text: /* glxhash.c -- Small hash table support for integer -> integer mapping
   * Taken from libdrm.
   *
   * 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 "glxhash.h"
  #include <X11/Xfuncproto.h>
  
  #define HASH_MAIN 0
  
  #include <stdio.h>
  #include <stdlib.h>
  #include <string.h>
  
  #define HASH_MAGIC 0xdeadbeef
  #define HASH_DEBUG 0
  #define HASH_SIZE  512          /* Good for about 100 entries */
                                  /* If you change this value, you probably
                                     have to change the HashHash hashing
                                     function! */
  
  #define HASH_ALLOC malloc
  #define HASH_FREE  free
  #ifndef __GLIBC__
  #define HASH_RANDOM_DECL	char *ps, rs[256]
  #define HASH_RANDOM_INIT(seed)	ps = initstate(seed, rs, sizeof(rs))
  #define HASH_RANDOM		random()
  #define HASH_RANDOM_DESTROY	setstate(ps)
  #else
  #define HASH_RANDOM_DECL	struct random_data rd; int32_t rv; char rs[256]
  #define HASH_RANDOM_INIT(seed)					\
     do {								\
        (void) memset(&rd, 0, sizeof(rd));			\
        (void) initstate_r(seed, rs, sizeof(rs), &rd);		\
     } while(0)
  #define HASH_RANDOM             ((void) random_r(&rd, &rv), rv)
  #define HASH_RANDOM_DESTROY
  #endif
  
  typedef struct __glxHashBucket
  {
     unsigned long key;
     void *value;
     struct __glxHashBucket *next;
  } __glxHashBucket, *__glxHashBucketPtr;
  
  typedef struct __glxHashTable *__glxHashTablePtr;
  struct __glxHashTable
  {
     unsigned long magic;
     unsigned long hits;          /* At top of linked list */
     unsigned long partials;      /* Not at top of linked list */
     unsigned long misses;        /* Not in table */
     __glxHashBucketPtr buckets[HASH_SIZE];
     int p0;
     __glxHashBucketPtr p1;
  };
  
  static unsigned long
  HashHash(unsigned long key)
  {
     unsigned long hash = 0;
     unsigned long tmp = key;
     static int init = 0;
     static unsigned long scatter[256];
     int i;
  
     if (!init) {
        HASH_RANDOM_DECL;
        HASH_RANDOM_INIT(37);
        for (i = 0; i < 256; i++)
           scatter[i] = HASH_RANDOM;
        HASH_RANDOM_DESTROY;
        ++init;
     }
  
     while (tmp) {
        hash = (hash << 1) + scatter[tmp & 0xff];
        tmp >>= 8;
     }
  
     hash %= HASH_SIZE;
  #if HASH_DEBUG
     printf("Hash(%d) = %d\n", key, hash);
  #endif
     return hash;
  }
  
  _X_HIDDEN __glxHashTable *
  __glxHashCreate(void)
  {
     __glxHashTablePtr table;
     int i;
  
     table = HASH_ALLOC(sizeof(*table));
     if (!table)
        return NULL;
     table->magic = HASH_MAGIC;
     table->hits = 0;
     table->partials = 0;
     table->misses = 0;
  
     for (i = 0; i < HASH_SIZE; i++)
        table->buckets[i] = NULL;
     return table;
  }
  
  _X_HIDDEN int
  __glxHashDestroy(__glxHashTable * t)
  {
     __glxHashTablePtr table = (__glxHashTablePtr) t;
     __glxHashBucketPtr bucket;
     __glxHashBucketPtr next;
     int i;
  
     if (table->magic != HASH_MAGIC)
        return -1;                /* Bad magic */
  
     for (i = 0; i < HASH_SIZE; i++) {
        for (bucket = table->buckets[i]; bucket;) {
           next = bucket->next;
           HASH_FREE(bucket);
           bucket = next;
        }
     }
     HASH_FREE(table);
     return 0;
  }
  
  /* Find the bucket and organize the list so that this bucket is at the
     top. */
  
  static __glxHashBucketPtr
  HashFind(__glxHashTablePtr table, unsigned long key, unsigned long *h)
  {
     unsigned long hash = HashHash(key);
     __glxHashBucketPtr prev = NULL;
     __glxHashBucketPtr bucket;
  
     if (h)
        *h = hash;
  
     for (bucket = table->buckets[hash]; bucket; bucket = bucket->next) {
        if (bucket->key == key) {
           if (prev) {
              /* Organize */
              prev->next = bucket->next;
              bucket->next = table->buckets[hash];
              table->buckets[hash] = bucket;
              ++table->partials;
           }
           else {
              ++table->hits;
           }
           return bucket;
        }
        prev = bucket;
     }
     ++table->misses;
     return NULL;
  }
  
  _X_HIDDEN int
  __glxHashLookup(__glxHashTable * t, unsigned long key, void **value)
  {
     __glxHashTablePtr table = (__glxHashTablePtr) t;
     __glxHashBucketPtr bucket;
  
     if (!table || table->magic != HASH_MAGIC)
        return -1;                /* Bad magic */
  
     bucket = HashFind(table, key, NULL);
     if (!bucket)
        return 1;                 /* Not found */
     *value = bucket->value;
     return 0;                    /* Found */
  }
  
  _X_HIDDEN int
  __glxHashInsert(__glxHashTable * t, unsigned long key, void *value)
  {
     __glxHashTablePtr table = (__glxHashTablePtr) t;
     __glxHashBucketPtr bucket;
     unsigned long hash;
  
     if (table->magic != HASH_MAGIC)
        return -1;                /* Bad magic */
  
     if (HashFind(table, key, &hash))
        return 1;                 /* Already in table */
  
     bucket = HASH_ALLOC(sizeof(*bucket));
     if (!bucket)
        return -1;                /* Error */
     bucket->key = key;
     bucket->value = value;
     bucket->next = table->buckets[hash];
     table->buckets[hash] = bucket;
  #if HASH_DEBUG
     printf("Inserted %d at %d/%p\n", key, hash, bucket);
  #endif
     return 0;                    /* Added to table */
  }
  
  _X_HIDDEN int
  __glxHashDelete(__glxHashTable * t, unsigned long key)
  {
     __glxHashTablePtr table = (__glxHashTablePtr) t;
     unsigned long hash;
     __glxHashBucketPtr bucket;
  
     if (table->magic != HASH_MAGIC)
        return -1;                /* Bad magic */
  
     bucket = HashFind(table, key, &hash);
  
     if (!bucket)
        return 1;                 /* Not found */
  
     table->buckets[hash] = bucket->next;
     HASH_FREE(bucket);
     return 0;
  }
  
  _X_HIDDEN int
  __glxHashNext(__glxHashTable * t, unsigned long *key, void **value)
  {
     __glxHashTablePtr table = (__glxHashTablePtr) t;
  
     while (table->p0 < HASH_SIZE) {
        if (table->p1) {
           *key = table->p1->key;
           *value = table->p1->value;
           table->p1 = table->p1->next;
           return 1;
        }
        table->p1 = table->buckets[table->p0];
        ++table->p0;
     }
     return 0;
  }
  
  _X_HIDDEN int
  __glxHashFirst(__glxHashTable * t, unsigned long *key, void **value)
  {
     __glxHashTablePtr table = (__glxHashTablePtr) t;
  
     if (table->magic != HASH_MAGIC)
        return -1;                /* Bad magic */
  
     table->p0 = 0;
     table->p1 = table->buckets[0];
     return __glxHashNext(table, key, value);
  }
  
  #if HASH_MAIN
  #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(__glxHashBucketPtr 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(__glxHashTablePtr table)
  {
     int i;
     __glxHashBucketPtr bucket;
  
     printf("Hits = %ld, partials = %ld, misses = %ld\n",
            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 void
  check_table(__glxHashTablePtr table, unsigned long key, unsigned long value)
  {
     unsigned long retval = 0;
     int retcode = __glxHashLookup(table, key, &retval);
  
     switch (retcode) {
     case -1:
        printf("Bad magic = 0x%08lx:"
               " key = %lu, expected = %lu, returned = %lu\n",
               table->magic, key, value, retval);
        break;
     case 1:
        printf("Not found: key = %lu, expected = %lu returned = %lu\n",
               key, value, retval);
        break;
     case 0:
        if (value != retval)
           printf("Bad value: key = %lu, expected = %lu, returned = %lu\n",
                  key, value, retval);
        break;
     default:
        printf("Bad retcode = %d: key = %lu, expected = %lu, returned = %lu\n",
               retcode, key, value, retval);
        break;
     }
  }
  
  int
  main(void)
  {
     __glxHashTablePtr table;
     int i;
  
     printf("\n***** 256 consecutive integers ****\n");
     table = __glxHashCreate();
     for (i = 0; i < 256; i++)
        __glxHashInsert(table, i, i);
     for (i = 0; i < 256; i++)
        check_table(table, i, i);
     for (i = 256; i >= 0; i--)
        check_table(table, i, i);
     compute_dist(table);
     __glxHashDestroy(table);
  
     printf("\n***** 1024 consecutive integers ****\n");
     table = __glxHashCreate();
     for (i = 0; i < 1024; i++)
        __glxHashInsert(table, i, i);
     for (i = 0; i < 1024; i++)
        check_table(table, i, i);
     for (i = 1024; i >= 0; i--)
        check_table(table, i, i);
     compute_dist(table);
     __glxHashDestroy(table);
  
     printf("\n***** 1024 consecutive page addresses (4k pages) ****\n");
     table = __glxHashCreate();
     for (i = 0; i < 1024; i++)
        __glxHashInsert(table, i * 4096, i);
     for (i = 0; i < 1024; i++)
        check_table(table, i * 4096, i);
     for (i = 1024; i >= 0; i--)
        check_table(table, i * 4096, i);
     compute_dist(table);
     __glxHashDestroy(table);
  
     printf("\n***** 1024 random integers ****\n");
     table = __glxHashCreate();
     srandom(0xbeefbeef);
     for (i = 0; i < 1024; i++)
        __glxHashInsert(table, random(), i);
     srandom(0xbeefbeef);
     for (i = 0; i < 1024; i++)
        check_table(table, random(), i);
     srandom(0xbeefbeef);
     for (i = 0; i < 1024; i++)
        check_table(table, random(), i);
     compute_dist(table);
     __glxHashDestroy(table);
  
     printf("\n***** 5000 random integers ****\n");
     table = __glxHashCreate();
     srandom(0xbeefbeef);
     for (i = 0; i < 5000; i++)
        __glxHashInsert(table, random(), i);
     srandom(0xbeefbeef);
     for (i = 0; i < 5000; i++)
        check_table(table, random(), i);
     srandom(0xbeefbeef);
     for (i = 0; i < 5000; i++)
        check_table(table, random(), i);
     compute_dist(table);
     __glxHashDestroy(table);
  
     return 0;
  }
  #endif
  