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+/* An expandable hash tables datatype.
+   Copyright (C) 1999, 2000, 2002, 2003, 2004, 2005, 2009, 2010
+   Free Software Foundation, Inc.
+   Contributed by Vladimir Makarov (vmakarov@cygnus.com).
+
+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 of the License, 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; see the file COPYING.  If not, write to
+the Free Software Foundation, 51 Franklin Street - Fifth Floor,
+Boston, MA 02110-1301, USA.  */
+
+/* This package implements basic hash table functionality.  It is possible
+   to search for an entry, create an entry and destroy an entry.
+
+   Elements in the table are generic pointers.
+
+   The size of the table is not fixed; if the occupancy of the table
+   grows too high the hash table will be expanded.
+
+   The abstract data implementation is based on generalized Algorithm D
+   from Knuth's book "The art of computer programming".  Hash table is
+   expanded by creation of new hash table and transferring elements from
+   the old table to the new table.  */
+
+#ifndef __HASHTAB_H__
+#define __HASHTAB_H__
+
+#ifdef __cplusplus
+extern "C" {
+#endif /* __cplusplus */
+
+/* The type for a hash code.  */
+typedef unsigned int hashval_t;
+
+/* Callback function pointer types.  */
+
+/* Calculate hash of a table entry.  */
+typedef hashval_t (*htab_hash) (const void *);
+
+/* Compare a table entry with a possible entry.  The entry already in
+   the table always comes first, so the second element can be of a
+   different type (but in this case htab_find and htab_find_slot
+   cannot be used; instead the variants that accept a hash value
+   must be used).  */
+typedef int (*htab_eq) (const void *, const void *);
+
+/* Cleanup function called whenever a live element is removed from
+   the hash table.  */
+typedef void (*htab_del) (void *);
+
+/* Function called by htab_traverse for each live element.  The first
+   arg is the slot of the element (which can be passed to htab_clear_slot
+   if desired), the second arg is the auxiliary pointer handed to
+   htab_traverse.  Return 1 to continue scan, 0 to stop.  */
+typedef int (*htab_trav) (void **, void *);
+
+/* Hash tables are of the following type.  The structure
+   (implementation) of this type is not needed for using the hash
+   tables.  All work with hash table should be executed only through
+   functions mentioned below. */
+
+struct htab
+{
+  /* Pointer to hash function.  */
+  htab_hash hash_f;
+
+  /* Pointer to comparison function.  */
+  htab_eq eq_f;
+
+  /* Pointer to cleanup function.  */
+  htab_del del_f;
+
+  /* Table itself.  */
+  void **entries;
+
+  /* Current size (in entries) of the hash table */
+  size_t size;
+
+  /* Current number of elements including also deleted elements */
+  size_t n_elements;
+
+  /* Current number of deleted elements in the table */
+  size_t n_deleted;
+
+  /* The following member is used for debugging. Its value is number
+     of all calls of `htab_find_slot' for the hash table. */
+  unsigned int searches;
+
+  /* The following member is used for debugging.  Its value is number
+     of collisions fixed for time of work with the hash table. */
+  unsigned int collisions;
+
+  /* This is non-zero if we are allowed to return NULL for function calls
+     that allocate memory.  */
+  int return_allocation_failure;
+};
+
+typedef struct htab *htab_t;
+
+/* An enum saying whether we insert into the hash table or not.  */
+enum insert_option {NO_INSERT, INSERT};
+
+/* The prototypes of the package functions. */
+
+/* This function is like htab_create, but may return NULL if memory
+   allocation fails, and also signals that htab_find_slot_with_hash and
+   htab_find_slot are allowed to return NULL when inserting.  */
+extern htab_t	htab_try_create	(size_t, htab_hash, htab_eq, htab_del);
+extern void	htab_delete	(htab_t);
+extern void	htab_empty	(htab_t);
+
+extern void    *htab_find	(htab_t, const void *);
+extern void    **htab_find_slot	(htab_t, const void *, enum insert_option);
+extern void    *htab_find_with_hash (htab_t, const void *, hashval_t);
+extern void    **htab_find_slot_with_hash (htab_t, const void *, hashval_t,
+					  enum insert_option);
+extern void	htab_clear_slot	(htab_t, void **);
+extern void	htab_remove_elt	(htab_t, void *);
+
+extern void	htab_traverse	(htab_t, htab_trav, void *);
+
+extern size_t	htab_size	(htab_t);
+extern size_t	htab_elements	(htab_t);
+extern double	htab_collisions	(htab_t);
+
+/* Utility function.  */
+unsigned long higher_prime_number (unsigned long);
+
+/* A hash function for pointers.  */
+extern htab_hash htab_hash_pointer;
+
+/* An equality function for pointers.  */
+extern htab_eq htab_eq_pointer;
+
+#ifndef NDEBUG
+
+#include <stdio.h>
+
+typedef void (*htab_dumpfn) (FILE *, const void *);
+typedef void *(*htab_restorefn) (FILE *);
+
+extern void	htab_dump (htab_t, const char *, htab_dumpfn);
+extern void	htab_restore (htab_t, const char *, htab_restorefn);
+
+#endif
+
+#ifdef __cplusplus
+}
+#endif /* __cplusplus */
+
+#endif /* __HASHTAB_H */