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hash.c

/*----------------------------------------------------------------------------
 * (C) 1997-1998 Armin Biere 
 *
 *     $Id: hash.c,v 1.2 2001/12/04 09:46:41 biere Exp $
 *----------------------------------------------------------------------------
 */

#include "hash.h"

/* ------------------------------------------------------------------------ */

#include <stdlib.h>
#include <stdio.h>
#include <signal.h>

/* ------------------------------------------------------------------------ */

typedef struct HashTableBucket
{
  void *data;                 /* do not move this !!!! */
  struct HashTableBucket *next;
}
HashTableBucket;

/* ------------------------------------------------------------------------ */

typedef struct HashTable_
{
  int count;
  int size;
  int threshold;
  int num_resizes;
  int primes_idx;

  HashTableBucket **table;

  int (*cmp_keys) (void *key1, void *key2);
  int (*hash_key) (void *key);
  void *(*get_key_from_data) (void *data);
  void (*free_data) (void *);
  void (*error) (char *);
}
HashTable_;

/* ------------------------------------------------------------------------ */

/* let s be the current size and s' the desired next size
 * we request a larger size iff n = 80% s where n is
 * the number of valid nodes. Now we want to have
 * n = 50% s' for not wasting too much space. 
 * This gives the formula
 *
 *    s' = (8/5) s
 *
 *  the primes can be generated with the following awk program:
 *
 *    BEGIN {
 *      P = 3; M = 2147483647 # 2**31
 *      while(P<M) {
 *        print P ",";
 *        P = int(8*P/5); "primes " P | getline; P = $1
 *      }
 *    }
 */

static int primes[] = {
  3, 7, 13, 31, 61,
  127, 251, 509, 1021, 2039,
  4093, 8191, 16381, 26209, 41941,
  67121, 107441, 171917, 275083, 440159,
  704269, 1126831, 1802989, 2884787, 4615661,
  7385057, 11816111, 18905813, 30249367, 48399019,
  77438437, 123901501, 198242441, 317187907, 507500657,
  812001067, 1299201731, 2078722769
};

/* ------------------------------------------------------------------------ */

static int
simple_cmp_keys (void *k1, void *k2)
{
  if (k1 == k2)
    return 0;
  else if (k1 < k2)
    return 1;
  else
    return -1;
}

/* ------------------------------------------------------------------------ */

static int
simple_hash_key (void *key)
{
  return (int) key;
}

/* ------------------------------------------------------------------------ */

static void *
simple_get_key_from_data (void *a)
{
  return a;
}

/* ------------------------------------------------------------------------ */

static void
simple_free_data (void *data)
{
  (void) data;
}

/* ------------------------------------------------------------------------ */

static void
simple_error (char *errmsg)
{
  fprintf (stderr, "*** in hash.c: %s\n", errmsg);
  fflush (stderr);
  kill (0, SIGSEGV);
}

/* ------------------------------------------------------------------------ */

#define setToSimpleIfZero(a) a ? a : simple_ ## a

/* ------------------------------------------------------------------------ */

HashTable
new_HashTable (int minimal_size,
             int (*cmp_keys) (void *key1, void *key2),
             int (*hash_key) (void *key),
             void *(*get_key_from_data) (void *data),
             void (*free_data) (void *), void (*error) (char *))
{
  HashTable res = (HashTable) malloc (sizeof (HashTable_));
  int primes_idx = 0, i;

  while (minimal_size > primes[primes_idx])
    primes_idx++;

  res->primes_idx = primes_idx;
  res->size = primes[primes_idx];
  res->count = 0;

  res->cmp_keys = setToSimpleIfZero (cmp_keys);
  res->hash_key = setToSimpleIfZero (hash_key);
  res->get_key_from_data = setToSimpleIfZero (get_key_from_data);
  res->free_data = setToSimpleIfZero (free_data);
  res->error = setToSimpleIfZero (error);

  /* ceil(0.8 * res -> size) */

  res->threshold = (((res->size) << 2) + 4) / 5;
  res->num_resizes = 0;

  res->table = (HashTableBucket **)
    malloc (res->size * sizeof (HashTableBucket *));

  for (i = 0; i < res->size; i++)
    res->table[i] = 0;

  return res;
}

/* ------------------------------------------------------------------------ */

void
free_HashTable (HashTable ht)
{
  int i;
  void (*free_data) (void *);
  free_data = ht->free_data;

  for (i = 0; i < ht->size; i++)
    {
      HashTableBucket *p, *tmp;
      for (p = ht->table[i]; p; p = tmp)
      {
        tmp = p->next;
        free_data (p->data);
        free (p);
      }
    }

  free (ht->table);
  free (ht);
}

/* ------------------------------------------------------------------------ */

static void
resize_HashTable (HashTable ht)
{
  HashTable new_ht = new_HashTable (primes[ht->primes_idx + 1],
                            ht->cmp_keys,
                            ht->hash_key,
                            ht->get_key_from_data,
                            ht->free_data,
                            ht->error);
  int i;
  void *(*get_key_from_data) (void *) = ht->get_key_from_data;

  for (i = 0; i < ht->size; i++)
    {
      HashTableBucket *p, *tmp;
      for (p = ht->table[i]; p; p = tmp)
      {
        HashTableBucket **position = (HashTableBucket **)
          get_position_of_key_in_HashTable (new_ht, get_key_from_data
                                    (p->data));
        tmp = p->next;
        p->next = *position;
        *position = p;
        new_ht->count++;
      }
    }

  free (ht->table);
  new_ht->num_resizes = ht->num_resizes + 1;
  *ht = *new_ht;
  free (new_ht);
}

/* ------------------------------------------------------------------------ */

void **
get_position_of_key_in_HashTable (HashTable ht, void *key)
{
  int h = ht->hash_key (key);
  HashTableBucket **p;
  int (*cmp_keys) (void *, void *) = ht->cmp_keys;
  void *(*get_key_from_data) (void *) = ht->get_key_from_data;

  if (h < 0)
    h = -h;
  h %= ht->size;
  p = &(ht->table[h]);

  while (*p)
    {
      if (cmp_keys (key, get_key_from_data ((*p)->data)) == 0)
      {
        return (void **) p;
      }
      else
      p = &((*p)->next);
    }

  return (void **) p;
}

/* ------------------------------------------------------------------------ */

void *
get_data_from_position_in_HashTable (HashTable ht, void **position)
{
  (void) ht;
  return (*(HashTableBucket **) position)->data;
}

/* ------------------------------------------------------------------------ */

int
get_size_of_HashTable (HashTable ht)
{
  return ht->count;           /* do not mess up with ht -> size ! */
}

/* ------------------------------------------------------------------------ */

const char *
get_statistics_for_HashTable (HashTable ht)
{
  static char buffer[200];
  int collisions = 0, maxchain = 0, i;

  for (i = 0; i < ht->size; i++)
    {
      HashTableBucket *b = ht->table[i];
      if (b)
      {
        int j = 1;
        for (b = b->next; b; b = b->next)
          j++;

        if (maxchain < j)
          maxchain = j;
        if (j > 1)
          collisions += j - 1;
      }
    }

  sprintf (buffer,
         "elements=%d size=%d resizes=%d collisions=%d maxchain=%d",
         ht->count, ht->size, ht->num_resizes, collisions, maxchain);

  return buffer;
}

/* ------------------------------------------------------------------------ */

void
insert_at_position_into_HashTable (HashTable ht, void **_position, void *data)
{
  HashTableBucket *b, **position = (HashTableBucket **) _position;

  if (!position)
    (ht->error) ("insert_at_position_into_HashTable: non valid position");

  if (ht->count >= ht->threshold)
    {
      resize_HashTable (ht);
      position = (HashTableBucket **)
      get_position_of_key_in_HashTable (ht, (ht->get_key_from_data) (data));
    }

  b = (HashTableBucket *) malloc (sizeof (HashTableBucket));
  b->data = data;
  b->next = *position;
  *position = b;
  ht->count++;
}

/* ------------------------------------------------------------------------ */

void
overwrite_at_position_in_HashTable (HashTable ht, void *_position, void *data)
{
  HashTableBucket **position = (HashTableBucket **) _position, *tmp;

  if (!position)
    (ht->error) ("overwrite_at_position_in_HashTable: non valid position");

  tmp = *position;

# ifndef NDEBUG
  {
    void *keyOld = (ht->get_key_from_data) (tmp->data);
    void *keyNew = (ht->get_key_from_data) (data);

    if ((ht->cmp_keys) (keyOld, keyNew) != 0)
      (ht->error) ("overwrite_at_position_in_HashTable: keys do not match");
  }
# endif

  (ht->free_data) (tmp->data);
  tmp->data = data;
}

/* ------------------------------------------------------------------------ */

int
insert_into_HashTable (HashTable ht, void *data)
{
  void **position =
    get_position_of_key_in_HashTable (ht, (ht->get_key_from_data) (data));

  if (!*position)
    {
      insert_at_position_into_HashTable (ht, position, data);
      return 0;
    }
  else
    return 1;
}

/* ------------------------------------------------------------------------ */

void
overwrite_in_HashTable (HashTable ht, void *data)
{
  void **position =
    get_position_of_key_in_HashTable (ht, (ht->get_key_from_data) (data));

  if (*position)
    {
      insert_at_position_into_HashTable (ht, position, data);
    }
  else
    {
      overwrite_at_position_in_HashTable (ht, position, data);
    }
}

/* ------------------------------------------------------------------------ */

void *
get_data_from_HashTable (HashTable ht, void *key)
{
  HashTableBucket *bucket =
    *(HashTableBucket **) get_position_of_key_in_HashTable (ht, key);

  return bucket ? bucket->data : 0;
}

/* ------------------------------------------------------------------------ */

void
remove_from_HashTable (HashTable ht, void *key)
{
  HashTableBucket *tmp, **position =
    (HashTableBucket **) get_position_of_key_in_HashTable (ht, key);

  if ((tmp = *position))
    {
      *position = tmp->next;
      ht->free_data (tmp->data);
      free (tmp);
    }
}

/* ------------------------------------------------------------------------ */

void
setup_HashTableIterator (HashTable ht, HashTableIterator * iterator)
{
  iterator->ht = ht;
  iterator->pos = -1;         /* have a look at increment_HashTableIterator */
  iterator->cursor = 0;
  increment_HashTableIterator (iterator);
}

/* ------------------------------------------------------------------------ */

void
increment_HashTableIterator (HashTableIterator * iterator)
{
  HashTableBucket *current = (HashTableBucket *) iterator->cursor;

  if (current && current->next)
    {
      iterator->cursor = current->next;
    }
  else
    {
      int i = iterator->pos + 1;
      int sz = iterator->ht->size;
      HashTableBucket **table = iterator->ht->table;

      while (i < sz)
      {
        if (table[i])
          {
            iterator->pos = i;
            iterator->cursor = table[i];
            return;
          }
        else
          i++;
      }

      iterator->cursor = 0;
      iterator->pos = sz;
    }
}

/* ------------------------------------------------------------------------ */

int
is_done_HashTableIterator (HashTableIterator * iterator)
{
  return iterator->cursor == 0;
}

/* ------------------------------------------------------------------------ */

void *
get_data_from_HashTableIterator (HashTableIterator * iterator)
{
  HashTableBucket *bucket = (HashTableBucket *) iterator->cursor;

  if (!bucket)
    return 0;
  else
    return bucket->data;
}

/* ------------------------------------------------------------------------ */

/*---------------------------------------------------------------------------.
 | the following function is the famous hash function of P.J. Weinberger as  |
 | desribed in the dragon book of A.V. Aho, R. Sethi and J.D. Ullman.        |
 `---------------------------------------------------------------------------*/

#define HASHPJWSHIFT ((sizeof(int))*8-4)

int
hashpjw_HashTable (void *_s)
{
  const char *s = (char *) _s, *p;
  int h = 0, g;

  for (p = s; *p != '\0'; p++)
    {
      h = (h << 4) + *p;
      if ((g = h & (0xf << HASHPJWSHIFT)))
      {
        h = h ^ (g >> HASHPJWSHIFT);
        h = h ^ g;
      }
    }

  return h > 0 ? h : -h;      // no modulo but positive
}

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