[bpt/guile.git] / libguile / hashtab.c

/* Copyright (C) 1995,1996,1998,1999,2000,2001, 2003, 2004, 2006 Free Software Foundation, Inc.
 * 
 * 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 Street, Fifth Floor, Boston, MA 02110-1301 USA
 */


\f

#include <stdio.h>

#include "libguile/_scm.h"
#include "libguile/alist.h"
#include "libguile/hash.h"
#include "libguile/eval.h"
#include "libguile/root.h"
#include "libguile/vectors.h"
#include "libguile/ports.h"

#include "libguile/validate.h"
#include "libguile/hashtab.h"

#include <gc/gc.h>
#include <gc/gc_typed.h>


\f

/* NOTES
 *
 * 1. The current hash table implementation uses weak alist vectors
 *    (implementation in weaks.c) internally, but we do the scanning
 *    ourselves (in scan_weak_hashtables) because we need to update the
 *    hash table structure when items are dropped during GC.
 *
 * 2. All hash table operations still work on alist vectors.
 *
 */

/* Hash tables are either vectors of association lists or smobs
 * containing such vectors.  Currently, the vector version represents
 * constant size tables while those wrapped in a smob represents
 * resizing tables.
 *
 * Growing or shrinking, with following rehashing, is triggered when
 * the load factor
 *
 *   L = N / S    (N: number of items in table, S: bucket vector length)
 *
 * passes an upper limit of 0.9 or a lower limit of 0.25.
 *
 * The implementation stores the upper and lower number of items which
 * trigger a resize in the hashtable object.
 *
 * Possible hash table sizes (primes) are stored in the array
 * hashtable_size.
 */

scm_t_bits scm_tc16_hashtable;

static unsigned long hashtable_size[] = {
  31, 61, 113, 223, 443, 883, 1759, 3517, 7027, 14051, 28099, 56197, 112363,
  224717, 449419, 898823, 1797641, 3595271, 7190537, 14381041
#if 0
  /* vectors are currently restricted to 2^24-1 = 16777215 elements. */
  28762081, 57524111, 115048217, 230096423, 460192829
  /* larger values can't be represented as INUMs */
#endif
};

#define HASHTABLE_SIZE_N (sizeof(hashtable_size)/sizeof(unsigned long))

static char *s_hashtable = "hashtable";

SCM weak_hashtables = SCM_EOL;


\f
/* Weak cells for use in weak alist vectors (aka. weak hash tables).

   We have weal-car cells, weak-cdr cells, and doubly weak cells.  In weak
   cells, the weak component(s) are not scanned for pointers and are
   registered as disapperaring links; therefore, the weak component may be
   set to NULL by the garbage collector when no other reference to that word
   exist.  Thus, we use `scm_fixup_weak_alist ()' to check for nullified weak
   cells and remove them.  */


/* Type descriptors for weak-c[ad]r cells.  */
static GC_descr wcar_cell_descr, wcdr_cell_descr;


static SCM
scm_weak_car_cell (SCM car, SCM cdr)
{
  scm_t_cell *cell;

  cell = (scm_t_cell *)GC_malloc_explicitly_typed (sizeof (*cell),
						   wcar_cell_descr);

  cell->word_0 = car;
  cell->word_1 = cdr;

  if (SCM_NIMP (car))
    {
      /* Weak car cells make sense iff the car is non-immediate.  */
      GC_GENERAL_REGISTER_DISAPPEARING_LINK ((GC_PTR)&cell->word_0,
					     (GC_PTR)SCM_UNPACK (car));
    }

  return (SCM_PACK (cell));
}

static SCM
scm_weak_cdr_cell (SCM car, SCM cdr)
{
  scm_t_cell *cell;

  cell = (scm_t_cell *)GC_malloc_explicitly_typed (sizeof (*cell),
						   wcdr_cell_descr);

  cell->word_0 = car;
  cell->word_1 = cdr;

  if (SCM_NIMP (cdr))
    {
      /* Weak cdr cells make sense iff the cdr is non-immediate.  */
      GC_GENERAL_REGISTER_DISAPPEARING_LINK ((GC_PTR)&cell->word_1,
					     (GC_PTR)SCM_UNPACK (cdr));
    }

  return (SCM_PACK (cell));
}

static SCM
scm_doubly_weak_cell (SCM car, SCM cdr)
{
  /* Doubly weak cells shall not be scanned at all for pointers.  */
  scm_t_cell *cell = (scm_t_cell *)scm_gc_malloc_pointerless (sizeof (*cell),
							      "weak cell");

  cell->word_0 = car;
  cell->word_1 = cdr;

  if (SCM_NIMP (car))
    {
      GC_GENERAL_REGISTER_DISAPPEARING_LINK ((GC_PTR)&cell->word_0,
					     (GC_PTR)SCM_UNPACK (car));
    }
  if (SCM_NIMP (cdr))
    {
      GC_GENERAL_REGISTER_DISAPPEARING_LINK ((GC_PTR)&cell->word_1,
					     (GC_PTR)SCM_UNPACK (cdr));
    }

  return (SCM_PACK (cell));
}

/* Testing the weak component(s) of a cell for reachability.  */
#define SCM_WEAK_CELL_WORD_DELETED_P(_cell, _word)		\
  (SCM_CELL_OBJECT ((_cell), (_word)) == SCM_PACK (NULL))
#define SCM_WEAK_CELL_CAR_DELETED_P(_cell)	\
  (SCM_WEAK_CELL_WORD_DELETED_P ((_cell), 0))
#define SCM_WEAK_CELL_CDR_DELETED_P(_cell)	\
  (SCM_WEAK_CELL_WORD_DELETED_P ((_cell), 1))

/* Accessing the components of a weak cell.  */
#define SCM_WEAK_CELL_WORD(_cell, _word)		\
  ((SCM_WEAK_CELL_WORD_DELETED_P ((_cell), (_word)))	\
   ? SCM_BOOL_F : SCM_CAR (pair))
#define SCM_WEAK_CELL_CAR(_cell)  (SCM_WEAK_CELL_WORD ((_cell), 0))
#define SCM_WEAK_CELL_CDR(_cell)  (SCM_WEAK_CELL_WORD ((_cell), 1))


/* Return a ``usable'' version of ALIST, an alist of weak pairs.  By
   ``usable'', we mean that it contains only valid Scheme objects.  On
   return, REMOVE_ITEMS is set to the number of pairs that have been
   deleted.  */
static SCM
scm_fixup_weak_alist (SCM alist, size_t *removed_items)
{
  SCM result;
  SCM prev = SCM_EOL;

  *removed_items = 0;
  for (result = alist;
       scm_is_pair (alist);
       prev = alist, alist = SCM_CDR (alist))
    {
      SCM pair = SCM_CAR (alist);

      if (scm_is_pair (pair))
	{
	  if ((SCM_WEAK_CELL_CAR_DELETED_P (pair))
	      || (SCM_WEAK_CELL_CDR_DELETED_P (pair)))
	    {
	      /* Remove from ALIST weak pair PAIR whose car/cdr has been
		 nullified by the GC.  */
	      if (prev == SCM_EOL)
		result = SCM_CDR (alist);
	      else
		SCM_SETCDR (prev, SCM_CDR (alist));

	      (*removed_items)++;
	      continue;
	    }
	}
    }

  return result;
}


/* Helper macros.  */

/* Return true if OBJ is either a weak hash table or a weak alist vector (as
   defined in `weaks.[ch]').
   FIXME: We should eventually keep only weah hash tables.  */
/* XXX: We assume that if OBJ is a vector, then it's a _weak_ vector.  */
#define IS_WEAK_THING(_obj)					\
  ((SCM_HASHTABLE_P (table) && (SCM_HASHTABLE_WEAK_P (table)))	\
   || (SCM_I_IS_VECTOR (table)))

/* Fixup BUCKET, an alist part of weak hash table OBJ.  BUCKETS is the full
   bucket vector for OBJ and IDX is the index of BUCKET within this
   vector.  */
#define START_WEAK_BUCKET_FIXUP(_obj, _buckets, _idx, _bucket)		   \
do									   \
  {									   \
    size_t _removed;							   \
									   \
    /* Disable the GC so that ALIST remains valid until ASSOC_FN has	   \
       returned.  */							   \
    /* FIXME: We could maybe trigger a rehash here depending on whether	   \
       `scm_fixup_weak_alist ()' noticed some change.  */		   \
    GC_disable ();							   \
    (_bucket) = scm_fixup_weak_alist ((_bucket), &_removed);		   \
    SCM_SIMPLE_VECTOR_SET ((_buckets), (_idx), (_bucket));		   \
									   \
    if ((_removed) && (SCM_HASHTABLE_P (_obj)))				   \
      SCM_SET_HASHTABLE_N_ITEMS ((_obj),				   \
				 SCM_HASHTABLE_N_ITEMS (_obj) - _removed); \
  }									   \
while (0)

/* Terminate a weak bucket fixup phase.  */
#define END_WEAK_BUCKET_FIXUP(_obj, _buckets, _idx, _bucket)	\
  do { GC_enable (); } while (0)


\f
static SCM
make_hash_table (int flags, unsigned long k, const char *func_name) 
{
  SCM table, vector;
  scm_t_hashtable *t;
  int i = 0, n = k ? k : 31;
  while (i < HASHTABLE_SIZE_N && n > hashtable_size[i])
    ++i;
  n = hashtable_size[i];

  /* In both cases, i.e., regardless of whether we are creating a weak hash
     table, we return a non-weak vector.  This is because the vector itself
     is not weak in the case of a weak hash table: the alist pairs are.  */
  vector = scm_c_make_vector (n, SCM_EOL);

  t = scm_gc_malloc_pointerless (sizeof (*t), s_hashtable);
  t->min_size_index = t->size_index = i;
  t->n_items = 0;
  t->lower = 0;
  t->upper = 9 * n / 10;
  t->flags = flags;
  t->hash_fn = NULL;
  if (flags)
    {
      /* FIXME: We should eventually remove WEAK_HASHTABLES.  */
      SCM_NEWSMOB3 (table, scm_tc16_hashtable, vector, t, weak_hashtables);
      weak_hashtables = table;
    }
  else
    SCM_NEWSMOB3 (table, scm_tc16_hashtable, vector, t, SCM_EOL);
  return table;
}

void
scm_i_rehash (SCM table,
	      unsigned long (*hash_fn)(),
	      void *closure,
	      const char* func_name)
{
  SCM buckets, new_buckets;
  int i;
  unsigned long old_size;
  unsigned long new_size;

  if (SCM_HASHTABLE_N_ITEMS (table) < SCM_HASHTABLE_LOWER (table))
    {
      /* rehashing is not triggered when i <= min_size */
      i = SCM_HASHTABLE (table)->size_index;
      do
	--i;
      while (i > SCM_HASHTABLE (table)->min_size_index
	     && SCM_HASHTABLE_N_ITEMS (table) < hashtable_size[i] / 4);
    }
  else
    {
      i = SCM_HASHTABLE (table)->size_index + 1;
      if (i >= HASHTABLE_SIZE_N)
	/* don't rehash */
	return;

      /* Remember HASH_FN for rehash_after_gc, but only when CLOSURE
	 is not needed since CLOSURE can not be guaranteed to be valid
	 after this function returns.
      */
      if (closure == NULL)
	SCM_HASHTABLE (table)->hash_fn = hash_fn;
    }
  SCM_HASHTABLE (table)->size_index = i;
  
  new_size = hashtable_size[i];
  if (i <= SCM_HASHTABLE (table)->min_size_index)
    SCM_HASHTABLE (table)->lower = 0;
  else
    SCM_HASHTABLE (table)->lower = new_size / 4;
  SCM_HASHTABLE (table)->upper = 9 * new_size / 10;
  buckets = SCM_HASHTABLE_VECTOR (table);

  new_buckets = scm_c_make_vector (new_size, SCM_EOL);

  /* When this is a weak hashtable, running the GC might change it.
     We need to cope with this while rehashing its elements.  We do
     this by first installing the new, empty bucket vector.  Then we
     remove the elements from the old bucket vector and insert them
     into the new one.
  */

  SCM_SET_HASHTABLE_VECTOR (table, new_buckets);
  SCM_SET_HASHTABLE_N_ITEMS (table, 0);

  old_size = SCM_SIMPLE_VECTOR_LENGTH (buckets);
  for (i = 0; i < old_size; ++i)
    {
      SCM ls, cell, handle;

      ls = SCM_SIMPLE_VECTOR_REF (buckets, i);
      SCM_SIMPLE_VECTOR_SET (buckets, i, SCM_EOL);

      while (scm_is_pair (ls))
	{
	  unsigned long h;
	  cell = ls;
	  handle = SCM_CAR (cell);
	  ls = SCM_CDR (ls);
	  h = hash_fn (SCM_CAR (handle), new_size, closure);
	  if (h >= new_size)
	    scm_out_of_range (func_name, scm_from_ulong (h));
	  SCM_SETCDR (cell, SCM_SIMPLE_VECTOR_REF (new_buckets, h));
	  SCM_SIMPLE_VECTOR_SET (new_buckets, h, cell);
	  SCM_HASHTABLE_INCREMENT (table);
	}
    }
}


static int
hashtable_print (SCM exp, SCM port, scm_print_state *pstate SCM_UNUSED)
{
  scm_puts ("#<", port);
  if (SCM_HASHTABLE_WEAK_KEY_P (exp))
    scm_puts ("weak-key-", port);
  else if (SCM_HASHTABLE_WEAK_VALUE_P (exp))
    scm_puts ("weak-value-", port);
  else if (SCM_HASHTABLE_DOUBLY_WEAK_P (exp))
    scm_puts ("doubly-weak-", port);
  scm_puts ("hash-table ", port);
  scm_uintprint (SCM_HASHTABLE_N_ITEMS (exp), 10, port);
  scm_putc ('/', port);
  scm_uintprint (SCM_SIMPLE_VECTOR_LENGTH (SCM_HASHTABLE_VECTOR (exp)),
		 10, port);
  scm_puts (">", port);
  return 1;
}

/* FIXME */
#define UNMARKED_CELL_P(x) 0 /* (SCM_NIMP(x) && !SCM_GC_MARK_P (x)) */

/* keep track of hash tables that need to shrink after scan */
static SCM to_rehash = SCM_EOL;

/* scan hash tables and update hash tables item count */
void
scm_i_scan_weak_hashtables ()
{
#if 0 /* FIXME */
  SCM *next = &weak_hashtables;
  SCM h = *next;
  while (!scm_is_null (h))
    {
      if (!SCM_GC_MARK_P (h))
	*next = h = SCM_HASHTABLE_NEXT (h);
      else
	{
	  SCM vec = SCM_HASHTABLE_VECTOR (h);
	  size_t delta = SCM_I_WVECT_DELTA (vec);
	  SCM_I_SET_WVECT_DELTA (vec, 0);
	  SCM_SET_HASHTABLE_N_ITEMS (h, SCM_HASHTABLE_N_ITEMS (h) - delta);

	  if (SCM_HASHTABLE_N_ITEMS (h) < SCM_HASHTABLE_LOWER (h))
	    {
	      SCM tmp = SCM_HASHTABLE_NEXT (h);
	      /* temporarily move table from weak_hashtables to to_rehash */
	      SCM_SET_HASHTABLE_NEXT (h, to_rehash);
	      to_rehash = h;
	      *next = h = tmp;
	    }
	  else
	    {
	      next = SCM_HASHTABLE_NEXTLOC (h);
	      h = SCM_HASHTABLE_NEXT (h);
	    }
	}
    }
#endif
}

static void *
rehash_after_gc (void *dummy1 SCM_UNUSED,
		 void *dummy2 SCM_UNUSED,
		 void *dummy3 SCM_UNUSED)
{
  if (!scm_is_null (to_rehash))
    {
      SCM first = to_rehash, last, h;
      /* important to clear to_rehash here so that we don't get stuck
	 in an infinite loop if scm_i_rehash causes GC */
      to_rehash = SCM_EOL;
      h = first;
      do
	{
	  /* Rehash only when we have a hash_fn.
	   */
	  if (SCM_HASHTABLE (h)->hash_fn)
	    scm_i_rehash (h, SCM_HASHTABLE (h)->hash_fn, NULL,
			  "rehash_after_gc");
	  last = h;
	  h = SCM_HASHTABLE_NEXT (h);
	} while (!scm_is_null (h));
      /* move tables back to weak_hashtables */
      SCM_SET_HASHTABLE_NEXT (last, weak_hashtables);
      weak_hashtables = first;
    }
  return 0;
}

static size_t
hashtable_free (SCM obj)
{
  scm_gc_free (SCM_HASHTABLE (obj), sizeof (scm_t_hashtable), s_hashtable);
  return 0;
}


SCM
scm_c_make_hash_table (unsigned long k)
{
  return make_hash_table (0, k, "scm_c_make_hash_table");
}

SCM_DEFINE (scm_make_hash_table, "make-hash-table", 0, 1, 0,
	    (SCM n),
	    "Make a new abstract hash table object with minimum number of buckets @var{n}\n")
#define FUNC_NAME s_scm_make_hash_table
{
  if (SCM_UNBNDP (n))
    return make_hash_table (0, 0, FUNC_NAME);
  else
    return make_hash_table (0, scm_to_ulong (n), FUNC_NAME);
}
#undef FUNC_NAME

SCM_DEFINE (scm_make_weak_key_hash_table, "make-weak-key-hash-table", 0, 1, 0, 
	    (SCM n),
	    "@deffnx {Scheme Procedure} make-weak-value-hash-table size\n"
	    "@deffnx {Scheme Procedure} make-doubly-weak-hash-table size\n"
	    "Return a weak hash table with @var{size} buckets.\n"
	    "\n"
	    "You can modify weak hash tables in exactly the same way you\n"
	    "would modify regular hash tables. (@pxref{Hash Tables})")
#define FUNC_NAME s_scm_make_weak_key_hash_table
{
  if (SCM_UNBNDP (n))
    return make_hash_table (SCM_HASHTABLEF_WEAK_CAR, 0, FUNC_NAME);
  else
    return make_hash_table (SCM_HASHTABLEF_WEAK_CAR,
			    scm_to_ulong (n), FUNC_NAME);
}
#undef FUNC_NAME


SCM_DEFINE (scm_make_weak_value_hash_table, "make-weak-value-hash-table", 0, 1, 0, 
            (SCM n),
	    "Return a hash table with weak values with @var{size} buckets.\n"
	    "(@pxref{Hash Tables})")
#define FUNC_NAME s_scm_make_weak_value_hash_table
{
  if (SCM_UNBNDP (n))
    return make_hash_table (SCM_HASHTABLEF_WEAK_CDR, 0, FUNC_NAME);
  else
    {
      return make_hash_table (SCM_HASHTABLEF_WEAK_CDR,
			      scm_to_ulong (n), FUNC_NAME);
    }
}
#undef FUNC_NAME


SCM_DEFINE (scm_make_doubly_weak_hash_table, "make-doubly-weak-hash-table", 1, 0, 0, 
            (SCM n),
	    "Return a hash table with weak keys and values with @var{size}\n"
	    "buckets.  (@pxref{Hash Tables})")
#define FUNC_NAME s_scm_make_doubly_weak_hash_table
{
  if (SCM_UNBNDP (n))
    return make_hash_table (SCM_HASHTABLEF_WEAK_CAR | SCM_HASHTABLEF_WEAK_CDR,
			    0,
			    FUNC_NAME);
  else
    {
      return make_hash_table (SCM_HASHTABLEF_WEAK_CAR | SCM_HASHTABLEF_WEAK_CDR,
			      scm_to_ulong (n),
			      FUNC_NAME);
    }
}
#undef FUNC_NAME


SCM_DEFINE (scm_hash_table_p, "hash-table?", 1, 0, 0, 
            (SCM obj),
	    "Return @code{#t} if @var{obj} is an abstract hash table object.")
#define FUNC_NAME s_scm_hash_table_p
{
  return scm_from_bool (SCM_HASHTABLE_P (obj));
}
#undef FUNC_NAME


SCM_DEFINE (scm_weak_key_hash_table_p, "weak-key-hash-table?", 1, 0, 0, 
           (SCM obj),
	    "@deffnx {Scheme Procedure} weak-value-hash-table? obj\n"
	    "@deffnx {Scheme Procedure} doubly-weak-hash-table? obj\n"
	    "Return @code{#t} if @var{obj} is the specified weak hash\n"
	    "table. Note that a doubly weak hash table is neither a weak key\n"
	    "nor a weak value hash table.")
#define FUNC_NAME s_scm_weak_key_hash_table_p
{
  return scm_from_bool (SCM_HASHTABLE_P (obj) && SCM_HASHTABLE_WEAK_KEY_P (obj));
}
#undef FUNC_NAME


SCM_DEFINE (scm_weak_value_hash_table_p, "weak-value-hash-table?", 1, 0, 0, 
            (SCM obj),
	    "Return @code{#t} if @var{obj} is a weak value hash table.")
#define FUNC_NAME s_scm_weak_value_hash_table_p
{
  return scm_from_bool (SCM_HASHTABLE_P (obj) && SCM_HASHTABLE_WEAK_VALUE_P (obj));
}
#undef FUNC_NAME


SCM_DEFINE (scm_doubly_weak_hash_table_p, "doubly-weak-hash-table?", 1, 0, 0, 
            (SCM obj),
	    "Return @code{#t} if @var{obj} is a doubly weak hash table.")
#define FUNC_NAME s_scm_doubly_weak_hash_table_p
{
  return scm_from_bool (SCM_HASHTABLE_P (obj) && SCM_HASHTABLE_DOUBLY_WEAK_P (obj));
}
#undef FUNC_NAME


SCM
scm_hash_fn_get_handle (SCM table, SCM obj, unsigned long (*hash_fn)(), SCM (*assoc_fn)(), void * closure)
#define FUNC_NAME "scm_hash_fn_get_handle"
{
  int weak = 0;
  unsigned long k;
  SCM buckets, alist, h;

  if (SCM_HASHTABLE_P (table))
    buckets = SCM_HASHTABLE_VECTOR (table);
  else
    {
      SCM_VALIDATE_VECTOR (1, table);
      buckets = table;
    }

  if (SCM_SIMPLE_VECTOR_LENGTH (buckets) == 0)
    return SCM_BOOL_F;
  k = hash_fn (obj, SCM_SIMPLE_VECTOR_LENGTH (buckets), closure);
  if (k >= SCM_SIMPLE_VECTOR_LENGTH (buckets))
    scm_out_of_range ("hash_fn_get_handle", scm_from_ulong (k));

  weak = IS_WEAK_THING (table);
  alist = SCM_SIMPLE_VECTOR_REF (buckets, k);

  if (weak)
    START_WEAK_BUCKET_FIXUP (table, buckets, k, alist);

  h = assoc_fn (obj, alist, closure);
  if (weak)
    END_WEAK_BUCKET_FIXUP (table, buckets, k, alist);

  return h;
}
#undef FUNC_NAME


SCM
scm_hash_fn_create_handle_x (SCM table, SCM obj, SCM init, unsigned long (*hash_fn)(),
                             SCM (*assoc_fn)(), void * closure)
#define FUNC_NAME "scm_hash_fn_create_handle_x"
{
  int weak = 0;
  unsigned long k;
  SCM buckets, alist, it;

  if (SCM_HASHTABLE_P (table))
    buckets = SCM_HASHTABLE_VECTOR (table);
  else
    {
      SCM_ASSERT (scm_is_simple_vector (table),
		  table, SCM_ARG1, "hash_fn_create_handle_x");
      buckets = table;
    }
  if (SCM_SIMPLE_VECTOR_LENGTH (buckets) == 0)
    SCM_MISC_ERROR ("void hashtable", SCM_EOL);

  k = hash_fn (obj, SCM_SIMPLE_VECTOR_LENGTH (buckets), closure);
  if (k >= SCM_SIMPLE_VECTOR_LENGTH (buckets))
    scm_out_of_range ("hash_fn_create_handle_x", scm_from_ulong (k));

  weak = IS_WEAK_THING (table);
  alist = SCM_SIMPLE_VECTOR_REF (buckets, k);
  if (weak)
    START_WEAK_BUCKET_FIXUP (table, buckets, k, alist);

  it = assoc_fn (obj, alist, closure);
  if (weak)
    END_WEAK_BUCKET_FIXUP (table, buckets, k, alist);

  if (scm_is_true (it))
    return it;
  else
    {
      /* When this is a weak hashtable, running the GC can change it.
	 Thus, we must allocate the new cells first and can only then
	 access BUCKETS.  Also, we need to fetch the bucket vector
	 again since the hashtable might have been rehashed.  This
	 necessitates a new hash value as well.
      */
      SCM handle, new_bucket;

      if ((SCM_HASHTABLE_P (table) && (SCM_HASHTABLE_WEAK_P (table)))
	  || (SCM_I_IS_VECTOR (table)))
	{
	  /* Use a weak cell.  */
	  if (SCM_HASHTABLE_DOUBLY_WEAK_P (table))
	    handle = scm_doubly_weak_cell (obj, init);
	  else if (SCM_HASHTABLE_WEAK_KEY_P (table))
	    handle = scm_weak_car_cell (obj, init);
	  else
	    handle = scm_weak_cdr_cell (obj, init);
	}
      else
	/* Use a regular, non-weak cell.  */
	handle = scm_cons (obj, init);

      new_bucket = scm_cons (handle, SCM_EOL);

      if (!scm_is_eq (table, buckets)
	  && !scm_is_eq (SCM_HASHTABLE_VECTOR (table), buckets))
	{
	  buckets = SCM_HASHTABLE_VECTOR (table);
	  k = hash_fn (obj, SCM_SIMPLE_VECTOR_LENGTH (buckets), closure);
	  if (k >= SCM_SIMPLE_VECTOR_LENGTH (buckets))
	    scm_out_of_range ("hash_fn_create_handle_x", scm_from_ulong (k));
	}
      SCM_SETCDR (new_bucket, SCM_SIMPLE_VECTOR_REF (buckets, k));
      SCM_SIMPLE_VECTOR_SET (buckets, k, new_bucket);
      if (!scm_is_eq (table, buckets))
	{
	  /* Update element count and maybe rehash the table.  The
	     table might have too few entries here since weak hash
	     tables used with the hashx_* functions can not be
	     rehashed after GC.
	  */
	  SCM_HASHTABLE_INCREMENT (table);
	  if (SCM_HASHTABLE_N_ITEMS (table) < SCM_HASHTABLE_LOWER (table)
	      || SCM_HASHTABLE_N_ITEMS (table) > SCM_HASHTABLE_UPPER (table))
	    scm_i_rehash (table, hash_fn, closure, FUNC_NAME);
	}
      return SCM_CAR (new_bucket);
    }
}
#undef FUNC_NAME


SCM 
scm_hash_fn_ref (SCM table, SCM obj, SCM dflt, unsigned long (*hash_fn)(),
                 SCM (*assoc_fn)(), void * closure)
{
  SCM it = scm_hash_fn_get_handle (table, obj, hash_fn, assoc_fn, closure);
  if (scm_is_pair (it))
    return SCM_CDR (it);
  else
    return dflt;
}


SCM 
scm_hash_fn_set_x (SCM table, SCM obj, SCM val, unsigned long (*hash_fn)(),
                   SCM (*assoc_fn)(), void * closure)
{
  SCM it;

  it = scm_hash_fn_create_handle_x (table, obj, SCM_BOOL_F, hash_fn, assoc_fn, closure);
  SCM_SETCDR (it, val);
  return val;
}


SCM
scm_hash_fn_remove_x (SCM table, SCM obj,
		      unsigned long (*hash_fn)(),
		      SCM (*assoc_fn)(),
                      void *closure)
{
  int weak = 0;
  unsigned long k;
  SCM buckets, alist, h;

  if (SCM_HASHTABLE_P (table))
    buckets = SCM_HASHTABLE_VECTOR (table);
  else
    {
      SCM_ASSERT (scm_is_simple_vector (table), table,
		  SCM_ARG1, "hash_fn_remove_x");
      buckets = table;
    }
  if (SCM_SIMPLE_VECTOR_LENGTH (table) == 0)
    return SCM_EOL;

  k = hash_fn (obj, SCM_SIMPLE_VECTOR_LENGTH (buckets), closure);
  if (k >= SCM_SIMPLE_VECTOR_LENGTH (buckets))
    scm_out_of_range ("hash_fn_remove_x", scm_from_ulong (k));

  weak = IS_WEAK_THING (table);
  alist = SCM_SIMPLE_VECTOR_REF (buckets, k);
  if (weak)
    START_WEAK_BUCKET_FIXUP (table, buckets, k, alist);

  h = assoc_fn (obj, alist, closure);
  if (weak)
    END_WEAK_BUCKET_FIXUP (table, buckets, k, alist);

  if (scm_is_true (h))
    {
      SCM_SIMPLE_VECTOR_SET 
	(buckets, k, scm_delq_x (h, SCM_SIMPLE_VECTOR_REF (buckets, k)));
      if (!scm_is_eq (table, buckets))
	{
	  SCM_HASHTABLE_DECREMENT (table);
	  if (SCM_HASHTABLE_N_ITEMS (table) < SCM_HASHTABLE_LOWER (table))
	    scm_i_rehash (table, hash_fn, closure, "scm_hash_fn_remove_x");
	}
    }
  return h;
}

SCM_DEFINE (scm_hash_clear_x, "hash-clear!", 1, 0, 0,
	    (SCM table),
	    "Remove all items from @var{table} (without triggering a resize).")
#define FUNC_NAME s_scm_hash_clear_x
{
  if (SCM_HASHTABLE_P (table))
    {
      scm_vector_fill_x (SCM_HASHTABLE_VECTOR (table), SCM_EOL);
      SCM_SET_HASHTABLE_N_ITEMS (table, 0);
    }
  else
    scm_vector_fill_x (table, SCM_EOL);
  return SCM_UNSPECIFIED;
}
#undef FUNC_NAME

\f

SCM_DEFINE (scm_hashq_get_handle, "hashq-get-handle", 2, 0, 0,
            (SCM table, SCM key),
	    "This procedure returns the @code{(key . value)} pair from the\n"
	    "hash table @var{table}.  If @var{table} does not hold an\n"
	    "associated value for @var{key}, @code{#f} is returned.\n"
	    "Uses @code{eq?} for equality testing.")
#define FUNC_NAME s_scm_hashq_get_handle
{
  return scm_hash_fn_get_handle (table, key, scm_ihashq, scm_sloppy_assq, 0);
}
#undef FUNC_NAME


SCM_DEFINE (scm_hashq_create_handle_x, "hashq-create-handle!", 3, 0, 0,
            (SCM table, SCM key, SCM init),
	    "This function looks up @var{key} in @var{table} and returns its handle.\n"
	    "If @var{key} is not already present, a new handle is created which\n"
	    "associates @var{key} with @var{init}.")
#define FUNC_NAME s_scm_hashq_create_handle_x
{
  return scm_hash_fn_create_handle_x (table, key, init, scm_ihashq, scm_sloppy_assq, 0);
}
#undef FUNC_NAME


SCM_DEFINE (scm_hashq_ref, "hashq-ref", 2, 1, 0,
            (SCM table, SCM key, SCM dflt),
	    "Look up @var{key} in the hash table @var{table}, and return the\n"
	    "value (if any) associated with it.  If @var{key} is not found,\n"
	    "return @var{default} (or @code{#f} if no @var{default} argument\n"
	    "is supplied).  Uses @code{eq?} for equality testing.")
#define FUNC_NAME s_scm_hashq_ref
{
  if (SCM_UNBNDP (dflt))
    dflt = SCM_BOOL_F;
  return scm_hash_fn_ref (table, key, dflt, scm_ihashq, scm_sloppy_assq, 0);
}
#undef FUNC_NAME


SCM_DEFINE (scm_hashq_set_x, "hashq-set!", 3, 0, 0,
            (SCM table, SCM key, SCM val),
	    "Find the entry in @var{table} associated with @var{key}, and\n"
	    "store @var{value} there. Uses @code{eq?} for equality testing.")
#define FUNC_NAME s_scm_hashq_set_x
{
  return scm_hash_fn_set_x (table, key, val, scm_ihashq, scm_sloppy_assq, 0);
}
#undef FUNC_NAME


SCM_DEFINE (scm_hashq_remove_x, "hashq-remove!", 2, 0, 0,
            (SCM table, SCM key),
	    "Remove @var{key} (and any value associated with it) from\n"
	    "@var{table}.  Uses @code{eq?} for equality tests.")
#define FUNC_NAME s_scm_hashq_remove_x
{
  return scm_hash_fn_remove_x (table, key, scm_ihashq, scm_sloppy_assq, 0);
}
#undef FUNC_NAME


\f

SCM_DEFINE (scm_hashv_get_handle, "hashv-get-handle", 2, 0, 0,
            (SCM table, SCM key),
	    "This procedure returns the @code{(key . value)} pair from the\n"
	    "hash table @var{table}.  If @var{table} does not hold an\n"
	    "associated value for @var{key}, @code{#f} is returned.\n"
	    "Uses @code{eqv?} for equality testing.")
#define FUNC_NAME s_scm_hashv_get_handle
{
  return scm_hash_fn_get_handle (table, key, scm_ihashv, scm_sloppy_assv, 0);
}
#undef FUNC_NAME


SCM_DEFINE (scm_hashv_create_handle_x, "hashv-create-handle!", 3, 0, 0,
            (SCM table, SCM key, SCM init),
	    "This function looks up @var{key} in @var{table} and returns its handle.\n"
	    "If @var{key} is not already present, a new handle is created which\n"
	    "associates @var{key} with @var{init}.")
#define FUNC_NAME s_scm_hashv_create_handle_x
{
  return scm_hash_fn_create_handle_x (table, key, init, scm_ihashv,
				      scm_sloppy_assv, 0);
}
#undef FUNC_NAME


SCM_DEFINE (scm_hashv_ref, "hashv-ref", 2, 1, 0,
            (SCM table, SCM key, SCM dflt),
	    "Look up @var{key} in the hash table @var{table}, and return the\n"
	    "value (if any) associated with it.  If @var{key} is not found,\n"
	    "return @var{default} (or @code{#f} if no @var{default} argument\n"
	    "is supplied).  Uses @code{eqv?} for equality testing.")
#define FUNC_NAME s_scm_hashv_ref
{
  if (SCM_UNBNDP (dflt))
    dflt = SCM_BOOL_F;
  return scm_hash_fn_ref (table, key, dflt, scm_ihashv, scm_sloppy_assv, 0);
}
#undef FUNC_NAME


SCM_DEFINE (scm_hashv_set_x, "hashv-set!", 3, 0, 0,
            (SCM table, SCM key, SCM val),
	    "Find the entry in @var{table} associated with @var{key}, and\n"
	    "store @var{value} there. Uses @code{eqv?} for equality testing.")
#define FUNC_NAME s_scm_hashv_set_x
{
  return scm_hash_fn_set_x (table, key, val, scm_ihashv, scm_sloppy_assv, 0);
}
#undef FUNC_NAME


SCM_DEFINE (scm_hashv_remove_x, "hashv-remove!", 2, 0, 0,
            (SCM table, SCM key),
	    "Remove @var{key} (and any value associated with it) from\n"
	    "@var{table}.  Uses @code{eqv?} for equality tests.")
#define FUNC_NAME s_scm_hashv_remove_x
{
  return scm_hash_fn_remove_x (table, key, scm_ihashv, scm_sloppy_assv, 0);
}
#undef FUNC_NAME

\f

SCM_DEFINE (scm_hash_get_handle, "hash-get-handle", 2, 0, 0,
            (SCM table, SCM key),
	    "This procedure returns the @code{(key . value)} pair from the\n"
	    "hash table @var{table}.  If @var{table} does not hold an\n"
	    "associated value for @var{key}, @code{#f} is returned.\n"
	    "Uses @code{equal?} for equality testing.")
#define FUNC_NAME s_scm_hash_get_handle
{
  return scm_hash_fn_get_handle (table, key, scm_ihash, scm_sloppy_assoc, 0);
}
#undef FUNC_NAME


SCM_DEFINE (scm_hash_create_handle_x, "hash-create-handle!", 3, 0, 0,
            (SCM table, SCM key, SCM init),
	    "This function looks up @var{key} in @var{table} and returns its handle.\n"
	    "If @var{key} is not already present, a new handle is created which\n"
	    "associates @var{key} with @var{init}.")
#define FUNC_NAME s_scm_hash_create_handle_x
{
  return scm_hash_fn_create_handle_x (table, key, init, scm_ihash, scm_sloppy_assoc, 0);
}
#undef FUNC_NAME


SCM_DEFINE (scm_hash_ref, "hash-ref", 2, 1, 0,
            (SCM table, SCM key, SCM dflt),
	    "Look up @var{key} in the hash table @var{table}, and return the\n"
	    "value (if any) associated with it.  If @var{key} is not found,\n"
	    "return @var{default} (or @code{#f} if no @var{default} argument\n"
	    "is supplied).  Uses @code{equal?} for equality testing.")
#define FUNC_NAME s_scm_hash_ref
{
  if (SCM_UNBNDP (dflt))
    dflt = SCM_BOOL_F;
  return scm_hash_fn_ref (table, key, dflt, scm_ihash, scm_sloppy_assoc, 0);
}
#undef FUNC_NAME


SCM_DEFINE (scm_hash_set_x, "hash-set!", 3, 0, 0,
            (SCM table, SCM key, SCM val),
	    "Find the entry in @var{table} associated with @var{key}, and\n"
	    "store @var{value} there. Uses @code{equal?} for equality\n"
	    "testing.")
#define FUNC_NAME s_scm_hash_set_x
{
  return scm_hash_fn_set_x (table, key, val, scm_ihash, scm_sloppy_assoc, 0);
}
#undef FUNC_NAME


SCM_DEFINE (scm_hash_remove_x, "hash-remove!", 2, 0, 0,
            (SCM table, SCM key),
	    "Remove @var{key} (and any value associated with it) from\n"
	    "@var{table}.  Uses @code{equal?} for equality tests.")
#define FUNC_NAME s_scm_hash_remove_x
{
  return scm_hash_fn_remove_x (table, key, scm_ihash, scm_sloppy_assoc, 0);
}
#undef FUNC_NAME

\f


typedef struct scm_t_ihashx_closure
{
  SCM hash;
  SCM assoc;
} scm_t_ihashx_closure;


static unsigned long
scm_ihashx (SCM obj, unsigned long n, scm_t_ihashx_closure *closure)
{
  SCM answer = scm_call_2 (closure->hash, obj, scm_from_ulong (n));
  return scm_to_ulong (answer);
}


static SCM
scm_sloppy_assx (SCM obj, SCM alist, scm_t_ihashx_closure *closure)
{
  return scm_call_2 (closure->assoc, obj, alist);
}


SCM_DEFINE (scm_hashx_get_handle, "hashx-get-handle", 4, 0, 0, 
            (SCM hash, SCM assoc, SCM table, SCM key),
	    "This behaves the same way as the corresponding\n"
	    "@code{-get-handle} function, but uses @var{hash} as a hash\n"
	    "function and @var{assoc} to compare keys.  @code{hash} must be\n"
	    "a function that takes two arguments, a key to be hashed and a\n"
	    "table size.  @code{assoc} must be an associator function, like\n"
	    "@code{assoc}, @code{assq} or @code{assv}.")
#define FUNC_NAME s_scm_hashx_get_handle
{
  scm_t_ihashx_closure closure;
  closure.hash = hash;
  closure.assoc = assoc;
  return scm_hash_fn_get_handle (table, key, scm_ihashx, scm_sloppy_assx,
				 (void *) &closure);
}
#undef FUNC_NAME


SCM_DEFINE (scm_hashx_create_handle_x, "hashx-create-handle!", 5, 0, 0, 
            (SCM hash, SCM assoc, SCM table, SCM key, SCM init),
	    "This behaves the same way as the corresponding\n"
	    "@code{-create-handle} function, but uses @var{hash} as a hash\n"
	    "function and @var{assoc} to compare keys.  @code{hash} must be\n"
	    "a function that takes two arguments, a key to be hashed and a\n"
	    "table size.  @code{assoc} must be an associator function, like\n"
	    "@code{assoc}, @code{assq} or @code{assv}.")
#define FUNC_NAME s_scm_hashx_create_handle_x
{
  scm_t_ihashx_closure closure;
  closure.hash = hash;
  closure.assoc = assoc;
  return scm_hash_fn_create_handle_x (table, key, init, scm_ihashx,
				      scm_sloppy_assx, (void *)&closure);
}
#undef FUNC_NAME


SCM_DEFINE (scm_hashx_ref, "hashx-ref", 4, 1, 0, 
            (SCM hash, SCM assoc, SCM table, SCM key, SCM dflt),
	    "This behaves the same way as the corresponding @code{ref}\n"
	    "function, but uses @var{hash} as a hash function and\n"
	    "@var{assoc} to compare keys.  @code{hash} must be a function\n"
	    "that takes two arguments, a key to be hashed and a table size.\n"
	    "@code{assoc} must be an associator function, like @code{assoc},\n"
	    "@code{assq} or @code{assv}.\n"
	    "\n"
	    "By way of illustration, @code{hashq-ref table key} is\n"
	    "equivalent to @code{hashx-ref hashq assq table key}.")
#define FUNC_NAME s_scm_hashx_ref
{
  scm_t_ihashx_closure closure;
  if (SCM_UNBNDP (dflt))
    dflt = SCM_BOOL_F;
  closure.hash = hash;
  closure.assoc = assoc;
  return scm_hash_fn_ref (table, key, dflt, scm_ihashx, scm_sloppy_assx,
			  (void *)&closure);
}
#undef FUNC_NAME


SCM_DEFINE (scm_hashx_set_x, "hashx-set!", 5, 0, 0,
            (SCM hash, SCM assoc, SCM table, SCM key, SCM val),
	    "This behaves the same way as the corresponding @code{set!}\n"
	    "function, but uses @var{hash} as a hash function and\n"
	    "@var{assoc} to compare keys.  @code{hash} must be a function\n"
	    "that takes two arguments, a key to be hashed and a table size.\n"
	    "@code{assoc} must be an associator function, like @code{assoc},\n"
	    "@code{assq} or @code{assv}.\n"
	    "\n"
	    " By way of illustration, @code{hashq-set! table key} is\n"
	    "equivalent to @code{hashx-set!  hashq assq table key}.")
#define FUNC_NAME s_scm_hashx_set_x
{
  scm_t_ihashx_closure closure;
  closure.hash = hash;
  closure.assoc = assoc;
  return scm_hash_fn_set_x (table, key, val, scm_ihashx, scm_sloppy_assx,
			    (void *)&closure);
}
#undef FUNC_NAME

SCM_DEFINE (scm_hashx_remove_x, "hashx-remove!", 4, 0, 0,
	    (SCM hash, SCM assoc, SCM table, SCM obj),
	    "This behaves the same way as the corresponding @code{remove!}\n"
	    "function, but uses @var{hash} as a hash function and\n"
	    "@var{assoc} to compare keys.  @code{hash} must be a function\n"
	    "that takes two arguments, a key to be hashed and a table size.\n"
	    "@code{assoc} must be an associator function, like @code{assoc},\n"
	    "@code{assq} or @code{assv}.\n"
	    "\n"
	    " By way of illustration, @code{hashq-remove! table key} is\n"
	    "equivalent to @code{hashx-remove!  hashq assq #f table key}.")
#define FUNC_NAME s_scm_hashx_remove_x
{
  scm_t_ihashx_closure closure;
  closure.hash = hash;
  closure.assoc = assoc;
  return scm_hash_fn_remove_x (table, obj, scm_ihashx, scm_sloppy_assx,
                               (void *) &closure);
}
#undef FUNC_NAME

/* Hash table iterators */

static const char s_scm_hash_fold[];

SCM
scm_internal_hash_fold (SCM (*fn) (), void *closure, SCM init, SCM table)
{
  long i, n;
  SCM buckets, result = init;
  
  if (SCM_HASHTABLE_P (table))
    buckets = SCM_HASHTABLE_VECTOR (table);
  else
    buckets = table;
  
  n = SCM_SIMPLE_VECTOR_LENGTH (buckets);
  for (i = 0; i < n; ++i)
    {
      SCM ls = SCM_SIMPLE_VECTOR_REF (buckets, i), handle;
      while (!scm_is_null (ls))
	{
	  if (!scm_is_pair (ls))
	    scm_wrong_type_arg (s_scm_hash_fold, SCM_ARG3, buckets);
	  handle = SCM_CAR (ls);
	  if (!scm_is_pair (handle))
	    scm_wrong_type_arg (s_scm_hash_fold, SCM_ARG3, buckets);
	  result = fn (closure, SCM_CAR (handle), SCM_CDR (handle), result);
	  ls = SCM_CDR (ls);
	}
    }

  return result;
}

/* The following redundant code is here in order to be able to support
   hash-for-each-handle.  An alternative would have been to replace
   this code and scm_internal_hash_fold above with a single
   scm_internal_hash_fold_handles, but we don't want to promote such
   an API. */

static const char s_scm_hash_for_each[];

void
scm_internal_hash_for_each_handle (SCM (*fn) (), void *closure, SCM table)
{
  long i, n;
  SCM buckets;
  
  if (SCM_HASHTABLE_P (table))
    buckets = SCM_HASHTABLE_VECTOR (table);
  else
    buckets = table;
  
  n = SCM_SIMPLE_VECTOR_LENGTH (buckets);
  for (i = 0; i < n; ++i)
    {
      SCM ls = SCM_SIMPLE_VECTOR_REF (buckets, i), handle;
      while (!scm_is_null (ls))
	{
	  if (!scm_is_pair (ls))
	    scm_wrong_type_arg (s_scm_hash_for_each, SCM_ARG3, buckets);
	  handle = SCM_CAR (ls);
	  if (!scm_is_pair (handle))
	    scm_wrong_type_arg (s_scm_hash_for_each, SCM_ARG3, buckets);
	  fn (closure, handle);
	  ls = SCM_CDR (ls);
	}
    }
}

SCM_DEFINE (scm_hash_fold, "hash-fold", 3, 0, 0, 
            (SCM proc, SCM init, SCM table),
	    "An iterator over hash-table elements.\n"
            "Accumulates and returns a result by applying PROC successively.\n"
            "The arguments to PROC are \"(key value prior-result)\" where key\n"
            "and value are successive pairs from the hash table TABLE, and\n"
            "prior-result is either INIT (for the first application of PROC)\n"
            "or the return value of the previous application of PROC.\n"
            "For example, @code{(hash-fold acons '() tab)} will convert a hash\n"
            "table into an a-list of key-value pairs.")
#define FUNC_NAME s_scm_hash_fold
{
  SCM_VALIDATE_PROC (1, proc);
  if (!SCM_HASHTABLE_P (table))
    SCM_VALIDATE_VECTOR (3, table);
  return scm_internal_hash_fold (scm_call_3, (void *) SCM_UNPACK (proc), init, table);
}
#undef FUNC_NAME

static SCM
for_each_proc (void *proc, SCM handle)
{
  return scm_call_2 (SCM_PACK (proc), SCM_CAR (handle), SCM_CDR (handle));
}

SCM_DEFINE (scm_hash_for_each, "hash-for-each", 2, 0, 0, 
            (SCM proc, SCM table),
	    "An iterator over hash-table elements.\n"
            "Applies PROC successively on all hash table items.\n"
            "The arguments to PROC are \"(key value)\" where key\n"
            "and value are successive pairs from the hash table TABLE.")
#define FUNC_NAME s_scm_hash_for_each
{
  SCM_VALIDATE_PROC (1, proc);
  if (!SCM_HASHTABLE_P (table))
    SCM_VALIDATE_VECTOR (2, table);
  
  scm_internal_hash_for_each_handle (for_each_proc,
				     (void *) SCM_UNPACK (proc),
				     table);
  return SCM_UNSPECIFIED;
}
#undef FUNC_NAME

SCM_DEFINE (scm_hash_for_each_handle, "hash-for-each-handle", 2, 0, 0, 
            (SCM proc, SCM table),
	    "An iterator over hash-table elements.\n"
            "Applies PROC successively on all hash table handles.")
#define FUNC_NAME s_scm_hash_for_each_handle
{
  scm_t_trampoline_1 call = scm_trampoline_1 (proc);
  SCM_ASSERT (call, proc, 1, FUNC_NAME);
  if (!SCM_HASHTABLE_P (table))
    SCM_VALIDATE_VECTOR (2, table);
  
  scm_internal_hash_for_each_handle (call,
				     (void *) SCM_UNPACK (proc),
				     table);
  return SCM_UNSPECIFIED;
}
#undef FUNC_NAME

static SCM
map_proc (void *proc, SCM key, SCM data, SCM value)
{
  return scm_cons (scm_call_2 (SCM_PACK (proc), key, data), value);
}

SCM_DEFINE (scm_hash_map_to_list, "hash-map->list", 2, 0, 0, 
            (SCM proc, SCM table),
	    "An iterator over hash-table elements.\n"
            "Accumulates and returns as a list the results of applying PROC successively.\n"
            "The arguments to PROC are \"(key value)\" where key\n"
            "and value are successive pairs from the hash table TABLE.")
#define FUNC_NAME s_scm_hash_map_to_list
{
  SCM_VALIDATE_PROC (1, proc);
  if (!SCM_HASHTABLE_P (table))
    SCM_VALIDATE_VECTOR (2, table);
  return scm_internal_hash_fold (map_proc,
				 (void *) SCM_UNPACK (proc),
				 SCM_EOL,
				 table);
}
#undef FUNC_NAME

\f


void
scm_hashtab_prehistory ()
{
  /* Initialize weak cells.  */
  GC_word wcar_cell_bitmap[GC_BITMAP_SIZE (scm_t_cell)] = { 0 };
  GC_word wcdr_cell_bitmap[GC_BITMAP_SIZE (scm_t_cell)] = { 0 };

  /* In a weak-car cell, only the second word must be scanned for
     pointers.  */
  GC_set_bit (wcar_cell_bitmap, GC_WORD_OFFSET (scm_t_cell, word_1));
  wcar_cell_descr = GC_make_descriptor (wcar_cell_bitmap,
					GC_WORD_LEN (scm_t_cell));

  /* Conversely, in a weak-cdr cell, only the first word must be scanned for
     pointers.  */
  GC_set_bit (wcdr_cell_bitmap, GC_WORD_OFFSET (scm_t_cell, word_0));
  wcdr_cell_descr = GC_make_descriptor (wcdr_cell_bitmap,
					GC_WORD_LEN (scm_t_cell));


  /* Initialize the hashtab SMOB type.  */
  scm_tc16_hashtable = scm_make_smob_type (s_hashtable, 0);
  scm_set_smob_mark (scm_tc16_hashtable, scm_markcdr);
  scm_set_smob_print (scm_tc16_hashtable, hashtable_print);
  scm_set_smob_free (scm_tc16_hashtable, hashtable_free);
  scm_c_hook_add (&scm_after_gc_c_hook, rehash_after_gc, 0, 0);
}

void
scm_init_hashtab ()
{
#include "libguile/hashtab.x"
}

/*
  Local Variables:
  c-file-style: "gnu"
  End:
*/