hash.c

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/*
 * hash.c       Non-thread-safe split-ordered hash table.
 *
 *  The weird "reverse" function is based on an idea from
 *  "Split-Ordered Lists - Lock-free Resizable Hash Tables", with
 *  modifications so that they're not lock-free. :(
 *
 *  However, the split-order idea allows a fast & easy splitting of the
 *  hash bucket chain when the hash table is resized.  Without it, we'd
 *  have to check & update the pointers for every node in the buck chain,
 *  rather than being able to move 1/2 of the entries in the chain with
 *  one update.
 *
 * Version:     $Id: 538151ef3bf5ca78be2dd9b4156883f7fc2a10a0 $
 *
 *   This library is free software; you can redistribute it and/or
 *   modify it under the terms of the GNU Lesser General Public
 *   License as published by the Free Software Foundation; either
 *   version 2.1 of the License, or (at your option) any later version.
 *
 *   This library is distributed in the hope that it will be useful,
 *   but WITHOUT ANY WARRANTY; without even the implied warranty of
 *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
 *   Lesser General Public License for more details.
 *
 *   You should have received a copy of the GNU Lesser General Public
 *   License along with this library; if not, write to the Free Software
 *   Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301, USA
 *
 *  Copyright 2005,2006  The FreeRADIUS server project
 */

RCSID("$Id: 538151ef3bf5ca78be2dd9b4156883f7fc2a10a0 $")

#include <freeradius-devel/libradius.h>

/*
 *      A reasonable number of buckets to start off with.
 *      Should be a power of two.
 */
#define FR_HASH_NUM_BUCKETS (64)

typedef struct fr_hash_entry_t {
        struct fr_hash_entry_t *next;
        uint32_t        reversed;
        uint32_t        key;
        void const      *data;
} fr_hash_entry_t;


struct fr_hash_table_t {
        int                     num_elements;
        int                     num_buckets; /* power of 2 */
        int                     next_grow;
        int                     mask;

        fr_hash_table_free_t    free;
        fr_hash_table_hash_t    hash;
        fr_hash_table_cmp_t     cmp;

        fr_hash_entry_t null;

        fr_hash_entry_t **buckets;
};

#ifdef TESTING
static int grow = 0;
#endif

/*
 * perl -e 'foreach $i (0..255) {$r = 0; foreach $j (0 .. 7 ) { if (($i & ( 1<< $j)) != 0) { $r |= (1 << (7 - $j));}} print $r, ", ";if (($i & 7) == 7) {print "\n";}}'
 */
static const uint8_t reversed_byte[256] = {
        0,  128, 64, 192, 32, 160, 96,  224,
        16, 144, 80, 208, 48, 176, 112, 240,
        8,  136, 72, 200, 40, 168, 104, 232,
        24, 152, 88, 216, 56, 184, 120, 248,
        4,  132, 68, 196, 36, 164, 100, 228,
        20, 148, 84, 212, 52, 180, 116, 244,
        12, 140, 76, 204, 44, 172, 108, 236,
        28, 156, 92, 220, 60, 188, 124, 252,
        2,  130, 66, 194, 34, 162, 98,  226,
        18, 146, 82, 210, 50, 178, 114, 242,
        10, 138, 74, 202, 42, 170, 106, 234,
        26, 154, 90, 218, 58, 186, 122, 250,
        6,  134, 70, 198, 38, 166, 102, 230,
        22, 150, 86, 214, 54, 182, 118, 246,
        14, 142, 78, 206, 46, 174, 110, 238,
        30, 158, 94, 222, 62, 190, 126, 254,
        1,  129, 65, 193, 33, 161, 97,  225,
        17, 145, 81, 209, 49, 177, 113, 241,
        9,  137, 73, 201, 41, 169, 105, 233,
        25, 153, 89, 217, 57, 185, 121, 249,
        5,  133, 69, 197, 37, 165, 101, 229,
        21, 149, 85, 213, 53, 181, 117, 245,
        13, 141, 77, 205, 45, 173, 109, 237,
        29, 157, 93, 221, 61, 189, 125, 253,
        3,  131, 67, 195, 35, 163, 99,  227,
        19, 147, 83, 211, 51, 179, 115, 243,
        11, 139, 75, 203, 43, 171, 107, 235,
        27, 155, 91, 219, 59, 187, 123, 251,
        7,  135, 71, 199, 39, 167, 103, 231,
        23, 151, 87, 215, 55, 183, 119, 247,
        15, 143, 79, 207, 47, 175, 111, 239,
        31, 159, 95, 223, 63, 191, 127, 255
};


/*
 * perl -e 'foreach $i (0..255) {$r = 0;foreach $j (0 .. 7) { $r = $i & (1 << (7 - $j)); last if ($r)} print $i & ~($r), ", ";if (($i & 7) == 7) {print "\n";}}'
 */
static uint8_t parent_byte[256] = {
        0, 0, 0, 1, 0, 1, 2, 3,
        0, 1, 2, 3, 4, 5, 6, 7,
        0, 1, 2, 3, 4, 5, 6, 7,
        8, 9, 10, 11, 12, 13, 14, 15,
        0, 1, 2, 3, 4, 5, 6, 7,
        8, 9, 10, 11, 12, 13, 14, 15,
        16, 17, 18, 19, 20, 21, 22, 23,
        24, 25, 26, 27, 28, 29, 30, 31,
        0, 1, 2, 3, 4, 5, 6, 7,
        8, 9, 10, 11, 12, 13, 14, 15,
        16, 17, 18, 19, 20, 21, 22, 23,
        24, 25, 26, 27, 28, 29, 30, 31,
        32, 33, 34, 35, 36, 37, 38, 39,
        40, 41, 42, 43, 44, 45, 46, 47,
        48, 49, 50, 51, 52, 53, 54, 55,
        56, 57, 58, 59, 60, 61, 62, 63,
        0, 1, 2, 3, 4, 5, 6, 7,
        8, 9, 10, 11, 12, 13, 14, 15,
        16, 17, 18, 19, 20, 21, 22, 23,
        24, 25, 26, 27, 28, 29, 30, 31,
        32, 33, 34, 35, 36, 37, 38, 39,
        40, 41, 42, 43, 44, 45, 46, 47,
        48, 49, 50, 51, 52, 53, 54, 55,
        56, 57, 58, 59, 60, 61, 62, 63,
        64, 65, 66, 67, 68, 69, 70, 71,
        72, 73, 74, 75, 76, 77, 78, 79,
        80, 81, 82, 83, 84, 85, 86, 87,
        88, 89, 90, 91, 92, 93, 94, 95,
        96, 97, 98, 99, 100, 101, 102, 103,
        104, 105, 106, 107, 108, 109, 110, 111,
        112, 113, 114, 115, 116, 117, 118, 119,
        120, 121, 122, 123, 124, 125, 126, 127
};


/*
 *      Reverse a key.
 */
static uint32_t reverse(uint32_t key)
{
        return ((reversed_byte[key & 0xff] << 24) |
                (reversed_byte[(key >> 8) & 0xff] << 16) |
                (reversed_byte[(key >> 16) & 0xff] << 8) |
                (reversed_byte[(key >> 24) & 0xff]));
}

/*
 *      Take the parent by discarding the highest bit that is set.
 */
static uint32_t parent_of(uint32_t key)
{
        if (key > 0x00ffffff)
                return (key & 0x00ffffff) | (parent_byte[key >> 24] << 24);

        if (key > 0x0000ffff)
                return (key & 0x0000ffff) | (parent_byte[key >> 16] << 16);

        if (key > 0x000000ff)
                return (key & 0x000000ff) | (parent_byte[key >> 8] << 8);

        return parent_byte[key];
}


static fr_hash_entry_t *list_find(fr_hash_table_t *ht,
                                    fr_hash_entry_t *head,
                                    uint32_t reversed,
                                    void const *data)
{
        fr_hash_entry_t *cur;

        for (cur = head; cur != &ht->null; cur = cur->next) {
                if (cur->reversed == reversed) {
                        if (ht->cmp) {
                                int cmp = ht->cmp(data, cur->data);
                                if (cmp > 0) break;
                                if (cmp < 0) continue;
                        }
                        return cur;
                }
                if (cur->reversed > reversed) break;
        }

        return NULL;
}


/*
 *      Inserts a new entry into the list, in order.
 */
static int list_insert(fr_hash_table_t *ht,
                       fr_hash_entry_t **head, fr_hash_entry_t *node)
{
        fr_hash_entry_t **last, *cur;

        last = head;

        for (cur = *head; cur != &ht->null; cur = cur->next) {
                if (cur->reversed > node->reversed) break;
                last = &(cur->next);

                if (cur->reversed == node->reversed) {
                        if (ht->cmp) {
                                int cmp = ht->cmp(node->data, cur->data);
                                if (cmp > 0) break;
                                if (cmp < 0) continue;
                        }
                        return 0;
                }
        }

        node->next = *last;
        *last = node;

        return 1;
}


/*
 *      Delete an entry from the list.
 */
static int list_delete(fr_hash_table_t *ht,
                       fr_hash_entry_t **head, fr_hash_entry_t *node)
{
        fr_hash_entry_t **last, *cur;

        last = head;

        for (cur = *head; cur != &ht->null; cur = cur->next) {
                if (cur == node) break;
                last = &(cur->next);
        }

        *last = node->next;
        return 1;
}


static int _fr_hash_table_free(fr_hash_table_t *ht)
{
        int i;
        fr_hash_entry_t *node, *next;

        /*
         *      Walk over the buckets, freeing them all.
         */
        for (i = 0; i < ht->num_buckets; i++) {
                if (ht->buckets[i]) for (node = ht->buckets[i];
                                         node != &ht->null;
                                         node = next) {
                        next = node->next;
                        if (!node->data) continue; /* dummy entry */

                        talloc_free(node);
                }
        }
        talloc_free(ht->buckets);

        return 0;
}

/*
 *      Create the table.
 *
 *      Memory usage in bytes is (20/3) * number of entries.
 */
fr_hash_table_t *fr_hash_table_create(TALLOC_CTX *ctx,
                                      fr_hash_table_hash_t hashNode,
                                      fr_hash_table_cmp_t cmpNode,
                                      fr_hash_table_free_t freeNode)
{
        fr_hash_table_t *ht;

        if (!hashNode) return NULL;

        ht = talloc_zero(NULL, fr_hash_table_t);
        if (!ht) return NULL;
        talloc_set_destructor(ht, _fr_hash_table_free);
        fr_talloc_link_ctx(ctx, ht);

        ht->free = freeNode;
        ht->hash = hashNode;
        ht->cmp = cmpNode;
        ht->num_buckets = FR_HASH_NUM_BUCKETS;
        ht->mask = ht->num_buckets - 1;

        /*
         *      Have a default load factor of 2.5.  In practice this
         *      means that the average load will hit 3 before the
         *      table grows.
         */
        ht->next_grow = (ht->num_buckets << 1) + (ht->num_buckets >> 1);

        ht->buckets = talloc_zero_array(NULL, fr_hash_entry_t *, ht->num_buckets);
        if (!ht->buckets) {
                talloc_free(ht);
                return NULL;
        }

        ht->null.reversed = ~0;
        ht->null.key = ~0;
        ht->null.next = &ht->null;
        ht->buckets[0] = &ht->null;

        return ht;
}


/*
 *      If the current bucket is uninitialized, initialize it
 *      by recursively copying information from the parent.
 *
 *      We may have a situation where entry E is a parent to 2 other
 *      entries E' and E".  If we split E into E and E', then the
 *      nodes meant for E" end up in E or E', either of which is
 *      wrong.  To solve that problem, we walk down the whole chain,
 *      inserting the elements into the correct place.
 */
static void fr_hash_table_fixup(fr_hash_table_t *ht, uint32_t entry)
{
        uint32_t parent_entry;
        fr_hash_entry_t **last, *cur;
        uint32_t this;

        parent_entry = parent_of(entry);

        /* parent_entry == entry if and only if entry == 0 */

        if (!ht->buckets[parent_entry]) {
                fr_hash_table_fixup(ht, parent_entry);
        }

        /*
         *      Keep walking down cur, trying to find entries that
         *      don't belong here any more.  There may be multiple
         *      ones, so we can't have a naive algorithm...
         */
        last = &ht->buckets[parent_entry];
        this = parent_entry;

        for (cur = *last; cur != &ht->null; cur = cur->next) {
                uint32_t real_entry;

                real_entry = cur->key & ht->mask;
                if (real_entry != this) { /* ht->buckets[real_entry] == NULL */
                        *last = &ht->null;
                        ht->buckets[real_entry] = cur;
                        this = real_entry;
                }

                last = &(cur->next);
        }

        /*
         *      We may NOT have initialized this bucket, so do it now.
         */
        if (!ht->buckets[entry]) ht->buckets[entry] = &ht->null;
}

/*
 *      This should be a power of two.  Changing it to 4 doesn't seem
 *      to make any difference.
 */
#define GROW_FACTOR (2)

/*
 *      Grow the hash table.
 */
static void fr_hash_table_grow(fr_hash_table_t *ht)
{
        fr_hash_entry_t **buckets;

        buckets = talloc_zero_array(NULL, fr_hash_entry_t *, GROW_FACTOR * ht->num_buckets);
        if (!buckets) return;

        memcpy(buckets, ht->buckets, sizeof(*buckets) * ht->num_buckets);
        talloc_free(ht->buckets); /* Free the old buckets */

        ht->buckets = buckets;
        ht->num_buckets *= GROW_FACTOR;
        ht->next_grow *= GROW_FACTOR;
        ht->mask = ht->num_buckets - 1;
#ifdef TESTING
        grow = 1;
        fprintf(stderr, "GROW TO %d\n", ht->num_buckets);
#endif
}


/*
 *      Insert data.
 */
int fr_hash_table_insert(fr_hash_table_t *ht, void const *data)
{
        uint32_t key;
        uint32_t entry;
        uint32_t reversed;
        fr_hash_entry_t *node;

        if (!ht || !data) return 0;

        key = ht->hash(data);
        entry = key & ht->mask;
        reversed = reverse(key);

        if (!ht->buckets[entry]) fr_hash_table_fixup(ht, entry);

        /*
         *      If we try to do our own memory allocation here, the
         *      speedup is only ~15% or so, which isn't worth it.
         */
        node = talloc_zero(NULL, fr_hash_entry_t);
        if (!node) return 0;

        node->next = &ht->null;
        node->reversed = reversed;
        node->key = key;
        node->data = data;

        /* already in the table, can't insert it */
        if (!list_insert(ht, &ht->buckets[entry], node)) {
                talloc_free(node);
                return 0;
        }

        /*
         *      Check the load factor, and grow the table if
         *      necessary.
         */
        ht->num_elements++;
        if (ht->num_elements >= ht->next_grow) fr_hash_table_grow(ht);

        return 1;
}


/*
 *      Internal find a node routine.
 */
static fr_hash_entry_t *fr_hash_table_find(fr_hash_table_t *ht, void const *data)
{
        uint32_t key;
        uint32_t entry;
        uint32_t reversed;

        if (!ht) return NULL;

        key = ht->hash(data);
        entry = key & ht->mask;
        reversed = reverse(key);

        if (!ht->buckets[entry]) fr_hash_table_fixup(ht, entry);

        return list_find(ht, ht->buckets[entry], reversed, data);
}


/*
 *      Replace old data with new data, OR insert if there is no old.
 */
int fr_hash_table_replace(fr_hash_table_t *ht, void const *data)
{
        fr_hash_entry_t *node;
        void *tofree;

        if (!ht || !data) return 0;

        node = fr_hash_table_find(ht, data);
        if (!node) return fr_hash_table_insert(ht, data);

        if (ht->free) {
                memcpy(&tofree, &node->data, sizeof(tofree));
                ht->free(tofree);
        }
        node->data = data;

        return 1;
}


/*
 *      Find data from a template
 */
void *fr_hash_table_finddata(fr_hash_table_t *ht, void const *data)
{
        fr_hash_entry_t *node;
        void *out;

        node = fr_hash_table_find(ht, data);
        if (!node) return NULL;

        memcpy(&out, &node->data, sizeof(out));

        return out;
}



/*
 *      Yank an entry from the hash table, without freeing the data.
 */
void *fr_hash_table_yank(fr_hash_table_t *ht, void const *data)
{
        uint32_t key;
        uint32_t entry;
        uint32_t reversed;
        void *old;
        fr_hash_entry_t *node;

        if (!ht) return NULL;

        key = ht->hash(data);
        entry = key & ht->mask;
        reversed = reverse(key);

        if (!ht->buckets[entry]) fr_hash_table_fixup(ht, entry);

        node = list_find(ht, ht->buckets[entry], reversed, data);
        if (!node) return NULL;

        list_delete(ht, &ht->buckets[entry], node);
        ht->num_elements--;

        memcpy(&old, &node->data, sizeof(old));
        talloc_free(node);

        return old;
}


/*
 *      Delete a piece of data from the hash table.
 */
int fr_hash_table_delete(fr_hash_table_t *ht, void const *data)
{
        void *old;

        old = fr_hash_table_yank(ht, data);
        if (!old) return 0;

        if (ht->free) ht->free(old);

        return 1;
}


/*
 *      Free a hash table
 */
void fr_hash_table_free(fr_hash_table_t *ht)
{
        int i;
        fr_hash_entry_t *node, *next;

        if (!ht) return;

        /*
         *      Walk over the buckets, freeing them all.
         */
        if (ht->free) {
                for (i = 0; i < ht->num_buckets; i++) {
                        if (ht->buckets[i]) for (node = ht->buckets[i];
                                                 node != &ht->null;
                                                 node = next) {
                                void *tofree;

                                next = node->next;
                                if (!node->data) continue; /* dummy entry */

                                memcpy(&tofree, &node->data, sizeof(tofree));
                                ht->free(tofree);
                        }
                }
        }

        /*
         *      Also frees nodes and buckets
         */
        talloc_free(ht);
}


/*
 *      Count number of elements
 */
int fr_hash_table_num_elements(fr_hash_table_t *ht)
{
        if (!ht) return 0;

        return ht->num_elements;
}


/*
 *      Walk over the nodes, allowing deletes & inserts to happen.
 */
int fr_hash_table_walk(fr_hash_table_t *ht,
                         fr_hash_table_walk_t callback,
                         void *context)
{
        int i, rcode;

        if (!ht || !callback) return 0;

        for (i = ht->num_buckets - 1; i >= 0; i--) {
                fr_hash_entry_t *node, *next;

                /*
                 *      Ensure that the current bucket is filled.
                 */
                if (!ht->buckets[i]) fr_hash_table_fixup(ht, i);

                for (node = ht->buckets[i]; node != &ht->null; node = next) {
                        void *arg;

                        next = node->next;

                        memcpy(&arg, node->data, sizeof(arg));
                        rcode = callback(context, arg);

                        if (rcode != 0) return rcode;
                }
        }

        return 0;
}


#ifdef TESTING
/*
 *      Show what the hash table is doing.
 */
int fr_hash_table_info(fr_hash_table_t *ht)
{
        int i, a, collisions, uninitialized;
        int array[256];

        if (!ht) return 0;

        uninitialized = collisions = 0;
        memset(array, 0, sizeof(array));

        for (i = 0; i < ht->num_buckets; i++) {
                uint32_t key;
                int load;
                fr_hash_entry_t *node, *next;

                /*
                 *      If we haven't inserted or looked up an entry
                 *      in a bucket, it's uninitialized.
                 */
                if (!ht->buckets[i]) {
                        uninitialized++;
                        continue;
                }

                load = 0;
                key = ~0;
                for (node = ht->buckets[i]; node != &ht->null; node = next) {
                        if (node->reversed == key) {
                                collisions++;
                        } else {
                                key = node->reversed;
                        }
                        next = node->next;
                        load++;
                }

                if (load > 255) load = 255;
                array[load]++;
        }

        printf("HASH TABLE %p\tbuckets: %d\t(%d uninitialized)\n", ht,
                ht->num_buckets, uninitialized);
        printf("\tnum entries %d\thash collisions %d\n",
                ht->num_elements, collisions);

        a = 0;
        for (i = 1; i < 256; i++) {
                if (!array[i]) continue;
                printf("%d\t%d\n", i, array[i]);

                /*
                 *      Since the entries are ordered, the lookup cost
                 *      for any one element in a chain is (on average)
                 *      the cost of walking half of the chain.
                 */
                if (i > 1) {
                        a += array[i] * i;
                }
        }
        a /= 2;
        a += array[1];

        printf("\texpected lookup cost = %d/%d or %f\n\n",
               ht->num_elements, a,
               (float) ht->num_elements / (float) a);

        return 0;
}
#endif


#define FNV_MAGIC_INIT (0x811c9dc5)
#define FNV_MAGIC_PRIME (0x01000193)

/*
 *      A fast hash function.  For details, see:
 *
 *      http://www.isthe.com/chongo/tech/comp/fnv/
 *
 *      Which also includes public domain source.  We've re-written
 *      it here for our purposes.
 */
uint32_t fr_hash(void const *data, size_t size)
{
        uint8_t const *p = data;
        uint8_t const *q = p + size;
        uint32_t      hash = FNV_MAGIC_INIT;

        /*
         *      FNV-1 hash each octet in the buffer
         */
        while (p != q) {
                /*
                 *      XOR the 8-bit quantity into the bottom of
                 *      the hash.
                 */
                hash ^= (uint32_t) (*p++);

                /*
                 *      Multiple by 32-bit magic FNV prime, mod 2^32
                 */
                hash *= FNV_MAGIC_PRIME;
#if 0
                /*
                 *      Potential optimization.
                 */
                hash += (hash<<1) + (hash<<4) + (hash<<7) + (hash<<8) + (hash<<24);
#endif
    }

    return hash;
}

/*
 *      Continue hashing data.
 */
uint32_t fr_hash_update(void const *data, size_t size, uint32_t hash)
{
        uint8_t const *p = data;
        uint8_t const *q = p + size;

        while (p != q) {
                hash *= FNV_MAGIC_PRIME;
                hash ^= (uint32_t) (*p++);
    }

    return hash;

}

/*
 *      Hash a C string, so we loop over it once.
 */
uint32_t fr_hash_string(char const *p)
{
        uint32_t      hash = FNV_MAGIC_INIT;

        while (*p) {
                hash *= FNV_MAGIC_PRIME;
                hash ^= (uint32_t) (*p++);
        }

        return hash;
}


#ifdef TESTING
/*
 *  cc -g -DTESTING -I ../include hash.c -o hash
 *
 *  ./hash
 */
static uint32_t hash_int(void const *data)
{
        return fr_hash((int *) data, sizeof(int));
}

#define MAX 1024*1024
int main(int argc, char **argv)
{
        int i, *p, *q, k;
        fr_hash_table_t *ht;
        int *array;

        ht = fr_hash_table_create(NULL, hash_int, NULL, NULL);
        if (!ht) {
                fprintf(stderr, "Hash create failed\n");
                fr_exit(1);
        }

        array = talloc_zero_array(NULL, int, MAX);
        if (!array) fr_exit(1);

        for (i = 0; i < MAX; i++) {
                p = array + i;
                *p = i;

                if (!fr_hash_table_insert(ht, p)) {
                        fprintf(stderr, "Failed insert %08x\n", i);
                        fr_exit(1);
                }
#ifdef TEST_INSERT
                q = fr_hash_table_finddata(ht, p);
                if (q != p) {
                        fprintf(stderr, "Bad data %d\n", i);
                        fr_exit(1);
                }
#endif
        }

        fr_hash_table_info(ht);

        /*
         *      Build this to see how lookups result in shortening
         *      of the hash chains.
         */
        if (1) {
                for (i = 0; i < MAX ; i++) {
                        q = fr_hash_table_finddata(ht, &i);
                        if (!q || *q != i) {
                                fprintf(stderr, "Failed finding %d\n", i);
                                fr_exit(1);
                        }

#if 0
                        if (!fr_hash_table_delete(ht, &i)) {
                                fprintf(stderr, "Failed deleting %d\n", i);
                                fr_exit(1);
                        }
                        q = fr_hash_table_finddata(ht, &i);
                        if (q) {
                                fprintf(stderr, "Failed to delete %08x\n", i);
                                fr_exit(1);
                        }
#endif
                }

                fr_hash_table_info(ht);
        }

        fr_hash_table_free(ht);
        talloc_free(array);

        fr_exit(0);
}
#endif