155 lines
4.3 KiB
Plaintext
155 lines
4.3 KiB
Plaintext
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.TH TREE 3 "5 April 1994"
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.\" from .TH TREE 3 "22 Jan 1993"
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.\" from .TH TREE 2 "23 June 1986"
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.UC 4
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.SH NAME
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tree_init, tree_mung, tree_srch, tree_add, tree_delete, tree_trav
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\- balanced binary tree routines
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.SH SYNOPSIS
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.nf
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.B void
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.B tree_init(tree)
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.B void **tree;
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.PP
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.B void *
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.B tree_srch(tree, compare, data)
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.B void **tree;
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.B int (*compare)();
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.B void *data;
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.PP
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.B void
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.B tree_add(tree, compare, data, del_uar)
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.B void **tree;
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.B int (*compare)();
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.B void *data;
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.B void (*del_uar)();
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.PP
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.B int
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.B tree_delete(tree, compare, data, del_uar)
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.B void **tree;
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.B int (*compare)();
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.B void *data;
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.B void (*del_uar)();
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.PP
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.B int
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.B tree_trav(tree, trav_uar)
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.B void **tree;
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.B int (*trav_uar)();
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.PP
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.B void
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.B tree_mung(tree, del_uar)
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.B void **tree;
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.B void (*del_uar)();
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.fi
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.SH DESCRIPTION
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These functions create and manipulate a balanced binary (AVL) tree. Each node
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of the tree contains the expected left & right subtree pointers, a short int
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balance indicator, and a pointer to the user data. On a 32 bit system, this
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means an overhead of 4+4+2+4 bytes per node (or, on a RISC or otherwise
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alignment constrained system with implied padding, 4+4+4+4 bytes per node).
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There is no key data type enforced by this package; a caller supplied
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compare routine is used to compare user data blocks.
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.PP
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Balanced binary trees are very fast on searches and replacements, but have a
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moderately high cost for additions and deletions. If your application does a
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lot more searches and replacements than it does additions and deletions, the
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balanced (AVL) binary tree is a good choice for a data structure.
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.PP
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.I Tree_init
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creates an empty tree and binds it to
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.I tree
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(which for this and all other routines in this package should be declared as
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a pointer to void or int, and passed by reference), which can then be used by
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other routines in this package. Note that more than one
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.I tree
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variable can exist at once; thus multiple trees can be manipulated
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simultaneously.
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.PP
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.I Tree_srch
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searches a tree for a specific node and returns either
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.I NULL
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if no node was found, or the value of the user data pointer if the node
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was found.
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.I compare
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is the address of a function to compare two user data blocks. This routine
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should work much the way
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.IR strcmp (3)
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does; in fact,
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.I strcmp
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could be used if the user data was a \s-2NUL\s+2 terminated string.
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.I data
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is the address of a user data block to be used by
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.I compare
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as the search criteria. The tree is searched for a node where
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.I compare
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returns 0.
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.PP
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.I Tree_add
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inserts or replaces a node in the specified tree. The tree specified by
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.I tree
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is searched as in
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.I tree_srch,
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and if a node is found to match
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.I data,
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then the
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.I del_uar
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function, if non\-\s-2NULL\s+2, is called with the address of the user data
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block for the node (this routine should deallocate any dynamic memory which
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is referenced exclusively by the node); the user data pointer for the node
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is then replaced by the value of
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.I data.
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If no node is found to match, a new node is added (which may or may not
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cause a transparent rebalance operation), with a user data pointer equal to
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.I data.
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A rebalance may or may not occur, depending on where the node is added
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and what the rest of the tree looks like.
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.I Tree_add
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will return the
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.I data
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pointer unless catastrophe occurs in which case it will return \s-2NULL\s+2.
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.PP
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.I Tree_delete
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deletes a node from
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.I tree.
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A rebalance may or may not occur, depending on where the node is removed from
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and what the rest of the tree looks like.
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.I Tree_delete
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returns TRUE if a node was deleted, FALSE otherwise.
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.PP
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.I Tree_trav
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traverses all of
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.I tree,
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calling
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.I trav_uar
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with the address of each user data block. If
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.I trav_uar
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returns FALSE at any time,
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.I tree_trav
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will immediately return FALSE to its caller. Otherwise all nodes will be
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reached and
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.I tree_trav
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will return TRUE.
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.PP
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.I Tree_mung
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deletes every node in
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.I tree,
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calling
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.I del_uar
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(if it is not \s-2NULL\s+2) with the user data address from each node (see
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.I tree_add
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and
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.I tree_delete
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above). The tree is left in the same state that
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.I tree_init
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leaves it in \- i.e., empty.
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.SH BUGS
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Should have a way for the caller to specify application specific
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.I malloc
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and
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.I free
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functions to be used internally when allocating meta data.
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.SH AUTHOR
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Paul Vixie, converted and augumented from Modula\-2 examples in
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.I Algorithms & Data Structures,
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Niklaus Wirth, Prentice\-Hall, ISBN 0\-13\-022005\-1.
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