klish/lub/bintree/bintree_findfirst.c

/*********************** -*- Mode: C -*- ***********************
 * File            : bintree_findfirst.c
 *---------------------------------------------------------------
 * Description
 * ===========
 * This operation returns the first "clientnode" present in the specified "tree"
 *
 * tree - the "tree" instance to invoke this operation upon
 *
 * RETURNS
 * "clientnode" instance or NULL if no nodes are present in this view.
 *
 *---------------------------------------------------------------
 * Author          : Graeme McKerrell
 * Created On      : Wed Jan 28 10:15:00 2004
 * Status          : TESTED
 *---------------------------------------------------------------
 * HISTORY
 * 7-Dec-2004		Graeme McKerrell	
 *    Renamed to the "lub_" namespace
 * 5-May-2004		Graeme McKerrell	
 *    updates following review
 * 2-Mar-2004		Graeme McKerrell	
 *    fixed comparison logic
 * 9-Feb-2004		Graeme McKerrell	
 *    update to use new getkey prototype, removed the now spurious
 *    nullgetkey() function
 * 28-Jan-2004		Graeme McKerrell	
 *   Initial version
 *---------------------------------------------------------------
 * Copyright (C) 2004 3Com Corporation. All Rights Reserved.
 **************************************************************** */
#include "private.h"

/* forward declare these functions */
static lub_bintree_compare_fn compareleft;

/*--------------------------------------------------------- */
void *
lub_bintree_findfirst(lub_bintree_t *this)
{
        lub_bintree_compare_fn *client_compare = this->compareFn;
        
        /*
         * put dummy functions in place
         * This will make the search faster and direct it to the left most
         * node
         */
        this->compareFn = compareleft;
        
        /*
         * the key doesn't matter here cos we've cobbled the compare function
         */
        this->root = lub_bintree_splay(this,this->root,NULL);
        
        /* restore the client functions */
        this->compareFn = client_compare;
        
        if(NULL == this->root)
                return NULL;
        else
                return lub_bintree_getclientnode(this,this->root);
}
/*--------------------------------------------------------- */
/*
 * This comparison operation always returns 1 hence will force a
 * search to the left most node.
 *
 * clientnode - node to compare (not used)
 * clientkey  - key to compare (not used)
 */
static int
compareleft(const void *clientnode,
            const void *clientkey)
{
        clientnode = clientnode;
        clientkey  = clientkey;
        return 1;
}
/*--------------------------------------------------------- */