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#ifndef _RING_H_INCLUDED_
#define _RING_H_INCLUDED_
/*++
/* NAME
/* ring 3h
/* SUMMARY
/* circular list management
/* SYNOPSIS
/* #include <ring.h>
/* DESCRIPTION
/* .nf
/*
* External interface.
*/
typedef struct RING RING;
struct RING {
RING *succ; /* successor */
RING *pred; /* predecessor */
};
extern void ring_init(RING *);
extern void ring_prepend(RING *, RING *);
extern void ring_append(RING *, RING *);
extern void ring_detach(RING *);
#define ring_succ(c) ((c)->succ)
#define ring_pred(c) ((c)->pred)
#define RING_FOREACH(entry, head) \
for (entry = ring_succ(head); entry != (head); entry = ring_succ(entry))
/*
* Typically, an application will embed a RING structure into a larger
* structure that also contains application-specific members. This approach
* gives us the best of both worlds. The application can still use the
* generic RING primitives for manipulating RING structures. The macro below
* transforms a pointer from RING structure to the structure that contains
* it.
*/
#define RING_TO_APPL(ring_ptr,app_type,ring_member) \
((app_type *) (((char *) (ring_ptr)) - offsetof(app_type,ring_member)))
/* LICENSE
/* .ad
/* .fi
/* The Secure Mailer license must be distributed with this software.
/* AUTHOR(S)
/* Wietse Venema
/* IBM T.J. Watson Research
/* P.O. Box 704
/* Yorktown Heights, NY 10598, USA
/* LAST MODIFICATION
/* Tue Jan 28 16:50:20 EST 1997
/*--*/
#endif
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