text: /* $NetBSD: gcq.h,v 1.2 2007/08/19 07:35:32 kiyohara Exp $ */
  /*
   * Not (c) 2007 Matthew Orgass
   * This file is public domain, meaning anyone can make any use of part or all 
   * of this file including copying into other works without credit.  Any use, 
   * modified or not, is solely the responsibility of the user.  If this file is 
   * part of a collection then use in the collection is governed by the terms of 
   * the collection.
   */
  
  /*
   * Generic Circular Queues: Pointer arithmetic is used to recover the 
   * enclosing object.  Merge operation is provided.  Items can be multiply 
   * removed, but queue traversal requires separate knowledge of the queue head.
   */
  
  #ifndef _GCQ_H
  #define _GCQ_H
  
  #ifdef _KERNEL
  #include <special_includes/sys/types.h>
  #include <special_includes/sys/null.h>
  #include <lib/libkern/libkern.h>
  #else
  #include <stdbool.h>
  #include <stdint.h>
  #include <stddef.h>
  #include <assert.h>
  #endif
  
  #ifdef GCQ_USE_ASSERT
  #define GCQ_ASSERT(x) assert(x)
  #else
  #ifdef _KERNEL
  #define GCQ_ASSERT(x) KASSERT(x)
  #else
  #define GCQ_ASSERT(x) _DIAGASSERT(x)
  #endif
  #endif
  
  struct gcq {
  	struct gcq *q_next;
  	struct gcq *q_prev;
  };
  
  struct gcq_head {
  	struct gcq hq;
  };
  
  #define GCQ_INIT(q) { &(q), &(q) }
  #define GCQ_INIT_HEAD(head) { GCQ_INIT((head).hq) }
  
  __attribute__((nonnull, always_inline)) static inline void
  gcq_init(struct gcq *q)
  {
  	q->q_next = q->q_prev = q;
  }
  
  __attribute__((nonnull, const, warn_unused_result, always_inline)) 
  static inline struct gcq *
  gcq_q(struct gcq *q)
  {
  	return q;
  }
  
  __attribute__((nonnull, const, warn_unused_result, always_inline)) 
  static inline struct gcq *
  gcq_hq(struct gcq_head *head)
  {
  	return (struct gcq *)head;
  }
  
  __attribute__((nonnull, const, warn_unused_result, always_inline)) 
  static inline struct gcq_head *
  gcq_head(struct gcq *q)
  {
  	return (struct gcq_head *)q;
  }
  
  __attribute__((nonnull, always_inline)) static inline void
  gcq_init_head(struct gcq_head *head)
  {
  	gcq_init(gcq_hq(head));
  }
  
  __attribute__((nonnull, pure, warn_unused_result, always_inline))
  static inline bool
  gcq_onlist(struct gcq *q)
  {
  	return (q->q_next != q);
  }
  
  __attribute__((nonnull, pure, warn_unused_result, always_inline))
  static inline bool
  gcq_empty(struct gcq_head *head)
  {
  	return (!gcq_onlist(gcq_hq(head)));
  }
  
  __attribute__((nonnull, pure, warn_unused_result, always_inline))
  static inline bool
  gcq_linked(struct gcq *prev, struct gcq *next)
  {
  	return (prev->q_next == next && next->q_prev == prev);
  }
  
  __attribute__((nonnull, always_inline)) static inline void
  gcq_insert_after(struct gcq *on, struct gcq *off)
  {
  	struct gcq *on_next;
  	GCQ_ASSERT(off->q_next == off && off->q_prev == off);
  	on_next = on->q_next;
  
  	off->q_prev = on;
  	off->q_next = on_next;
  	on_next->q_prev = off;
  	on->q_next = off;
  }
  
  __attribute__((nonnull)) static inline void
  gcq_insert_before(struct gcq *on, struct gcq *off)
  {
  	struct gcq *on_prev;
  	GCQ_ASSERT(off->q_next == off && off->q_prev == off);
  	on_prev = on->q_prev;
  
  	off->q_next = on;
  	off->q_prev = on_prev;
  	on_prev->q_next = off;
  	on->q_prev = off;
  }
  
  __attribute__((nonnull, always_inline)) static inline void
  gcq_insert_head(struct gcq_head *head, struct gcq *q)
  {
  	gcq_insert_after(gcq_hq(head), q);
  }
  
  __attribute__((nonnull, always_inline)) static inline void
  gcq_insert_tail(struct gcq_head *head, struct gcq *q)
  {
  	gcq_insert_before(gcq_hq(head), q);
  }
  
  __attribute__((nonnull)) static inline void
  gcq_tie(struct gcq *dst, struct gcq *src)
  {
  	struct gcq *dst_next, *src_prev;
  	dst_next = dst->q_next;
  	src_prev = src->q_prev;
  
  	src_prev->q_next = dst_next;
  	dst_next->q_prev = src_prev;
  	src->q_prev = dst;
  	dst->q_next = src;
  }
  
  __attribute__((nonnull, always_inline)) static inline void
  gcq_tie_after(struct gcq *dst, struct gcq *src)
  {
  	GCQ_ASSERT(dst != src && dst->q_prev != src);
  	gcq_tie(dst, src);
  }
  
  __attribute__((nonnull, always_inline)) static inline void
  gcq_tie_before(struct gcq *dst, struct gcq *src)
  {
  	gcq_tie_after(dst->q_prev, src);
  }
  
  __attribute__((nonnull)) static inline struct gcq *
  gcq_remove(struct gcq *q)
  {
  	struct gcq *next, *prev;
  	next = q->q_next;
  	prev = q->q_prev;
  
  	prev->q_next = next;
  	next->q_prev = prev;
  	gcq_init(q);
  	return q;
  }
  
  #ifdef GCQ_UNCONDITIONAL_MERGE
  __attribute__((nonnull)) static inline void
  gcq_merge(struct gcq *dst, struct gcq *src)
  {
  	GCQ_ASSERT(dst != src && dst->q_prev != src);
  	gcq_tie(dst, src);
  	gcq_tie(src, src);
  }
  
  __attribute__((nonnull, always_inline)) static inline void
  gcq_merge_head(struct gcq_head *dst, struct gcq_head *src)
  {
  	gcq_merge(gcq_hq(dst), gcq_hq(src));
  }
  
  __attribute__((nonnull, always_inline)) static inline void
  gcq_merge_tail(struct gcq_head *dst, struct gcq_head *src)
  {
  	gcq_merge(gcq_hq(dst)->q_prev, gcq_hq(src));
  }
  #else
  __attribute__((nonnull)) static inline void
  gcq_merge(struct gcq *dst, struct gcq *src)
  {
  	struct gcq *dst_next, *src_prev, *src_next;
  	GCQ_ASSERT(dst != src && dst->q_prev != src);
  
  	if (gcq_onlist(src)) {
  		dst_next = dst->q_next;
  		src_prev = src->q_prev;
  		src_next = src->q_next;
  
  		dst_next->q_prev = src_prev;
  		src_prev->q_next = dst_next;
  		dst->q_next = src_next;
  		src_next->q_prev = dst;
  		gcq_init(src);
  	}
  }
  
  __attribute__((nonnull, always_inline)) static inline void
  gcq_merge_head(struct gcq_head *dst, struct gcq_head *src)
  {
  	gcq_merge(gcq_hq(dst), gcq_hq(src));
  }
  
  __attribute__((nonnull, always_inline)) static inline void
  gcq_merge_tail(struct gcq_head *dst, struct gcq_head *src)
  {
  	gcq_merge(gcq_hq(dst)->q_prev, gcq_hq(src));
  }
  #endif
  
  __attribute__((nonnull)) static inline void
  gcq_clear(struct gcq *q)
  {
  	struct gcq *nq, *next;
  	nq=q;
  	do {
  		next = nq->q_next;
  		gcq_init(nq);
  		nq = next;
  	} while (next != q);
  }
  
  __attribute__((nonnull, always_inline)) static inline void
  gcq_remove_all(struct gcq_head *head)
  {
  	gcq_clear(gcq_hq(head));
  }
  
  __attribute__((nonnull, always_inline)) static inline struct gcq *
  _gcq_next(struct gcq *current, struct gcq_head *head, struct gcq *start)
  {
  	struct gcq *q, *hq;
  	hq = gcq_hq(head);
  	q = current->q_next;
  	if (hq != start && q == hq)
  		q = hq->q_next;
  	if (current != start)
  		GCQ_ASSERT(gcq_onlist(current));
  	return q;
  }
  
  __attribute__((nonnull, always_inline)) static inline struct gcq *
  _gcq_prev(struct gcq *current, struct gcq_head *head, struct gcq *start)
  {
  	struct gcq *q, *hq;
  	hq = gcq_hq(head);
  	q = current->q_prev;
  	if (hq != start && q == hq)
  		q = hq->q_prev;
  	if (current != start)
  		GCQ_ASSERT(gcq_onlist(current));
  	return q;
  }
  
  
  #define GCQ_ITEM(q, type, name) 					\
      ((type *)(void *)((uint8_t *)gcq_q(q) - offsetof(type, name)))
  
  
  #define _GCQ_GDQ(var, h, ptr, fn) (gcq_hq(h)->ptr != gcq_hq(h) ?	\
      (var = fn(gcq_hq(h)->ptr), true) : (var = NULL, false))
  #define _GCQ_GDQ_TYPED(tvar, h, type, name, ptr, fn)			\
      (gcq_hq(h)->ptr != gcq_hq(h) ? (tvar = GCQ_ITEM(fn(gcq_hq(h)->ptr),	\
      type, name), true) : (tvar = NULL, false))
  #define _GCQ_NP(var, current, head, start, np, fn)			\
      (np(current, head, start) != (start) ? 				\
      (var = fn(np(current, head, start)), true) : (var = NULL, false))
  #define _GCQ_NP_TYPED(tvar, current, head, start, type, name, np, fn) 	\
      (np(current, head, start) != (start) ? 				\
      (tvar = GCQ_ITEM(fn(np(current, head, start)), type, name), true) :	\
      (tvar = NULL, false))
  
  #define _GCQ_GDQ_COND(var, h, ptr, rem, cond)				\
      (gcq_hq(h)->ptr != gcq_hq(h) ? (var = gcq_hq(h)->ptr, 		\
      ((cond) ? (rem, true) : (var = NULL, false))) : 			\
      (var = NULL, false))
  #define _GCQ_GDQ_COND_TYPED(tvar, h, type, name, ptr, rem, cond)  	\
      (gcq_hq(h)->ptr != gcq_hq(h) ? (tvar = GCQ_ITEM(gcq_hq(h)->ptr,	\
      type, name), ((cond) ? (rem, true) : (tvar = NULL, false))) : 	\
      (tvar = NULL, false))
  #define _GCQ_NP_COND(var, current, head, start, np, rem, cond) 		\
      (np(current, head, start) != (start) ? 				\
      (var = fn(np(current, head, start)), ((cond) ? (rem), true) : 	\
      (var = NULL, false))) : (var = NULL, false))
  #define _GCQ_NP_COND_TYPED(tvar, current, head, start, type, name, np, 	\
      rem, cond) (np(current, head, start) != (start) ? 			\
      (tvar = GCQ_ITEM(fn(np(current, head, start)), type, name), 	\
      ((cond) ? (rem, true) : (var = NULL, false))) : 			\
      (tvar = NULL, false))
  
  #define GCQ_GOT_FIRST(var, h) _GCQ_GDQ(var, h, q_next, gcq_q)
  #define GCQ_GOT_LAST(var, h) _GCQ_GDQ(var, h, q_prev, gcq_q)
  #define GCQ_DEQUEUED_FIRST(var, h) _GCQ_GDQ(var, h, q_next, gcq_remove)
  #define GCQ_DEQUEUED_LAST(var, h) _GCQ_GDQ(var, h, q_prev, gcq_remove)
  #define GCQ_GOT_FIRST_TYPED(tvar, h, type, name)  			\
      _GCQ_GDQ_TYPED(tvar, h, type, name, q_next, gcq_q)
  #define GCQ_GOT_LAST_TYPED(tvar, h, type, name)  			\
      _GCQ_GDQ_TYPED(tvar, h, type, name, q_prev, gcq_q)
  #define GCQ_DEQUEUED_FIRST_TYPED(tvar, h, type, name)			\
      _GCQ_GDQ_TYPED(tvar, h, type, name, q_next, gcq_remove)
  #define GCQ_DEQUEUED_LAST_TYPED(tvar, h, type, name)			\
      _GCQ_GDQ_TYPED(tvar, h, type, name, q_prev, gcq_remove)
  #define GCQ_GOT_NEXT(var, current, head, start)				\
      _GCQ_NP(var, current, head, start, _gcq_next, gcq_q)
  #define GCQ_GOT_PREV(var, current, head, start)				\
      _GCQ_NP(var, current, head, start, _gcq_prev, gcq_q)
  #define GCQ_DEQUEUED_NEXT(var, current, head, start)			\
      _GCQ_NP(var, current, head, start, _gcq_next, gcq_remove)
  #define GCQ_DEQUEUED_PREV(var, current, head, start)			\
      _GCQ_NP(var, current, head, start, _gcq_prev, gcq_remove)
  #define GCQ_GOT_NEXT_TYPED(tvar, current, head, start, type, name)	\
      _GCQ_NP_TYPED(tvar, current, head, start, type, name,		\
      _gcq_next, gcq_q)
  #define GCQ_GOT_PREV_TYPED(tvar, current, head, start, type, name)	\
      _GCQ_NP_TYPED(tvar, current, head, start, type, name,		\
      _gcq_prev, gcq_q)
  #define GCQ_DEQUEUED_NEXT_TYPED(tvar, current, head, start, type, name)	\
      _GCQ_NP_TYPED(tvar, current, head, start, type, name,		\
      _gcq_next, gcq_remove)
  #define GCQ_DEQUEUED_PREV_TYPED(tvar, current, head, start, type, name)	\
      _GCQ_NP_TYPED(tvar, current, head, start, type, name,		\
      _gcq_prev, gcq_remove)
  
  #define GCQ_GOT_FIRST_COND(var, h, cond)				\
      _GCQ_GDQ_COND(var, h, q_next, ((void)0), cond)
  #define GCQ_GOT_LAST_COND(var, h, cond) 				\
      _GCQ_GDQ_COND(var, h, q_prev, ((void)0), cond)
  #define GCQ_DEQUEUED_FIRST_COND(var, h, cond) 				\
      _GCQ_GDQ_COND(var, h, q_next, gcq_remove(var), cond)
  #define GCQ_DEQUEUED_LAST_COND(var, h, cond)				\
      _GCQ_GDQ_COND(var, h, q_prev, gcq_remove(var), cond)
  #define GCQ_GOT_FIRST_COND_TYPED(tvar, h, type, name, cond)  		\
      _GCQ_GDQ_COND_TYPED(tvar, h, type, name, q_next, ((void)0), cond)
  #define GCQ_GOT_LAST_COND_TYPED(tvar, h, type, name, cond)  		\
      _GCQ_GDQ_COND_TYPED(tvar, h, type, name, q_prev, ((void)0), cond)
  #define GCQ_DEQUEUED_FIRST_COND_TYPED(tvar, h, type, name, cond)	\
      _GCQ_GDQ_COND_TYPED(tvar, h, type, name, q_next, 			\
      gcq_remove(&(tvar)->name), cond)
  #define GCQ_DEQUEUED_LAST_COND_TYPED(tvar, h, type, name, cond)		\
      _GCQ_GDQ_COND_TYPED(tvar, h, type, name, q_prev, 			\
      gcq_remove(&(tvar)->name), cond)
  #define GCQ_GOT_NEXT_COND(var, current, head, start, cond)		\
      _GCQ_NP_COND(var, current, head, start, _gcq_next, ((void)0), cond)
  #define GCQ_GOT_PREV_COND(var, current, head, start, cond)		\
      _GCQ_NP_COND(var, current, head, start, _gcq_prev, ((void)0), cond)
  #define GCQ_DEQUEUED_NEXT_COND(var, current, head, start, cond)		\
      _GCQ_NP_COND(var, current, head, start, _gcq_next, gcq_remove(var), \
      cond)
  #define GCQ_DEQUEUED_PREV_COND(var, current, head, start, cond)		\
      _GCQ_NP_COND(var, current, head, start, _gcq_prev, gcq_remove(var), \
      cond)
  #define GCQ_GOT_NEXT_COND_TYPED(tvar, current, head, start, type, name, \
      cond) _GCQ_NP_COND_TYPED(tvar, current, head, start, type, name,	\
      _gcq_next, ((void)0), cond)
  #define GCQ_GOT_PREV_COND_TYPED(tvar, current, head, start, type, name, \
      cond) _GCQ_NP_COND_TYPED(tvar, current, head, start, type, name,	\
      _gcq_prev, ((void)0), cond)
  #define GCQ_DEQUEUED_NEXT_COND_TYPED(tvar, current, head, start, type, 	\
      name, cond) _GCQ_NP_COND_TYPED(tvar, current, head, start, type, 	\
      name, _gcq_next, gcq_remove(&(tvar)->name), cond)
  #define GCQ_DEQUEUED_PREV_COND_TYPED(tvar, current, head, start, type, 	\
      name, cond) _GCQ_NP_COND_TYPED(tvar, current, head, start, type, 	\
      name, _gcq_prev, gcq_remove(&(tvar)->name), cond)
  
  
  #define _GCQ_FOREACH(var, h, tnull, item, ptr) 				\
      for ((var)=gcq_hq(h)->ptr; ((var) != gcq_hq(h) && 			\
      (GCQ_ASSERT(gcq_onlist(var)), item, true)) ||			\
      (tnull, false); (var)=(var)->ptr)
  #define _GCQ_FOREACH_NVAR(var, nvar, h, tnull, item, ptr, ol, rem, ro) 	\
      for ((nvar)=gcq_hq(h)->ptr; (((var)=(nvar), (nvar) != gcq_hq(h)) &&	\
      (ol, (nvar)=(nvar)->ptr, rem, item, true)) || (tnull, false); ro)
  
  #define GCQ_FOREACH(var, h)						\
      _GCQ_FOREACH(var, h, ((void)0), ((void)0), q_next)
  #define GCQ_FOREACH_REV(var, h)						\
      _GCQ_FOREACH(var, h, ((void)0), ((void)0), q_prev)
  #define GCQ_FOREACH_NVAR(var, nvar, h) 					\
      _GCQ_FOREACH_NVAR(var, nvar, h, ((void)0), ((void)0),		\
      q_next, GCQ_ASSERT(gcq_onlist(nvar)), ((void)0), ((void)0))
  #define GCQ_FOREACH_NVAR_REV(var, nvar, h) 				\
      _GCQ_FOREACH_NVAR(var, nvar, h, ((void)0), ((void)0),		\
      q_prev, GCQ_ASSERT(gcq_onlist(nvar)), ((void)0), ((void)0))
  #define GCQ_FOREACH_RO(var, nvar, h)					\
      _GCQ_FOREACH_NVAR(var, nvar, h, ((void)0), ((void)0),		\
      q_next, ((void)0), ((void)0), GCQ_ASSERT(gcq_linked(var, nvar)))
  #define GCQ_FOREACH_RO_REV(var, nvar, h)				\
      _GCQ_FOREACH_NVAR(var, nvar, h, ((void)0), ((void)0),		\
      q_prev, ((void)0), ((void)0), GCQ_ASSERT(gcq_linked(nvar, var)))
  #define GCQ_FOREACH_DEQUEUED(var, nvar, h)				\
      _GCQ_FOREACH_NVAR(var, nvar, h, ((void)0), ((void)0),		\
      q_next, GCQ_ASSERT(gcq_onlist(nvar)), gcq_remove(var), ((void)0)
  #define GCQ_FOREACH_DEQUEUED_REV(var, nvar, h)				\
      _GCQ_FOREACH_NVAR(var, nvar, h, ((void)0), ((void)0),		\
      q_prev, GCQ_ASSERT(gcq_onlist(nvar)), gcq_remove(var), ((void)0)
  
  #define GCQ_FOREACH_TYPED(var, h, tvar, type, name)			\
      _GCQ_FOREACH(var, h, (tvar)=NULL, (tvar)=GCQ_ITEM(var, type, name), \
      q_next)
  #define GCQ_FOREACH_TYPED_REV(var, h, tvar, type, name)			\
      _GCQ_FOREACH(var, h, (tvar)=NULL, (tvar)=GCQ_ITEM(var, type, name), \
      q_prev)
  #define GCQ_FOREACH_NVAR_TYPED(var, nvar, h, tvar, type, name)		\
      _GCQ_FOREACH_NVAR(var, nvar, h, (tvar)=NULL, 			\
      (tvar)=GCQ_ITEM(var, type, name),					\
      q_next, GCQ_ASSERT(gcq_onlist(nvar)), ((void)0), ((void)0))
  #define GCQ_FOREACH_NVAR_REV_TYPED(var, nvar, h, tvar, type, name)	\
      _GCQ_FOREACH_NVAR(var, nvar, h, (tvar)=NULL, 			\
      (tvar)=GCQ_ITEM(var, type, name),					\
      q_prev, GCQ_ASSERT(gcq_onlist(nvar)), ((void)0), ((void)0))
  #define GCQ_FOREACH_RO_TYPED(var, nvar, h, tvar, type, name)		\
      _GCQ_FOREACH_NVAR(var, nvar, h, (tvar)=NULL, 			\
      (tvar)=GCQ_ITEM(var, type, name),					\
      q_next, ((void)0), ((void)0), GCQ_ASSERT(gcq_lined(var, nvar)))
  #define GCQ_FOREACH_RO_REV_TYPED(var, nvar, h, tvar, type, name)	\
      _GCQ_FOREACH_NVAR(var, nvar, h, (tvar)=NULL, 			\
      (tvar)=GCQ_ITEM(var, type, name),					\
      q_prev, ((void)0), ((void)0), GCQ_ASSERT(gcq_linked(nvar, var)))
  #define GCQ_FOREACH_DEQUEUED_TYPED(var, nvar, h, tvar, type, name)	\
      _GCQ_FOREACH_NVAR(var, nvar, h, (tvar)=NULL, 			\
      (tvar)=GCQ_ITEM(var, type, name),					\
      q_next, GCQ_ASSERT(gcq_onlist(nvar)), gcq_remove(var), ((void)0))
  #define GCQ_FOREACH_DEQUEUED_REV_TYPED(var, nvar, h, tvar, type, name)	\
      _GCQ_FOREACH_NVAR(var, nvar, h, (tvar)=NULL, 			\
      (tvar)=GCQ_ITEM(var, type, name),					\
      q_prev, GCQ_ASSERT(gcq_onlist(nvar)), gcq_remove(var), ((void)0))
  
  #define _GCQ_COND(fe, cond) do { fe { if (cond) break; } } while (0)
  
  #define GCQ_FIND(var, h, cond) _GCQ_COND(GCQ_FOREACH(var, h), cond)
  #define GCQ_FIND_REV(var, h, cond) _GCQ_COND(GCQ_FOREACH_REV(var, h), cond)
  #define GCQ_FIND_TYPED(var, h, tvar, type, name, cond) 			\
      _GCQ_COND(GCQ_FOREACH_TYPED(var, h, tvar, type, name), cond)
  #define GCQ_FIND_TYPED_REV(var, h, tvar, type, name, cond) 		\
      _GCQ_COND(GCQ_FOREACH_REV_TYPED(var, h, tvar, type, name), cond)
  
  #endif /* _GCQ_H */
  