list.c

unix环境下实现的cmm语言编译器

/*list.c:管理循环列表*/
#include "cmm.h"

static List freelist;	/*指向空闲的链*/

/*append将元素x添加至链尾list*/
List append(void *x, List list)
{
	List new;

	if ((new = freelist) != NULL)
		freelist = freelist->link;
	else
		NEW(new, PERM);
	if (list) {	
		new->link = list->link;
		list->link = new;
	} else
		new->link = new;
	new->x = x;
	return new;
}

/*length返回list的长度*/
int length(List list)
{
	int n = 0;
	List p;
	if (list == NULL) return n;

	/*list指向循环列表的最后一个元素，list->link为列表的首个元素*/
	for (n=1,p = list->link; p != list; p = p->link)
		n++;
	return n;
}

/*ltov将链表转换成一数组保存于a的存储区，并释放list*/
void *ltov(List *list, unsigned a)
{	
	List p=*list;
	int i=0,n = length(p);	
	void **array = newarray(n+1,sizeof(void *),a);

	if (p) 
		for (p=p->link; i<n; i++) {
			array[i] = p->x;
			p = p->link;
		}
	array[i] = NULL;
	if(*list) { /*将*list放置于空闲链*/
		freelist = (*list)->link;
		(*list)->link = NULL;	/*断开循环*/
		*list = NULL;			/*释放列表*/
	}
	return array;
}
void listmap(List list,
			void (*apply)(void *x,void *c1), void *c1)
{
	List p;
	if(NULL==list) return;
	for( p=list->link; p!=list; p=p->link)
		(*apply)(p->x,c1);
	(*apply)(p->x,c1);
	return;
}