8.2.x/libltdl/slist.c

/* slist.c -- generalised singly linked lists

   Copyright (C) 2000, 2004, 2007-2009, 2011-2015 Free Software
   Foundation, Inc.
   Written by Gary V. Vaughan, 2000

   NOTE: The canonical source of this file is maintained with the
   GNU Libtool package.  Report bugs to bug-libtool@gnu.org.

GNU Libltdl 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 of the License, or (at your option) any later version.

As a special exception to the GNU Lesser General Public License,
if you distribute this file as part of a program or library that
is built using GNU Libtool, you may include this file under the
same distribution terms that you use for the rest of that program.

GNU Libltdl 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 GNU Libltdl; see the file COPYING.LIB.  If not, a
copy can be downloaded from  http://www.gnu.org/licenses/lgpl.html,
or obtained by writing to the Free Software Foundation, Inc.,
51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
*/

#include <assert.h>

#include "slist.h"
#include <stdlib.h>

static SList *  slist_sort_merge    (SList *left, SList *right,
                                     SListCompare *compare, void *userdata);


/* Call DELETE repeatedly on each element of HEAD.

   CAVEAT: If you call this when HEAD is the start of a list of boxed
           items, you must remember that each item passed back to your
           DELETE function will be a boxed item that must be slist_unbox()ed
           before operating on its contents.

   e.g. void boxed_delete (void *item) { item_free (slist_unbox (item)); }
        ...
          slist = slist_delete (slist, boxed_delete);
        ...
*/
SList *
slist_delete (SList *head, void (*delete_fct) (void *item))
{
  assert (delete_fct);

  while (head)
    {
      SList *next = head->next;
      (*delete_fct) (head);
      head = next;
    }

  return 0;
}

/* Call FIND repeatedly with MATCHDATA and each item of *PHEAD, until
   FIND returns non-NULL, or the list is exhausted.  If a match is found
   the matching item is destructively removed from *PHEAD, and the value
   returned by the matching call to FIND is returned.

   CAVEAT: To avoid memory leaks, unless you already have the address of
           the stale item, you should probably return that from FIND if
           it makes a successful match.  Don't forget to slist_unbox()
           every item in a boxed list before operating on its contents.   */
SList *
slist_remove (SList **phead, SListCallback *find, void *matchdata)
{
  SList *stale = 0;
  void *result = 0;

  assert (find);

  if (!phead || !*phead)
    return 0;

  /* Does the head of the passed list match? */
  result = (*find) (*phead, matchdata);
  if (result)
    {
      stale = *phead;
      *phead = stale->next;
    }
  /* what about the rest of the elements? */
  else
    {
      SList *head;
      for (head = *phead; head->next; head = head->next)
        {
          result = (*find) (head->next, matchdata);
          if (result)
            {
              stale             = head->next;
              head->next        = stale->next;
              break;
            }
        }
    }

  return (SList *) result;
}

/* Call FIND repeatedly with each element of SLIST and MATCHDATA, until
   FIND returns non-NULL, or the list is exhausted.  If a match is found
   the value returned by the matching call to FIND is returned. */
void *
slist_find (SList *slist, SListCallback *find, void *matchdata)
{
  void *result = 0;

  assert (find);

  for (; slist; slist = slist->next)
    {
      result = (*find) (slist, matchdata);
      if (result)
        break;
    }

  return result;
}

/* Return a single list, composed by destructively concatenating the
   items in HEAD and TAIL.  The values of HEAD and TAIL are undefined
   after calling this function.

   CAVEAT: Don't mix boxed and unboxed items in a single list.

   e.g.  slist1 = slist_concat (slist1, slist2);  */
SList *
slist_concat (SList *head, SList *tail)
{
  SList *last;

  if (!head)
    {
      return tail;
    }

  last = head;
  while (last->next)
    last = last->next;

  last->next = tail;

  return head;
}

/* Return a single list, composed by destructively appending all of
   the items in SLIST to ITEM.  The values of ITEM and SLIST are undefined
   after calling this function.

   CAVEAT:  Don't mix boxed and unboxed items in a single list.

   e.g.  slist1 = slist_cons (slist_box (data), slist1);  */
SList *
slist_cons (SList *item, SList *slist)
{
  if (!item)
    {
      return slist;
    }

  assert (!item->next);

  item->next = slist;
  return item;
}

/* Return a list starting at the second item of SLIST.  */
SList *
slist_tail (SList *slist)
{
  return slist ? slist->next : NULL;
}

/* Return a list starting at the Nth item of SLIST.  If SLIST is less
   than N items long, NULL is returned.  Just to be confusing, list items
   are counted from 1, to get the 2nd element of slist:

   e.g. shared_list = slist_nth (slist, 2);  */
SList *
slist_nth (SList *slist, size_t n)
{
  for (;n > 1 && slist; n--)
    slist = slist->next;

  return slist;
}

/* Return the number of items in SLIST.  We start counting from 1, so
   the length of a list with no items is 0, and so on.  */
size_t
slist_length (SList *slist)
{
  size_t n;

  for (n = 0; slist; ++n)
    slist = slist->next;

  return n;
}

/* Destructively reverse the order of items in SLIST.  The value of SLIST
   is undefined after calling this function.

  CAVEAT: You must store the result of this function, or you might not
          be able to get all the items except the first one back again.

  e.g.    slist = slist_reverse (slist);  */
SList *
slist_reverse (SList *slist)
{
  SList *result = 0;
  SList *next;

  while (slist)
    {
      next              = slist->next;
      slist->next       = result;
      result            = slist;
      slist             = next;
    }

  return result;
}

/* Call FOREACH once for each item in SLIST, passing both the item and
   USERDATA on each call. */
void *
slist_foreach (SList *slist, SListCallback *foreach, void *userdata)
{
  void *result = 0;

  assert (foreach);

  while (slist)
    {
      SList *next = slist->next;
      result = (*foreach) (slist, userdata);

      if (result)
        break;

      slist = next;
    }

  return result;
}

/* Destructively merge the items of two ordered lists LEFT and RIGHT,
   returning a single sorted list containing the items of both --  Part of
   the quicksort algorithm.  The values of LEFT and RIGHT are undefined
   after calling this function.

   At each iteration, add another item to the merged list by taking the
   lowest valued item from the head of either LEFT or RIGHT, determined
   by passing those items and USERDATA to COMPARE.  COMPARE should return
   less than 0 if the head of LEFT has the lower value, greater than 0 if
   the head of RIGHT has the lower value, otherwise 0.  */
static SList *
slist_sort_merge (SList *left, SList *right, SListCompare *compare,
                  void *userdata)
{
  SList merged, *insert;

  insert = &merged;

  while (left && right)
    {
      if ((*compare) (left, right, userdata) <= 0)
        {
          insert = insert->next = left;
          left = left->next;
        }
      else
        {
          insert = insert->next = right;
          right = right->next;
        }
    }

  insert->next = left ? left : right;

  return merged.next;
}

/* Perform a destructive quicksort on the items in SLIST, by repeatedly
   calling COMPARE with a pair of items from SLIST along with USERDATA
   at every iteration.  COMPARE is a function as defined above for
   slist_sort_merge().  The value of SLIST is undefined after calling
   this function.

   e.g.  slist = slist_sort (slist, compare, 0);  */
SList *
slist_sort (SList *slist, SListCompare *compare, void *userdata)
{
  SList *left, *right;

  if (!slist)
    return slist;

  /* Be sure that LEFT and RIGHT never contain the same item.  */
  left = slist;
  right = slist->next;

  if (!right)
    return left;

  /* Skip two items with RIGHT and one with SLIST, until RIGHT falls off
     the end.  SLIST must be about half way along.  */
  while (right && (right = right->next))
    {
      if (!right || !(right = right->next))
        break;
      slist = slist->next;
    }
  right = slist->next;
  slist->next = 0;

  /* Sort LEFT and RIGHT, then merge the two.  */
  return slist_sort_merge (slist_sort (left, compare, userdata),
                           slist_sort (right, compare, userdata),
                           compare, userdata);
}


/* Aside from using the functions above to manage chained structures of
   any type that has a NEXT pointer as its first field, SLISTs can
   be comprised of boxed items.  The boxes are chained together in
   that case, so there is no need for a NEXT field in the item proper.
   Some care must be taken to slist_box and slist_unbox each item in
   a boxed list at the appropriate points to avoid leaking the memory
   used for the boxes.  It us usually a very bad idea to mix boxed and
   non-boxed items in a single list.  */

/* Return a 'boxed' freshly mallocated 1 element list containing
   USERDATA.  */
SList *
slist_box (const void *userdata)
{
  SList *item = (SList *) malloc (sizeof *item);

  if (item)
    {
      item->next     = 0;
      item->userdata = userdata;
    }

  return item;
}

/* Return the contents of a 'boxed' ITEM, recycling the box itself.  */
void *
slist_unbox (SList *item)
{
  void *userdata = 0;

  if (item)
    {
      /* Strip the const, because responsibility for this memory
         passes to the caller on return.  */
      userdata = (void *) item->userdata;
      free (item);
    }

  return userdata;
}
1	/* slist.c -- generalised singly linked lists
2
3	Copyright (C) 2000, 2004, 2007-2009, 2011-2015 Free Software
4	Foundation, Inc.
5	Written by Gary V. Vaughan, 2000
6
7	NOTE: The canonical source of this file is maintained with the
8	GNU Libtool package. Report bugs to bug-libtool@gnu.org.
9
10	GNU Libltdl is free software; you can redistribute it and/or
11	modify it under the terms of the GNU Lesser General Public
12	License as published by the Free Software Foundation; either
13	version 2 of the License, or (at your option) any later version.
14
15	As a special exception to the GNU Lesser General Public License,
16	if you distribute this file as part of a program or library that
17	is built using GNU Libtool, you may include this file under the
18	same distribution terms that you use for the rest of that program.
19
20	GNU Libltdl is distributed in the hope that it will be useful,
21	but WITHOUT ANY WARRANTY; without even the implied warranty of
22	MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
23	GNU Lesser General Public License for more details.
24
25	You should have received a copy of the GNU Lesser General Public
26	License along with GNU Libltdl; see the file COPYING.LIB. If not, a
27	copy can be downloaded from http://www.gnu.org/licenses/lgpl.html,
28	or obtained by writing to the Free Software Foundation, Inc.,
29	51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
30	*/
31
32	#include <assert.h>
33
34	#include "slist.h"
35	#include <stdlib.h>
36
37	static SList * slist_sort_merge (SList left, SList right,
38	SListCompare compare, void userdata);
39
40
41	/* Call DELETE repeatedly on each element of HEAD.
42
43	CAVEAT: If you call this when HEAD is the start of a list of boxed
44	items, you must remember that each item passed back to your
45	DELETE function will be a boxed item that must be slist_unbox()ed
46	before operating on its contents.
47
48	e.g. void boxed_delete (void *item) { item_free (slist_unbox (item)); }
49	...
50	slist = slist_delete (slist, boxed_delete);
51	...
52	*/
53	SList *
54	slist_delete (SList head, void (delete_fct) (void *item))
55	{
56	assert (delete_fct);
57
58	while (head)
59	{
60	SList *next = head->next;
61	(*delete_fct) (head);
62	head = next;
63	}
64
65	return 0;
66	}
67
68	/* Call FIND repeatedly with MATCHDATA and each item of *PHEAD, until
69	FIND returns non-NULL, or the list is exhausted. If a match is found
70	the matching item is destructively removed from *PHEAD, and the value
71	returned by the matching call to FIND is returned.
72
73	CAVEAT: To avoid memory leaks, unless you already have the address of
74	the stale item, you should probably return that from FIND if
75	it makes a successful match. Don't forget to slist_unbox()
76	every item in a boxed list before operating on its contents. */
77	SList *
78	slist_remove (SList *phead, SListCallback find, void *matchdata)
79	{
80	SList *stale = 0;
81	void *result = 0;
82
83	assert (find);
84
85	if (!phead \|\| !*phead)
86	return 0;
87
88	/* Does the head of the passed list match? */
89	result = (find) (phead, matchdata);
90	if (result)
91	{
92	stale = *phead;
93	*phead = stale->next;
94	}
95	/* what about the rest of the elements? */
96	else
97	{
98	SList *head;
99	for (head = *phead; head->next; head = head->next)
100	{
101	result = (*find) (head->next, matchdata);
102	if (result)
103	{
104	stale = head->next;
105	head->next = stale->next;
106	break;
107	}
108	}
109	}
110
111	return (SList *) result;
112	}
113
114	/* Call FIND repeatedly with each element of SLIST and MATCHDATA, until
115	FIND returns non-NULL, or the list is exhausted. If a match is found
116	the value returned by the matching call to FIND is returned. */
117	void *
118	slist_find (SList slist, SListCallback find, void *matchdata)
119	{
120	void *result = 0;
121
122	assert (find);
123
124	for (; slist; slist = slist->next)
125	{
126	result = (*find) (slist, matchdata);
127	if (result)
128	break;
129	}
130
131	return result;
132	}
133
134	/* Return a single list, composed by destructively concatenating the
135	items in HEAD and TAIL. The values of HEAD and TAIL are undefined
136	after calling this function.
137
138	CAVEAT: Don't mix boxed and unboxed items in a single list.
139
140	e.g. slist1 = slist_concat (slist1, slist2); */
141	SList *
142	slist_concat (SList head, SList tail)
143	{
144	SList *last;
145
146	if (!head)
147	{
148	return tail;
149	}
150
151	last = head;
152	while (last->next)
153	last = last->next;
154
155	last->next = tail;
156
157	return head;
158	}
159
160	/* Return a single list, composed by destructively appending all of
161	the items in SLIST to ITEM. The values of ITEM and SLIST are undefined
162	after calling this function.
163
164	CAVEAT: Don't mix boxed and unboxed items in a single list.
165
166	e.g. slist1 = slist_cons (slist_box (data), slist1); */
167	SList *
168	slist_cons (SList item, SList slist)
169	{
170	if (!item)
171	{
172	return slist;
173	}
174
175	assert (!item->next);
176
177	item->next = slist;
178	return item;
179	}
180
181	/* Return a list starting at the second item of SLIST. */
182	SList *
183	slist_tail (SList *slist)
184	{
185	return slist ? slist->next : NULL;
186	}
187
188	/* Return a list starting at the Nth item of SLIST. If SLIST is less
189	than N items long, NULL is returned. Just to be confusing, list items
190	are counted from 1, to get the 2nd element of slist:
191
192	e.g. shared_list = slist_nth (slist, 2); */
193	SList *
194	slist_nth (SList *slist, size_t n)
195	{
196	for (;n > 1 && slist; n--)
197	slist = slist->next;
198
199	return slist;
200	}
201
202	/* Return the number of items in SLIST. We start counting from 1, so
203	the length of a list with no items is 0, and so on. */
204	size_t
205	slist_length (SList *slist)
206	{
207	size_t n;
208
209	for (n = 0; slist; ++n)
210	slist = slist->next;
211
212	return n;
213	}
214
215	/* Destructively reverse the order of items in SLIST. The value of SLIST
216	is undefined after calling this function.
217
218	CAVEAT: You must store the result of this function, or you might not
219	be able to get all the items except the first one back again.
220
221	e.g. slist = slist_reverse (slist); */
222	SList *
223	slist_reverse (SList *slist)
224	{
225	SList *result = 0;
226	SList *next;
227
228	while (slist)
229	{
230	next = slist->next;
231	slist->next = result;
232	result = slist;
233	slist = next;
234	}
235
236	return result;
237	}
238
239	/* Call FOREACH once for each item in SLIST, passing both the item and
240	USERDATA on each call. */
241	void *
242	slist_foreach (SList slist, SListCallback foreach, void *userdata)
243	{
244	void *result = 0;
245
246	assert (foreach);
247
248	while (slist)
249	{
250	SList *next = slist->next;
251	result = (*foreach) (slist, userdata);
252
253	if (result)
254	break;
255
256	slist = next;
257	}
258
259	return result;
260	}
261
262	/* Destructively merge the items of two ordered lists LEFT and RIGHT,
263	returning a single sorted list containing the items of both -- Part of
264	the quicksort algorithm. The values of LEFT and RIGHT are undefined
265	after calling this function.
266
267	At each iteration, add another item to the merged list by taking the
268	lowest valued item from the head of either LEFT or RIGHT, determined
269	by passing those items and USERDATA to COMPARE. COMPARE should return
270	less than 0 if the head of LEFT has the lower value, greater than 0 if
271	the head of RIGHT has the lower value, otherwise 0. */
272	static SList *
273	slist_sort_merge (SList left, SList right, SListCompare *compare,
274	void *userdata)
275	{
276	SList merged, *insert;
277
278	insert = &merged;
279
280	while (left && right)
281	{
282	if ((*compare) (left, right, userdata) <= 0)
283	{
284	insert = insert->next = left;
285	left = left->next;
286	}
287	else
288	{
289	insert = insert->next = right;
290	right = right->next;
291	}
292	}
293
294	insert->next = left ? left : right;
295
296	return merged.next;
297	}
298
299	/* Perform a destructive quicksort on the items in SLIST, by repeatedly
300	calling COMPARE with a pair of items from SLIST along with USERDATA
301	at every iteration. COMPARE is a function as defined above for
302	slist_sort_merge(). The value of SLIST is undefined after calling
303	this function.
304
305	e.g. slist = slist_sort (slist, compare, 0); */
306	SList *
307	slist_sort (SList slist, SListCompare compare, void *userdata)
308	{
309	SList left, right;
310
311	if (!slist)
312	return slist;
313
314	/* Be sure that LEFT and RIGHT never contain the same item. */
315	left = slist;
316	right = slist->next;
317
318	if (!right)
319	return left;
320
321	/* Skip two items with RIGHT and one with SLIST, until RIGHT falls off
322	the end. SLIST must be about half way along. */
323	while (right && (right = right->next))
324	{
325	if (!right \|\| !(right = right->next))
326	break;
327	slist = slist->next;
328	}
329	right = slist->next;
330	slist->next = 0;
331
332	/* Sort LEFT and RIGHT, then merge the two. */
333	return slist_sort_merge (slist_sort (left, compare, userdata),
334	slist_sort (right, compare, userdata),
335	compare, userdata);
336	}
337
338
339	/* Aside from using the functions above to manage chained structures of
340	any type that has a NEXT pointer as its first field, SLISTs can
341	be comprised of boxed items. The boxes are chained together in
342	that case, so there is no need for a NEXT field in the item proper.
343	Some care must be taken to slist_box and slist_unbox each item in
344	a boxed list at the appropriate points to avoid leaking the memory
345	used for the boxes. It us usually a very bad idea to mix boxed and
346	non-boxed items in a single list. */
347
348	/* Return a 'boxed' freshly mallocated 1 element list containing
349	USERDATA. */
350	SList *
351	slist_box (const void *userdata)
352	{
353	SList item = (SList ) malloc (sizeof *item);
354
355	if (item)
356	{
357	item->next = 0;
358	item->userdata = userdata;
359	}
360
361	return item;
362	}
363
364	/* Return the contents of a 'boxed' ITEM, recycling the box itself. */
365	void *
366	slist_unbox (SList *item)
367	{
368	void *userdata = 0;
369
370	if (item)
371	{
372	/* Strip the const, because responsibility for this memory
373	passes to the caller on return. */
374	userdata = (void *) item->userdata;
375	free (item);
376	}
377
378	return userdata;
379	}
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