/* $NetBSD: gcq.h,v 1.3 2018/04/19 21:19:07 christos 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 <sys/types.h>
#include <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 */