#include "bomber.h"
#include "list.h"
#include "utils.h"

/* doesn't use prev link */
static genericlistitem *things=0;
static listhead *free_things;

void allocthings(void) {
	int i;
	const int num = MAXTHINGS;

	if (!things) {
		things = calloc(sizeof(genericlistitem), num);
	} else {
		memset(things, 0, sizeof(genericlistitem)*num);
	}
	if(!things) nomem("Trying to allocate thing memory");
	for(i=0;i<num-1;++i) {
		things[i].h.next = (listhead*) &things[i+1];
	}
	things[i].h.next = 0;
	free_things = (listhead*) things;
}

void *allocentry(void) {
	listhead *entry = free_things;

	if (free_things) {
		free_things = free_things->next;
		memset(entry, 0, sizeof(genericlistitem));
	}
	return entry;
}

static void freeentry(void *_entry) {
	listhead *entry = _entry;

	entry->next = free_things;
	entry->prev = NULL;
	free_things = entry;
}

void _addtail(listhead *head, listhead *entry) {
	entry->next = head;
	entry->prev = head->prev;
	head->prev->next = entry;
	head->prev = entry;
}

listhead* delinkhead(listhead *entry) {
	listhead *result = entry->prev;

	entry->next->prev = entry->prev;
	entry->prev->next = entry->next;

	freeentry(entry);
	return result;
}

void initheader(listhead *head) {
	head->next = head;
	head->prev = head;
}