--- a/ChangeLog	Tue Dec 11 20:44:55 2018 +0100
+++ b/ChangeLog	Tue Dec 11 20:56:20 2018 +0100
@@ -1,3 +1,10 @@
+2018-12-11  Bruno Haible  <bruno@clisp.org>
+
+	omap: New module.
+	* lib/gl_omap.h: New file.
+	* lib/gl_omap.c: New file.
+	* modules/omap: New file.
+
 2018-12-11  Bruno Haible  <bruno@clisp.org>
 
 	hash-set, linkedhash-set: Reduce code duplication.

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/lib/gl_omap.c	Tue Dec 11 20:56:20 2018 +0100
@@ -0,0 +1,3 @@
+#include <config.h>
+#define GL_OMAP_INLINE _GL_EXTERN_INLINE
+#include "gl_omap.h"

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/lib/gl_omap.h	Tue Dec 11 20:56:20 2018 +0100
@@ -0,0 +1,379 @@
+/* Abstract ordered map data type.
+   Copyright (C) 2006-2007, 2009-2018 Free Software Foundation, Inc.
+   Written by Bruno Haible <bruno@clisp.org>, 2018.
+
+   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 3 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.  If not, see <https://www.gnu.org/licenses/>.  */
+
+#ifndef _GL_OMAP_H
+#define _GL_OMAP_H
+
+#include <stdbool.h>
+#include <stddef.h>
+
+#ifndef _GL_INLINE_HEADER_BEGIN
+ #error "Please include config.h first."
+#endif
+_GL_INLINE_HEADER_BEGIN
+#ifndef GL_OMAP_INLINE
+# define GL_OMAP_INLINE _GL_INLINE
+#endif
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+
+/* gl_omap is an abstract ordered map data type.  It can contain any number
+   of (key, value) pairs, where
+     - keys and values are objects ('void *' or 'const void *' pointers),
+     - The (key, value) pairs are ordered by the key, in the order of a given
+       comparator function.
+     - There are no (key, value1) and (key, value2) pairs with the same key
+       (in the sense of the comparator function).
+
+   There are several implementations of this ordered map datatype, optimized
+   for different operations or for memory.  You can start using the simplest
+   ordered map implementation, GL_ARRAY_OMAP, and switch to a different
+   implementation later, when you realize which operations are performed
+   the most frequently.  The API of the different implementations is exactly
+   the same; when switching to a different implementation, you only have to
+   change the gl_omap_create call.
+
+   The implementations are:
+     GL_ARRAY_OMAP        a growable array
+     GL_AVLTREE_OMAP      a binary tree (AVL tree)
+     GL_RBTREE_OMAP       a binary tree (red-black tree)
+
+   The memory consumption is asymptotically the same: O(1) for every pair
+   in the map.  When looking more closely at the average memory consumed
+   for an pair, GL_ARRAY_OMAP is the most compact representation, and
+   GL_AVLTREE_OMAP, GL_RBTREE_OMAP need more memory.
+
+   The guaranteed average performance of the operations is, for a map of
+   n pairs:
+
+   Operation                  ARRAY     TREE
+
+   gl_omap_size                O(1)     O(1)
+   gl_omap_get               O(log n) O(log n)
+   gl_omap_put                 O(n)   O(log n)
+   gl_omap_remove              O(n)   O(log n)
+   gl_omap_search            O(log n) O(log n)
+   gl_omap_search_atleast    O(log n) O(log n)
+   gl_omap_iterator            O(1)   O(log n)
+   gl_omap_iterator_next       O(1)   O(log n)
+ */
+
+/* -------------------------- gl_omap_t Data Type -------------------------- */
+
+/* Type of function used to compare two keys.  Same as for qsort().
+   NULL denotes pointer comparison.  */
+typedef int (*gl_mapkey_compar_fn) (const void *key1, const void *key2);
+
+/* Type of function used to dispose a key once a (key, value) pair is removed
+   from a map.  NULL denotes a no-op.  */
+typedef void (*gl_mapkey_dispose_fn) (const void *key);
+
+/* Type of function used to dispose a value once a (key, value) pair is removed
+   from a map.  NULL denotes a no-op.  */
+typedef void (*gl_mapvalue_dispose_fn) (const void *value);
+
+/* Type of function used to compare a key with a threshold.
+   Return true if the key is greater or equal than the threshold.  */
+typedef bool (*gl_mapkey_threshold_fn) (const void *key, const void *threshold);
+
+struct gl_omap_impl;
+/* Type representing an entire ordered map.  */
+typedef struct gl_omap_impl * gl_omap_t;
+
+struct gl_omap_implementation;
+/* Type representing a ordered map datatype implementation.  */
+typedef const struct gl_omap_implementation * gl_omap_implementation_t;
+
+#if 0 /* Unless otherwise specified, these are defined inline below.  */
+
+/* Create an empty map.
+   IMPLEMENTATION is one of GL_ARRAY_OMAP, GL_AVLTREE_OMAP, GL_RBTREE_OMAP.
+   COMPAR_FN is a key comparison function or NULL.
+   KDISPOSE_FN is a key disposal function or NULL.
+   VDISPOSE_FN is a value disposal function or NULL.  */
+/* declared in gl_xomap.h */
+extern gl_omap_t gl_omap_create_empty (gl_omap_implementation_t implementation,
+                                       gl_mapkey_compar_fn compar_fn,
+                                       gl_mapkey_dispose_fn kdispose_fn,
+                                       gl_mapvalue_dispose_fn vdispose_fn);
+/* Likewise.  Return NULL upon out-of-memory.  */
+extern gl_omap_t gl_omap_nx_create_empty (gl_omap_implementation_t implementation,
+                                          gl_mapkey_compar_fn compar_fn,
+                                          gl_mapkey_dispose_fn kdispose_fn,
+                                          gl_mapvalue_dispose_fn vdispose_fn);
+
+/* Return the current number of pairs in an ordered map.  */
+extern size_t gl_omap_size (gl_omap_t map);
+
+/* Search whether a pair with the given key is already in the ordered map.
+   Return the value if found, or NULL if not present in the map.  */
+extern const void * gl_omap_get (gl_omap_t map, const void *key);
+
+/* Search whether a pair with the given key is already in the ordered map.
+   Return true and set *VALUEP to the value if found.
+   Return false if not present in the map.  */
+extern bool gl_omap_search (gl_omap_t map, const void *key,
+                            const void **valuep);
+
+/* Search the pair with the least key in the ordered map that compares
+   greater or equal to the given THRESHOLD.  The representation of the
+   THRESHOLD is defined by the THRESHOLD_FN.
+   Return true and store the found pair in *KEYP and *VALUEP if found.
+   Otherwise return false.  */
+extern bool gl_omap_search_atleast (gl_omap_t map,
+                                    gl_mapkey_threshold_fn threshold_fn,
+                                    const void *threshold,
+                                    const void **keyp, const void **valuep);
+
+/* Add a pair to an ordered map.
+   Return true if a pair with the given key was not already in the map and so
+   this pair was added.
+   Return false if a pair with the given key was already in the map and only
+   its value was replaced.  */
+/* declared in gl_xomap.h */
+extern bool gl_omap_put (gl_omap_t map, const void *key, const void *value);
+/* Likewise.  Return -1 upon out-of-memory.  */
+extern int gl_omap_nx_put (gl_omap_t map, const void *key, const void *value)
+#if __GNUC__ > 3 || (__GNUC__ == 3 && __GNUC_MINOR__ >= 4)
+  __attribute__ ((__warn_unused_result__))
+#endif
+  ;
+
+/* Add a pair to an ordered map and retrieve the previous value.
+   Return true if a pair with the given key was not already in the map and so
+   this pair was added.
+   Return false and set *OLDVALUEP to the previous value, if a pair with the
+   given key was already in the map and only its value was replaced.  */
+/* declared in gl_xomap.h */
+extern bool gl_omap_getput (gl_omap_t map, const void *key, const void *value,
+                            const void **oldvaluep);
+/* Likewise.  Return -1 upon out-of-memory.  */
+extern int gl_omap_nx_getput (gl_omap_t map, const void *key, const void *value,
+                              const void **oldvaluep)
+#if __GNUC__ > 3 || (__GNUC__ == 3 && __GNUC_MINOR__ >= 4)
+  __attribute__ ((__warn_unused_result__))
+#endif
+  ;
+
+/* Remove a pair from an ordered map.
+   Return true if the key was found and its pair removed.
+   Return false otherwise.  */
+extern bool gl_omap_remove (gl_omap_t map, const void *key);
+
+/* Remove a pair from an ordered map and retrieve the previous value.
+   Return true and set *OLDVALUEP to the previous value, if the key was found
+   and its pair removed.
+   Return false otherwise.  */
+extern bool gl_omap_getremove (gl_omap_t map, const void *key,
+                               const void **oldvaluep);
+
+/* Free an entire ordered map.
+   (But this call does not free the keys and values of the pairs in the map.
+   It only invokes the KDISPOSE_FN on each key and the VDISPOSE_FN on each value
+   of the pairs in the map.)  */
+extern void gl_omap_free (gl_omap_t map);
+
+#endif /* End of inline and gl_xomap.h-defined functions.  */
+
+/* ---------------------- gl_omap_iterator_t Data Type ---------------------- */
+
+/* Functions for iterating through an ordered map.  */
+
+/* Type of an iterator that traverses an ordered map.
+   This is a fixed-size struct, so that creation of an iterator doesn't need
+   memory allocation on the heap.  */
+typedef struct
+{
+  /* For fast dispatch of gl_omap_iterator_next.  */
+  const struct gl_omap_implementation *vtable;
+  /* For detecting whether the last returned pair was removed.  */
+  gl_omap_t map;
+  size_t count;
+  /* Other, implementation-private fields.  */
+  void *p; void *q;
+  size_t i; size_t j;
+} gl_omap_iterator_t;
+
+#if 0 /* These are defined inline below.  */
+
+/* Create an iterator traversing an ordered map.
+   The map's contents must not be modified while the iterator is in use,
+   except for modifying the value of the last returned key or removing the
+   last returned pair.  */
+extern gl_omap_iterator_t gl_omap_iterator (gl_omap_t map);
+
+/* If there is a next pair, store the next pair in *KEYP and *VALUEP, advance
+   the iterator, and return true.  Otherwise, return false.  */
+extern bool gl_omap_iterator_next (gl_omap_iterator_t *iterator,
+                                   const void **keyp, const void **valuep);
+
+/* Free an iterator.  */
+extern void gl_omap_iterator_free (gl_omap_iterator_t *iterator);
+
+#endif /* End of inline functions.  */
+
+/* ------------------------- Implementation Details ------------------------- */
+
+struct gl_omap_implementation
+{
+  /* gl_omap_t functions.  */
+  gl_omap_t (*nx_create_empty) (gl_omap_implementation_t implementation,
+                                gl_mapkey_compar_fn compar_fn,
+                                gl_mapkey_dispose_fn kdispose_fn,
+                                gl_mapvalue_dispose_fn vdispose_fn);
+  size_t (*size) (gl_omap_t map);
+  bool (*search) (gl_omap_t map, const void *key, const void **valuep);
+  bool (*search_atleast) (gl_omap_t map,
+                          gl_mapkey_threshold_fn threshold_fn,
+                          const void *threshold,
+                          const void **keyp, const void **valuep);
+  int (*nx_getput) (gl_omap_t map, const void *key, const void *value,
+                    const void **oldvaluep);
+  bool (*getremove) (gl_omap_t map, const void *key, const void **oldvaluep);
+  void (*omap_free) (gl_omap_t map);
+  /* gl_omap_iterator_t functions.  */
+  gl_omap_iterator_t (*iterator) (gl_omap_t map);
+  bool (*iterator_next) (gl_omap_iterator_t *iterator,
+                         const void **keyp, const void **valuep);
+  void (*iterator_free) (gl_omap_iterator_t *iterator);
+};
+
+struct gl_omap_impl_base
+{
+  const struct gl_omap_implementation *vtable;
+  gl_mapkey_compar_fn compar_fn;
+  gl_mapkey_dispose_fn kdispose_fn;
+  gl_mapvalue_dispose_fn vdispose_fn;
+};
+
+/* Define most functions of this file as accesses to the
+   struct gl_omap_implementation.  */
+
+GL_OMAP_INLINE gl_omap_t
+gl_omap_nx_create_empty (gl_omap_implementation_t implementation,
+                         gl_mapkey_compar_fn compar_fn,
+                         gl_mapkey_dispose_fn kdispose_fn,
+                         gl_mapvalue_dispose_fn vdispose_fn)
+{
+  return implementation->nx_create_empty (implementation, compar_fn,
+                                          kdispose_fn, vdispose_fn);
+}
+
+GL_OMAP_INLINE size_t
+gl_omap_size (gl_omap_t map)
+{
+  return ((const struct gl_omap_impl_base *) map)->vtable->size (map);
+}
+
+GL_OMAP_INLINE bool
+gl_omap_search (gl_omap_t map, const void *key, const void **valuep)
+{
+  return ((const struct gl_omap_impl_base *) map)->vtable
+         ->search (map, key, valuep);
+}
+
+GL_OMAP_INLINE bool
+gl_omap_search_atleast (gl_omap_t map,
+                        gl_mapkey_threshold_fn threshold_fn,
+                        const void *threshold,
+                        const void **keyp, const void **valuep)
+{
+  return ((const struct gl_omap_impl_base *) map)->vtable
+         ->search_atleast (map, threshold_fn, threshold, keyp, valuep);
+}
+
+GL_OMAP_INLINE int
+#if __GNUC__ > 3 || (__GNUC__ == 3 && __GNUC_MINOR__ >= 4)
+  __attribute__ ((__warn_unused_result__))
+#endif
+gl_omap_nx_getput (gl_omap_t map, const void *key, const void *value,
+                   const void **oldvaluep)
+{
+  return ((const struct gl_omap_impl_base *) map)->vtable
+         ->nx_getput (map, key, value, oldvaluep);
+}
+
+GL_OMAP_INLINE bool
+gl_omap_getremove (gl_omap_t map, const void *key, const void **oldvaluep)
+{
+  return ((const struct gl_omap_impl_base *) map)->vtable
+         ->getremove (map, key, oldvaluep);
+}
+
+GL_OMAP_INLINE void
+gl_omap_free (gl_omap_t map)
+{
+  ((const struct gl_omap_impl_base *) map)->vtable->omap_free (map);
+}
+
+GL_OMAP_INLINE gl_omap_iterator_t
+gl_omap_iterator (gl_omap_t map)
+{
+  return ((const struct gl_omap_impl_base *) map)->vtable->iterator (map);
+}
+
+GL_OMAP_INLINE bool
+gl_omap_iterator_next (gl_omap_iterator_t *iterator,
+                       const void **keyp, const void **valuep)
+{
+  return iterator->vtable->iterator_next (iterator, keyp, valuep);
+}
+
+GL_OMAP_INLINE void
+gl_omap_iterator_free (gl_omap_iterator_t *iterator)
+{
+  iterator->vtable->iterator_free (iterator);
+}
+
+/* Define the convenience functions, that is, the functions that are independent
+   of the implementation.  */
+
+GL_OMAP_INLINE const void *
+gl_omap_get (gl_omap_t map, const void *key)
+{
+  const void *value = NULL;
+  gl_omap_search (map, key, &value);
+  return value;
+}
+
+GL_OMAP_INLINE int
+#if __GNUC__ > 3 || (__GNUC__ == 3 && __GNUC_MINOR__ >= 4)
+  __attribute__ ((__warn_unused_result__))
+#endif
+gl_omap_nx_put (gl_omap_t map, const void *key, const void *value)
+{
+  const void *oldvalue;
+  return gl_omap_nx_getput (map, key, value, &oldvalue);
+}
+
+GL_OMAP_INLINE bool
+gl_omap_remove (gl_omap_t map, const void *key)
+{
+  const void *oldvalue;
+  return gl_omap_getremove (map, key, &oldvalue);
+}
+
+#ifdef __cplusplus
+}
+#endif
+
+_GL_INLINE_HEADER_END
+
+#endif /* _GL_OMAP_H */

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/modules/omap	Tue Dec 11 20:56:20 2018 +0100
@@ -0,0 +1,24 @@
+Description:
+Abstract ordered map data type.
+
+Files:
+lib/gl_omap.h
+lib/gl_omap.c
+
+Depends-on:
+extern-inline
+stdbool
+
+configure.ac:
+
+Makefile.am:
+lib_SOURCES += gl_omap.h gl_omap.c
+
+Include:
+"gl_omap.h"
+
+License:
+GPL
+
+Maintainer:
+all