/* vx_list.h - simple circular doubly-linked list type and macros */

#ifndef VX_LIST_H
#define VX_LIST_H

#ifdef __cplusplus
extern "C" {
#endif

typedef struct Circ_list_struct Circ_list;

struct Circ_list_struct
{
    Circ_list * prev;
    Circ_list * next;
};

/*
 * CIRC_LIST_INIT(l) initializes the list node l as a list
 * containing a single node (itself). Used for list heads/sentinels.
 */
#define CIRC_LIST_INIT(l) \
    do  { \
        Circ_list * l_ = (l); \
	l_->prev = l_; \
	l_->next = l_; \
        } while ((0))

/*
 * CIRC_LIST_REMOVE(n) removes the node n from the list
 * that it is in. (n must be in a list).
 * n is left with dangling references to the list.
 * If n is alone in the list, this is a no-op.
 */
#define CIRC_LIST_REMOVE(n) \
    do  { \
        Circ_list * n_ = (n); \
	Circ_list * nxt_ = n_->next; \
        n_->prev->next = nxt_; \
        nxt_->prev = n_->prev; \
        } while ((0))

/*
 * CIRC_LIST_INSERT_AFTER(l, n) inserts node n after node l
 * in the list that l currently belongs to. n should
 * be a free node.  If l represents the 'head' of the list
 * rather than an 'item', this operation inserts n as the
 * first item in list.
 */
#define CIRC_LIST_INSERT_AFTER(l, n) \
    do  { \
        Circ_list * l_ = (l); \
        Circ_list * n_ = (n); \
        n_->prev = l_; \
	n_->next = l_->next; \
	l_->next->prev = n_; \
	l_->next = n_; \
        } while ((0))

/*
 * CIRC_LIST_INSERT_BEFORE(l, n) inserts node n before node l
 * in the list that l currently belongs to. n should
 * be a free node.  If l represents the head of the list,
 * this operation corresponds to inserting n at the tail.
 */
#define CIRC_LIST_INSERT_BEFORE(l, n) \
    do  { \
        Circ_list * l_ = (l); \
        Circ_list * n_ = (n); \
        n_->next = l_; \
	n_->prev = l_->prev; \
	l_->prev->next = n_; \
	l_->prev = n_; \
        } while ((0))

#ifdef __cplusplus
}
#endif

#endif /* VX_LIST_H */