* Copyright (c) 2008 The NetBSD Foundation, Inc.

/* $NetBSD: ptree.c,v 1.15 2025/04/25 21:12:31 andvar Exp $ */

/*-
* Copyright (c) 2008 The NetBSD Foundation, Inc.
* All rights reserved.
*
* This code is derived from software contributed to The NetBSD Foundation
* by Matt Thomas <[email protected]>.
*
* 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 NETBSD FOUNDATION, INC. AND CONTRIBUTORS
* ``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 FOUNDATION OR CONTRIBUTORS
* 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.
*/

#define _PT_PRIVATE

#if defined(PTCHECK) && !defined(PTDEBUG)
#define PTDEBUG
#endif

#if defined(_KERNEL) || defined(_STANDALONE)
#include <sys/param.h>
#include <sys/types.h>
#include <sys/systm.h>
#include <lib/libkern/libkern.h>
__KERNEL_RCSID(0, "$NetBSD: ptree.c,v 1.15 2025/04/25 21:12:31 andvar Exp $");
#else
#include <stddef.h>
#include <stdint.h>
#include <limits.h>
#include <stdbool.h>
#include <string.h>
#ifdef PTDEBUG
#include <assert.h>
#define KASSERT(e) assert(e)
#else
#define KASSERT(e) do { } while (0)
#endif
__RCSID("$NetBSD: ptree.c,v 1.15 2025/04/25 21:12:31 andvar Exp $");
#endif /* _KERNEL || _STANDALONE */

#ifdef _LIBC
#include "namespace.h"
#endif

#ifdef PTTEST
#include "ptree.h"
#else
#include <sys/ptree.h>
#endif

/*
* This is an implementation of a radix / PATRICIA tree. As in a traditional
* patricia tree, all the data is at the leaves of the tree. An N-value
* tree would have N leaves, N-1 branching nodes, and a root pointer. Each
* branching node would have left(0) and right(1) pointers that either point
* to another branching node or a leaf node. The root pointer would also
* point to either the first branching node or a leaf node. Leaf nodes
* have no need for pointers.
*
* However, allocation for these branching nodes is problematic since the
* allocation could fail. This would cause insertions to fail for reasons
* beyond the user's control. So to prevent this, in this implementation
* each node has two identities: its leaf identity and its branch identity.
* Each is separate from the other. Every branch is tagged as to whether
* it points to a leaf or a branch. This is not an attribute of the object
* but of the pointer to the object. The low bit of the pointer is used as
* the tag to determine whether it points to a leaf or branch identity, with
* branch identities having the low bit set.
*
* A node's branch identity has one rule: when traversing the tree from the
* root to the node's leaf identity, one of the branches traversed will be via
* the node's branch identity. Of course, that has an exception: since to
* store N leaves, you need N-1 branches. That one node whose branch identity
* isn't used is stored as "oddman"-out in the root.
*
* Branching nodes also has a bit offset and a bit length which determines
* which branch slot is used. The bit length can be zero resulting in a
* one-way branch. This happens in two special cases: the root and
* interior mask nodes.
*
* To support longest match first lookups, when a mask node (one that only
* match the first N bits) has children who first N bits match the mask nodes,
* that mask node is converted from being a leaf node to being a one-way
* branch-node. The mask becomes fixed in position in the tree. The mask
* will always be the longest mask match for its descendants (unless they
* traverse an even longer match).
*/

#define NODETOITEM(pt, ptn) \
((void *)((uintptr_t)(ptn) - (pt)->pt_node_offset))
#define NODETOKEY(pt, ptn) \
((void *)((uintptr_t)(ptn) - (pt)->pt_node_offset + pt->pt_key_offset))
#define ITEMTONODE(pt, ptn) \
((pt_node_t *)((uintptr_t)(ptn) + (pt)->pt_node_offset))

#if PTCHECK > 1
#define PTREE_CHECK(pt) ptree_check(pt)
#else
#define PTREE_CHECK(pt) do { } while (0)
#endif

static inline bool
ptree_matchnode(const pt_tree_t *pt, const pt_node_t *target,
const pt_node_t *ptn, pt_bitoff_t max_bitoff,
pt_bitoff_t *bitoff_p, pt_slot_t *slots_p)
{
return (*pt->pt_ops->ptto_matchnode)(NODETOKEY(pt, target),
(ptn != NULL ? NODETOKEY(pt, ptn) : NULL),
max_bitoff, bitoff_p, slots_p, pt->pt_context);
}

static inline pt_slot_t
ptree_testnode(const pt_tree_t *pt, const pt_node_t *target,
const pt_node_t *ptn)
{
const pt_bitlen_t bitlen = PTN_BRANCH_BITLEN(ptn);
if (bitlen == 0)
return PT_SLOT_ROOT; /* mask or root, doesn't matter */
return (*pt->pt_ops->ptto_testnode)(NODETOKEY(pt, target),
PTN_BRANCH_BITOFF(ptn), bitlen, pt->pt_context);
}

static inline bool
ptree_matchkey(const pt_tree_t *pt, const void *key,
const pt_node_t *ptn, pt_bitoff_t bitoff, pt_bitlen_t bitlen)
{
return (*pt->pt_ops->ptto_matchkey)(key, NODETOKEY(pt, ptn),
bitoff, bitlen, pt->pt_context);
}

static inline pt_slot_t
ptree_testkey(const pt_tree_t *pt, const void *key, const pt_node_t *ptn)
{
const pt_bitlen_t bitlen = PTN_BRANCH_BITLEN(ptn);
if (bitlen == 0)
return PT_SLOT_ROOT; /* mask or root, doesn't matter */
return (*pt->pt_ops->ptto_testkey)(key, PTN_BRANCH_BITOFF(ptn),
PTN_BRANCH_BITLEN(ptn), pt->pt_context);
}

static inline void
ptree_set_position(uintptr_t node, pt_slot_t position)
{
if (PT_LEAF_P(node))
PTN_SET_LEAF_POSITION(PT_NODE(node), position);
else
PTN_SET_BRANCH_POSITION(PT_NODE(node), position);
}

void
ptree_init(pt_tree_t *pt, const pt_tree_ops_t *ops, void *context,
size_t node_offset, size_t key_offset)
{
memset(pt, 0, sizeof(*pt));
pt->pt_node_offset = node_offset;
pt->pt_key_offset = key_offset;
pt->pt_context = context;
pt->pt_ops = ops;
}

typedef struct {
uintptr_t *id_insertp;
pt_node_t *id_parent;
uintptr_t id_node;
pt_slot_t id_parent_slot;
pt_bitoff_t id_bitoff;
pt_slot_t id_slot;
} pt_insertdata_t;

typedef bool (*pt_insertfunc_t)(pt_tree_t *, pt_node_t *, pt_insertdata_t *);

/*
* Move a branch identify from src to dst. The leaves don't care since
* nothing for them has changed.
*/
/*ARGSUSED*/
static uintptr_t
ptree_move_branch(pt_tree_t * const pt, pt_node_t * const dst,
const pt_node_t * const src)
{
KASSERT(PTN_BRANCH_BITLEN(src) == 1);
/* set branch bitlen and bitoff in one step. */
dst->ptn_branchdata = src->ptn_branchdata;
PTN_SET_BRANCH_POSITION(dst, PTN_BRANCH_POSITION(src));
PTN_COPY_BRANCH_SLOTS(dst, src);
return PTN_BRANCH(dst);
}

#ifndef PTNOMASK
static inline uintptr_t *
ptree_find_branch(pt_tree_t * const pt, uintptr_t branch_node)
{
pt_node_t * const branch = PT_NODE(branch_node);
pt_node_t *parent;

for (parent = &pt->pt_rootnode;;) {
uintptr_t *nodep =
&PTN_BRANCH_SLOT(parent, ptree_testnode(pt, branch, parent));
if (*nodep == branch_node)
return nodep;
if (PT_LEAF_P(*nodep))
return NULL;
parent = PT_NODE(*nodep);
}
}

static bool
ptree_insert_leaf_after_mask(pt_tree_t * const pt, pt_node_t * const target,
pt_insertdata_t * const id)
{
const uintptr_t target_node = PTN_LEAF(target);
const uintptr_t mask_node = id->id_node;
pt_node_t * const mask = PT_NODE(mask_node);
const pt_bitlen_t mask_len = PTN_MASK_BITLEN(mask);

KASSERT(PT_LEAF_P(mask_node));
KASSERT(PTN_LEAF_POSITION(mask) == id->id_parent_slot);
KASSERT(mask_len <= id->id_bitoff);
KASSERT(PTN_ISMASK_P(mask));
KASSERT(!PTN_ISMASK_P(target) || mask_len < PTN_MASK_BITLEN(target));

if (mask_node == PTN_BRANCH_ODDMAN_SLOT(&pt->pt_rootnode)) {
KASSERT(id->id_parent != mask);
/*
* Nice, mask was an oddman. So just set the oddman to target.
*/
PTN_BRANCH_ODDMAN_SLOT(&pt->pt_rootnode) = target_node;
} else {
/*
* We need to find out who's pointing to mask's branch
* identity. We know that between root and the leaf identity,
* we must traverse the node's branch identity.
*/
uintptr_t * const mask_nodep = ptree_find_branch(pt, PTN_BRANCH(mask));
KASSERT(mask_nodep != NULL);
KASSERT(*mask_nodep == PTN_BRANCH(mask));
KASSERT(PTN_BRANCH_BITLEN(mask) == 1);

/*
* Alas, mask was used as a branch. Since the mask is becoming
* a one-way branch, we need make target take over mask's
* branching responsibilities. Only then can we change it.
*/
*mask_nodep = ptree_move_branch(pt, target, mask);

/*
* However, it's possible that mask's parent is itself. If
* that's true, update the insert point to use target since it
* has taken over mask's branching duties.
*/
if (id->id_parent == mask)
id->id_insertp = &PTN_BRANCH_SLOT(target,
id->id_parent_slot);
}

PTN_SET_BRANCH_BITLEN(mask, 0);
PTN_SET_BRANCH_BITOFF(mask, mask_len);

PTN_BRANCH_ROOT_SLOT(mask) = target_node;
PTN_BRANCH_ODDMAN_SLOT(mask) = PT_NULL;
PTN_SET_LEAF_POSITION(target, PT_SLOT_ROOT);
PTN_SET_BRANCH_POSITION(mask, id->id_parent_slot);

/*
* Now that everything is done, to make target visible we need to
* change mask from a leaf to a branch.
*/
*id->id_insertp = PTN_BRANCH(mask);
PTREE_CHECK(pt);
return true;
}

/*ARGSUSED*/
static bool
ptree_insert_mask_before_node(pt_tree_t * const pt, pt_node_t * const target,
pt_insertdata_t * const id)
{
const uintptr_t node = id->id_node;
pt_node_t * const ptn = PT_NODE(node);
const pt_slot_t mask_len = PTN_MASK_BITLEN(target);
const pt_bitlen_t node_mask_len = PTN_MASK_BITLEN(ptn);

KASSERT(PT_LEAF_P(node) || id->id_parent_slot == PTN_BRANCH_POSITION(ptn));
KASSERT(PT_BRANCH_P(node) || id->id_parent_slot == PTN_LEAF_POSITION(ptn));
KASSERT(PTN_ISMASK_P(target));

/*
* If the node we are placing ourself in front is a mask with the
* same mask length as us, return failure.
*/
if (PTN_ISMASK_P(ptn) && node_mask_len == mask_len)
return false;

PTN_SET_BRANCH_BITLEN(target, 0);
PTN_SET_BRANCH_BITOFF(target, mask_len);

PTN_BRANCH_SLOT(target, PT_SLOT_ROOT) = node;
*id->id_insertp = PTN_BRANCH(target);

PTN_SET_BRANCH_POSITION(target, id->id_parent_slot);
ptree_set_position(node, PT_SLOT_ROOT);

PTREE_CHECK(pt);
return true;
}
#endif /* !PTNOMASK */

/*ARGSUSED*/
static bool
ptree_insert_branch_at_node(pt_tree_t * const pt, pt_node_t * const target,
pt_insertdata_t * const id)
{
const uintptr_t target_node = PTN_LEAF(target);
const uintptr_t node = id->id_node;
const pt_slot_t other_slot = id->id_slot ^ PT_SLOT_OTHER;

KASSERT(PT_BRANCH_P(node) || id->id_parent_slot == PTN_LEAF_POSITION(PT_NODE(node)));
KASSERT(PT_LEAF_P(node) || id->id_parent_slot == PTN_BRANCH_POSITION(PT_NODE(node)));
KASSERT((node == pt->pt_root) == (id->id_parent == &pt->pt_rootnode));
#ifndef PTNOMASK
KASSERT(!PTN_ISMASK_P(target) || id->id_bitoff <= PTN_MASK_BITLEN(target));
#endif
KASSERT(node == pt->pt_root || PTN_BRANCH_BITOFF(id->id_parent) + PTN_BRANCH_BITLEN(id->id_parent) <= id->id_bitoff);

PTN_SET_BRANCH_BITOFF(target, id->id_bitoff);
PTN_SET_BRANCH_BITLEN(target, 1);

PTN_BRANCH_SLOT(target, id->id_slot) = target_node;
PTN_BRANCH_SLOT(target, other_slot) = node;
*id->id_insertp = PTN_BRANCH(target);

PTN_SET_LEAF_POSITION(target, id->id_slot);
ptree_set_position(node, other_slot);

PTN_SET_BRANCH_POSITION(target, id->id_parent_slot);
PTREE_CHECK(pt);
return true;
}

static bool
ptree_insert_leaf(pt_tree_t * const pt, pt_node_t * const target,
pt_insertdata_t * const id)
{
const uintptr_t leaf_node = id->id_node;
pt_node_t * const leaf = PT_NODE(leaf_node);
#ifdef PTNOMASK
const bool inserting_mask = false;
const bool at_mask = false;
#else
const bool inserting_mask = PTN_ISMASK_P(target);
const bool at_mask = PTN_ISMASK_P(leaf);
const pt_bitlen_t leaf_masklen = PTN_MASK_BITLEN(leaf);
const pt_bitlen_t target_masklen = PTN_MASK_BITLEN(target);
#endif
pt_insertfunc_t insertfunc = ptree_insert_branch_at_node;
bool matched;

/*
* In all likelyhood we are going simply going to insert a branch
* where this leaf is which will point to the old and new leaves.
*/
KASSERT(PT_LEAF_P(leaf_node));
KASSERT(PTN_LEAF_POSITION(leaf) == id->id_parent_slot);
matched = ptree_matchnode(pt, target, leaf, UINT_MAX,
&id->id_bitoff, &id->id_slot);
if (__predict_false(!inserting_mask)) {
/*
* We aren't inserting a mask nor is the leaf a mask, which
* means we are trying to insert a duplicate leaf. Can't do
* that.
*/
if (!at_mask && matched)
return false;

#ifndef PTNOMASK
/*
* We are at a mask and the leaf we are about to insert
* is at or beyond the mask, we need to convert the mask
* from a leaf to a one-way branch interior mask.
*/
if (at_mask && id->id_bitoff >= leaf_masklen)
insertfunc = ptree_insert_leaf_after_mask;
#endif /* PTNOMASK */
}
#ifndef PTNOMASK
else {
/*
* We are inserting a mask.
*/
if (matched) {
/*
* If the leaf isn't a mask, we obviously have to
* insert the new mask before non-mask leaf. If the
* leaf is a mask, and the new node has a LEQ mask
* length it too needs to inserted before leaf (*).
*
* In other cases, we place the new mask as leaf after
* leaf mask. Which mask comes first will be a one-way
* branch interior mask node which has the other mask
* node as a child.
*
* (*) ptree_insert_mask_before_node can detect a
* duplicate mask and return failure if needed.
*/
if (!at_mask || target_masklen <= leaf_masklen)
insertfunc = ptree_insert_mask_before_node;
else
insertfunc = ptree_insert_leaf_after_mask;
} else if (at_mask && id->id_bitoff >= leaf_masklen) {
/*
* If the new mask has a bit offset GEQ than the leaf's
* mask length, convert the left to a one-way branch
* interior mask and make that point to the new [leaf]
* mask.
*/
insertfunc = ptree_insert_leaf_after_mask;
} else {
/*
* The new mask has a bit offset less than the leaf's
* mask length or if the leaf isn't a mask at all, the
* new mask deserves to be its own leaf so we use the
* default insertfunc to do that.
*/
}
}
#endif /* PTNOMASK */

return (*insertfunc)(pt, target, id);
}

static bool
ptree_insert_node_common(pt_tree_t *pt, void *item)
{
pt_node_t * const target = ITEMTONODE(pt, item);
#ifndef PTNOMASK
const bool inserting_mask = PTN_ISMASK_P(target);
const pt_bitlen_t target_masklen = PTN_MASK_BITLEN(target);
#endif
pt_insertfunc_t insertfunc;
pt_insertdata_t id;

/*
* If this node already exists in the tree, return failure.
*/
if (target == PT_NODE(pt->pt_root))
return false;

/*
* We need a leaf so we can match against. Until we get a leaf
* we having nothing to test against.
*/
if (__predict_false(PT_NULL_P(pt->pt_root))) {
PTN_BRANCH_ROOT_SLOT(&pt->pt_rootnode) = PTN_LEAF(target);
PTN_BRANCH_ODDMAN_SLOT(&pt->pt_rootnode) = PTN_LEAF(target);
PTN_SET_LEAF_POSITION(target, PT_SLOT_ROOT);
PTREE_CHECK(pt);
return true;
}

id.id_bitoff = 0;
id.id_parent = &pt->pt_rootnode;
id.id_parent_slot = PT_SLOT_ROOT;
id.id_insertp = &PTN_BRANCH_ROOT_SLOT(id.id_parent);
for (;;) {
pt_bitoff_t branch_bitoff;
pt_node_t * const ptn = PT_NODE(*id.id_insertp);
id.id_node = *id.id_insertp;

/*
* If this node already exists in the tree, return failure.
*/
if (target == ptn)
return false;

/*
* If we hit a leaf, try to insert target at leaf. We could
* have inlined ptree_insert_leaf here but that would have
* made this routine much harder to understand. Trust the
* compiler to optimize this properly.
*/
if (PT_LEAF_P(id.id_node)) {
KASSERT(PTN_LEAF_POSITION(ptn) == id.id_parent_slot);
insertfunc = ptree_insert_leaf;
break;
}

/*
* If we aren't a leaf, we must be a branch. Make sure we are
* in the slot we think we are.
*/
KASSERT(PT_BRANCH_P(id.id_node));
KASSERT(PTN_BRANCH_POSITION(ptn) == id.id_parent_slot);

/*
* Where is this branch?
*/
branch_bitoff = PTN_BRANCH_BITOFF(ptn);

#ifndef PTNOMASK
/*
* If this is a one-way mask node, its offset must equal
* its mask's bitlen.
*/
KASSERT(!(PTN_ISMASK_P(ptn) && PTN_BRANCH_BITLEN(ptn) == 0) || PTN_MASK_BITLEN(ptn) == branch_bitoff);

/*
* If we are inserting a mask, and we know that at this point
* all bits before the current bit offset match both the target
* and the branch. If the target's mask length is LEQ than
* this branch's bit offset, then this is where the mask needs
* to added to the tree.
*/
if (__predict_false(inserting_mask)
&& (PTN_ISROOT_P(pt, id.id_parent)
|| id.id_bitoff < target_masklen)
&& target_masklen <= branch_bitoff) {
/*
* We don't know about the bits (if any) between
* id.id_bitoff and the target's mask length match
* both the target and the branch. If the target's
* mask length is greater than the current bit offset
* make sure the untested bits match both the target
* and the branch.
*/
if (target_masklen == id.id_bitoff
|| ptree_matchnode(pt, target, ptn, target_masklen,
&id.id_bitoff, &id.id_slot)) {
/*
* The bits matched, so insert the mask as a
* one-way branch.
*/
insertfunc = ptree_insert_mask_before_node;
break;
} else if (id.id_bitoff < branch_bitoff) {
/*
* They didn't match, so create a normal branch
* because this mask needs to a be a new leaf.
*/
insertfunc = ptree_insert_branch_at_node;
break;
}
}
#endif /* PTNOMASK */

/*
* If we are skipping some bits, verify they match the node.
* If they don't match, it means we have a leaf to insert.
* Note that if we are advancing bit by bit, we'll skip
* doing matchnode and walk the tree bit by bit via testnode.
*/
if (id.id_bitoff < branch_bitoff
&& !ptree_matchnode(pt, target, ptn, branch_bitoff,
&id.id_bitoff, &id.id_slot)) {
KASSERT(id.id_bitoff < branch_bitoff);
insertfunc = ptree_insert_branch_at_node;
break;
}

/*
* At this point, all bits before branch_bitoff are known
* to match the target.
*/
KASSERT(id.id_bitoff >= branch_bitoff);

/*
* Descend the tree one level.
*/
id.id_parent = ptn;
id.id_parent_slot = ptree_testnode(pt, target, id.id_parent);
id.id_bitoff += PTN_BRANCH_BITLEN(id.id_parent);
id.id_insertp = &PTN_BRANCH_SLOT(id.id_parent, id.id_parent_slot);
}

/*
* Do the actual insertion.
*/
return (*insertfunc)(pt, target, &id);
}

bool
ptree_insert_node(pt_tree_t *pt, void *item)
{
pt_node_t * const target = ITEMTONODE(pt, item);

memset(target, 0, sizeof(*target));
return ptree_insert_node_common(pt, target);
}

#ifndef PTNOMASK
bool
ptree_insert_mask_node(pt_tree_t *pt, void *item, pt_bitlen_t mask_len)
{
pt_node_t * const target = ITEMTONODE(pt, item);
pt_bitoff_t bitoff = mask_len;
pt_slot_t slot;

memset(target, 0, sizeof(*target));
KASSERT(mask_len == 0 || (~PT__MASK(PTN_MASK_BITLEN) & mask_len) == 0);
/*
* Only the first <mask_len> bits can be non-zero.
* All other bits must be 0.
*/
if (!ptree_matchnode(pt, target, NULL, UINT_MAX, &bitoff, &slot))
return false;
PTN_SET_MASK_BITLEN(target, mask_len);
PTN_MARK_MASK(target);
return ptree_insert_node_common(pt, target);
}
#endif /* !PTNOMASH */

void *
ptree_find_filtered_node(pt_tree_t *pt, const void *key, pt_filter_t filter,
void *filter_arg)
{
#ifndef PTNOMASK
pt_node_t *mask = NULL;
#endif
bool at_mask = false;
pt_node_t *ptn, *parent;
pt_bitoff_t bitoff;
pt_slot_t parent_slot;

if (PT_NULL_P(PTN_BRANCH_ROOT_SLOT(&pt->pt_rootnode)))
return NULL;

bitoff = 0;
parent = &pt->pt_rootnode;
parent_slot = PT_SLOT_ROOT;
for (;;) {
const uintptr_t node = PTN_BRANCH_SLOT(parent, parent_slot);
const pt_slot_t branch_bitoff = PTN_BRANCH_BITOFF(PT_NODE(node));
ptn = PT_NODE(node);

if (PT_LEAF_P(node)) {
#ifndef PTNOMASK
at_mask = PTN_ISMASK_P(ptn);
#endif
break;
}

if (bitoff < branch_bitoff) {
if (!ptree_matchkey(pt, key, ptn, bitoff, branch_bitoff - bitoff)) {
#ifndef PTNOMASK
if (mask != NULL)
return NODETOITEM(pt, mask);
#endif
return NULL;
}
bitoff = branch_bitoff;
}

#ifndef PTNOMASK
if (PTN_ISMASK_P(ptn) && PTN_BRANCH_BITLEN(ptn) == 0
&& (!filter
|| (*filter)(filter_arg, NODETOITEM(pt, ptn),
PT_FILTER_MASK)))
mask = ptn;
#endif

parent = ptn;
parent_slot = ptree_testkey(pt, key, parent);
bitoff += PTN_BRANCH_BITLEN(parent);
}

KASSERT(PTN_ISROOT_P(pt, parent) || PTN_BRANCH_BITOFF(parent) + PTN_BRANCH_BITLEN(parent) == bitoff);
if (!filter || (*filter)(filter_arg, NODETOITEM(pt, ptn), at_mask ? PT_FILTER_MASK : 0)) {
#ifndef PTNOMASK
if (PTN_ISMASK_P(ptn)) {
const pt_bitlen_t mask_len = PTN_MASK_BITLEN(ptn);
if (bitoff == PTN_MASK_BITLEN(ptn))
return NODETOITEM(pt, ptn);
if (ptree_matchkey(pt, key, ptn, bitoff, mask_len - bitoff))
return NODETOITEM(pt, ptn);
} else
#endif /* !PTNOMASK */
if (ptree_matchkey(pt, key, ptn, bitoff, UINT_MAX))
return NODETOITEM(pt, ptn);
}

#ifndef PTNOMASK
/*
* By virtue of how the mask was placed in the tree,
* all nodes descended from it will match it. But the bits
* before the mask still need to be checked and since the
* mask was a branch, that was done implicitly.
*/
if (mask != NULL) {
KASSERT(ptree_matchkey(pt, key, mask, 0, PTN_MASK_BITLEN(mask)));
return NODETOITEM(pt, mask);
}
#endif /* !PTNOMASK */

/*
* Nothing matched.
*/
return NULL;
}

void *
ptree_iterate(pt_tree_t *pt, const void *item, pt_direction_t direction)
{
const pt_node_t * const target = ITEMTONODE(pt, item);
uintptr_t node, next_node;

if (direction != PT_ASCENDING && direction != PT_DESCENDING)
return NULL;

node = PTN_BRANCH_ROOT_SLOT(&pt->pt_rootnode);
if (PT_NULL_P(node))
return NULL;

if (item == NULL) {
pt_node_t * const ptn = PT_NODE(node);
if (direction == PT_ASCENDING
&& PTN_ISMASK_P(ptn) && PTN_BRANCH_BITLEN(ptn) == 0)
return NODETOITEM(pt, ptn);
next_node = node;
} else {
#ifndef PTNOMASK
uintptr_t mask_node = PT_NULL;
#endif /* !PTNOMASK */
next_node = PT_NULL;
while (!PT_LEAF_P(node)) {
pt_node_t * const ptn = PT_NODE(node);
pt_slot_t slot;
#ifndef PTNOMASK
if (PTN_ISMASK_P(ptn) && PTN_BRANCH_BITLEN(ptn) == 0) {
if (ptn == target)
break;
if (direction == PT_DESCENDING) {
mask_node = node;
next_node = PT_NULL;
}
}
#endif /* !PTNOMASK */
slot = ptree_testnode(pt, target, ptn);
node = PTN_BRANCH_SLOT(ptn, slot);
if (direction == PT_ASCENDING) {
if (slot != (pt_slot_t)((1 << PTN_BRANCH_BITLEN(ptn)) - 1))
next_node = PTN_BRANCH_SLOT(ptn, slot + 1);
} else {
if (slot > 0) {
#ifndef PTNOMASK
mask_node = PT_NULL;
#endif /* !PTNOMASK */
next_node = PTN_BRANCH_SLOT(ptn, slot - 1);
}
}
}
if (PT_NODE(node) != target)
return NULL;
#ifndef PTNOMASK
if (PT_BRANCH_P(node)) {
pt_node_t *ptn = PT_NODE(node);
KASSERT(PTN_ISMASK_P(PT_NODE(node)) && PTN_BRANCH_BITLEN(PT_NODE(node)) == 0);
if (direction == PT_ASCENDING) {
next_node = PTN_BRANCH_ROOT_SLOT(ptn);
ptn = PT_NODE(next_node);
}
}
/*
* When descending, if we countered a mask node then that's
* we want to return.
*/
if (direction == PT_DESCENDING && !PT_NULL_P(mask_node)) {
KASSERT(PT_NULL_P(next_node));
return NODETOITEM(pt, PT_NODE(mask_node));
}
#endif /* !PTNOMASK */
}

node = next_node;
if (PT_NULL_P(node))
return NULL;

while (!PT_LEAF_P(node)) {
pt_node_t * const ptn = PT_NODE(node);
pt_slot_t slot;
if (direction == PT_ASCENDING) {
#ifndef PTNOMASK
if (PT_BRANCH_P(node)
&& PTN_ISMASK_P(ptn)
&& PTN_BRANCH_BITLEN(ptn) == 0)
return NODETOITEM(pt, ptn);
#endif /* !PTNOMASK */
slot = PT_SLOT_LEFT;
} else {
slot = (1 << PTN_BRANCH_BITLEN(ptn)) - 1;
}
node = PTN_BRANCH_SLOT(ptn, slot);
}
return NODETOITEM(pt, PT_NODE(node));
}

void
ptree_remove_node(pt_tree_t *pt, void *item)
{
pt_node_t * const target = ITEMTONODE(pt, item);
const pt_slot_t leaf_slot = PTN_LEAF_POSITION(target);
const pt_slot_t branch_slot = PTN_BRANCH_POSITION(target);
pt_node_t *ptn, *parent;
uintptr_t node;
uintptr_t *removep;
uintptr_t *nodep;
pt_bitoff_t bitoff;
pt_slot_t parent_slot;
#ifndef PTNOMASK
bool at_mask;
#endif

if (PT_NULL_P(PTN_BRANCH_ROOT_SLOT(&pt->pt_rootnode))) {
KASSERT(!PT_NULL_P(PTN_BRANCH_ROOT_SLOT(&pt->pt_rootnode)));
return;
}

bitoff = 0;
removep = NULL;
nodep = NULL;
parent = &pt->pt_rootnode;
parent_slot = PT_SLOT_ROOT;
for (;;) {
node = PTN_BRANCH_SLOT(parent, parent_slot);
ptn = PT_NODE(node);
#ifndef PTNOMASK
at_mask = PTN_ISMASK_P(ptn);
#endif

if (PT_LEAF_P(node))
break;

/*
* If we are at the target, then we are looking at its branch
* identity. We need to remember who's pointing at it so we
* stop them from doing that.
*/
if (__predict_false(ptn == target)) {
KASSERT(nodep == NULL);
#ifndef PTNOMASK
/*
* Interior mask nodes are trivial to get rid of.
*/
if (at_mask && PTN_BRANCH_BITLEN(ptn) == 0) {
PTN_BRANCH_SLOT(parent, parent_slot) =
PTN_BRANCH_ROOT_SLOT(ptn);
KASSERT(PT_NULL_P(PTN_BRANCH_ODDMAN_SLOT(ptn)));
PTREE_CHECK(pt);
return;
}
#endif /* !PTNOMASK */
nodep = &PTN_BRANCH_SLOT(parent, parent_slot);
KASSERT(*nodep == PTN_BRANCH(target));
}
/*
* We need also need to know who's pointing at our parent.
* After we remove ourselves from our parent, he'll only
* have one child and that's unacceptable. So we replace
* the pointer to the parent with our abandoned sibling.
*/
removep = &PTN_BRANCH_SLOT(parent, parent_slot);

/*
* Descend into the tree.
*/
parent = ptn;
parent_slot = ptree_testnode(pt, target, parent);
bitoff += PTN_BRANCH_BITLEN(parent);
}

/*
* We better have found that the leaf we are looking for is target.
*/
if (target != ptn) {
KASSERT(target == ptn);
return;
}

/*
* If we didn't encounter target as branch, then target must be the
* oddman-out.
*/
if (nodep == NULL) {
KASSERT(PTN_BRANCH_ODDMAN_SLOT(&pt->pt_rootnode) == PTN_LEAF(target));
KASSERT(nodep == NULL);
nodep = &PTN_BRANCH_ODDMAN_SLOT(&pt->pt_rootnode);
}

KASSERT((removep == NULL) == (parent == &pt->pt_rootnode));

/*
* We have to special remove the last leaf from the root since
* the only time the tree can a PT_NULL node is when it's empty.
*/
if (__predict_false(PTN_ISROOT_P(pt, parent))) {
KASSERT(removep == NULL);
KASSERT(parent == &pt->pt_rootnode);
KASSERT(nodep == &PTN_BRANCH_ODDMAN_SLOT(&pt->pt_rootnode));
KASSERT(*nodep == PTN_LEAF(target));
PTN_BRANCH_ROOT_SLOT(&pt->pt_rootnode) = PT_NULL;
PTN_BRANCH_ODDMAN_SLOT(&pt->pt_rootnode) = PT_NULL;
return;
}

KASSERT((parent == target) == (removep == nodep));
if (PTN_BRANCH(parent) == PTN_BRANCH_SLOT(target, PTN_BRANCH_POSITION(parent))) {
/*
* The pointer to the parent actually lives in the target's
* branch identity. We can't just move the target's branch
* identity since that would result in the parent pointing
* to its own branch identity and that's forbidden.
*/
const pt_slot_t slot = PTN_BRANCH_POSITION(parent);
const pt_slot_t other_slot = slot ^ PT_SLOT_OTHER;
const pt_bitlen_t parent_bitlen = PTN_BRANCH_BITLEN(parent);

KASSERT(PTN_BRANCH_BITOFF(target) < PTN_BRANCH_BITOFF(parent));

/*
* This gets so confusing. The target's branch identity
* points to the branch identity of the parent of the target's
* leaf identity:
*
* TB = { X, PB = { TL, Y } }
* or TB = { X, PB = { TL } }
*
* So we can't move the target's branch identity to the parent
* because that would corrupt the tree.
*/
if (__predict_true(parent_bitlen > 0)) {
/*
* The parent is a two-way branch. We have to have
* do to this change in two steps to keep internally
* consistent. First step is to copy our sibling from
* our parent to where we are pointing to parent's
* branch identity. This remove all references to his
* branch identity from the tree. We then simply make
* the parent assume the target's branching duties.
*
* TB = { X, PB = { Y, TL } } --> PB = { X, Y }.
* TB = { X, PB = { TL, Y } } --> PB = { X, Y }.
* TB = { PB = { Y, TL }, X } --> PB = { Y, X }.
* TB = { PB = { TL, Y }, X } --> PB = { Y, X }.
*/
PTN_BRANCH_SLOT(target, slot) =
PTN_BRANCH_SLOT(parent, parent_slot ^ PT_SLOT_OTHER);
*nodep = ptree_move_branch(pt, parent, target);
PTREE_CHECK(pt);
return;
} else {
/*
* If parent was a one-way branch, it must have been
* mask which pointed to a single leaf which we are
* removing. This means we have to convert the
* parent back to a leaf node. So in the same
* position that target pointed to parent, we place
* leaf pointer to parent. In the other position,
* we just put the other node from target.
*
* TB = { X, PB = { TL } } --> PB = { X, PL }
*/
KASSERT(PTN_ISMASK_P(parent));
KASSERT(slot == ptree_testnode(pt, parent, target));
PTN_BRANCH_SLOT(parent, slot) = PTN_LEAF(parent);
PTN_BRANCH_SLOT(parent, other_slot) =
PTN_BRANCH_SLOT(target, other_slot);
PTN_SET_LEAF_POSITION(parent,slot);
PTN_SET_BRANCH_BITLEN(parent, 1);
}
PTN_SET_BRANCH_BITOFF(parent, PTN_BRANCH_BITOFF(target));
PTN_SET_BRANCH_POSITION(parent, PTN_BRANCH_POSITION(target));

*nodep = PTN_BRANCH(parent);
PTREE_CHECK(pt);
return;
}

#ifndef PTNOMASK
if (__predict_false(PTN_BRANCH_BITLEN(parent) == 0)) {
/*
* Parent was a one-way branch which is changing back to a leaf.
* Since parent is no longer a one-way branch, it can take over
* target's branching duties.
*
* GB = { PB = { TL } } --> GB = { PL }
* TB = { X, Y } --> PB = { X, Y }
*/
KASSERT(PTN_ISMASK_P(parent));
KASSERT(parent != target);
*removep = PTN_LEAF(parent);
} else
#endif /* !PTNOMASK */
{
/*
* Now we are the normal removal case. Since after the
* target's leaf identity is removed from the its parent,
* that parent will only have one descendant. So we can
* just as easily replace the node that has the parent's
* branch identity with the surviving node. This freeing
* parent from its branching duties which means it can
* take over target's branching duties.
*
* GB = { PB = { X, TL } } --> GB = { X }
* TB = { V, W } --> PB = { V, W }
*/
const pt_slot_t other_slot = parent_slot ^ PT_SLOT_OTHER;
uintptr_t other_node = PTN_BRANCH_SLOT(parent, other_slot);
const pt_slot_t target_slot = (parent == target ? branch_slot : leaf_slot);

*removep = other_node;

ptree_set_position(other_node, target_slot);

/*
* If target's branch identity contained its leaf identity, we
* have nothing left to do. We've already moved 'X' so there
* is no longer anything in the target's branch identity that
* has to be preserved.
*/
if (parent == target) {
/*
* GB = { TB = { X, TL } } --> GB = { X }
* TB = { X, TL } --> don't care
*/
PTREE_CHECK(pt);
return;
}
}

/*
* If target wasn't used as a branch, then it must have been the
* oddman-out of the tree (the one node that doesn't have a branch
* identity). This makes parent the new oddman-out.
*/
if (*nodep == PTN_LEAF(target)) {
KASSERT(nodep == &PTN_BRANCH_ODDMAN_SLOT(&pt->pt_rootnode));
PTN_BRANCH_ODDMAN_SLOT(&pt->pt_rootnode) = PTN_LEAF(parent);
PTREE_CHECK(pt);
return;
}

/*
* Finally move the target's branching duties to the parent.
*/
KASSERT(PTN_BRANCH_BITOFF(parent) > PTN_BRANCH_BITOFF(target));
*nodep = ptree_move_branch(pt, parent, target);
PTREE_CHECK(pt);
}

#ifdef PTCHECK
static const pt_node_t *
ptree_check_find_node2(const pt_tree_t *pt, const pt_node_t *parent,
uintptr_t target)
{
const pt_bitlen_t slots = 1 << PTN_BRANCH_BITLEN(parent);
pt_slot_t slot;

for (slot = 0; slot < slots; slot++) {
const uintptr_t node = PTN_BRANCH_SLOT(parent, slot);
if (PTN_BRANCH_SLOT(parent, slot) == node)
return parent;
}
for (slot = 0; slot < slots; slot++) {
const uintptr_t node = PTN_BRANCH_SLOT(parent, slot);
const pt_node_t *branch;
if (!PT_BRANCH_P(node))
continue;
branch = ptree_check_find_node2(pt, PT_NODE(node), target);
if (branch != NULL)
return branch;
}

return NULL;
}

static bool
ptree_check_leaf(const pt_tree_t *pt, const pt_node_t *parent,
const pt_node_t *ptn)
{
const pt_bitoff_t leaf_position = PTN_LEAF_POSITION(ptn);
const pt_bitlen_t bitlen = PTN_BRANCH_BITLEN(ptn);
const pt_bitlen_t mask_len = PTN_MASK_BITLEN(ptn);
const uintptr_t leaf_node = PTN_LEAF(ptn);
const bool is_parent_root = (parent == &pt->pt_rootnode);
const bool is_mask = PTN_ISMASK_P(ptn);
bool ok = true;

if (is_parent_root) {
ok = ok && PTN_BRANCH_ODDMAN_SLOT(parent) == leaf_node;
KASSERT(ok);
return ok;
}

if (is_mask && PTN_ISMASK_P(parent) && PTN_BRANCH_BITLEN(parent) == 0) {
ok = ok && PTN_MASK_BITLEN(parent) < mask_len;
KASSERT(ok);
ok = ok && PTN_BRANCH_BITOFF(parent) < mask_len;
KASSERT(ok);
}
ok = ok && PTN_BRANCH_SLOT(parent, leaf_position) == leaf_node;
KASSERT(ok);
ok = ok && leaf_position == ptree_testnode(pt, ptn, parent);
KASSERT(ok);
if (PTN_BRANCH_ODDMAN_SLOT(&pt->pt_rootnode) != leaf_node) {
ok = ok && bitlen > 0;
KASSERT(ok);
ok = ok && ptn == ptree_check_find_node2(pt, ptn, PTN_LEAF(ptn));
KASSERT(ok);
}
return ok;
}

static bool
ptree_check_branch(const pt_tree_t *pt, const pt_node_t *parent,
const pt_node_t *ptn)
{
const bool is_parent_root = (parent == &pt->pt_rootnode);
const pt_slot_t branch_slot = PTN_BRANCH_POSITION(ptn);
const pt_bitoff_t bitoff = PTN_BRANCH_BITOFF(ptn);
const pt_bitoff_t bitlen = PTN_BRANCH_BITLEN(ptn);
const pt_bitoff_t parent_bitoff = PTN_BRANCH_BITOFF(parent);
const pt_bitoff_t parent_bitlen = PTN_BRANCH_BITLEN(parent);
const bool is_parent_mask = PTN_ISMASK_P(parent) && parent_bitlen == 0;
const bool is_mask = PTN_ISMASK_P(ptn) && bitlen == 0;
const pt_bitoff_t parent_mask_len = PTN_MASK_BITLEN(parent);
const pt_bitoff_t mask_len = PTN_MASK_BITLEN(ptn);
const pt_bitlen_t slots = 1 << bitlen;
pt_slot_t slot;
bool ok = true;

ok = ok && PTN_BRANCH_SLOT(parent, branch_slot) == PTN_BRANCH(ptn);
KASSERT(ok);
ok = ok && branch_slot == ptree_testnode(pt, ptn, parent);
KASSERT(ok);

if (is_mask) {
ok = ok && bitoff == mask_len;
KASSERT(ok);
if (is_parent_mask) {
ok = ok && parent_mask_len < mask_len;
KASSERT(ok);
ok = ok && parent_bitoff < bitoff;
KASSERT(ok);
}
} else {
if (is_parent_mask) {
ok = ok && parent_bitoff <= bitoff;
} else if (!is_parent_root) {
ok = ok && parent_bitoff < bitoff;
}
KASSERT(ok);
}

for (slot = 0; slot < slots; slot++) {
const uintptr_t node = PTN_BRANCH_SLOT(ptn, slot);
pt_bitoff_t tmp_bitoff = 0;
pt_slot_t tmp_slot;
ok = ok && node != PTN_BRANCH(ptn);
KASSERT(ok);
if (bitlen > 0) {
ok = ok && ptree_matchnode(pt, PT_NODE(node), ptn, bitoff, &tmp_bitoff, &tmp_slot);
KASSERT(ok);
tmp_slot = ptree_testnode(pt, PT_NODE(node), ptn);
ok = ok && slot == tmp_slot;
KASSERT(ok);
}
if (PT_LEAF_P(node))
ok = ok && ptree_check_leaf(pt, ptn, PT_NODE(node));
else
ok = ok && ptree_check_branch(pt, ptn, PT_NODE(node));
}

return ok;
}
#endif /* PTCHECK */

/*ARGSUSED*/
bool
ptree_check(const pt_tree_t *pt)
{
bool ok = true;
#ifdef PTCHECK
const pt_node_t * const parent = &pt->pt_rootnode;
const uintptr_t node = pt->pt_root;
const pt_node_t * const ptn = PT_NODE(node);

ok = ok && PTN_BRANCH_BITOFF(parent) == 0;
ok = ok && !PTN_ISMASK_P(parent);

if (PT_NULL_P(node))
return ok;

if (PT_LEAF_P(node))
ok = ok && ptree_check_leaf(pt, parent, ptn);
else
ok = ok && ptree_check_branch(pt, parent, ptn);
#endif
return ok;
}

bool
ptree_mask_node_p(pt_tree_t *pt, const void *item, pt_bitlen_t *lenp)
{
const pt_node_t * const mask = ITEMTONODE(pt, item);

if (!PTN_ISMASK_P(mask))
return false;

if (lenp != NULL)
*lenp = PTN_MASK_BITLEN(mask);

return true;
}