// Filename 		: LIST.C
// Coded by 		: Scott Evans
// Created/Modified : 15/2/98
// Description		: Routines to handle generic linked lists


#include "list.h"


// Free nodes, pointer to first free node

LIST_NODE free_nodes[MAX_FREE_NODES];
LIST_NODE *first_free_node=0;


// Function			: InitFreeNodes()
// Coded by			: Scott Evans
// Created/Modified	: 15/2/98
// Description		: Set up an a list of free nodes

// Parameters		: None

// Returns			: None

// Notes			: Need to call this before othe list functions


void InitFreeNodes(void)
{
	u_word i;
	
	for(i=0;i<MAX_FREE_NODES-1;i++)
		free_nodes[i].next=&free_nodes[i+1];
		
	free_nodes[MAX_FREE_NODES].next=0;
	first_free_node=&free_nodes[0];
}


// Function			: AddToList()
// Coded by			: Scott Evans
// Created/Modified	: 15/2/98
// Description		: Add a node to a list

// Parameters		: Pointer to header of list

// Returns			: New node added to list
//				  	  NULL if no nodes free

// Notes			: None


LIST_NODE *AddToList(LIST_HEADER *h)
{
	LIST_NODE *new_node;
	
	// Do we have any free nodes
	
	if(first_free_node)
	{
		// Update size of current list
		
		h->no_nodes++;
		
		// Get free node
		
		new_node=first_free_node;
		first_free_node=first_free_node->next;
		new_node->next=0;
		
		// Add new node to end of list
		
		if(h->start)
		{
			LIST_NODE *node=h->start;
			
			while(node->next)
				node=node->next;
				
			node->next=new_node;
		}
		else
			h->start=new_node;	
		
		return(new_node);
	}
	
	return(0);
}


// Function			: RemoveFromList()
// Coded by			: Scott Evans
// Created/Modified	: 15/2/98
// Description		: Remove a node from a list

// Parameters		: h - pointer to header of list
//				  	  dead_node - pointer to node to remove

// Returns			: None

// Notes			: None


void RemoveFromList(LIST_HEADER *h,LIST_NODE *dead_node)
{
	LIST_NODE *node;
	
	// Are there any nodes to remove from list
	
	if(node=h->start)
	{
		h->no_nodes--;
		
		// Removing from start of list
		
		if(node==dead_node)
			h->start=dead_node->next;
		else
		{
			// Removing from the middle
			
			while(node->next!=dead_node)
				node=node->next;
				
			node->next=dead_node->next;
		}
		
		// Return node to free node list
		
		node=first_free_node;
		
		if(node)
		{
			
			while(node->next)
				node=node->next;
				
			node->next=dead_node;
		}
		else
			first_free_node=dead_node;
			
		dead_node->next=0;
	}
}