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This commit is contained in:
Brian Behlendorf
2008-11-20 12:01:55 -08:00
commit 34dc7c2f25
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zfs/lib/libavl/Makefile.in
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subdir-m += include
DISTFILES = avl.c
MODULE := zavl
LIBRARY := libavl
# Compile as kernel module. Needed symlinks created for all
# k* objects created by top level configure script.
EXTRA_CFLAGS = @KERNELCPPFLAGS@
EXTRA_CFLAGS += -I@LIBDIR@/libavl/include
obj-m := ${MODULE}.o
${MODULE}-objs += kavl.o # Generic AVL support
# Compile as shared library. There's an extra useless host program
# here called 'zu' because it was the easiest way I could convince
# the kernel build system to construct a user space shared library.
HOSTCFLAGS += @HOSTCFLAGS@
HOSTCFLAGS += -I@LIBDIR@/libsolcompat/include
HOSTCFLAGS += -I@LIBDIR@/libport/include
HOSTCFLAGS += -I@LIBDIR@/libavl/include
hostprogs-y := zu
always := $(hostprogs-y)
zu-objs := zu.o ${LIBRARY}.so
${LIBRARY}-objs += uavl.o
zfs/lib/libavl/avl.c
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/*
* CDDL HEADER START
*
* The contents of this file are subject to the terms of the
* Common Development and Distribution License (the "License").
* You may not use this file except in compliance with the License.
*
* You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
* or http://www.opensolaris.org/os/licensing.
* See the License for the specific language governing permissions
* and limitations under the License.
*
* When distributing Covered Code, include this CDDL HEADER in each
* file and include the License file at usr/src/OPENSOLARIS.LICENSE.
* If applicable, add the following below this CDDL HEADER, with the
* fields enclosed by brackets "[]" replaced with your own identifying
* information: Portions Copyright [yyyy] [name of copyright owner]
*
* CDDL HEADER END
*/
/*
* Copyright 2006 Sun Microsystems, Inc. All rights reserved.
* Use is subject to license terms.
*/
/*
* AVL - generic AVL tree implementation for kernel use
*
* A complete description of AVL trees can be found in many CS textbooks.
*
* Here is a very brief overview. An AVL tree is a binary search tree that is
* almost perfectly balanced. By "almost" perfectly balanced, we mean that at
* any given node, the left and right subtrees are allowed to differ in height
* by at most 1 level.
*
* This relaxation from a perfectly balanced binary tree allows doing
* insertion and deletion relatively efficiently. Searching the tree is
* still a fast operation, roughly O(log(N)).
*
* The key to insertion and deletion is a set of tree maniuplations called
* rotations, which bring unbalanced subtrees back into the semi-balanced state.
*
* This implementation of AVL trees has the following peculiarities:
*
* - The AVL specific data structures are physically embedded as fields
* in the "using" data structures. To maintain generality the code
* must constantly translate between "avl_node_t *" and containing
* data structure "void *"s by adding/subracting the avl_offset.
*
* - Since the AVL data is always embedded in other structures, there is
* no locking or memory allocation in the AVL routines. This must be
* provided for by the enclosing data structure's semantics. Typically,
* avl_insert()/_add()/_remove()/avl_insert_here() require some kind of
* exclusive write lock. Other operations require a read lock.
*
* - The implementation uses iteration instead of explicit recursion,
* since it is intended to run on limited size kernel stacks. Since
* there is no recursion stack present to move "up" in the tree,
* there is an explicit "parent" link in the avl_node_t.
*
* - The left/right children pointers of a node are in an array.
* In the code, variables (instead of constants) are used to represent
* left and right indices. The implementation is written as if it only
* dealt with left handed manipulations. By changing the value assigned
* to "left", the code also works for right handed trees. The
* following variables/terms are frequently used:
*
* int left; // 0 when dealing with left children,
* // 1 for dealing with right children
*
* int left_heavy; // -1 when left subtree is taller at some node,
* // +1 when right subtree is taller
*
* int right; // will be the opposite of left (0 or 1)
* int right_heavy;// will be the opposite of left_heavy (-1 or 1)
*
* int direction; // 0 for "<" (ie. left child); 1 for ">" (right)
*
* Though it is a little more confusing to read the code, the approach
* allows using half as much code (and hence cache footprint) for tree
* manipulations and eliminates many conditional branches.
*
* - The avl_index_t is an opaque "cookie" used to find nodes at or
* adjacent to where a new value would be inserted in the tree. The value
* is a modified "avl_node_t *". The bottom bit (normally 0 for a
* pointer) is set to indicate if that the new node has a value greater
* than the value of the indicated "avl_node_t *".
*/
#include <sys/types.h>
#include <sys/param.h>
#include <sys/debug.h>
#include <sys/avl.h>
#include <sys/cmn_err.h>
/*
* Small arrays to translate between balance (or diff) values and child indeces.
*
* Code that deals with binary tree data structures will randomly use
* left and right children when examining a tree. C "if()" statements
* which evaluate randomly suffer from very poor hardware branch prediction.
* In this code we avoid some of the branch mispredictions by using the
* following translation arrays. They replace random branches with an
* additional memory reference. Since the translation arrays are both very
* small the data should remain efficiently in cache.
*/
static const int avl_child2balance[2] = {-1, 1};
static const int avl_balance2child[] = {0, 0, 1};
/*
* Walk from one node to the previous valued node (ie. an infix walk
* towards the left). At any given node we do one of 2 things:
*
* - If there is a left child, go to it, then to it's rightmost descendant.
*
* - otherwise we return thru parent nodes until we've come from a right child.
*
* Return Value:
* NULL - if at the end of the nodes
* otherwise next node
*/
void *
avl_walk(avl_tree_t *tree, void *oldnode, int left)
{
size_t off = tree->avl_offset;
avl_node_t *node = AVL_DATA2NODE(oldnode, off);
int right = 1 - left;
int was_child;
/*
* nowhere to walk to if tree is empty
*/
if (node == NULL)
return (NULL);
/*
* Visit the previous valued node. There are two possibilities:
*
* If this node has a left child, go down one left, then all
* the way right.
*/
if (node->avl_child[left] != NULL) {
for (node = node->avl_child[left];
node->avl_child[right] != NULL;
node = node->avl_child[right])
;
/*
* Otherwise, return thru left children as far as we can.
*/
} else {
for (;;) {
was_child = AVL_XCHILD(node);
node = AVL_XPARENT(node);
if (node == NULL)
return (NULL);
if (was_child == right)
break;
}
}
return (AVL_NODE2DATA(node, off));
}
/*
* Return the lowest valued node in a tree or NULL.
* (leftmost child from root of tree)
*/
void *
avl_first(avl_tree_t *tree)
{
avl_node_t *node;
avl_node_t *prev = NULL;
size_t off = tree->avl_offset;
for (node = tree->avl_root; node != NULL; node = node->avl_child[0])
prev = node;
if (prev != NULL)
return (AVL_NODE2DATA(prev, off));
return (NULL);
}
/*
* Return the highest valued node in a tree or NULL.
* (rightmost child from root of tree)
*/
void *
avl_last(avl_tree_t *tree)
{
avl_node_t *node;
avl_node_t *prev = NULL;
size_t off = tree->avl_offset;
for (node = tree->avl_root; node != NULL; node = node->avl_child[1])
prev = node;
if (prev != NULL)
return (AVL_NODE2DATA(prev, off));
return (NULL);
}
/*
* Access the node immediately before or after an insertion point.
*
* "avl_index_t" is a (avl_node_t *) with the bottom bit indicating a child
*
* Return value:
* NULL: no node in the given direction
* "void *" of the found tree node
*/
void *
avl_nearest(avl_tree_t *tree, avl_index_t where, int direction)
{
int child = AVL_INDEX2CHILD(where);
avl_node_t *node = AVL_INDEX2NODE(where);
void *data;
size_t off = tree->avl_offset;
if (node == NULL) {
ASSERT(tree->avl_root == NULL);
return (NULL);
}
data = AVL_NODE2DATA(node, off);
if (child != direction)
return (data);
return (avl_walk(tree, data, direction));
}
/*
* Search for the node which contains "value". The algorithm is a
* simple binary tree search.
*
* return value:
* NULL: the value is not in the AVL tree
* *where (if not NULL) is set to indicate the insertion point
* "void *" of the found tree node
*/
void *
avl_find(avl_tree_t *tree, void *value, avl_index_t *where)
{
avl_node_t *node;
avl_node_t *prev = NULL;
int child = 0;
int diff;
size_t off = tree->avl_offset;
for (node = tree->avl_root; node != NULL;
node = node->avl_child[child]) {
prev = node;
diff = tree->avl_compar(value, AVL_NODE2DATA(node, off));
ASSERT(-1 <= diff && diff <= 1);
if (diff == 0) {
#ifdef DEBUG
if (where != NULL)
*where = 0;
#endif
return (AVL_NODE2DATA(node, off));
}
child = avl_balance2child[1 + diff];
}
if (where != NULL)
*where = AVL_MKINDEX(prev, child);
return (NULL);
}
/*
* Perform a rotation to restore balance at the subtree given by depth.
*
* This routine is used by both insertion and deletion. The return value
* indicates:
* 0 : subtree did not change height
* !0 : subtree was reduced in height
*
* The code is written as if handling left rotations, right rotations are
* symmetric and handled by swapping values of variables right/left[_heavy]
*
* On input balance is the "new" balance at "node". This value is either
* -2 or +2.
*/
static int
avl_rotation(avl_tree_t *tree, avl_node_t *node, int balance)
{
int left = !(balance < 0); /* when balance = -2, left will be 0 */
int right = 1 - left;
int left_heavy = balance >> 1;
int right_heavy = -left_heavy;
avl_node_t *parent = AVL_XPARENT(node);
avl_node_t *child = node->avl_child[left];
avl_node_t *cright;
avl_node_t *gchild;
avl_node_t *gright;
avl_node_t *gleft;
int which_child = AVL_XCHILD(node);
int child_bal = AVL_XBALANCE(child);
/* BEGIN CSTYLED */
/*
* case 1 : node is overly left heavy, the left child is balanced or
* also left heavy. This requires the following rotation.
*
* (node bal:-2)
* / \
* / \
* (child bal:0 or -1)
* / \
* / \
* cright
*
* becomes:
*
* (child bal:1 or 0)
* / \
* / \
* (node bal:-1 or 0)
* / \
* / \
* cright
*
* we detect this situation by noting that child's balance is not
* right_heavy.
*/
/* END CSTYLED */
if (child_bal != right_heavy) {
/*
* compute new balance of nodes
*
* If child used to be left heavy (now balanced) we reduced
* the height of this sub-tree -- used in "return...;" below
*/
child_bal += right_heavy; /* adjust towards right */
/*
* move "cright" to be node's left child
*/
cright = child->avl_child[right];
node->avl_child[left] = cright;
if (cright != NULL) {
AVL_SETPARENT(cright, node);
AVL_SETCHILD(cright, left);
}
/*
* move node to be child's right child
*/
child->avl_child[right] = node;
AVL_SETBALANCE(node, -child_bal);
AVL_SETCHILD(node, right);
AVL_SETPARENT(node, child);
/*
* update the pointer into this subtree
*/
AVL_SETBALANCE(child, child_bal);
AVL_SETCHILD(child, which_child);
AVL_SETPARENT(child, parent);
if (parent != NULL)
parent->avl_child[which_child] = child;
else
tree->avl_root = child;
return (child_bal == 0);
}
/* BEGIN CSTYLED */
/*
* case 2 : When node is left heavy, but child is right heavy we use
* a different rotation.
*
* (node b:-2)
* / \
* / \
* / \
* (child b:+1)
* / \
* / \
* (gchild b: != 0)
* / \
* / \
* gleft gright
*
* becomes:
*
* (gchild b:0)
* / \
* / \
* / \
* (child b:?) (node b:?)
* / \ / \
* / \ / \
* gleft gright
*
* computing the new balances is more complicated. As an example:
* if gchild was right_heavy, then child is now left heavy
* else it is balanced
*/
/* END CSTYLED */
gchild = child->avl_child[right];
gleft = gchild->avl_child[left];
gright = gchild->avl_child[right];
/*
* move gright to left child of node and
*
* move gleft to right child of node
*/
node->avl_child[left] = gright;
if (gright != NULL) {
AVL_SETPARENT(gright, node);
AVL_SETCHILD(gright, left);
}
child->avl_child[right] = gleft;
if (gleft != NULL) {
AVL_SETPARENT(gleft, child);
AVL_SETCHILD(gleft, right);
}
/*
* move child to left child of gchild and
*
* move node to right child of gchild and
*
* fixup parent of all this to point to gchild
*/
balance = AVL_XBALANCE(gchild);
gchild->avl_child[left] = child;
AVL_SETBALANCE(child, (balance == right_heavy ? left_heavy : 0));
AVL_SETPARENT(child, gchild);
AVL_SETCHILD(child, left);
gchild->avl_child[right] = node;
AVL_SETBALANCE(node, (balance == left_heavy ? right_heavy : 0));
AVL_SETPARENT(node, gchild);
AVL_SETCHILD(node, right);
AVL_SETBALANCE(gchild, 0);
AVL_SETPARENT(gchild, parent);
AVL_SETCHILD(gchild, which_child);
if (parent != NULL)
parent->avl_child[which_child] = gchild;
else
tree->avl_root = gchild;
return (1); /* the new tree is always shorter */
}
/*
* Insert a new node into an AVL tree at the specified (from avl_find()) place.
*
* Newly inserted nodes are always leaf nodes in the tree, since avl_find()
* searches out to the leaf positions. The avl_index_t indicates the node
* which will be the parent of the new node.
*
* After the node is inserted, a single rotation further up the tree may
* be necessary to maintain an acceptable AVL balance.
*/
void
avl_insert(avl_tree_t *tree, void *new_data, avl_index_t where)
{
avl_node_t *node;
avl_node_t *parent = AVL_INDEX2NODE(where);
int old_balance;
int new_balance;
int which_child = AVL_INDEX2CHILD(where);
size_t off = tree->avl_offset;
ASSERT(tree);
#ifdef _LP64
ASSERT(((uintptr_t)new_data & 0x7) == 0);
#endif
node = AVL_DATA2NODE(new_data, off);
/*
* First, add the node to the tree at the indicated position.
*/
++tree->avl_numnodes;
node->avl_child[0] = NULL;
node->avl_child[1] = NULL;
AVL_SETCHILD(node, which_child);
AVL_SETBALANCE(node, 0);
AVL_SETPARENT(node, parent);
if (parent != NULL) {
ASSERT(parent->avl_child[which_child] == NULL);
parent->avl_child[which_child] = node;
} else {
ASSERT(tree->avl_root == NULL);
tree->avl_root = node;
}
/*
* Now, back up the tree modifying the balance of all nodes above the
* insertion point. If we get to a highly unbalanced ancestor, we
* need to do a rotation. If we back out of the tree we are done.
* If we brought any subtree into perfect balance (0), we are also done.
*/
for (;;) {
node = parent;
if (node == NULL)
return;
/*
* Compute the new balance
*/
old_balance = AVL_XBALANCE(node);
new_balance = old_balance + avl_child2balance[which_child];
/*
* If we introduced equal balance, then we are done immediately
*/
if (new_balance == 0) {
AVL_SETBALANCE(node, 0);
return;
}
/*
* If both old and new are not zero we went
* from -1 to -2 balance, do a rotation.
*/
if (old_balance != 0)
break;
AVL_SETBALANCE(node, new_balance);
parent = AVL_XPARENT(node);
which_child = AVL_XCHILD(node);
}
/*
* perform a rotation to fix the tree and return
*/
(void) avl_rotation(tree, node, new_balance);
}
/*
* Insert "new_data" in "tree" in the given "direction" either after or
* before (AVL_AFTER, AVL_BEFORE) the data "here".
*
* Insertions can only be done at empty leaf points in the tree, therefore
* if the given child of the node is already present we move to either
* the AVL_PREV or AVL_NEXT and reverse the insertion direction. Since
* every other node in the tree is a leaf, this always works.
*
* To help developers using this interface, we assert that the new node
* is correctly ordered at every step of the way in DEBUG kernels.
*/
void
avl_insert_here(
avl_tree_t *tree,
void *new_data,
void *here,
int direction)
{
avl_node_t *node;
int child = direction; /* rely on AVL_BEFORE == 0, AVL_AFTER == 1 */
#ifdef DEBUG
int diff;
#endif
ASSERT(tree != NULL);
ASSERT(new_data != NULL);
ASSERT(here != NULL);
ASSERT(direction == AVL_BEFORE || direction == AVL_AFTER);
/*
* If corresponding child of node is not NULL, go to the neighboring
* node and reverse the insertion direction.
*/
node = AVL_DATA2NODE(here, tree->avl_offset);
#ifdef DEBUG
diff = tree->avl_compar(new_data, here);
ASSERT(-1 <= diff && diff <= 1);
ASSERT(diff != 0);
ASSERT(diff > 0 ? child == 1 : child == 0);
#endif
if (node->avl_child[child] != NULL) {
node = node->avl_child[child];
child = 1 - child;
while (node->avl_child[child] != NULL) {
#ifdef DEBUG
diff = tree->avl_compar(new_data,
AVL_NODE2DATA(node, tree->avl_offset));
ASSERT(-1 <= diff && diff <= 1);
ASSERT(diff != 0);
ASSERT(diff > 0 ? child == 1 : child == 0);
#endif
node = node->avl_child[child];
}
#ifdef DEBUG
diff = tree->avl_compar(new_data,
AVL_NODE2DATA(node, tree->avl_offset));
ASSERT(-1 <= diff && diff <= 1);
ASSERT(diff != 0);
ASSERT(diff > 0 ? child == 1 : child == 0);
#endif
}
ASSERT(node->avl_child[child] == NULL);
avl_insert(tree, new_data, AVL_MKINDEX(node, child));
}
/*
* Add a new node to an AVL tree.
*/
void
avl_add(avl_tree_t *tree, void *new_node)
{
avl_index_t where;
/*
* This is unfortunate. We want to call panic() here, even for
* non-DEBUG kernels. In userland, however, we can't depend on anything
* in libc or else the rtld build process gets confused. So, all we can
* do in userland is resort to a normal ASSERT().
*/
if (avl_find(tree, new_node, &where) != NULL)
#ifdef _KERNEL
panic("avl_find() succeeded inside avl_add()");
#else
ASSERT(0);
#endif
avl_insert(tree, new_node, where);
}
/*
* Delete a node from the AVL tree. Deletion is similar to insertion, but
* with 2 complications.
*
* First, we may be deleting an interior node. Consider the following subtree:
*
* d c c
* / \ / \ / \
* b e b e b e
* / \ / \ /
* a c a a
*
* When we are deleting node (d), we find and bring up an adjacent valued leaf
* node, say (c), to take the interior node's place. In the code this is
* handled by temporarily swapping (d) and (c) in the tree and then using
* common code to delete (d) from the leaf position.
*
* Secondly, an interior deletion from a deep tree may require more than one
* rotation to fix the balance. This is handled by moving up the tree through
* parents and applying rotations as needed. The return value from
* avl_rotation() is used to detect when a subtree did not change overall
* height due to a rotation.
*/
void
avl_remove(avl_tree_t *tree, void *data)
{
avl_node_t *delete;
avl_node_t *parent;
avl_node_t *node;
avl_node_t tmp;
int old_balance;
int new_balance;
int left;
int right;
int which_child;
size_t off = tree->avl_offset;
ASSERT(tree);
delete = AVL_DATA2NODE(data, off);
/*
* Deletion is easiest with a node that has at most 1 child.
* We swap a node with 2 children with a sequentially valued
* neighbor node. That node will have at most 1 child. Note this
* has no effect on the ordering of the remaining nodes.
*
* As an optimization, we choose the greater neighbor if the tree
* is right heavy, otherwise the left neighbor. This reduces the
* number of rotations needed.
*/
if (delete->avl_child[0] != NULL && delete->avl_child[1] != NULL) {
/*
* choose node to swap from whichever side is taller
*/
old_balance = AVL_XBALANCE(delete);
left = avl_balance2child[old_balance + 1];
right = 1 - left;
/*
* get to the previous value'd node
* (down 1 left, as far as possible right)
*/
for (node = delete->avl_child[left];
node->avl_child[right] != NULL;
node = node->avl_child[right])
;
/*
* create a temp placeholder for 'node'
* move 'node' to delete's spot in the tree
*/
tmp = *node;
*node = *delete;
if (node->avl_child[left] == node)
node->avl_child[left] = &tmp;
parent = AVL_XPARENT(node);
if (parent != NULL)
parent->avl_child[AVL_XCHILD(node)] = node;
else
tree->avl_root = node;
AVL_SETPARENT(node->avl_child[left], node);
AVL_SETPARENT(node->avl_child[right], node);
/*
* Put tmp where node used to be (just temporary).
* It always has a parent and at most 1 child.
*/
delete = &tmp;
parent = AVL_XPARENT(delete);
parent->avl_child[AVL_XCHILD(delete)] = delete;
which_child = (delete->avl_child[1] != 0);
if (delete->avl_child[which_child] != NULL)
AVL_SETPARENT(delete->avl_child[which_child], delete);
}
/*
* Here we know "delete" is at least partially a leaf node. It can
* be easily removed from the tree.
*/
ASSERT(tree->avl_numnodes > 0);
--tree->avl_numnodes;
parent = AVL_XPARENT(delete);
which_child = AVL_XCHILD(delete);
if (delete->avl_child[0] != NULL)
node = delete->avl_child[0];
else
node = delete->avl_child[1];
/*
* Connect parent directly to node (leaving out delete).
*/
if (node != NULL) {
AVL_SETPARENT(node, parent);
AVL_SETCHILD(node, which_child);
}
if (parent == NULL) {
tree->avl_root = node;
return;
}
parent->avl_child[which_child] = node;
/*
* Since the subtree is now shorter, begin adjusting parent balances
* and performing any needed rotations.
*/
do {
/*
* Move up the tree and adjust the balance
*
* Capture the parent and which_child values for the next
* iteration before any rotations occur.
*/
node = parent;
old_balance = AVL_XBALANCE(node);
new_balance = old_balance - avl_child2balance[which_child];
parent = AVL_XPARENT(node);
which_child = AVL_XCHILD(node);
/*
* If a node was in perfect balance but isn't anymore then
* we can stop, since the height didn't change above this point
* due to a deletion.
*/
if (old_balance == 0) {
AVL_SETBALANCE(node, new_balance);
break;
}
/*
* If the new balance is zero, we don't need to rotate
* else
* need a rotation to fix the balance.
* If the rotation doesn't change the height
* of the sub-tree we have finished adjusting.
*/
if (new_balance == 0)
AVL_SETBALANCE(node, new_balance);
else if (!avl_rotation(tree, node, new_balance))
break;
} while (parent != NULL);
}
/*
* initialize a new AVL tree
*/
void
avl_create(avl_tree_t *tree, int (*compar) (const void *, const void *),
size_t size, size_t offset)
{
ASSERT(tree);
ASSERT(compar);
ASSERT(size > 0);
ASSERT(size >= offset + sizeof (avl_node_t));
#ifdef _LP64
ASSERT((offset & 0x7) == 0);
#endif
tree->avl_compar = compar;
tree->avl_root = NULL;
tree->avl_numnodes = 0;
tree->avl_size = size;
tree->avl_offset = offset;
}
/*
* Delete a tree.
*/
/* ARGSUSED */
void
avl_destroy(avl_tree_t *tree)
{
ASSERT(tree);
ASSERT(tree->avl_numnodes == 0);
ASSERT(tree->avl_root == NULL);
}
/*
* Return the number of nodes in an AVL tree.
*/
ulong_t
avl_numnodes(avl_tree_t *tree)
{
ASSERT(tree);
return (tree->avl_numnodes);
}
#define CHILDBIT (1L)
/*
* Post-order tree walk used to visit all tree nodes and destroy the tree
* in post order. This is used for destroying a tree w/o paying any cost
* for rebalancing it.
*
* example:
*
* void *cookie = NULL;
* my_data_t *node;
*
* while ((node = avl_destroy_nodes(tree, &cookie)) != NULL)
* free(node);
* avl_destroy(tree);
*
* The cookie is really an avl_node_t to the current node's parent and
* an indication of which child you looked at last.
*
* On input, a cookie value of CHILDBIT indicates the tree is done.
*/
void *
avl_destroy_nodes(avl_tree_t *tree, void **cookie)
{
avl_node_t *node;
avl_node_t *parent;
int child;
void *first;
size_t off = tree->avl_offset;
/*
* Initial calls go to the first node or it's right descendant.
*/
if (*cookie == NULL) {
first = avl_first(tree);
/*
* deal with an empty tree
*/
if (first == NULL) {
*cookie = (void *)CHILDBIT;
return (NULL);
}
node = AVL_DATA2NODE(first, off);
parent = AVL_XPARENT(node);
goto check_right_side;
}
/*
* If there is no parent to return to we are done.
*/
parent = (avl_node_t *)((uintptr_t)(*cookie) & ~CHILDBIT);
if (parent == NULL) {
if (tree->avl_root != NULL) {
ASSERT(tree->avl_numnodes == 1);
tree->avl_root = NULL;
tree->avl_numnodes = 0;
}
return (NULL);
}
/*
* Remove the child pointer we just visited from the parent and tree.
*/
child = (uintptr_t)(*cookie) & CHILDBIT;
parent->avl_child[child] = NULL;
ASSERT(tree->avl_numnodes > 1);
--tree->avl_numnodes;
/*
* If we just did a right child or there isn't one, go up to parent.
*/
if (child == 1 || parent->avl_child[1] == NULL) {
node = parent;
parent = AVL_XPARENT(parent);
goto done;
}
/*
* Do parent's right child, then leftmost descendent.
*/
node = parent->avl_child[1];
while (node->avl_child[0] != NULL) {
parent = node;
node = node->avl_child[0];
}
/*
* If here, we moved to a left child. It may have one
* child on the right (when balance == +1).
*/
check_right_side:
if (node->avl_child[1] != NULL) {
ASSERT(AVL_XBALANCE(node) == 1);
parent = node;
node = node->avl_child[1];
ASSERT(node->avl_child[0] == NULL &&
node->avl_child[1] == NULL);
} else {
ASSERT(AVL_XBALANCE(node) <= 0);
}
done:
if (parent == NULL) {
*cookie = (void *)CHILDBIT;
ASSERT(node == tree->avl_root);
} else {
*cookie = (void *)((uintptr_t)parent | AVL_XCHILD(node));
}
return (AVL_NODE2DATA(node, off));
}
zfs/lib/libavl/include/Makefile.in
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subdir-m += sys
zfs/lib/libavl/include/sys/Makefile.in
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DISTFILES = avl.h avl_impl.h
zfs/lib/libavl/include/sys/avl.h
+298
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/*
* CDDL HEADER START
*
* The contents of this file are subject to the terms of the
* Common Development and Distribution License, Version 1.0 only
* (the "License"). You may not use this file except in compliance
* with the License.
*
* You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
* or http://www.opensolaris.org/os/licensing.
* See the License for the specific language governing permissions
* and limitations under the License.
*
* When distributing Covered Code, include this CDDL HEADER in each
* file and include the License file at usr/src/OPENSOLARIS.LICENSE.
* If applicable, add the following below this CDDL HEADER, with the
* fields enclosed by brackets "[]" replaced with your own identifying
* information: Portions Copyright [yyyy] [name of copyright owner]
*
* CDDL HEADER END
*/
/*
* Copyright 2005 Sun Microsystems, Inc. All rights reserved.
* Use is subject to license terms.
*/
#ifndef _AVL_H
#define _AVL_H
/*
* This is a private header file. Applications should not directly include
* this file.
*/
#ifdef __cplusplus
extern "C" {
#endif
#include <sys/avl_impl.h>
/*
* This is a generic implemenatation of AVL trees for use in the Solaris kernel.
* The interfaces provide an efficient way of implementing an ordered set of
* data structures.
*
* AVL trees provide an alternative to using an ordered linked list. Using AVL
* trees will usually be faster, however they requires more storage. An ordered
* linked list in general requires 2 pointers in each data structure. The
* AVL tree implementation uses 3 pointers. The following chart gives the
* approximate performance of operations with the different approaches:
*
* Operation Link List AVL tree
* --------- -------- --------
* lookup O(n) O(log(n))
*
* insert 1 node constant constant
*
* delete 1 node constant between constant and O(log(n))
*
* delete all nodes O(n) O(n)
*
* visit the next
* or prev node constant between constant and O(log(n))
*
*
* The data structure nodes are anchored at an "avl_tree_t" (the equivalent
* of a list header) and the individual nodes will have a field of
* type "avl_node_t" (corresponding to list pointers).
*
* The type "avl_index_t" is used to indicate a position in the list for
* certain calls.
*
* The usage scenario is generally:
*
* 1. Create the list/tree with: avl_create()
*
* followed by any mixture of:
*
* 2a. Insert nodes with: avl_add(), or avl_find() and avl_insert()
*
* 2b. Visited elements with:
* avl_first() - returns the lowest valued node
* avl_last() - returns the highest valued node
* AVL_NEXT() - given a node go to next higher one
* AVL_PREV() - given a node go to previous lower one
*
* 2c. Find the node with the closest value either less than or greater
* than a given value with avl_nearest().
*
* 2d. Remove individual nodes from the list/tree with avl_remove().
*
* and finally when the list is being destroyed
*
* 3. Use avl_destroy_nodes() to quickly process/free up any remaining nodes.
* Note that once you use avl_destroy_nodes(), you can no longer
* use any routine except avl_destroy_nodes() and avl_destoy().
*
* 4. Use avl_destroy() to destroy the AVL tree itself.
*
* Any locking for multiple thread access is up to the user to provide, just
* as is needed for any linked list implementation.
*/
/*
* Type used for the root of the AVL tree.
*/
typedef struct avl_tree avl_tree_t;
/*
* The data nodes in the AVL tree must have a field of this type.
*/
typedef struct avl_node avl_node_t;
/*
* An opaque type used to locate a position in the tree where a node
* would be inserted.
*/
typedef uintptr_t avl_index_t;
/*
* Direction constants used for avl_nearest().
*/
#define AVL_BEFORE (0)
#define AVL_AFTER (1)
/*
* Prototypes
*
* Where not otherwise mentioned, "void *" arguments are a pointer to the
* user data structure which must contain a field of type avl_node_t.
*
* Also assume the user data structures looks like:
* stuct my_type {
* ...
* avl_node_t my_link;
* ...
* };
*/
/*
* Initialize an AVL tree. Arguments are:
*
* tree - the tree to be initialized
* compar - function to compare two nodes, it must return exactly: -1, 0, or +1
* -1 for <, 0 for ==, and +1 for >
* size - the value of sizeof(struct my_type)
* offset - the value of OFFSETOF(struct my_type, my_link)
*/
extern void avl_create(avl_tree_t *tree,
int (*compar) (const void *, const void *), size_t size, size_t offset);
/*
* Find a node with a matching value in the tree. Returns the matching node
* found. If not found, it returns NULL and then if "where" is not NULL it sets
* "where" for use with avl_insert() or avl_nearest().
*
* node - node that has the value being looked for
* where - position for use with avl_nearest() or avl_insert(), may be NULL
*/
extern void *avl_find(avl_tree_t *tree, void *node, avl_index_t *where);
/*
* Insert a node into the tree.
*
* node - the node to insert
* where - position as returned from avl_find()
*/
extern void avl_insert(avl_tree_t *tree, void *node, avl_index_t where);
/*
* Insert "new_data" in "tree" in the given "direction" either after
* or before the data "here".
*
* This might be usefull for avl clients caching recently accessed
* data to avoid doing avl_find() again for insertion.
*
* new_data - new data to insert
* here - existing node in "tree"
* direction - either AVL_AFTER or AVL_BEFORE the data "here".
*/
extern void avl_insert_here(avl_tree_t *tree, void *new_data, void *here,
int direction);
/*
* Return the first or last valued node in the tree. Will return NULL
* if the tree is empty.
*
*/
extern void *avl_first(avl_tree_t *tree);
extern void *avl_last(avl_tree_t *tree);
/*
* Return the next or previous valued node in the tree.
* AVL_NEXT() will return NULL if at the last node.
* AVL_PREV() will return NULL if at the first node.
*
* node - the node from which the next or previous node is found
*/
#define AVL_NEXT(tree, node) avl_walk(tree, node, AVL_AFTER)
#define AVL_PREV(tree, node) avl_walk(tree, node, AVL_BEFORE)
/*
* Find the node with the nearest value either greater or less than
* the value from a previous avl_find(). Returns the node or NULL if
* there isn't a matching one.
*
* where - position as returned from avl_find()
* direction - either AVL_BEFORE or AVL_AFTER
*
* EXAMPLE get the greatest node that is less than a given value:
*
* avl_tree_t *tree;
* struct my_data look_for_value = {....};
* struct my_data *node;
* struct my_data *less;
* avl_index_t where;
*
* node = avl_find(tree, &look_for_value, &where);
* if (node != NULL)
* less = AVL_PREV(tree, node);
* else
* less = avl_nearest(tree, where, AVL_BEFORE);
*/
extern void *avl_nearest(avl_tree_t *tree, avl_index_t where, int direction);
/*
* Add a single node to the tree.
* The node must not be in the tree, and it must not
* compare equal to any other node already in the tree.
*
* node - the node to add
*/
extern void avl_add(avl_tree_t *tree, void *node);
/*
* Remove a single node from the tree. The node must be in the tree.
*
* node - the node to remove
*/
extern void avl_remove(avl_tree_t *tree, void *node);
/*
* Return the number of nodes in the tree
*/
extern ulong_t avl_numnodes(avl_tree_t *tree);
/*
* Used to destroy any remaining nodes in a tree. The cookie argument should
* be initialized to NULL before the first call. Returns a node that has been
* removed from the tree and may be free()'d. Returns NULL when the tree is
* empty.
*
* Once you call avl_destroy_nodes(), you can only continuing calling it and
* finally avl_destroy(). No other AVL routines will be valid.
*
* cookie - a "void *" used to save state between calls to avl_destroy_nodes()
*
* EXAMPLE:
* avl_tree_t *tree;
* struct my_data *node;
* void *cookie;
*
* cookie = NULL;
* while ((node = avl_destroy_nodes(tree, &cookie)) != NULL)
* free(node);
* avl_destroy(tree);
*/
extern void *avl_destroy_nodes(avl_tree_t *tree, void **cookie);
/*
* Final destroy of an AVL tree. Arguments are:
*
* tree - the empty tree to destroy
*/
extern void avl_destroy(avl_tree_t *tree);
#ifdef __cplusplus
}
#endif
#endif /* _AVL_H */
zfs/lib/libavl/include/sys/avl_impl.h
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/*
* CDDL HEADER START
*
* The contents of this file are subject to the terms of the
* Common Development and Distribution License, Version 1.0 only
* (the "License"). You may not use this file except in compliance
* with the License.
*
* You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
* or http://www.opensolaris.org/os/licensing.
* See the License for the specific language governing permissions
* and limitations under the License.
*
* When distributing Covered Code, include this CDDL HEADER in each
* file and include the License file at usr/src/OPENSOLARIS.LICENSE.
* If applicable, add the following below this CDDL HEADER, with the
* fields enclosed by brackets "[]" replaced with your own identifying
* information: Portions Copyright [yyyy] [name of copyright owner]
*
* CDDL HEADER END
*/
/*
* Copyright 2004 Sun Microsystems, Inc. All rights reserved.
* Use is subject to license terms.
*/
#ifndef _AVL_IMPL_H
#define _AVL_IMPL_H
/*
* This is a private header file. Applications should not directly include
* this file.
*/
#include <sys/types.h>
#ifdef __cplusplus
extern "C" {
#endif
/*
* generic AVL tree implementation for kernel use
*
* There are 5 pieces of information stored for each node in an AVL tree
*
* pointer to less than child
* pointer to greater than child
* a pointer to the parent of this node
* an indication [0/1] of which child I am of my parent
* a "balance" (-1, 0, +1) indicating which child tree is taller
*
* Since they only need 3 bits, the last two fields are packed into the
* bottom bits of the parent pointer on 64 bit machines to save on space.
*/
#ifndef _LP64
struct avl_node {
struct avl_node *avl_child[2]; /* left/right children */
struct avl_node *avl_parent; /* this node's parent */
unsigned short avl_child_index; /* my index in parent's avl_child[] */
short avl_balance; /* balance value: -1, 0, +1 */
};
#define AVL_XPARENT(n) ((n)->avl_parent)
#define AVL_SETPARENT(n, p) ((n)->avl_parent = (p))
#define AVL_XCHILD(n) ((n)->avl_child_index)
#define AVL_SETCHILD(n, c) ((n)->avl_child_index = (unsigned short)(c))
#define AVL_XBALANCE(n) ((n)->avl_balance)
#define AVL_SETBALANCE(n, b) ((n)->avl_balance = (short)(b))
#else /* _LP64 */
/*
* for 64 bit machines, avl_pcb contains parent pointer, balance and child_index
* values packed in the following manner:
*
* |63 3| 2 |1 0 |
* |-------------------------------------|-----------------|-------------|
* | avl_parent hi order bits | avl_child_index | avl_balance |
* | | | + 1 |
* |-------------------------------------|-----------------|-------------|
*
*/
struct avl_node {
struct avl_node *avl_child[2]; /* left/right children nodes */
uintptr_t avl_pcb; /* parent, child_index, balance */
};
/*
* macros to extract/set fields in avl_pcb
*
* pointer to the parent of the current node is the high order bits
*/
#define AVL_XPARENT(n) ((struct avl_node *)((n)->avl_pcb & ~7))
#define AVL_SETPARENT(n, p) \
((n)->avl_pcb = (((n)->avl_pcb & 7) | (uintptr_t)(p)))
/*
* index of this node in its parent's avl_child[]: bit #2
*/
#define AVL_XCHILD(n) (((n)->avl_pcb >> 2) & 1)
#define AVL_SETCHILD(n, c) \
((n)->avl_pcb = (uintptr_t)(((n)->avl_pcb & ~4) | ((c) << 2)))
/*
* balance indication for a node, lowest 2 bits. A valid balance is
* -1, 0, or +1, and is encoded by adding 1 to the value to get the
* unsigned values of 0, 1, 2.
*/
#define AVL_XBALANCE(n) ((int)(((n)->avl_pcb & 3) - 1))
#define AVL_SETBALANCE(n, b) \
((n)->avl_pcb = (uintptr_t)((((n)->avl_pcb & ~3) | ((b) + 1))))
#endif /* _LP64 */
/*
* switch between a node and data pointer for a given tree
* the value of "o" is tree->avl_offset
*/
#define AVL_NODE2DATA(n, o) ((void *)((uintptr_t)(n) - (o)))
#define AVL_DATA2NODE(d, o) ((struct avl_node *)((uintptr_t)(d) + (o)))
/*
* macros used to create/access an avl_index_t
*/
#define AVL_INDEX2NODE(x) ((avl_node_t *)((x) & ~1))
#define AVL_INDEX2CHILD(x) ((x) & 1)
#define AVL_MKINDEX(n, c) ((avl_index_t)(n) | (c))
/*
* The tree structure. The fields avl_root, avl_compar, and avl_offset come
* first since they are needed for avl_find(). We want them to fit into
* a single 64 byte cache line to make avl_find() as fast as possible.
*/
struct avl_tree {
struct avl_node *avl_root; /* root node in tree */
int (*avl_compar)(const void *, const void *);
size_t avl_offset; /* offsetof(type, avl_link_t field) */
ulong_t avl_numnodes; /* number of nodes in the tree */
size_t avl_size; /* sizeof user type struct */
};
/*
* This will only by used via AVL_NEXT() or AVL_PREV()
*/
extern void *avl_walk(struct avl_tree *, void *, int);
#ifdef __cplusplus
}
#endif
#endif /* _AVL_IMPL_H */