From e1814ce372d6d7e0df001226bd74254c9ac43b6a Mon Sep 17 00:00:00 2001
From: Werner Almesberger <werner@openmoko.org>
Date: Fri, 19 Nov 2010 21:17:08 -0300
Subject: [PATCH] qpkg: converted dumb binary trees to red-black trees (in
 progress)

This is a change of the underlying mechanism but it's not polished or
optimized yet. The compare functions haven't been updated, so they work
but produce compiler warnings because of type mismatches.

- Makefile (OBJS): added jrb.o
- id.h, id.c: use jrb instead of own dumb binary trees
- TODO: brag about the efficiency improvement
---
 qpkg/Makefile |  2 +-
 qpkg/TODO     |  4 +++
 qpkg/id.c     | 76 ++++++++++-----------------------------------------
 qpkg/id.h     | 15 +++-------
 4 files changed, 23 insertions(+), 74 deletions(-)

diff --git a/qpkg/Makefile b/qpkg/Makefile
index 78932c0..5a20d33 100644
--- a/qpkg/Makefile
+++ b/qpkg/Makefile
@@ -2,7 +2,7 @@ CFLAGS = -Wall -Wshadow -Wmissing-prototypes -g -O
 # -O, so that we get data flow analysis, which helps to find more bugs
 #LDFLAGS=-pg
 
-OBJS = gobble.o id.o prereq.o qpkg.o
+OBJS = gobble.o id.o prereq.o qpkg.o jrb.o
 OBJS_rbtest = rbtest.o jrb.o
 
 all:	qpkg rbtest
diff --git a/qpkg/TODO b/qpkg/TODO
index 8fc24e2..1a6e33f 100644
--- a/qpkg/TODO
+++ b/qpkg/TODO
@@ -8,6 +8,10 @@
 
   So the tree is clearly degenerated.
 
+  Update: after switching to red-black trees, we get only 1497604 calls
+  to comp_id. This is 130% of the "good case" estimate above. Insertion
+  of a new node is currently done with two lookup, so we'll get rid of
+  some more lookups after further optimization.
 
 - check whether introducing a new package would cause a conflict
 
diff --git a/qpkg/id.c b/qpkg/id.c
index 54a6cc3..e625805 100644
--- a/qpkg/id.c
+++ b/qpkg/id.c
@@ -4,9 +4,6 @@
 #include "id.h"
 
 
-#define	NODE2ID(n)	((struct id *) n)
-
-
 static struct id *free_id = NULL;
 
 
@@ -28,39 +25,15 @@ struct tree *make_tree(int (*comp)(const struct id *a, const struct id *b))
 
 	tree = alloc_type(struct tree);
 	tree->comp = comp;
-	tree->root = NULL;
+	tree->root = make_jrb();
 	return tree;
 }
 
 
-static struct node *add_node(struct tree *tree, struct node *node)
-{
-	struct node **p, *last;
-	int cmp;
-
-	p = &tree->root;
-	last = NULL;
-	while (*p) {
-		last = *p;
-		cmp = tree->comp(NODE2ID(node), NODE2ID(*p));
-		if (cmp < 0)
-			p = &(*p)->left;
-		else if (cmp > 0)
-			p = &(*p)->right;
-		else
-			return *p;
-	}
-	*p = node;
-	node->up = last;
-	node->left = node->right = NULL;
-	return NULL;
-}
-
-
 struct id *make_id(struct tree *tree, const char *s, size_t len)
 {
 	struct id *id;
-	struct node *node;
+	struct jrb *node;
 
 	if (!free_id)
 		free_id = alloc_type(struct id);
@@ -68,9 +41,10 @@ struct id *make_id(struct tree *tree, const char *s, size_t len)
 	id->s = s;
 	id->len = len;
 	id->value = NULL;
-	node = add_node(tree, &id->node);
+	node = jrb_find(tree->root, id, tree->comp);
 	if (node)
-		return NODE2ID(node);
+		return node->key;
+	id->jrb = jrb_insert(tree->root, id, NULL, tree->comp);
 	free_id = NULL;
 	return id;
 }
@@ -82,48 +56,26 @@ const struct id *find_id(const struct tree *tree, const char *s, size_t len)
 		.s = s,
 		.len = len
 	};
-	const struct node *n = tree->root;
-	int cmp;
+	struct jrb *node;
 
-	while (n) {
-		cmp = tree->comp(&id, NODE2ID(n));
-		if (cmp < 0)
-			n = n->left;
-		else if (cmp > 0)
-			n = n->right;
-		else
-			return NODE2ID(n);
-	}
-	return NULL;
+	node = jrb_find(tree->root, &id, tree->comp);
+	return node ? node->key : NULL;
 }
 
 
 const struct id *first_id(const struct tree *tree)
 {
-	const struct node *n = tree->root;
+	struct jrb *node;
 
-	if (!n)
-		return NULL;
-	while (n->left)
-		n = n->left;
-	return NODE2ID(n);
+	node = jrb_first(tree->root);
+	return node ? node->key : NULL;
 }
 
 
 const struct id *next_id(const struct id *id)
 {
-	const struct node *n = &id->node;
+	struct jrb *next;
 
-	if (n->right) {
-		n = n->right;
-		while (n->left)
-			n = n->left;
-		return NODE2ID(n);
-	}
-	while (n->up) {
-		if (n == n->up->left)
-			return NODE2ID(n->up);
-		n = n->up;
-	}
-	return NULL;
+	next = jrb_next(id->jrb);
+	return next ? next->key : NULL;
 }
diff --git a/qpkg/id.h b/qpkg/id.h
index b13738f..a4ab86a 100644
--- a/qpkg/id.h
+++ b/qpkg/id.h
@@ -3,25 +3,18 @@
 
 #include <sys/types.h>
 
+#include "jrb.h"
+
 
 struct id;
 
-/*
- * @@@ basic binary trees are not a good choice. should use rb.
- * To ease future migration, we separate the node structure from the rest.
- */
-
-struct node {
-	struct node *up, *left, *right;
-};
-
 struct tree {
 	int (*comp)(const struct id *a, const struct id *b);
-	struct node *root;
+	struct jrb *root;
 };
 
 struct id {
-	struct node node;
+	struct jrb *jrb;
 	const char *s;
 	size_t len;
 	void *value;