/* Copyright (c) 2008, 2009 The Board of Trustees of The Leland Stanford
 * Junior University
 *
 * We are making the OpenFlow specification and associated documentation
 * (Software) available for public use and benefit with the expectation
 * that others will use, modify and enhance the Software and contribute
 * those enhancements back to the community. However, since we would
 * like to make the Software available for broadest use, with as few
 * restrictions as possible permission is hereby granted, free of
 * charge, to any person obtaining a copy of this Software to deal in
 * the Software under the copyrights without restriction, including
 * without limitation the rights to use, copy, modify, merge, publish,
 * distribute, sublicense, and/or sell copies of the Software, and to
 * permit persons to whom the Software is furnished to do so, subject to
 * the following conditions:
 *
 * The above copyright notice and this permission notice shall be
 * included in all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
 * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
 * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
 * NONINFRINGEMENT.  IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
 * BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
 * ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
 * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 * SOFTWARE.
 *
 * The name and trademarks of copyright holder(s) may NOT be used in
 * advertising or publicity pertaining to the Software or any
 * derivatives without specific, written prior permission.
 */

#ifndef HMAP_H
#define HMAP_H 1

#include <stdbool.h>
#include <stdlib.h>
#include "util.h"

/* A hash map node, to be embedded inside the data structure being mapped. */
struct hmap_node {
    size_t hash;                /* Hash value. */
    struct hmap_node *next;     /* Next in linked list. */
};

/* Returns the hash value embedded in 'node'. */
static inline size_t hmap_node_hash(const struct hmap_node *node)
{
    return node->hash;
}

/* A hash map. */
struct hmap {
    struct hmap_node **buckets;
    struct hmap_node *one;
    size_t mask;
    size_t n;
};

/* Initializer for an empty hash map. */
#define HMAP_INITIALIZER(HMAP) { &(HMAP)->one, NULL, 0, 0 }

/* Initialization. */
void hmap_init(struct hmap *);
void hmap_destroy(struct hmap *);
void hmap_swap(struct hmap *a, struct hmap *b);
static inline size_t hmap_count(const struct hmap *);
static inline bool hmap_is_empty(const struct hmap *);

/* Adjusting capacity. */
void hmap_expand(struct hmap *);
void hmap_shrink(struct hmap *);
void hmap_reserve(struct hmap *, size_t capacity);

/* Insertion and deletion. */
static inline void hmap_insert_fast(struct hmap *,
                                    struct hmap_node *, size_t hash);
static inline void hmap_insert(struct hmap *, struct hmap_node *, size_t hash);
static inline void hmap_remove(struct hmap *, struct hmap_node *);

/* Search. */
#define HMAP_FOR_EACH_WITH_HASH(NODE, STRUCT, MEMBER, HASH, HMAP)       \
    for ((NODE) = CONTAINER_OF(hmap_first_with_hash(HMAP, HASH),        \
                               STRUCT, MEMBER);                         \
         &(NODE)->MEMBER != NULL;                                       \
         (NODE) = CONTAINER_OF(hmap_next_with_hash(&(NODE)->MEMBER),    \
                               STRUCT, MEMBER))

static inline struct hmap_node *hmap_first_with_hash(const struct hmap *,
                                                     size_t hash);
static inline struct hmap_node *hmap_next_with_hash(const struct hmap_node *);

/* Iteration.
 *
 * The _SAFE version is needed when NODE may be freed.  It is not needed when
 * NODE may be removed from the hash map but its members remain accessible and
 * intact. */
#define HMAP_FOR_EACH(NODE, STRUCT, MEMBER, HMAP)                   \
    for ((NODE) = CONTAINER_OF(hmap_first(HMAP), STRUCT, MEMBER);   \
         &(NODE)->MEMBER != NULL;                                   \
         (NODE) = CONTAINER_OF(hmap_next(HMAP, &(NODE)->MEMBER),    \
                               STRUCT, MEMBER))

#define HMAP_FOR_EACH_SAFE(NODE, NEXT, STRUCT, MEMBER, HMAP)        \
    for ((NODE) = CONTAINER_OF(hmap_first(HMAP), STRUCT, MEMBER);   \
         (&(NODE)->MEMBER != NULL                                   \
          ? (NEXT) = CONTAINER_OF(hmap_next(HMAP, &(NODE)->MEMBER), \
                                  STRUCT, MEMBER), 1                \
          : 0);                                                     \
         (NODE) = (NEXT))

static inline struct hmap_node *hmap_first(const struct hmap *);
static inline struct hmap_node *hmap_next(const struct hmap *,
                                          const struct hmap_node *);

/* Returns the number of nodes currently in 'hmap'. */
static inline size_t
hmap_count(const struct hmap *hmap)
{
    return hmap->n;
}

/* Returns true if 'hmap' currently contains no nodes,
 * false otherwise. */
static inline bool
hmap_is_empty(const struct hmap *hmap)
{
    return hmap->n == 0;
}

/* Inserts 'node', with the given 'hash', into 'hmap'.  'hmap' is never
 * expanded automatically. */
static inline void
hmap_insert_fast(struct hmap *hmap, struct hmap_node *node, size_t hash)
{
    struct hmap_node **bucket = &hmap->buckets[hash & hmap->mask];
    node->hash = hash;
    node->next = *bucket;
    *bucket = node;
    hmap->n++;
}

/* Inserts 'node', with the given 'hash', into 'hmap', and expands 'hmap' if
 * necessary to optimize search performance. */
static inline void
hmap_insert(struct hmap *hmap, struct hmap_node *node, size_t hash)
{
    hmap_insert_fast(hmap, node, hash);
    if (hmap->n / 2 > hmap->mask) {
        hmap_expand(hmap);
    }
}

/* Removes 'node' from 'hmap'.  Does not shrink the hash table; call
 * hmap_shrink() directly if desired. */
static inline void
hmap_remove(struct hmap *hmap, struct hmap_node *node)
{
    struct hmap_node **bucket = &hmap->buckets[node->hash & hmap->mask];
    while (*bucket != node) {
        bucket = &(*bucket)->next;
    }
    *bucket = node->next;
    hmap->n--;
}

static inline struct hmap_node *
hmap_next_with_hash__(const struct hmap_node *node, size_t hash)
{
    while (node != NULL && node->hash != hash) {
        node = node->next;
    }
    return (struct hmap_node *) node;
}

/* Returns the first node in 'hmap' with the given 'hash', or a null pointer if
 * no nodes have that hash value. */
static inline struct hmap_node *
hmap_first_with_hash(const struct hmap *hmap, size_t hash)
{
    return hmap_next_with_hash__(hmap->buckets[hash & hmap->mask], hash);
}

/* Returns the next node in the same hash map as 'node' with the same hash
 * value, or a null pointer if no more nodes have that hash value.
 *
 * If the hash map has been reallocated since 'node' was visited, some nodes
 * may be skipped; if new nodes with the same hash value have been added, they
 * will be skipped.  (Removing 'node' from the hash map does not prevent
 * calling this function, since node->next is preserved, although freeing
 * 'node' of course does.) */
static inline struct hmap_node *
hmap_next_with_hash(const struct hmap_node *node)
{
    return hmap_next_with_hash__(node->next, node->hash);
}

static inline struct hmap_node *
hmap_next__(const struct hmap *hmap, size_t start)
{
    size_t i;
    for (i = start; i <= hmap->mask; i++) {
        struct hmap_node *node = hmap->buckets[i];
        if (node) {
            return node;
        }
    }
    return NULL;
}

/* Returns the first node in 'hmap', in arbitrary order, or a null pointer if
 * 'hmap' is empty. */
static inline struct hmap_node *
hmap_first(const struct hmap *hmap)
{
    return hmap_next__(hmap, 0);
}

/* Returns the next node in 'hmap' following 'node', in arbitrary order, or a
 * null pointer if 'node' is the last node in 'hmap'.
 *
 * If the hash map has been reallocated since 'node' was visited, some nodes
 * may be skipped or visited twice.  (Removing 'node' from the hash map does
 * not prevent calling this function, since node->next is preserved, although
 * freeing 'node' of course does.) */
static inline struct hmap_node *
hmap_next(const struct hmap *hmap, const struct hmap_node *node)
{
    return (node->next
            ? node->next
            : hmap_next__(hmap, (node->hash & hmap->mask) + 1));
}

#endif /* hmap.h */