/* $OpenBSD: ohash.c,v 1.1 2014/06/02 18:52:03 deraadt Exp $ */

/* Copyright (c) 1999, 2004 Marc Espie <espie@openbsd.org>
 *
 * Permission to use, copy, modify, and distribute this software for any
 * purpose with or without fee is hereby granted, provided that the above
 * copyright notice and this permission notice appear in all copies.
 *
 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
 * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
 * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
 * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
 */

#include <stddef.h>
#include <stdint.h>
#include <stdlib.h>
#include <string.h>
#include <limits.h>
#include "ohash.h"

struct _ohash_record {
        uint32_t        hv;
        const char      *p;
};

#define DELETED         ((const char *)h)
#define NONE            (h->size)

/* Don't bother changing the hash table if the change is small enough.  */
#define MINSIZE         (1UL << 4)
#define MINDELETED      4

static void ohash_resize(struct ohash *);


/* This handles the common case of variable length keys, where the
 * key is stored at the end of the record.
 */
void *
ohash_create_entry(struct ohash_info *i, const char *start, const char **end)
{
        char *p;

        if (!*end)
                *end = start + strlen(start);
        p = (i->alloc)(i->key_offset + (*end - start) + 1, i->data);
        if (p) {
                memcpy(p+i->key_offset, start, *end-start);
                p[i->key_offset + (*end - start)] = '\0';
        }
        return (void *)p;
}

/* hash_delete only frees the hash structure. Use hash_first/hash_next
 * to free entries as well.  */
void
ohash_delete(struct ohash *h)
{
        (h->info.free)(h->t, h->info.data);
#ifndef NDEBUG
        h->t = NULL;
#endif
}

static void
ohash_resize(struct ohash *h)
{
        struct _ohash_record *n;
        size_t ns;
        unsigned int    j;
        unsigned int    i, incr;

        if (4 * h->deleted < h->total) {
                if (h->size >= (UINT_MAX >> 1U))
                        ns = UINT_MAX;
                else
                        ns = h->size << 1U;
        } else if (3 * h->deleted > 2 * h->total)
                ns = h->size >> 1U;
        else
                ns = h->size;
        if (ns < MINSIZE)
                ns = MINSIZE;
#ifdef STATS_HASH
        STAT_HASH_EXPAND++;
        STAT_HASH_SIZE += ns - h->size;
#endif

        n = (h->info.calloc)(ns, sizeof(struct _ohash_record), h->info.data);
        if (!n)
                return;

        for (j = 0; j < h->size; j++) {
                if (h->t[j].p != NULL && h->t[j].p != DELETED) {
                        i = h->t[j].hv % ns;
                        incr = ((h->t[j].hv % (ns - 2)) & ~1) + 1;
                        while (n[i].p != NULL) {
                                i += incr;
                                if (i >= ns)
                                        i -= ns;
                        }
                        n[i].hv = h->t[j].hv;
                        n[i].p = h->t[j].p;
                }
        }
        (h->info.free)(h->t, h->info.data);
        h->t = n;
        h->size = ns;
        h->total -= h->deleted;
        h->deleted = 0;
}

void *
ohash_remove(struct ohash *h, unsigned int i)
{
        void            *result = (void *)h->t[i].p;

        if (result == NULL || result == DELETED)
                return NULL;

#ifdef STATS_HASH
        STAT_HASH_ENTRIES--;
#endif
        h->t[i].p = DELETED;
        h->deleted++;
        if (h->deleted >= MINDELETED && 4 * h->deleted > h->total)
                ohash_resize(h);
        return result;
}

void *
ohash_find(struct ohash *h, unsigned int i)
{
        if (h->t[i].p == DELETED)
                return NULL;
        else
                return (void *)h->t[i].p;
}

void *
ohash_insert(struct ohash *h, unsigned int i, void *p)
{
#ifdef STATS_HASH
        STAT_HASH_ENTRIES++;
#endif
        if (h->t[i].p == DELETED) {
                h->deleted--;
                h->t[i].p = p;
        } else {
                h->t[i].p = p;
                /* Arbitrary resize boundary.  Tweak if not efficient enough.  */
                if (++h->total * 4 > h->size * 3)
                        ohash_resize(h);
        }
        return p;
}

unsigned int
ohash_entries(struct ohash *h)
{
        return h->total - h->deleted;
}

void *
ohash_first(struct ohash *h, unsigned int *pos)
{
        *pos = 0;
        return ohash_next(h, pos);
}

void *
ohash_next(struct ohash *h, unsigned int *pos)
{
        for (; *pos < h->size; (*pos)++)
                if (h->t[*pos].p != DELETED && h->t[*pos].p != NULL)
                        return (void *)h->t[(*pos)++].p;
        return NULL;
}

void
ohash_init(struct ohash *h, unsigned int size, struct ohash_info *info)
{
        h->size = 1UL << size;
        if (h->size < MINSIZE)
                h->size = MINSIZE;
#ifdef STATS_HASH
        STAT_HASH_CREATION++;
        STAT_HASH_SIZE += h->size;
#endif
        /* Copy info so that caller may free it.  */
        h->info.key_offset = info->key_offset;
        h->info.calloc = info->calloc;
        h->info.free = info->free;
        h->info.alloc = info->alloc;
        h->info.data = info->data;
        h->t = (h->info.calloc)(h->size, sizeof(struct _ohash_record),
                    h->info.data);
        h->total = h->deleted = 0;
}

uint32_t
ohash_interval(const char *s, const char **e)
{
        uint32_t k;

        if (!*e)
                *e = s + strlen(s);
        if (s == *e)
                k = 0;
        else
                k = *s++;
        while (s != *e)
                k =  ((k << 2) | (k >> 30)) ^ *s++;
        return k;
}

unsigned int
ohash_lookup_interval(struct ohash *h, const char *start, const char *end,
    uint32_t hv)
{
        unsigned int    i, incr;
        unsigned int    empty;

#ifdef STATS_HASH
        STAT_HASH_LOOKUP++;
#endif
        empty = NONE;
        i = hv % h->size;
        incr = ((hv % (h->size-2)) & ~1) + 1;
        while (h->t[i].p != NULL) {
#ifdef STATS_HASH
                STAT_HASH_LENGTH++;
#endif
                if (h->t[i].p == DELETED) {
                        if (empty == NONE)
                                empty = i;
                } else if (h->t[i].hv == hv &&
                    strncmp(h->t[i].p+h->info.key_offset, start,
                        end - start) == 0 &&
                    (h->t[i].p+h->info.key_offset)[end-start] == '\0') {
                        if (empty != NONE) {
                                h->t[empty].hv = hv;
                                h->t[empty].p = h->t[i].p;
                                h->t[i].p = DELETED;
                                return empty;
                        } else {
#ifdef STATS_HASH
                                STAT_HASH_POSITIVE++;
#endif
                                return i;
                        }
                }
                i += incr;
                if (i >= h->size)
                        i -= h->size;
        }

        /* Found an empty position.  */
        if (empty != NONE)
                i = empty;
        h->t[i].hv = hv;
        return i;
}

unsigned int
ohash_lookup_memory(struct ohash *h, const char *k, size_t size, uint32_t hv)
{
        unsigned int    i, incr;
        unsigned int    empty;

#ifdef STATS_HASH
        STAT_HASH_LOOKUP++;
#endif
        empty = NONE;
        i = hv % h->size;
        incr = ((hv % (h->size-2)) & ~1) + 1;
        while (h->t[i].p != NULL) {
#ifdef STATS_HASH
                STAT_HASH_LENGTH++;
#endif
                if (h->t[i].p == DELETED) {
                        if (empty == NONE)
                                empty = i;
                } else if (h->t[i].hv == hv &&
                    memcmp(h->t[i].p+h->info.key_offset, k, size) == 0) {
                        if (empty != NONE) {
                                h->t[empty].hv = hv;
                                h->t[empty].p = h->t[i].p;
                                h->t[i].p = DELETED;
                                return empty;
                        } else {
#ifdef STATS_HASH
                                STAT_HASH_POSITIVE++;
#endif
                        }       return i;
                }
                i += incr;
                if (i >= h->size)
                        i -= h->size;
        }

        /* Found an empty position.  */
        if (empty != NONE)
                i = empty;
        h->t[i].hv = hv;
        return i;
}

unsigned int
ohash_qlookup(struct ohash *h, const char *s)
{
        const char *e = NULL;
        return ohash_qlookupi(h, s, &e);
}

unsigned int
ohash_qlookupi(struct ohash *h, const char *s, const char **e)
{
        uint32_t hv;

        hv = ohash_interval(s, e);
        return ohash_lookup_interval(h, s, *e, hv);
}