NAME
srpl_rc_init,
SRPL_HEAD, SRPL_ENTRY,
SRPL_INIT, SRPL_FIRST,
SRPL_NEXT, SRPL_FOLLOW,
SRPL_FOREACH, SRPL_LEAVE,
SRPL_RC_INITIALIZER —
singly-linked shared reference pointer
list
SYNOPSIS
#include
<sys/srp.h>
struct srpl_rc;
void
srpl_rc_init(struct srpl_rc *rc,
void (*ref)(void *, void *), void
(*unref)(void *, void *), void *ctx);
SRPL_HEAD(HEADNAME,
TYPE);
SRPL_ENTRY(TYPE);
void
SRPL_INIT(SRPL_HEAD
*sl);
void *
SRPL_FIRST(struct
srp_ref *sr, SRPL_HEAD
*sl);
void *
SRPL_NEXT(struct
srp_ref *sr, struct TYPE
*listelm,
FIELDNAME);
void *
SRPL_FOLLOW(struct
srp_ref *sr, struct TYPE
*listelm,
FIELDNAME);
SRPL_FOREACH(VARNAME,
struct srp_ref *sr, SRPL_HEAD
*sl, FIELDNAME);
void
SRPL_LEAVE(struct
srp_ref *sr);
SRPL_RC_INITIALIZER(void
(*ref)(void *, void *), void (*unref)(void *, void
*), void *ctx);
DESCRIPTION
The SRPL list macros build a linked list on top of shared reference pointers. This allows concurrent traversal of a linked list and access to the items on the list.
SRP lists are a generic type represented by a SRPL_HEAD. The elements inserted into the list must be structures that contain a SRPL_ENTRY field. Further, the elements must also support reference counting as insertion and removal operations can cause items to be temporarily referenced by multiple SRPs within the list at the same time.
srpl_rc_init()
initialises the SRP list refcounts rc structure so it
can be used to manage the reference counts on elements in the list. The
insertion or removal of an element in an SRP list will increment the
reference counts on elements within the list via calls to
ref. As these references are released by the SRP
infrastructure, the reference counts will be decremented by calls to
unref. unref is also responsible
for freeing the element when the reference count reaches 0. Both
ref and unref will be called
with ctx as their first argument and a pointer to the
element as their second argument.
SRPL_INIT()
initialises the SRP list sl to an empty state.
SRPL_FIRST()
accesses the first element in the SRP list sl and
holds its reference via sr.
SRPL_NEXT()
accesses the element in the SRP list after listelm and
holds its reference via sr.
SRPL_FOLLOW()
accesses the element in the SRP list after listelm and
swaps the previous reference held via sr for the
reference of the newly accessed item.
SRPL_FOREACH()
creates a loop for traversing the list. Every call to
SRPL_FOREACH() must have a corresponding call to
SRPL_LEAVE() to release references to the list and
its elements.
SRPL_LEAVE()
releases references to the list and its elements held by previous calls to
SRPL_FIRST(), SRPL_NEXT(),
SRPL_FOLLOW(), or
SRPL_FOREACH().
An srpl_rc declaration can be initialised
with the
SRPL_RC_INITIALIZER()
macro.
CONTEXT
SRPL_INIT(),
SRPL_FIRST(), SRPL_NEXT(),
SRPL_FOLLOW(),
SRPL_FOREACH(), and
SRPL_LEAVE() may be called during autoconf, from
process context, or from interrupt context.
srpl_rc_init(), may be called during
autoconf or from process context.
RETURN VALUES
SRPL_FIRST(),
SRPL_NEXT(), and
SRPL_FOLLOW() return a pointer to elements in the
SRP list, or NULL if there are no more elements.
SEE ALSO
HISTORY
The srp API was originally written by Jonathan Matthew <jmatthew@openbsd.org> and David Gwynne <dlg@openbsd.org>. The SRP list API first appeared in OpenBSD 5.9.