Initial revision

1 files changed, 292 insertions, 0 deletions

diff --git a/libihash/ihash.c b/libihash/ihash.c
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+/* Integer-keyed hash table functions.
+
+   Copyright (C) 1993, 1994, 1995 Free Software Foundation, Inc.
+   
+   This file is part of the GNU Hurd.
+
+   Written by Michael I. Bushnell; revised by Miles Bader <miles@gnu>.
+   
+   The GNU Hurd is free software; you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation; either version 2, or (at your option)
+   any later version.
+   
+   The GNU Hurd 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 General Public License for more details.
+   
+   You should have received a copy of the GNU General Public License
+   along with the GNU Hurd; see the file COPYING.  If not, write to
+   the Free Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA.  */
+
+#include <string.h>
+#include <stdlib.h>
+
+#include "ihash.h"
+
+/* ---------------------------------------------------------------- */
+
+/* When an entry in a hashtable's TAB array is HASH_EMPTY, that location is
+   available, and none of the other arrays are valid at that index.  */
+#define HASH_EMPTY 0
+
+/* When an entry in a hashtable's TAB array is HASH_DEL, that location is
+   available, and none of the other arrays are valid at that index.  The
+   difference from HASH_EMPTY is that searches continue though HASH_DEL and
+   stop at HASH_EMPTY.  */
+#define HASH_DEL ((void *) -1)
+
+/* Returns an initial index in HT for the key ID, for search for an entry.  */
+#define HASH(ht, id) ((id) % (ht)->size)
+/* Returns subsequent indices in HT for the key ID, given the previous one.  */
+#define REHASH(ht, id, h) (((id) + (h)) % (ht)->size)
+
+/* ---------------------------------------------------------------- */
+
+static inline int
+index_empty(ihash_t ht, int index)
+{
+  return ht->tab[index] == HASH_EMPTY || ht->tab[index] == HASH_DEL;
+}
+
+static inline int
+index_valid(ihash_t ht, int index, int id)
+{
+  return !index_empty(ht, index) && ht->ids[index] == id;
+}
+
+/* Given a hash table HT, and a key ID, finds the index in the table of that
+   key.  You must subsequently check to see whether the given index is valid
+   (with index_valid() or index_empty()).  */
+static inline int
+find_index(ihash_t ht, int id)
+{
+  int h, firsth = -1;
+
+  for (h = HASH(ht, id); 
+       ht->tab[h] != HASH_EMPTY && ht->ids[h] != id && h != firsth;
+       h = REHASH(ht, id, h))
+    if (firsth == -1)
+      firsth = h;
+
+  return h;
+}
+
+/* ---------------------------------------------------------------- */
+
+/* Create an integer hash table and return it in HT.  If a memory allocation
+   error occurs, ENOMEM is returned, otherwise 0.  */
+error_t
+ihash_create(ihash_t *ht)
+{
+  *ht = malloc(sizeof(struct ihash));
+  if (*ht == NULL)
+    return ENOMEM;
+  (*ht)->size = 0;
+  return 0;
+}
+
+/* Free HT and all resources it consumes.  */
+void 
+ihash_free(ihash_t ht)
+{
+  void (*cleanup)(void *value, void *arg) = ht->cleanup;
+
+  if (cleanup)
+    {
+      int i;
+      void *arg = ht->cleanup_arg;
+      for (i = 0; i < ht->size; i++)
+	if (!index_empty(ht, i))
+	  (*cleanup)(ht->tab[i], arg);
+    }
+
+  if (ht->size > 0)
+    {
+      free(ht->tab);
+      free(ht->ids);
+      free(ht->locps);
+    }
+
+  free(ht);
+}
+
+/* Sets HT's element cleanup function to CLEANUP, and its second argument to
+   ARG.  CLEANUP will be called on the value of any element to be
+   subsequently overwritten or deleted, with ARG as the second argument.  */
+void
+ihash_set_cleanup(ihash_t ht,
+		  void (*cleanup)(void *value, void *arg),
+		  void *arg)
+{
+  ht->cleanup = cleanup;
+  ht->cleanup_arg = arg;
+}
+
+/* ---------------------------------------------------------------- */
+
+/* Add ITEM to the hash table HT under the key ID.  LOCP is the address of a
+   pointer located in ITEM; If non-NULL, LOCP should point to a variable of
+   type void **, and will be filled with a pointer that may be used as an
+   argument to ihash_locp_remove().  The variable pointed to by LOCP may be
+   written to subsequently between this called and when the element is
+   deleted, so you can't stash its value elsewhere and hope to use the
+   stashed value with ihash_locp_remove().  If a memory allocation error
+   occurs, ENOMEM is returned, otherwise 0.  */
+error_t
+ihash_add(ihash_t ht, int id, void *item, void ***locp)
+{
+  if (ht->size)
+    {
+      int h, firsth = -1;
+
+      /* Search for for an empty or deleted space.  */
+      for (h = HASH(ht, id); 
+	   ht->tab[h] != HASH_EMPTY && ht->tab[h] != HASH_DEL && h != firsth;
+	   h = REHASH(ht, id, h))
+	if (firsth == -1)
+	  firsth = h;
+
+      if (index_empty(ht, h) || ht->ids[h] == id)
+	{
+	  if (!index_empty(ht, h) && ht->cleanup)
+	    ht->cleanup(ht->tab[h], ht->cleanup_arg);
+
+	  ht->tab[h] = item;
+	  ht->ids[h] = id;
+	  ht->locps[h] = locp;
+
+	  if (locp)
+	    *locp = &ht->tab[h];
+
+	  return 0;
+	}
+    }
+
+  {
+    int i;
+    void **entry;
+    int old_size = ht->size;
+    void **old_tab = ht->tab;
+    void ****old_locps = ht->locps;
+    int *old_ids = ht->ids;
+
+    ht->size = nextprime (2 * old_size);
+    ht->tab = malloc(ht->size * sizeof (void *));
+    ht->locps = malloc (ht->size * sizeof (void ***));
+    ht->ids = malloc (ht->size * sizeof (int));
+      
+    if (ht->tab == NULL || ht->locps == NULL || ht->ids == NULL)
+      /* Memory allocation error; back out our changes and fail...  */
+      {
+	if (ht->tab) free(ht->tab);
+	if (ht->locps) free(ht->locps);
+	if (ht->ids) free(ht->ids);
+
+	ht->size = old_size;
+	ht->tab = old_tab;
+	ht->locps = old_locps;
+	ht->ids = old_ids;
+
+	return ENOMEM;
+      }
+
+    for (i = ht->size, entry = ht->tab; i > 0; i--, entry++)
+      *entry = HASH_EMPTY;
+
+    /* We have to rehash this again?  */
+    if (old_size > 0)
+      for (i = 0; i < old_size; i++)
+	if (old_tab[i] != HASH_EMPTY && old_tab[i] != HASH_DEL)
+	  ihash_add(ht, old_ids[i], old_tab[i], old_locps[i]);
+
+    /* Finally add the new element!  */
+    ihash_add(ht, id, item, locp);
+  
+    if (old_size > 0)
+      {
+	free(old_tab);
+	free(old_locps);
+	free(old_ids);
+      }
+
+    return 0;
+  }
+}
+
+/* Find and return the item in hash table HT with key ID, or NULL if it
+   doesn't exist.  */
+void *
+ihash_find (ihash_t ht, int id)
+{
+  if (ht->size == 0)
+    return 0;
+  else
+    {
+      int index = find_index(ht, id);
+      return index_valid(ht, index, id) ? ht->tab[index] : 0;
+    }
+}
+
+/* ---------------------------------------------------------------- */
+
+/* Call function FUN of one arg for each element of HT.  FUN's only arg is a
+   pointer to the value stored in the hash table.  If FUN ever returns
+   non-zero, then iteration stops and ihash_iterate returns that value,
+   otherwise it (eventually) returns 0.  */
+error_t
+ihash_iterate(ihash_t ht, error_t (*fun)(void *))
+{
+  int i;
+  for (i = 0; i < ht->size; i++)
+    if (!index_empty(ht, i))
+      {
+	error_t err = fun(ht->tab[i]);
+	if (err)
+	  return err;
+      }
+  return 0;
+}
+
+/* Remove the entry at LOCP from the hashtable HT.  LOCP is as returned from
+   an earlier call to ihash_add().  This call should be faster than
+   ihash_remove().  HT can be NULL, in which case the call still succeeds,
+   but no cleanup can be done.  */
+void
+ihash_locp_remove(ihash_t ht, void **locp)
+{
+  void *tag = HASH_DEL;
+
+  if (ht != NULL)
+    {
+      int index = locp - ht->tab;
+      int next_index = REHASH(ht, ht->ids[index], index);
+
+      if (ht && ht->cleanup)
+	ht->cleanup(*locp, ht->cleanup_arg);
+
+      /* If the next position in this hash chain is empty, then we don't need
+	 to use HASH_DEL (which only serves to prevent breaking the chain to
+	 preserve lookups past this point).  */
+      if (ht->tab[next_index] == HASH_EMPTY)
+	tag = HASH_EMPTY;
+    }
+
+  *locp = tag;
+}
+
+/* Remove the entry with a key of ID from HT.  If anything was actually
+   removed, 1 is returned, otherwise (if there was no such element), 0.  */
+int
+ihash_remove(ihash_t ht, int id)
+{
+  int index = find_index(ht, id);
+  if (index_valid(ht, index, id))
+    {
+      ihash_locp_remove(ht, &ht->tab[index]);
+      return 1;
+    }
+  else
+    return 0;
+}