@@ -49,6 +49,7 @@ CIRCLEQ_LOOP_PREV,
CIRCLEQ_NEXT,
CIRCLEQ_PREV,
CIRCLEQ_REMOVE
+\- implementation of a double-linked circular queue
.SH SYNOPSIS
.nf
.B #include <sys/queue.h>
@@ -96,6 +97,8 @@ CIRCLEQ_REMOVE
.PP
.BI "void CIRCLEQ_REMOVE(CIRCLEQ_HEAD *" head ", TYPE *" elm ", CIRCLEQ_ENTRY " NAME ");"
.SH DESCRIPTION
+These macros define and operate on doubly-linked circular queues.
+.PP
In the macro definitions,
.I TYPE
is the name of a user-defined structure,
@@ -252,11 +255,44 @@ removes the element
.I elm
from the circular queue.
.SH RETURN VALUE
+.BR CIRCLEQ_EMPTY ()
+returns nonzero if the queue is empty,
+and zero if the queue contains at least one entry.
+.PP
+.BR CIRCLEQ_FIRST (),
+.BR CIRCLEQ_LAST (),
+.BR CIRCLEQ_NEXT (),
+and
+.BR CIRCLEQ_PREV ()
+return a pointer to the first, last, next or previous
+.I CIRCLEQ_ENTRY
+structure, respectively.
+.PP
+.BR CIRCLEQ_HEAD_INITIALIZER ()
+returns an initializer that can be assigned to the queue
+.IR head .
.SH CONFORMING TO
Not in POSIX.1, POSIX.1-2001 or POSIX.1-2008.
Present on the BSDs
(CIRCLEQ macros first appeared in 4.4BSD).
.SH BUGS
+The macros
+.BR CIRCLEQ_FOREACH ()
+and
+.BR CIRCLEQ_FOREACH_REVERSE ()
+don't allow
+.I var
+to be removed or freed within the loop,
+as it would interfere with the traversal.
+The macros
+.BR CIRCLEQ_FOREACH_SAFE ()
+and
+.BR CIRCLEQ_FOREACH_REVERSE_SAFE (),
+which are present on the BSDs but are not present in glibc,
+fix this limitation by allowing
+.I var
+to safely be removed from the list and freed from within the loop
+without interfering with the traversal.
.SH EXAMPLES
.EX
#include <stddef.h>
@@ -314,3 +350,5 @@ main(void)
}
.EE
.SH SEE ALSO
+.BR insque (3),
+.BR queue (3)