This is xnu-8019. See this file in:
/*
 * Copyright (c) 1998-2000 Apple Computer, Inc. All rights reserved.
 *
 * @APPLE_OSREFERENCE_LICENSE_HEADER_START@
 *
 * This file contains Original Code and/or Modifications of Original Code
 * as defined in and that are subject to the Apple Public Source License
 * Version 2.0 (the 'License'). You may not use this file except in
 * compliance with the License. The rights granted to you under the License
 * may not be used to create, or enable the creation or redistribution of,
 * unlawful or unlicensed copies of an Apple operating system, or to
 * circumvent, violate, or enable the circumvention or violation of, any
 * terms of an Apple operating system software license agreement.
 *
 * Please obtain a copy of the License at
 * http://www.opensource.apple.com/apsl/ and read it before using this file.
 *
 * The Original Code and all software distributed under the License are
 * distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER
 * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
 * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT.
 * Please see the License for the specific language governing rights and
 * limitations under the License.
 *
 * @APPLE_OSREFERENCE_LICENSE_HEADER_END@
 */
#include <IOKit/pwr_mgt/IOPM.h>
#include <IOKit/pwr_mgt/IOPMPowerSourceList.h>
#include <IOKit/pwr_mgt/IOPMPowerSource.h>

#define super OSObject
OSDefineMetaClassAndStructors(IOPMPowerSourceList, OSObject)

//******************************************************************************
// init
//
//******************************************************************************
void
IOPMPowerSourceList::initialize( void )
{
	firstItem = NULL;
	length = 0;
}

//******************************************************************************
// addToList
//
//******************************************************************************

IOReturn
IOPMPowerSourceList::addToList(IOPMPowerSource *newPowerSource)
{
	IOPMPowerSource * nextPowerSource;

	// Is new object already in the list?
	nextPowerSource = firstItem;
	while (nextPowerSource != NULL) {
		if (nextPowerSource == newPowerSource) {
			// yes, just return
			return IOPMNoErr;
		}
		nextPowerSource = nextInList(nextPowerSource);
	}

	// add it to list
	newPowerSource->nextInList = firstItem;
	firstItem = newPowerSource;
	length++;
	return IOPMNoErr;
}


//******************************************************************************
// firstInList
//
//******************************************************************************

IOPMPowerSource *
IOPMPowerSourceList::firstInList( void )
{
	return firstItem;
}

//******************************************************************************
// nextInList
//
//******************************************************************************

IOPMPowerSource *
IOPMPowerSourceList::nextInList(IOPMPowerSource *currentItem)
{
	if (currentItem != NULL) {
		return currentItem->nextInList;
	}
	return NULL;
}

//******************************************************************************
// numberOfItems
//
//******************************************************************************

unsigned long
IOPMPowerSourceList::numberOfItems( void )
{
	return length;
}

//******************************************************************************
// removeFromList
//
// Find the item in the list, unlink it, and free it.
//******************************************************************************

IOReturn
IOPMPowerSourceList::removeFromList( IOPMPowerSource * theItem )
{
	IOPMPowerSource * item = firstItem;
	IOPMPowerSource * temp;

	if (NULL == item) {
		goto exit;
	}

	if (item == theItem) {
		firstItem = item->nextInList;
		length--;
		item->release();
		return IOPMNoErr;
	}
	while (item->nextInList != NULL) {
		if (item->nextInList == theItem) {
			temp = item->nextInList;
			item->nextInList = temp->nextInList;
			length--;
			temp->release();
			return IOPMNoErr;
		}
		item = item->nextInList;
	}

exit:
	return IOPMNoErr;
}


//******************************************************************************
// free
//
// Free all items in the list, and then free the list itself
//******************************************************************************

void
IOPMPowerSourceList::free(void )
{
	IOPMPowerSource * next = firstItem;

	while (next != NULL) {
		firstItem = next->nextInList;
		length--;
		next->release();
		next = firstItem;
	}
	super::free();
}