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+/* Integer-keyed hash table functions.
+
+   Copyright (C) 1995 Free Software Foundation, Inc.
+
+   Written by Miles Bader <miles@gnu.ai.mit.edu>
+
+   This program 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.
+
+   This program 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 this program; if not, write to the Free Software
+   Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA. */
+
+#ifndef __IHASH_H__
+#define __IHASH_H__
+
+/* ---------------------------------------------------------------- */
+
+typedef struct ihash *ihash_t;
+
+struct ihash
+{
+  /* An array storing the elements in the hash table (each a void *).  */
+  void **tab;
+
+  /* An array storing the integer key for each element.  */
+  int *ids;
+
+  /* An array storing pointers to the `location pointers' for each element.
+     These are used as cookies for quick 'n' easy removal.  */
+  void ****locps;		/* four, count them, four stars */
+
+  /* The length of all these arrays.  */
+  int size;
+
+  /* When freeing or overwriting an element, this function, if non-NULL, is
+     called with the value as the first argument, and CLEANUP_ARG as the
+     second argument.  */
+  void (*cleanup)(void *element, void *arg);
+  void *cleanup_arg;
+};
+
+/* 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);
+
+/* Free HT and all resources it consumes.  */
+void ihash_free(ihash_t 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);
+
+/* 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 call 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);
+
+/* 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);
+
+/* 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 *));
+
+/* 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);
+
+/* 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 **ht_locp);
+
+#endif /* __IHASH_H__ */