path: root/debian/patches/0007-librbtree-add-a-red-black-tree-implementation.patch

From c5615b30ec661f66fff1b2733c30cd2b0efd31c5 Mon Sep 17 00:00:00 2001
From: Justus Winter <4winter@informatik.uni-hamburg.de>
Date: Fri, 16 May 2014 20:21:48 +0200
Subject: [PATCH 07/18] librbtree: add a red-black tree implementation

Red-black trees offer search, insert, and delete operations with worst
case runtime in O(log n).  They are also very space efficient.

This is an verbatim copy from git://git.sceen.net/rbraun/librbraun.git
as of 45fef4ad.  Only macros.h has been slightly amended.  This file
defines two macros, which are also defined in cthreads.h.  Undefine
the macros first to work around this problem.

* librbtree/Makefile: New file.
* librbtree/rbtree.c: Likewise.
* librbtree/rbtree.h: Likewise.
* librbtree/rbtree_i.h: Likewise.
* librbtree/macros.h: Likewise.  Also, undefine MACRO_{BEGIN,END}.
* Makefile (lib-subdirs): Add librbtree.
---
 Makefile             |   3 +
 librbtree/Makefile   |  27 +++
 librbtree/macros.h   |  70 ++++++++
 librbtree/rbtree.c   | 498 +++++++++++++++++++++++++++++++++++++++++++++++++++
 librbtree/rbtree.h   | 310 ++++++++++++++++++++++++++++++++
 librbtree/rbtree_i.h | 196 ++++++++++++++++++++
 6 files changed, 1104 insertions(+)
 create mode 100644 librbtree/Makefile
 create mode 100644 librbtree/macros.h
 create mode 100644 librbtree/rbtree.c
 create mode 100644 librbtree/rbtree.h
 create mode 100644 librbtree/rbtree_i.h

diff --git a/Makefile b/Makefile
index 106f2f6..8a0be83 100644
--- a/Makefile
+++ b/Makefile
@@ -46,6 +46,9 @@ endif
 # Other directories
 other-subdirs = hurd doc config release include
 
+# XXX
+lib-subdirs += librbtree
+
 # All the subdirectories together
 subdirs = $(lib-subdirs) $(prog-subdirs) $(other-subdirs)
 
diff --git a/librbtree/Makefile b/librbtree/Makefile
new file mode 100644
index 0000000..0f33358
--- /dev/null
+++ b/librbtree/Makefile
@@ -0,0 +1,27 @@
+#   Copyright (C) 2014 Free Software Foundation, Inc.
+#
+#   This file is part of the GNU Hurd.
+#
+#   The GNU Hurd is free software; you can redistribute it and/or
+#   modify it under the terms of the GNU General Public License as
+#   published by the Free Software Foundation; either version 2, or (at
+#   your option) any later version.
+#
+#   The GNU Hurd is distributed in the hope that it will be useful, but
+#   WITHOUT ANY WARRANTY; without even the implied warranty of
+#   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+#   General Public License for more details.
+#
+#   You should have received a copy of the GNU General Public License
+#   along with the GNU Hurd.  If not, see <http://www.gnu.org/licenses/>.
+
+dir := librbtree
+makemode := library
+
+libname := librbtree
+SRCS = rbtree.c
+installhdrs = rbtree.h rbtree_i.h macros.h
+
+OBJS = $(SRCS:.c=.o)
+
+include ../Makeconf
diff --git a/librbtree/macros.h b/librbtree/macros.h
new file mode 100644
index 0000000..f0960a3
--- /dev/null
+++ b/librbtree/macros.h
@@ -0,0 +1,70 @@
+/*
+ * Copyright (c) 2009, 2010 Richard Braun.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
+ * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
+ * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
+ * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
+ * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
+ * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ *
+ *
+ * Helper macros.
+ */
+
+#ifndef _MACROS_H
+#define _MACROS_H
+
+#include <stddef.h>
+
+#undef MACRO_BEGIN
+#undef MACRO_END
+#define MACRO_BEGIN     ({
+#define MACRO_END       })
+
+#define XQUOTE(x)       #x
+#define QUOTE(x)        XQUOTE(x)
+
+#define STRLEN(x)       (sizeof(x) - 1)
+#define ARRAY_SIZE(x)   (sizeof(x) / sizeof((x)[0]))
+
+#define MIN(a, b)       ((a) < (b) ? (a) : (b))
+#define MAX(a, b)       ((a) > (b) ? (a) : (b))
+
+#define P2ALIGNED(x, a) (((x) & ((a) - 1)) == 0)
+#define ISP2(x)         P2ALIGNED(x, x)
+#define P2ALIGN(x, a)   ((x) & -(a))
+#define P2ROUND(x, a)   (-(-(x) & -(a)))
+#define P2END(x, a)     (-(~(x) & -(a)))
+
+#define structof(ptr, type, member) \
+    ((type *)((char *)(ptr) - offsetof(type, member)))
+
+#define alignof(x)      __alignof__(x)
+
+#define likely(expr)    __builtin_expect(!!(expr), 1)
+#define unlikely(expr)  __builtin_expect(!!(expr), 0)
+
+#define barrier()       asm volatile("" : : : "memory")
+
+#define __noreturn      __attribute__((noreturn))
+#define __aligned(x)    __attribute__((aligned(x)))
+
+#define __format_printf(fmt, args) \
+    __attribute__((format(printf, fmt, args)))
+
+#endif /* _MACROS_H */
diff --git a/librbtree/rbtree.c b/librbtree/rbtree.c
new file mode 100644
index 0000000..969a18d
--- /dev/null
+++ b/librbtree/rbtree.c
@@ -0,0 +1,498 @@
+/*
+ * Copyright (c) 2010, 2012 Richard Braun.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
+ * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
+ * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
+ * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
+ * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
+ * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#include <assert.h>
+#include <stddef.h>
+
+#include "macros.h"
+#include "rbtree.h"
+#include "rbtree_i.h"
+
+/*
+ * Return the index of a node in the children array of its parent.
+ *
+ * The parent parameter must not be NULL, and must be the parent of the
+ * given node.
+ */
+static inline int
+rbtree_node_index(const struct rbtree_node *node,
+                  const struct rbtree_node *parent)
+{
+    assert(parent != NULL);
+    assert((node == NULL) || (rbtree_node_parent(node) == parent));
+
+    if (parent->children[RBTREE_LEFT] == node)
+        return RBTREE_LEFT;
+
+    assert(parent->children[RBTREE_RIGHT] == node);
+
+    return RBTREE_RIGHT;
+}
+
+/*
+ * Return the color of a node.
+ */
+static inline int
+rbtree_node_color(const struct rbtree_node *node)
+{
+    return node->parent & RBTREE_COLOR_MASK;
+}
+
+/*
+ * Return true if the node is red.
+ */
+static inline int
+rbtree_node_is_red(const struct rbtree_node *node)
+{
+    return rbtree_node_color(node) == RBTREE_COLOR_RED;
+}
+
+/*
+ * Return true if the node is black.
+ */
+static inline int
+rbtree_node_is_black(const struct rbtree_node *node)
+{
+    return rbtree_node_color(node) == RBTREE_COLOR_BLACK;
+}
+
+/*
+ * Set the parent of a node, retaining its current color.
+ */
+static inline void
+rbtree_node_set_parent(struct rbtree_node *node, struct rbtree_node *parent)
+{
+    assert(rbtree_node_check_alignment(node));
+    assert(rbtree_node_check_alignment(parent));
+
+    node->parent = (unsigned long)parent | (node->parent & RBTREE_COLOR_MASK);
+}
+
+/*
+ * Set the color of a node, retaining its current parent.
+ */
+static inline void
+rbtree_node_set_color(struct rbtree_node *node, int color)
+{
+    assert((color & ~RBTREE_COLOR_MASK) == 0);
+    node->parent = (node->parent & RBTREE_PARENT_MASK) | color;
+}
+
+/*
+ * Set the color of a node to red, retaining its current parent.
+ */
+static inline void
+rbtree_node_set_red(struct rbtree_node *node)
+{
+    rbtree_node_set_color(node, RBTREE_COLOR_RED);
+}
+
+/*
+ * Set the color of a node to black, retaining its current parent.
+ */
+static inline void
+rbtree_node_set_black(struct rbtree_node *node)
+{
+    rbtree_node_set_color(node, RBTREE_COLOR_BLACK);
+}
+
+/*
+ * Return the left-most deepest child node of the given node.
+ */
+static struct rbtree_node *
+rbtree_node_find_deepest(struct rbtree_node *node)
+{
+    struct rbtree_node *parent;
+
+    assert(node != NULL);
+
+    for (;;) {
+        parent = node;
+        node = node->children[RBTREE_LEFT];
+
+        if (node == NULL) {
+            node = parent->children[RBTREE_RIGHT];
+
+            if (node == NULL)
+                return parent;
+        }
+    }
+}
+
+/*
+ * Perform a tree rotation, rooted at the given node.
+ *
+ * The direction parameter defines the rotation direction and is either
+ * RBTREE_LEFT or RBTREE_RIGHT.
+ */
+static void
+rbtree_rotate(struct rbtree *tree, struct rbtree_node *node, int direction)
+{
+    struct rbtree_node *parent, *rnode;
+    int left, right;
+
+    left = direction;
+    right = 1 - left;
+    parent = rbtree_node_parent(node);
+    rnode = node->children[right];
+
+    node->children[right] = rnode->children[left];
+
+    if (rnode->children[left] != NULL)
+        rbtree_node_set_parent(rnode->children[left], node);
+
+    rnode->children[left] = node;
+    rbtree_node_set_parent(rnode, parent);
+
+    if (unlikely(parent == NULL))
+        tree->root = rnode;
+    else
+        parent->children[rbtree_node_index(node, parent)] = rnode;
+
+    rbtree_node_set_parent(node, rnode);
+}
+
+void
+rbtree_insert_rebalance(struct rbtree *tree, struct rbtree_node *parent,
+                        int index, struct rbtree_node *node)
+{
+    struct rbtree_node *grand_parent, *uncle, *tmp;
+    int left, right;
+
+    assert(rbtree_node_check_alignment(parent));
+    assert(rbtree_node_check_alignment(node));
+
+    node->parent = (unsigned long)parent | RBTREE_COLOR_RED;
+    node->children[RBTREE_LEFT] = NULL;
+    node->children[RBTREE_RIGHT] = NULL;
+
+    if (unlikely(parent == NULL))
+        tree->root = node;
+    else
+        parent->children[index] = node;
+
+    for (;;) {
+        if (parent == NULL) {
+            rbtree_node_set_black(node);
+            break;
+        }
+
+        if (rbtree_node_is_black(parent))
+            break;
+
+        grand_parent = rbtree_node_parent(parent);
+        assert(grand_parent != NULL);
+
+        left = rbtree_node_index(parent, grand_parent);
+        right = 1 - left;
+
+        uncle = grand_parent->children[right];
+
+        /*
+         * Uncle is red. Flip colors and repeat at grand parent.
+         */
+        if ((uncle != NULL) && rbtree_node_is_red(uncle)) {
+            rbtree_node_set_black(uncle);
+            rbtree_node_set_black(parent);
+            rbtree_node_set_red(grand_parent);
+            node = grand_parent;
+            parent = rbtree_node_parent(node);
+            continue;
+        }
+
+        /*
+         * Node is the right child of its parent. Rotate left at parent.
+         */
+        if (parent->children[right] == node) {
+            rbtree_rotate(tree, parent, left);
+            tmp = node;
+            node = parent;
+            parent = tmp;
+        }
+
+        /*
+         * Node is the left child of its parent. Handle colors, rotate right
+         * at grand parent, and leave.
+         */
+        rbtree_node_set_black(parent);
+        rbtree_node_set_red(grand_parent);
+        rbtree_rotate(tree, grand_parent, right);
+        break;
+    }
+
+    assert(rbtree_node_is_black(tree->root));
+}
+
+void
+rbtree_remove(struct rbtree *tree, struct rbtree_node *node)
+{
+    struct rbtree_node *child, *parent, *brother;
+    int color, left, right;
+
+    if (node->children[RBTREE_LEFT] == NULL)
+        child = node->children[RBTREE_RIGHT];
+    else if (node->children[RBTREE_RIGHT] == NULL)
+        child = node->children[RBTREE_LEFT];
+    else {
+        struct rbtree_node *successor;
+
+        /*
+         * Two-children case: replace the node with its successor.
+         */
+
+        successor = node->children[RBTREE_RIGHT];
+
+        while (successor->children[RBTREE_LEFT] != NULL)
+            successor = successor->children[RBTREE_LEFT];
+
+        color = rbtree_node_color(successor);
+        child = successor->children[RBTREE_RIGHT];
+        parent = rbtree_node_parent(node);
+
+        if (unlikely(parent == NULL))
+            tree->root = successor;
+        else
+            parent->children[rbtree_node_index(node, parent)] = successor;
+
+        parent = rbtree_node_parent(successor);
+
+        /*
+         * Set parent directly to keep the original color.
+         */
+        successor->parent = node->parent;
+        successor->children[RBTREE_LEFT] = node->children[RBTREE_LEFT];
+        rbtree_node_set_parent(successor->children[RBTREE_LEFT], successor);
+
+        if (node == parent)
+            parent = successor;
+        else {
+            successor->children[RBTREE_RIGHT] = node->children[RBTREE_RIGHT];
+            rbtree_node_set_parent(successor->children[RBTREE_RIGHT],
+                                   successor);
+            parent->children[RBTREE_LEFT] = child;
+
+            if (child != NULL)
+                rbtree_node_set_parent(child, parent);
+        }
+
+        goto update_color;
+    }
+
+    /*
+     * Node has at most one child.
+     */
+
+    color = rbtree_node_color(node);
+    parent = rbtree_node_parent(node);
+
+    if (child != NULL)
+        rbtree_node_set_parent(child, parent);
+
+    if (unlikely(parent == NULL))
+        tree->root = child;
+    else
+        parent->children[rbtree_node_index(node, parent)] = child;
+
+    /*
+     * The node has been removed, update the colors. The child pointer can
+     * be NULL, in which case it is considered a black leaf.
+     */
+update_color:
+    if (color == RBTREE_COLOR_RED)
+        return;
+
+    for (;;) {
+        if ((child != NULL) && rbtree_node_is_red(child)) {
+            rbtree_node_set_black(child);
+            break;
+        }
+
+        if (parent == NULL)
+            break;
+
+        left = rbtree_node_index(child, parent);
+        right = 1 - left;
+
+        brother = parent->children[right];
+
+        /*
+         * Brother is red. Recolor and rotate left at parent so that brother
+         * becomes black.
+         */
+        if (rbtree_node_is_red(brother)) {
+            rbtree_node_set_black(brother);
+            rbtree_node_set_red(parent);
+            rbtree_rotate(tree, parent, left);
+            brother = parent->children[right];
+        }
+
+        /*
+         * Brother has no red child. Recolor and repeat at parent.
+         */
+        if (((brother->children[RBTREE_LEFT] == NULL)
+             || rbtree_node_is_black(brother->children[RBTREE_LEFT]))
+            && ((brother->children[RBTREE_RIGHT] == NULL)
+                || rbtree_node_is_black(brother->children[RBTREE_RIGHT]))) {
+            rbtree_node_set_red(brother);
+            child = parent;
+            parent = rbtree_node_parent(child);
+            continue;
+        }
+
+        /*
+         * Brother's right child is black. Recolor and rotate right at brother.
+         */
+        if ((brother->children[right] == NULL)
+            || rbtree_node_is_black(brother->children[right])) {
+            rbtree_node_set_black(brother->children[left]);
+            rbtree_node_set_red(brother);
+            rbtree_rotate(tree, brother, right);
+            brother = parent->children[right];
+        }
+
+        /*
+         * Brother's left child is black. Exchange parent and brother colors
+         * (we already know brother is black), set brother's right child black,
+         * rotate left at parent and leave.
+         */
+        rbtree_node_set_color(brother, rbtree_node_color(parent));
+        rbtree_node_set_black(parent);
+        rbtree_node_set_black(brother->children[right]);
+        rbtree_rotate(tree, parent, left);
+        break;
+    }
+
+    assert((tree->root == NULL) || rbtree_node_is_black(tree->root));
+}
+
+struct rbtree_node *
+rbtree_nearest(struct rbtree_node *parent, int index, int direction)
+{
+    assert(rbtree_check_index(direction));
+
+    if (parent == NULL)
+        return NULL;
+
+    assert(rbtree_check_index(index));
+
+    if (index != direction)
+        return parent;
+
+    return rbtree_walk(parent, direction);
+}
+
+struct rbtree_node *
+rbtree_firstlast(const struct rbtree *tree, int direction)
+{
+    struct rbtree_node *prev, *cur;
+
+    assert(rbtree_check_index(direction));
+
+    prev = NULL;
+
+    for (cur = tree->root; cur != NULL; cur = cur->children[direction])
+        prev = cur;
+
+    return prev;
+}
+
+struct rbtree_node *
+rbtree_walk(struct rbtree_node *node, int direction)
+{
+    int left, right;
+
+    assert(rbtree_check_index(direction));
+
+    left = direction;
+    right = 1 - left;
+
+    if (node == NULL)
+        return NULL;
+
+    if (node->children[left] != NULL) {
+        node = node->children[left];
+
+        while (node->children[right] != NULL)
+            node = node->children[right];
+    } else {
+        struct rbtree_node *parent;
+        int index;
+
+        for (;;) {
+            parent = rbtree_node_parent(node);
+
+            if (parent == NULL)
+                return NULL;
+
+            index = rbtree_node_index(node, parent);
+            node = parent;
+
+            if (index == right)
+                break;
+        }
+    }
+
+    return node;
+}
+
+struct rbtree_node *
+rbtree_postwalk_deepest(const struct rbtree *tree)
+{
+    struct rbtree_node *node;
+
+    node = tree->root;
+
+    if (node == NULL)
+        return NULL;
+
+    return rbtree_node_find_deepest(node);
+}
+
+struct rbtree_node *
+rbtree_postwalk_unlink(struct rbtree_node *node)
+{
+    struct rbtree_node *parent;
+    int index;
+
+    if (node == NULL)
+        return NULL;
+
+    assert(node->children[RBTREE_LEFT] == NULL);
+    assert(node->children[RBTREE_RIGHT] == NULL);
+
+    parent = rbtree_node_parent(node);
+
+    if (parent == NULL)
+        return NULL;
+
+    index = rbtree_node_index(node, parent);
+    parent->children[index] = NULL;
+    node = parent->children[RBTREE_RIGHT];
+
+    if (node == NULL)
+        return parent;
+
+    return rbtree_node_find_deepest(node);
+}
diff --git a/librbtree/rbtree.h b/librbtree/rbtree.h
new file mode 100644
index 0000000..cbb519e
--- /dev/null
+++ b/librbtree/rbtree.h
@@ -0,0 +1,310 @@
+/*
+ * Copyright (c) 2010, 2011, 2012 Richard Braun.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
+ * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
+ * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
+ * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
+ * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
+ * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ *
+ *
+ * Red-black tree.
+ */
+
+#ifndef _RBTREE_H
+#define _RBTREE_H
+
+#include <assert.h>
+#include <stddef.h>
+
+#include "macros.h"
+
+/*
+ * Indexes of the left and right nodes in the children array of a node.
+ */
+#define RBTREE_LEFT     0
+#define RBTREE_RIGHT    1
+
+/*
+ * Red-black node.
+ */
+struct rbtree_node;
+
+/*
+ * Red-black tree.
+ */
+struct rbtree;
+
+/*
+ * Static tree initializer.
+ */
+#define RBTREE_INITIALIZER { NULL }
+
+#include "rbtree_i.h"
+
+/*
+ * Initialize a tree.
+ */
+static inline void
+rbtree_init(struct rbtree *tree)
+{
+    tree->root = NULL;
+}
+
+/*
+ * Initialize a node.
+ *
+ * A node is in no tree when its parent points to itself.
+ */
+static inline void
+rbtree_node_init(struct rbtree_node *node)
+{
+    assert(rbtree_node_check_alignment(node));
+
+    node->parent = (unsigned long)node | RBTREE_COLOR_RED;
+    node->children[RBTREE_LEFT] = NULL;
+    node->children[RBTREE_RIGHT] = NULL;
+}
+
+/*
+ * Return true if node is in no tree.
+ */
+static inline int
+rbtree_node_unlinked(const struct rbtree_node *node)
+{
+    return rbtree_node_parent(node) == node;
+}
+
+/*
+ * Macro that evaluates to the address of the structure containing the
+ * given node based on the given type and member.
+ */
+#define rbtree_entry(node, type, member) structof(node, type, member)
+
+/*
+ * Return true if tree is empty.
+ */
+static inline int
+rbtree_empty(const struct rbtree *tree)
+{
+    return tree->root == NULL;
+}
+
+/*
+ * Look up a node in a tree.
+ *
+ * Note that implementing the lookup algorithm as a macro gives two benefits:
+ * First, it avoids the overhead of a callback function. Next, the type of the
+ * cmp_fn parameter isn't rigid. The only guarantee offered by this
+ * implementation is that the key parameter is the first parameter given to
+ * cmp_fn. This way, users can pass only the value they need for comparison
+ * instead of e.g. allocating a full structure on the stack.
+ *
+ * See rbtree_insert().
+ */
+#define rbtree_lookup(tree, key, cmp_fn)                \
+MACRO_BEGIN                                             \
+    struct rbtree_node *___cur;                         \
+    int ___diff;                                        \
+                                                        \
+    ___cur = (tree)->root;                              \
+                                                        \
+    while (___cur != NULL) {                            \
+        ___diff = cmp_fn(key, ___cur);                  \
+                                                        \
+        if (___diff == 0)                               \
+            break;                                      \
+                                                        \
+        ___cur = ___cur->children[rbtree_d2i(___diff)]; \
+    }                                                   \
+                                                        \
+    ___cur;                                             \
+MACRO_END
+
+/*
+ * Look up a node or one of its nearest nodes in a tree.
+ *
+ * This macro essentially acts as rbtree_lookup() but if no entry matched
+ * the key, an additional step is performed to obtain the next or previous
+ * node, depending on the direction (left or right).
+ *
+ * The constraints that apply to the key parameter are the same as for
+ * rbtree_lookup().
+ */
+#define rbtree_lookup_nearest(tree, key, cmp_fn, dir)       \
+MACRO_BEGIN                                                 \
+    struct rbtree_node *___cur, *___prev;                   \
+    int ___diff, ___index;                                  \
+                                                            \
+    ___prev = NULL;                                         \
+    ___index = -1;                                          \
+    ___cur = (tree)->root;                                  \
+                                                            \
+    while (___cur != NULL) {                                \
+        ___diff = cmp_fn(key, ___cur);                      \
+                                                            \
+        if (___diff == 0)                                   \
+            break;                                          \
+                                                            \
+        ___prev = ___cur;                                   \
+        ___index = rbtree_d2i(___diff);                     \
+        ___cur = ___cur->children[___index];                \
+    }                                                       \
+                                                            \
+    if (___cur == NULL)                                     \
+        ___cur = rbtree_nearest(___prev, ___index, dir);    \
+                                                            \
+    ___cur;                                                 \
+MACRO_END
+
+/*
+ * Insert a node in a tree.
+ *
+ * This macro performs a standard lookup to obtain the insertion point of
+ * the given node in the tree (it is assumed that the inserted node never
+ * compares equal to any other entry in the tree) and links the node. It
+ * then checks red-black rules violations, and rebalances the tree if
+ * necessary.
+ *
+ * Unlike rbtree_lookup(), the cmp_fn parameter must compare two complete
+ * entries, so it is suggested to use two different comparison inline
+ * functions, such as myobj_cmp_lookup() and myobj_cmp_insert(). There is no
+ * guarantee about the order of the nodes given to the comparison function.
+ *
+ * See rbtree_lookup().
+ */
+#define rbtree_insert(tree, node, cmp_fn)                   \
+MACRO_BEGIN                                                 \
+    struct rbtree_node *___cur, *___prev;                   \
+    int ___diff, ___index;                                  \
+                                                            \
+    ___prev = NULL;                                         \
+    ___index = -1;                                          \
+    ___cur = (tree)->root;                                  \
+                                                            \
+    while (___cur != NULL) {                                \
+        ___diff = cmp_fn(node, ___cur);                     \
+        assert(___diff != 0);                               \
+        ___prev = ___cur;                                   \
+        ___index = rbtree_d2i(___diff);                     \
+        ___cur = ___cur->children[___index];                \
+    }                                                       \
+                                                            \
+    rbtree_insert_rebalance(tree, ___prev, ___index, node); \
+MACRO_END
+
+/*
+ * Look up a node/slot pair in a tree.
+ *
+ * This macro essentially acts as rbtree_lookup() but in addition to a node,
+ * it also returns a slot, which identifies an insertion point in the tree.
+ * If the returned node is NULL, the slot can be used by rbtree_insert_slot()
+ * to insert without the overhead of an additional lookup. The slot is a
+ * simple unsigned long integer.
+ *
+ * The constraints that apply to the key parameter are the same as for
+ * rbtree_lookup().
+ */
+#define rbtree_lookup_slot(tree, key, cmp_fn, slot) \
+MACRO_BEGIN                                         \
+    struct rbtree_node *___cur, *___prev;           \
+    int ___diff, ___index;                          \
+                                                    \
+    ___prev = NULL;                                 \
+    ___index = 0;                                   \
+    ___cur = (tree)->root;                          \
+                                                    \
+    while (___cur != NULL) {                        \
+        ___diff = cmp_fn(key, ___cur);              \
+                                                    \
+        if (___diff == 0)                           \
+            break;                                  \
+                                                    \
+        ___prev = ___cur;                           \
+        ___index = rbtree_d2i(___diff);             \
+        ___cur = ___cur->children[___index];        \
+    }                                               \
+                                                    \
+    (slot) = rbtree_slot(___prev, ___index);        \
+    ___cur;                                         \
+MACRO_END
+
+/*
+ * Insert a node at an insertion point in a tree.
+ *
+ * This macro essentially acts as rbtree_insert() except that it doesn't
+ * obtain the insertion point with a standard lookup. The insertion point
+ * is obtained by calling rbtree_lookup_slot(). In addition, the new node
+ * must not compare equal to an existing node in the tree (i.e. the slot
+ * must denote a NULL node).
+ */
+static inline void
+rbtree_insert_slot(struct rbtree *tree, unsigned long slot,
+                   struct rbtree_node *node)
+{
+    struct rbtree_node *parent;
+    int index;
+
+    parent = rbtree_slot_parent(slot);
+    index = rbtree_slot_index(slot);
+    rbtree_insert_rebalance(tree, parent, index, node);
+}
+
+/*
+ * Remove a node from a tree.
+ *
+ * After completion, the node is stale.
+ */
+void rbtree_remove(struct rbtree *tree, struct rbtree_node *node);
+
+/*
+ * Return the first node of a tree.
+ */
+#define rbtree_first(tree) rbtree_firstlast(tree, RBTREE_LEFT)
+
+/*
+ * Return the last node of a tree.
+ */
+#define rbtree_last(tree) rbtree_firstlast(tree, RBTREE_RIGHT)
+
+/*
+ * Return the node previous to the given node.
+ */
+#define rbtree_prev(node) rbtree_walk(node, RBTREE_LEFT)
+
+/*
+ * Return the node next to the given node.
+ */
+#define rbtree_next(node) rbtree_walk(node, RBTREE_RIGHT)
+
+/*
+ * Forge a loop to process all nodes of a tree, removing them when visited.
+ *
+ * This macro can only be used to destroy a tree, so that the resources used
+ * by the entries can be released by the user. It basically removes all nodes
+ * without doing any color checking.
+ *
+ * After completion, all nodes and the tree root member are stale.
+ */
+#define rbtree_for_each_remove(tree, node, tmp)         \
+for (node = rbtree_postwalk_deepest(tree),              \
+     tmp = rbtree_postwalk_unlink(node);                \
+     node != NULL;                                      \
+     node = tmp, tmp = rbtree_postwalk_unlink(node))    \
+
+#endif /* _RBTREE_H */
diff --git a/librbtree/rbtree_i.h b/librbtree/rbtree_i.h
new file mode 100644
index 0000000..eb1619f
--- /dev/null
+++ b/librbtree/rbtree_i.h
@@ -0,0 +1,196 @@
+/*
+ * Copyright (c) 2010, 2011, 2012 Richard Braun.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
+ * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
+ * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
+ * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
+ * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
+ * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#ifndef _RBTREE_I_H
+#define _RBTREE_I_H
+
+#include <assert.h>
+#include <stddef.h>
+
+#include "macros.h"
+
+/*
+ * Red-black node structure.
+ *
+ * To reduce the number of branches and the instruction cache footprint,
+ * the left and right child pointers are stored in an array, and the symmetry
+ * of most tree operations is exploited by using left/right variables when
+ * referring to children.
+ *
+ * In addition, this implementation assumes that all nodes are 4-byte aligned,
+ * so that the least significant bit of the parent member can be used to store
+ * the color of the node. This is true for all modern 32 and 64 bits
+ * architectures, as long as the nodes aren't embedded in structures with
+ * special alignment constraints such as member packing.
+ */
+struct rbtree_node {
+    unsigned long parent;
+    struct rbtree_node *children[2];
+};
+
+/*
+ * Red-black tree structure.
+ */
+struct rbtree {
+    struct rbtree_node *root;
+};
+
+/*
+ * Masks applied on the parent member of a node to obtain either the
+ * color or the parent address.
+ */
+#define RBTREE_COLOR_MASK   0x1UL
+#define RBTREE_PARENT_MASK  (~0x3UL)
+
+/*
+ * Node colors.
+ */
+#define RBTREE_COLOR_RED    0
+#define RBTREE_COLOR_BLACK  1
+
+/*
+ * Masks applied on slots to obtain either the child index or the parent
+ * address.
+ */
+#define RBTREE_SLOT_INDEX_MASK  0x1UL
+#define RBTREE_SLOT_PARENT_MASK (~RBTREE_SLOT_INDEX_MASK)
+
+/*
+ * Return true if the given index is a valid child index.
+ */
+static inline int
+rbtree_check_index(int index)
+{
+    return index == (index & 1);
+}
+
+/*
+ * Convert the result of a comparison into an index in the children array
+ * (0 or 1).
+ *
+ * This function is mostly used when looking up a node.
+ */
+static inline int
+rbtree_d2i(int diff)
+{
+    return !(diff <= 0);
+}
+
+/*
+ * Return true if the given pointer is suitably aligned.
+ */
+static inline int
+rbtree_node_check_alignment(const struct rbtree_node *node)
+{
+    return ((unsigned long)node & (~RBTREE_PARENT_MASK)) == 0;
+}
+
+/*
+ * Return the parent of a node.
+ */
+static inline struct rbtree_node *
+rbtree_node_parent(const struct rbtree_node *node)
+{
+    return (struct rbtree_node *)(node->parent & RBTREE_PARENT_MASK);
+}
+
+/*
+ * Translate an insertion point into a slot.
+ */
+static inline unsigned long
+rbtree_slot(struct rbtree_node *parent, int index)
+{
+    assert(rbtree_node_check_alignment(parent));
+    assert(rbtree_check_index(index));
+    return (unsigned long)parent | index;
+}
+
+/*
+ * Extract the parent address from a slot.
+ */
+static inline struct rbtree_node *
+rbtree_slot_parent(unsigned long slot)
+{
+    return (struct rbtree_node *)(slot & RBTREE_SLOT_PARENT_MASK);
+}
+
+/*
+ * Extract the index from a slot.
+ */
+static inline int
+rbtree_slot_index(unsigned long slot)
+{
+    return slot & RBTREE_SLOT_INDEX_MASK;
+}
+
+/*
+ * Insert a node in a tree, rebalancing it if necessary.
+ *
+ * The index parameter is the index in the children array of the parent where
+ * the new node is to be inserted. It is ignored if the parent is NULL.
+ *
+ * This function is intended to be used by the rbtree_insert() macro only.
+ */
+void rbtree_insert_rebalance(struct rbtree *tree, struct rbtree_node *parent,
+                             int index, struct rbtree_node *node);
+
+/*
+ * Return the previous or next node relative to a location in a tree.
+ *
+ * The parent and index parameters define the location, which can be empty.
+ * The direction parameter is either RBTREE_LEFT (to obtain the previous
+ * node) or RBTREE_RIGHT (to obtain the next one).
+ */
+struct rbtree_node * rbtree_nearest(struct rbtree_node *parent, int index,
+                                    int direction);
+
+/*
+ * Return the first or last node of a tree.
+ *
+ * The direction parameter is either RBTREE_LEFT (to obtain the first node)
+ * or RBTREE_RIGHT (to obtain the last one).
+ */
+struct rbtree_node * rbtree_firstlast(const struct rbtree *tree, int direction);
+
+/*
+ * Return the node next to, or previous to the given node.
+ *
+ * The direction parameter is either RBTREE_LEFT (to obtain the previous node)
+ * or RBTREE_RIGHT (to obtain the next one).
+ */
+struct rbtree_node * rbtree_walk(struct rbtree_node *node, int direction);
+
+/*
+ * Return the left-most deepest node of a tree, which is the starting point of
+ * the postorder traversal performed by rbtree_for_each_remove().
+ */
+struct rbtree_node * rbtree_postwalk_deepest(const struct rbtree *tree);
+
+/*
+ * Unlink a node from its tree and return the next (right) node in postorder.
+ */
+struct rbtree_node * rbtree_postwalk_unlink(struct rbtree_node *node);
+
+#endif /* _RBTREE_I_H */
-- 
2.0.0.rc2