy_tree(rt->root, rt->dtr, rt->dtr_context);
+	free(rt);
+}
+
+static unsigned _count(struct node *n)
+{
+	unsigned r;
+
+	if (!n)
+		return 0;
+
+	r = _count(n->left);
+	r += _count(n->right);
+	r += _count(n->center);
+
+	if (n->has_value)
+		r++;
+
+	return r;
+}
+
+unsigned radix_tree_size(struct radix_tree *rt)
+{
+	return _count(rt->root);
+}
+
+static struct node **_lookup(struct node **pn, uint8_t *kb, uint8_t *ke)
+{
+	struct node *n = *pn;
+
+	if (!n || (kb == ke))
+		return pn;
+
+	if (*kb < n->key)
+		return _lookup(&n->left, kb, ke);
+
+	else if (*kb > n->key)
+		return _lookup(&n->right, kb, ke);
+
+	else
+		return _lookup(&n->center, kb + 1, ke);
+}
+
+static bool _insert(struct node **pn, uint8_t *kb, uint8_t *ke, union radix_value v)
+{
+	struct node *n = *pn;
+
+	if (!n) {
+		n = zalloc(sizeof(*n));
+		if (!n)
+			return false;
+
+		n->key = *kb;
+		*pn = n;
+	}
+
+	if (kb == ke) {
+		n->has_value = true;
+		n->value = v;
+		return true;
+	}
+
+	if (*kb < n->key)
+		return _insert(&n->left, kb, ke, v);
+
+	else if (*kb > n->key)
+		return _insert(&n->right, kb, ke, v);
+
+	else
+		return _insert(&n->center, kb + 1, ke, v);
+}
+
+bool radix_tree_insert(struct radix_tree *rt, uint8_t *kb, uint8_t *ke, union radix_value v)
+{
+	return _insert(&rt->root, kb, ke, v);
+}
+
+bool radix_tree_remove(struct radix_tree *rt, uint8_t *kb, uint8_t *ke)
+{
+	struct node **pn = _lookup(&rt->root, kb, ke);
+	struct node *n = *pn;
+
+	if (!n || !n->has_value)
+		return false;
+
+	else {
+		if (rt->dtr)
+			rt->dtr(rt->dtr_context, n->value);
+
+		if (n->left || n->center || n->right) {
+			n->has_value = false;
+			return true;
+
+		} else {
+			// FIXME: delete parent if this was the last entry
+			free(n);
+			*pn = NULL;
+		}
+
+		return true;
+	}
+}
+
+unsigned radix_tree_remove_prefix(struct radix_tree *rt, uint8_t *kb, uint8_t *ke)
+{
+	struct node **pn;
+	unsigned count;
+
+	pn = _lookup(&rt->root, kb, ke);
+
+	if (*pn) {
+		count = _destroy_tree(*pn, rt->dtr, rt->dtr_context);
+		*pn = NULL;
+	}
+
+	return count;
+}
+
+bool
+radix_tree_lookup(struct radix_tree *rt, uint8_t *kb, uint8_t *ke, union radix_value *result)
+{
+	struct node **pn = _lookup(&rt->root, kb, ke);
+	struct node *n = *pn;
+
+	if (n && n->has_value) {
+		*result = n->value;
+		return true;
+	} else
+		return false;
+}
+
+static void _iterate(struct node *n, struct radix_tree_iterator *it)
+{
+	if (!n)
+		return;
+
+	_iterate(n->left, it);
+
+	if (n->has_value)
+		// FIXME: fill out the key
+		it->visit(it, NULL, NULL, n->value);
+
+	_iterate(n->center, it);
+	_iterate(n->right, it);
+}
+
+void radix_tree_iterate(struct radix_tree *rt, uint8_t *kb, uint8_t *ke,
+                        struct radix_tree_iterator *it)
+{
+	if (kb == ke)
+		_iterate(rt->root, it);
+
+	else {
+		struct node **pn = _lookup(&rt->root, kb, ke);
+		struct node *n = *pn;
+
+		if (n) {
+			if (n->has_value)
+				it->visit(it, NULL, NULL, n->value);
+			_iterate(n->center, it);
+		}
+	}
+}
+
+bool radix_tree_is_well_formed(struct radix_tree *rt)
+{
+	return true;
+}
+
+void radix_tree_dump(struct radix_tree *rt, FILE *out)
+{
+}
+
+//----------------------------------------------------------------
+