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Diffstat (limited to 'src/util/ring.h')
| -rw-r--r-- | src/util/ring.h | 59 |
1 files changed, 59 insertions, 0 deletions
diff --git a/src/util/ring.h b/src/util/ring.h new file mode 100644 index 0000000..47749e2 --- /dev/null +++ b/src/util/ring.h @@ -0,0 +1,59 @@ +#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 |