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GCQ(3)                     Library Functions Manual                     GCQ(3)

NAME
     GCQ_INIT, GCQ_INIT_HEAD, gcq_init, gcq_init_head, gcq_q, gcq_hq,
     gcq_head, gcq_remove, gcq_onlist, gcq_empty, gcq_linked,
     gcq_insert_after, gcq_insert_before, gcq_insert_head, gcq_insert_tail,
     gcq_tie, gcq_tie_after, gcq_tie_before, gcq_merge, gcq_merge_head,
     gcq_merge_tail, gcq_clear, gcq_remove_all, GCQ_ITEM, GCQ_GOT_FIRST,
     GCQ_GOT_LAST, GCQ_GOT_NEXT, GCQ_GOT_PREV, GCQ_DEQUEUED_FIRST,
     GCQ_DEQUEUED_LAST, GCQ_DEQUEUED_NEXT, GCQ_DEQUEUED_PREV,
     GCQ_GOT_FIRST_TYPED, GCQ_GOT_LAST_TYPED, GCQ_GOT_NEXT_TYPED,
     GCQ_GOT_PREV_TYPED, GCQ_DEQUEUED_FIRST_TYPED, GCQ_DEQUEUED_LAST_TYPED,
     GCQ_DEQUEUED_NEXT_TYPED, GCQ_DEQUEUED_PREV_TYPED, GCQ_GOT_FIRST_COND,
     GCQ_GOT_LAST_COND, GCQ_GOT_NEXT_COND, GCQ_GOT_PREV_COND,
     GCQ_DEQUEUED_FIRST_COND, GCQ_DEQUEUED_LAST_COND, GCQ_DEQUEUED_NEXT_COND,
     GCQ_DEQUEUED_PREV_COND, GCQ_GOT_FIRST_COND_TYPED,
     GCQ_GOT_LAST_COND_TYPED, GCQ_GOT_NEXT_COND_TYPED,
     GCQ_GOT_PREV_COND_TYPED, GCQ_DEQUEUED_FIRST_COND_TYPED,
     GCQ_DEQUEUED_LAST_COND_TYPED, GCQ_DEQUEUED_NEXT_COND_TYPED,
     GCQ_DEQUEUED_PREV_COND_TYPED, GCQ_FOREACH, GCQ_FOREACH_REV,
     GCQ_FOREACH_NVAR, GCQ_FOREACH_NVAR_REV, GCQ_FOREACH_RO,
     GCQ_FOREACH_RO_REV, GCQ_FOREACH_DEQUEUED, GCQ_FOREACH_DEQUEUED_REV,
     GCQ_FOREACH_TYPED, GCQ_FOREACH_REV_TYPED, GCQ_FOREACH_NVAR_TYPED,
     GCQ_FOREACH_NVAR_REV_TYPED, GCQ_FOREACH_RO_TYPED,
     GCQ_FOREACH_RO_REV_TYPED, GCQ_FOREACH_DEQUEUED_TYPED,
     GCQ_FOREACH_DEQUEUED_REV_TYPED, GCQ_FIND, GCQ_FIND_REV, GCQ_FIND_TYPED,
     GCQ_FIND_REV_TYPED -- Generic Circular Queues

SYNOPSIS
     #include <&lt;sys/gcq.h>&gt;

     struct gcq;
     struct gcq_head;

     GCQ_INIT(name);

     GCQ_INIT_HEAD(name);

     static inline void
     gcq_init(struct gcq *q);

     static inline void
     gcq_init_head(struct gcq_head *head);

     static inline struct gcq *
     gcq_q(struct gcq_head *head);

     static inline struct gcq *
     gcq_hq(struct gcq_head *head);

     static inline struct gcq_head *
     gcq_head(struct gcq *q);

     static inline struct gcq *
     gcq_remove(struct gcq *q);

     static inline bool
     gcq_onlist(struct gcq *q);

     static inline bool
     gcq_empty(struct gcq_head *head);

     static inline bool
     gcq_linked(struct gcq *prev, struct gcq *next);

     static inline void
     gcq_insert_after(struct gcq *on, struct gcq *off);

     static inline void
     gcq_insert_before(struct gcq *on, struct gcq *off);

     static inline void
     gcq_insert_head(struct gcq_head *head, struct gcq *q);

     static inline void
     gcq_insert_tail(struct gcq_head *head, struct gcq *q);

     static inline void
     gcq_tie(struct gcq *dst, struct gcq *src);

     static inline void
     gcq_tie_after(struct gcq *dst, struct gcq *src);

     static inline void
     gcq_tie_before(struct gcq *dst, struct gcq *src);

     static inline void
     gcq_merge(struct gcq *dst, struct gcq *src);

     static inline void
     gcq_merge_tail(struct gcq_head *dst, struct gcq_head *src);

     static inline void
     gcq_merge_head(struct gcq_head *dst, struct gcq_head *src);

     static inline void
     gcq_clear(struct gcq *q);

     static inline void
     gcq_remove_all(struct gcq_head *head);

     type *
     GCQ_ITEM(q, type, name);

     bool
     GCQ_GOT_FIRST(var, head);

     bool
     GCQ_GOT_LAST(var, head);

     bool
     GCQ_GOT_NEXT(var, current, head, start);

     bool
     GCQ_GOT_PREV(var, current, head, start);

     bool
     GCQ_DEQUEUED_FIRST(var, head);

     bool
     GCQ_DEQUEUED_LAST(var, head);

     bool
     GCQ_DEQUEUED_NEXT(var, current, head, start);

     bool
     GCQ_DEQUEUED_PREV(var, current, head, start);

     bool
     GCQ_GOT_FIRST_TYPED(tvar, head, type, name);

     bool
     GCQ_GOT_LAST_TYPED(tvar, head, type, name);

     bool
     GCQ_GOT_NEXT_TYPED(tvar, current, head, start, type, name);

     bool
     GCQ_GOT_PREV_TYPED(tvar, current, head, start, type, name);

     bool
     GCQ_DEQUEUED_FIRST_TYPED(tvar, head, type, name);

     bool
     GCQ_DEQUEUED_LAST_TYPED(tvar, head, type, name);

     bool
     GCQ_DEQUEUED_NEXT_TYPED(tvar, current, head, start, type, name);

     bool
     GCQ_DEQUEUED_PREV_TYPED(tvar, current, head, start, type, name);

     bool
     GCQ_GOT_FIRST_COND(var, head, cond);

     bool
     GCQ_GOT_LAST_COND(var, head, cond);

     bool
     GCQ_GOT_NEXT_COND(var, current, head, start, cond);

     bool
     GCQ_GOT_PREV_COND(var, current, head, start, cond);

     bool
     GCQ_DEQUEUED_FIRST_COND(var, head, cond);

     bool
     GCQ_DEQUEUED_LAST_COND(var, head, cond);

     bool
     GCQ_DEQUEUED_NEXT_COND(var, current, head, start, cond);

     bool
     GCQ_DEQUEUED_PREV_COND(var, current, head, start, cond);

     bool
     GCQ_GOT_FIRST_COND_TYPED(tvar, head, type, name, cond);

     bool
     GCQ_GOT_LAST_COND_TYPED(tvar, head, type, name, cond);

     bool
     GCQ_GOT_NEXT_COND_TYPED(tvar, current, head, start, type, name, cond);

     bool
     GCQ_GOT_PREV_COND_TYPED(tvar, current, head, start, type, name, cond);

     bool
     GCQ_DEQUEUED_FIRST_COND_TYPED(tvar, head, type, name, cond);

     bool
     GCQ_DEQUEUED_LAST_COND_TYPED(tvar, head, type, name, cond);

     bool
     GCQ_DEQUEUED_NEXT_COND_TYPED(tvar,
     current, head, start, type, name, cond);

     bool
     GCQ_DEQUEUED_PREV_COND_TYPED(tvar,
     current, head, start, type, name, cond);

     GCQ_FOREACH(var, head);

     GCQ_FOREACH_REV(var, head);

     GCQ_FOREACH_NVAR(var, nvar, head);

     GCQ_FOREACH_NVAR_REV(var, nvar, head);

     GCQ_FOREACH_RO(var, nvar, head);

     GCQ_FOREACH_RO_REV(var, nvar, head);

     GCQ_FOREACH_DEQUEUED(var, nvar, head);

     GCQ_FOREACH_DEQUEUED_REV(var, nvar, head);

     GCQ_FOREACH_TYPED(var, head, tvar, type, name);

     GCQ_FOREACH_REV_TYPED(var, head, tvar, type, name);

     GCQ_FOREACH_NVAR_TYPED(var, nvar, head, tvar, type, name);

     GCQ_FOREACH_NVAR_REV_TYPED(var, nvar, head, tvar, type, name);

     GCQ_FOREACH_RO_TYPED(var, nvar, head, tvar, type, name);

     GCQ_FOREACH_RO_REV_TYPED(var, nvar, head, tvar, type, name);

     GCQ_FOREACH_DEQUEUED_TYPED(var, nvar, head, tvar, type, name);

     GCQ_FOREACH_DEQUEUED_REV_TYPED(var, nvar, head, tvar, type, name);

     GCQ_FIND(var, head, cond);

     GCQ_FIND_REV(var, head, cond);

     GCQ_FIND_TYPED(var, head, tvar, type, name, cond);

     GCQ_FIND_REV_TYPED(var, head, tvar, type, name, cond);

     GCQ_ASSERT(cond);

DESCRIPTION
     The generic circular queue is a doubly linked list designed for efficient
     merge operations and unconditional removal.  All basic operations can be
     performed with or without use of a separate head, allowing easy
     replacement of any pointers where efficient removal is desired.  The
     meaning of the data type will not change; direct use and defined
     operations can be mixed when convenient.  The basic type is:

           struct gcq {
                   struct gcq *q_next;
                   struct gcq *q_prev;
           };

     The structure must first be initialized such that the q_next and q_prev
     members point to the beginning of the struct gcq.  This can be done with
     gcq_init() and gcq_init_head() or with constant initializers GCQ_INIT()
     and GCQ_INIT_HEAD().  A struct gcq should never be given NULL values.

     The structure containing the struct gcq can be retrieved by pointer
     arithmetic in the GCQ_ITEM() macro.  List traversal normally requires
     knowledge of the list head to safely retrieve list items.

     Capitalized operation names are macros and should be assumed to cause
     multiple evaluation of arguments.  TYPED variants of macros set a typed
     pointer variable instead of or in addition to struct gcq * arguments.
     Additional type specific inlines and macros around some GCQ operations
     can be useful.

     A few assertions are provided when DIAGNOSTIC is defined in the kernel or
     _DIAGNOSTIC is defined in userland.  If GCQ_USE_ASSERT is defined prior
     to header inclusions then assert() will be used for assertions and NDEBUG
     can be used to turn them off.  GCQ_ASSERT() is a wrapper around the used
     assertion function.  None of the operations accept NULL arguments,
     however this is not tested by assertion.

     The head is separately named for type checking but contains only a struct
     gcq, a pointer to which can be retrieved via gcq_hq().  The reverse
     operation is performed by gcq_head(), turning the supplied struct gcq *
     into struct gcq_head *.  gcq_q() returns its struct gcq * argument and is
     used for type checking in GCQ_ITEM().  There are no functions for
     retrieving the raw q_prev and q_next pointers as these are usually
     clearer when used directly (if at all).

     gcq_remove() returns the element removed and is always a valid operation
     after initialization.  gcq_onlist() returns false if the structure links
     to itself and true otherwise.  gcq_empty() is the negation of this
     operation performed on a head.  gcq_linked() tests if prev->q_next ==
     next && next->q_prev == prev.

     gcq_tie() ties src after dst such that that if the old lists are DST,
     DST2 and SRC, SRC2, the new list is DST, SRC, SRC2, DST2.  If dst and src
     are on the same list then any elements between but not including dst and
     src are cut from the list.  If dst == src then the result is the same as
     gcq_remove().  gcq_tie() is equivalent to gcq_tie_after() except that the
     latter must only be used with arguments on separate lists or not on lists
     and asserts that src != dst && dst->q_prev != src.  gcq_tie_before()
     performs the same operation on dst->q_prev.

     gcq_merge() moves any elements on list src (but not src itself) to list
     dst.  It is normally used with two heads via gcq_merge_head() or
     gcq_merge_tail().  If GCQ_UNCONDITIONAL_MERGE is defined prior to header
     inclusion then the merge operations will always perform a tie then remove
     src from the new list, which may reduce code size slightly.

     gcq_clear() initializes all elements currently linked with q and is
     normally used with a head as gcq_remove_all().

     gcq_insert_after() and gcq_insert_before() are slightly optimized
     versions of gcq_tie() for the case where off is not on a list and include
     assertions to this effect, which are also useful to detect missing
     initialization.  gcq_insert_head() and gcq_insert_tail() are the same
     operations applied to a head.

     GCQ_GOT_FIRST() and GCQ_GOT_LAST() set var to a pointer to the first or
     last struct gcq in the list or NULL if the list is empty and return false
     if empty and true otherwise.  The boolean return is to emphasise that it
     is not normally safe and useful to directly pass the raw first/next/etc.
     pointer to another function.  The macros are written such that the NULL
     values will be optimized out if not otherwise used.  DEQUEUED variants
     also remove the member from the list.  COND variants take an additional
     condition that is evaluated when the macro would otherwise return true.
     If the condition is false var or tvar is set to NULL and no dequeue is
     performed.

     GCQ_GOT_NEXT() and variants take pointers to the current position, list
     head, and starting point as arguments.  The list head will be skipped
     when it is reached unless it is equal to the starting point; upon
     reaching the starting point var will be set to NULL and the macro will
     return false.  The next and prev macros also assert that current is on
     the list unless it is equal to start.  These macros are the only provided
     method for iterating through the list from an arbitrary point.  Traversal
     macros are only provided for list heads, however gcq_head() can be used
     to treat any item as a head.

     Foreach variants contain an embedded for statement for iterating over a
     list.  Those containing REV use the q_prev pointer for traversal, others
     use q_next.  The plain GCQ_FOREACH() uses a single variable.  NVAR
     variants save the next pointer at the top of the loop so that the current
     element can be removed without adjusting var.  This is useful when var is
     passed to a function that might remove it but will not otherwise modify
     the list.  When the head is reached both var and nvar elements are left
     pointing to the list head.  FOREACH asserts that var, and NVAR asserts
     that nvar does not point to itself when starting the next loop.  This
     assertion takes place after the variable is tested against the head so it
     is safe to remove all elements from the list.  RO variants also set nvar
     but assert that the two variables are linked at the end of each
     iteration.  This is useful when calling a function that is not supposed
     to remove the element passed.  DEQUEUED variants are like NVAR but remove
     each element before the code block is executed.  TYPED variants are
     equivalent to the untyped versions except that they take three extra
     arguments: a typed pointer, the type name, and the member name of the
     struct gcq used in this list.  tvar is set to NULL when the head is
     reached.

     GCQ_FIND() is a foreach loop that does nothing except break when the
     supplied condition is true.  REV and TYPED variants are available.

SEE ALSO
     gcc(1), _DIAGASSERT(3), assert(3), queue(3), KASSERT(9)

HISTORY
     GCQ appeared in NetBSD 5.0.

NetBSD 6.1.5                      May 1, 2007                     NetBSD 6.1.5