/* xf86drmHash.c -- Small hash table support for integer -> integer mapping

 * Created: Sun Apr 18 09:35:45 1999 by faith@precisioninsight.com

 *

 * Copyright 1999 Precision Insight, Inc., Cedar Park, Texas.

 * All Rights Reserved.

 *

 * Permission is hereby granted, free of charge, to any person obtaining a

 * copy of this software and associated documentation files (the "Software"),

 * to deal in the Software 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 (including the next

 * paragraph) 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

 * PRECISION INSIGHT AND/OR ITS SUPPLIERS 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.

 *

 * Authors: Rickard E. (Rik) Faith <faith@valinux.com>

 *

 * DESCRIPTION

 *

 * This file contains a straightforward implementation of a fixed-sized

 * hash table using self-organizing linked lists [Knuth73, pp. 398-399] for

 * collision resolution.  There are two potentially interesting things

 * about this implementation:

 *

 * 1) The table is power-of-two sized.  Prime sized tables are more

 * traditional, but do not have a significant advantage over power-of-two

 * sized table, especially when double hashing is not used for collision

 * resolution.

 *

 * 2) The hash computation uses a table of random integers [Hanson97,

 * pp. 39-41].

 *

 * FUTURE ENHANCEMENTS

 *

 * With a table size of 512, the current implementation is sufficient for a

 * few hundred keys.  Since this is well above the expected size of the

 * tables for which this implementation was designed, the implementation of

 * dynamic hash tables was postponed until the need arises.  A common (and

 * naive) approach to dynamic hash table implementation simply creates a

 * new hash table when necessary, rehashes all the data into the new table,

 * and destroys the old table.  The approach in [Larson88] is superior in

 * two ways: 1) only a portion of the table is expanded when needed,

 * distributing the expansion cost over several insertions, and 2) portions

 * of the table can be locked, enabling a scalable thread-safe

 * implementation.

 *

 * REFERENCES

 *

 * [Hanson97] David R. Hanson.  C Interfaces and Implementations:

 * Techniques for Creating Reusable Software.  Reading, Massachusetts:

 * Addison-Wesley, 1997.

 *

 * [Knuth73] Donald E. Knuth. The Art of Computer Programming.  Volume 3:

 * Sorting and Searching.  Reading, Massachusetts: Addison-Wesley, 1973.

 *

 * [Larson88] Per-Ake Larson. "Dynamic Hash Tables".  CACM 31(4), April

 * 1988, pp. 446-457.

 *

 */

#include <stdio.h>

#include <stdlib.h>

#include "xf86drm.h"

#include "xf86drmHash.h"

#define DIST_LIMIT 10

static int dist[DIST_LIMIT];

static void clear_dist(void) {

    int i;

    for (i = 0; i < DIST_LIMIT; i++)

        dist[i] = 0;

}

static int count_entries(HashBucketPtr bucket)

{

    int count = 0;

    for (; bucket; bucket = bucket->next)

        ++count;

    return count;

}

static void update_dist(int count)

{

    if (count >= DIST_LIMIT)

        ++dist[DIST_LIMIT-1];

    else

        ++dist[count];

}

static void compute_dist(HashTablePtr table)

{

    int           i;

    HashBucketPtr bucket;

    printf("Entries = %ld, hits = %ld, partials = %ld, misses = %ld\n",

          table->entries, table->hits, table->partials, table->misses);

    clear_dist();

    for (i = 0; i < HASH_SIZE; i++) {

        bucket = table->buckets[i];

        update_dist(count_entries(bucket));

    }

    for (i = 0; i < DIST_LIMIT; i++) {

        if (i != DIST_LIMIT-1)

            printf("%5d %10d\n", i, dist[i]);

        else

            printf("other %10d\n", dist[i]);

    }

}

static int check_table(HashTablePtr table,

                       unsigned long key, void * value)

{

    void *retval;

    int   retcode = drmHashLookup(table, key, &retval);

    switch (retcode) {

    case -1:

        printf("Bad magic = 0x%08lx:"

               " key = %lu, expected = %p, returned = %p\n",

               table->magic, key, value, retval);

        break;

    case 1:

        printf("Not found: key = %lu, expected = %p, returned = %p\n",

               key, value, retval);

        break;

    case 0:

        if (value != retval) {

            printf("Bad value: key = %lu, expected = %p, returned = %p\n",

                   key, value, retval);

            retcode = -1;

        }

        break;

    default:

        printf("Bad retcode = %d: key = %lu, expected = %p, returned = %p\n",

               retcode, key, value, retval);

        break;

    }

    return retcode;

}

int main(void)

{

    HashTablePtr  table;

    unsigned long i;

    int           ret = 0;

    printf("\n***** 256 consecutive integers ****\n");

    table = drmHashCreate();

    for (i = 0; i < 256; i++)

        drmHashInsert(table, i, (void *)(i << 16 | i));

    for (i = 0; i < 256; i++)

        ret |= check_table(table, i, (void *)(i << 16 | i));

    compute_dist(table);

    drmHashDestroy(table);

    printf("\n***** 1024 consecutive integers ****\n");

    table = drmHashCreate();

    for (i = 0; i < 1024; i++)

        drmHashInsert(table, i, (void *)(i << 16 | i));

    for (i = 0; i < 1024; i++)

        ret |= check_table(table, i, (void *)(i << 16 | i));

    compute_dist(table);

    drmHashDestroy(table);

    printf("\n***** 1024 consecutive page addresses (4k pages) ****\n");

    table = drmHashCreate();

    for (i = 0; i < 1024; i++)

        drmHashInsert(table, i*4096, (void *)(i << 16 | i));

    for (i = 0; i < 1024; i++)

        ret |= check_table(table, i*4096, (void *)(i << 16 | i));

    compute_dist(table);

    drmHashDestroy(table);

    printf("\n***** 1024 random integers ****\n");

    table = drmHashCreate();

    srandom(0xbeefbeef);

    for (i = 0; i < 1024; i++)

        drmHashInsert(table, random(), (void *)(i << 16 | i));

    srandom(0xbeefbeef);

    for (i = 0; i < 1024; i++)

        ret |= check_table(table, random(), (void *)(i << 16 | i));

    srandom(0xbeefbeef);

    for (i = 0; i < 1024; i++)

        ret |= check_table(table, random(), (void *)(i << 16 | i));

    compute_dist(table);

    drmHashDestroy(table);

    printf("\n***** 5000 random integers ****\n");

    table = drmHashCreate();

    srandom(0xbeefbeef);

    for (i = 0; i < 5000; i++)

        drmHashInsert(table, random(), (void *)(i << 16 | i));

    srandom(0xbeefbeef);

    for (i = 0; i < 5000; i++)

        ret |= check_table(table, random(), (void *)(i << 16 | i));

    srandom(0xbeefbeef);

    for (i = 0; i < 5000; i++)

        ret |= check_table(table, random(), (void *)(i << 16 | i));

    compute_dist(table);

    drmHashDestroy(table);

    return ret;

}