/*
	File:		GenLinkedList.c
	
	Contains:	Linked List utility routines

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*/

#include "GenLinkedList.h"

#pragma mark --- Data Structures ---

	/* This is the internal data structure for the nodes in the linked list.  		*/
	/*																				*/
	/* Note: The memory pointed to by pNext is owned by the list and is disposed of	*/
	/* in DestroyList.  It should not be disposed of in any other way.				*/
	/*																				*/
	/* Note: The memory pointed to by pData is owned by the caller of the linked	*/
	/* list.  The caller is responsible for disposing of this memory.  This can be	*/
	/* done	by simply implementing a DisposeDataProc that will be called on each	*/
	/* node in the list, giving the caller a chance to dispose of any memory		*/
	/* created.  The DisposeDataProc is called from DestroyList						*/ 
struct GenNode
{
	struct	GenNode				*pNext;	/* Pointer to the next node in the list		*/
			GenDataPtr			 pData;	/* The data for this node, owned by caller	*/
};
typedef struct GenNode GenNode;

#pragma mark --- List Implementation ---

	/* Initializes the given GenLinkedList to an empty list.  This MUST be			*/
	/* called before any operations are performed on the list, otherwise bad things	*/
	/* will	happen.																	*/
void 		InitLinkedList( GenLinkedList *pList, DisposeDataProcPtr disposeProcPtr)
{
	if( pList == NULL )
		return;

	pList->pHead = pList->pTail = NULL;
	pList->NumberOfItems	= 0;
	pList->DisposeProcPtr	= disposeProcPtr;
}

	/* returns the current number of items in the given list.						*/
	/* If pList == NULL, it returns 0												*/
ItemCount	GetNumberOfItems( GenLinkedList *pList )
{
	return (pList) ? pList->NumberOfItems : 0;
}
	
	/* Creates a new node, containing pData, and adds it to the tail of pList.		*/
	/* Note: if an error occurs, pList is unchanged.								*/
OSErr		AddToTail( GenLinkedList *pList, void *pData )
{
	OSErr		err			= paramErr;
	GenNode		*tmpNode	= NULL;
	
	if( pList == NULL || pData == NULL )
		return err;

		/* create memory for new node, if this fails we _must_ bail	*/
	err = ( ( tmpNode = (GenNode*) NewPtr( sizeof( GenNode ) ) ) != NULL ) ? noErr : MemError();
	if( err == noErr )
	{
		tmpNode->pData = pData;									/* Setup new node				*/
		tmpNode->pNext = NULL;
		
		if( pList->pTail != NULL )								/* more then one item already	*/
			((GenNode*) pList->pTail)->pNext = (void*) tmpNode;	/* so append to tail			*/
		else
			pList->pHead = (void*) tmpNode; 					/* no items, so adjust head		*/
		
		pList->pTail			= (void*) tmpNode;
		pList->NumberOfItems	+= 1;
	}	
	
	return err;
}

	/* Takes pSrcList and inserts it into pDestList at the location pIter points to.			*/
	/* The lists must have the same DisposeProcPtr, but the Data can be different.  If pSrcList	*/
	/* is empty, it does nothing and just returns												*/
	/*																							*/
	/* If pIter == NULL, insert pSrcList before the head										*/
	/* else If pIter == pTail, append pSrcList to the tail										*/
	/* else insert pSrcList in the middle somewhere 											*/
	/* On return: pSrcList is cleared and is an empty list.										*/
	/*            The data that was owned by pSrcList is now owned by pDestList					*/
void		InsertList( GenLinkedList *pDestList, GenLinkedList *pSrcList, GenIteratorPtr pIter )
{
	if( pDestList		== NULL || pSrcList			== NULL ||
		pSrcList->pHead	== NULL || pSrcList->pTail	== NULL ||
		pDestList->DisposeProcPtr != pSrcList->DisposeProcPtr )
		return;
		
	if( pDestList->pHead == NULL && pDestList->pTail == NULL )	/* empty list					*/
	{
		pDestList->pHead = pSrcList->pHead;
		pDestList->pTail = pSrcList->pTail;
	}
	else if( pIter == NULL )									/* insert before head			*/
	{				
			/* attach the list	*/
		((GenNode*)pSrcList->pTail)->pNext = pDestList->pHead;
			/* fix up head		*/
		pDestList->pHead = pSrcList->pHead;
	}
	else if( pIter == pDestList->pTail )						/* append to tail				*/
	{
			/* attach the list	*/
		((GenNode*)pDestList->pTail)->pNext = pSrcList->pHead;
			/* fix up tail		*/
		pDestList->pTail = pSrcList->pTail;
	}
	else														/* insert in middle somewhere	*/
	{
		GenNode	*tmpNode = ((GenNode*)pIter)->pNext;
		((GenNode*)pIter)->pNext = pSrcList->pHead;
		((GenNode*)pSrcList->pTail)->pNext = tmpNode;
	}

	pDestList->NumberOfItems += pSrcList->NumberOfItems;		/* sync up NumberOfItems		*/
	
	InitLinkedList( pSrcList, NULL);							/* reset the source list		*/
}

	/* Goes through the list and disposes of any memory we allocated.  Calls the DisposeProcPtr,*/
	/* if it exists, to give the caller a chance to free up their memory						*/
void		DestroyList( GenLinkedList	*pList )
{
	GenIteratorPtr	pIter		= NULL,
					pNextIter	= NULL;

	if( pList == NULL )
		return;
	
	for( InitIterator( pList, &pIter ), pNextIter = pIter; pIter != NULL; pIter = pNextIter )
	{
		Next( &pNextIter );	/* get the next node before we blow away the link */
		
		if( pList->DisposeProcPtr != NULL )
			CallDisposeDataProc( pList->DisposeProcPtr, GetData( pIter ) );
		DisposePtr( (char*) pIter );
	}
	
	InitLinkedList( pList, NULL);		
}

/*#############################################*/
/*#############################################*/
/*#############################################*/

#pragma mark -
#pragma mark --- Iterator Implementation ---

	/* Initializes pIter to point at the head of pList							*/
	/* This must be called before performing any operations with pIter			*/
void		InitIterator( GenLinkedList *pList, GenIteratorPtr *pIter )
{
	if( pList != NULL && pIter != NULL )
		*pIter = pList->pHead;
}

	/* On return, pIter points to the next node in the list.  NULL if its gone	*/
	/* past the end of the list													*/
void		Next( GenIteratorPtr *pIter )
{
	if( pIter != NULL )
		*pIter = ((GenNode*)*pIter)->pNext;
}

	/* Returns the data of the current node that pIter points to				*/
GenDataPtr	GetData( GenIteratorPtr pIter )
{
	return ( pIter != NULL ) ? ((GenNode*)pIter)->pData : NULL;
}
