klish/lub/bintree/bintree_findprevious.c

/*********************** -*- Mode: C -*- ***********************
 * File            : bintree_findprevious.c
 *---------------------------------------------------------------
 * Description
 * ===========
 * This operation searches the specified "tree" for a "clientnode" which is
 * the one which logically preceeds the specified "key"
 *
 * A "clientnode" with the specified "key" doesn't need to be in the tree.
 *
 * tree - the "tree" instance to invoke this operation upon
 * key  - the "key" to search with
 *
 * RETURNS
 * "clientnode" instance or NULL if no node is found.
 *---------------------------------------------------------------
 * Author          : Graeme McKerrell
 * Created On      : Wed Jan 28 10:33:12 2004
 * Status          : TESTED
 *---------------------------------------------------------------
 * HISTORY
 * 7-Dec-2004		Graeme McKerrell	
 *    Renamed to the "lub_" namespace
 * 5-May-2004		Graeme McKerrell	
 *    updates following review
 * 27-Feb-2004		Graeme McKerrell	
 *    Fixed to account for empty tree
 * 9-Feb-2004		Graeme McKerrell	
 *    updated to use new node,key comparison ordering
 * 28-Jan-2004		Graeme McKerrell	
 *   Initial verison 
 *---------------------------------------------------------------
 * Copyright (C) 2004 3Com Corporation. All Rights Reserved.
 **************************************************************** */
#include "private.h"

/*--------------------------------------------------------- */
void *
lub_bintree_findprevious(lub_bintree_t *this,
                         const void    *clientkey)
{
    lub_bintree_node_t *t = this->root;
    int                 comp;

    /*
     * have a look for a direct match
     */
    t = this->root = lub_bintree_splay(this,t,clientkey);
        
    if(NULL != t)
    {
        /* now look at what we have got */
        comp = lub_bintree_compare(this,t,clientkey);
        if(comp >= 0)
        {
            /*
             * time to fiddle with the left hand side of the tree
             * we need the closest node from the left hand side
             */
            t = t->left = lub_bintree_splay(this,t->left,clientkey);
        }
    }
    if(NULL == t)
    {
        return NULL;
    }
    else
    {
        return lub_bintree_getclientnode(this,t);
    }
}
/*--------------------------------------------------------- */