1 /* str-llist.c: implementation of a linked list of strings.
2
3 Copyright 1993, 2008 Karl Berry.
4
5 This library is free software; you can redistribute it and/or
6 modify it under the terms of the GNU Lesser General Public
7 License as published by the Free Software Foundation; either
8 version 2.1 of the License, or (at your option) any later version.
9
10 This library is distributed in the hope that it will be useful,
11 but WITHOUT ANY WARRANTY; without even the implied warranty of
12 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
13 Lesser General Public License for more details.
14
15 You should have received a copy of the GNU Lesser General Public License
16 along with this library; if not, see <http://www.gnu.org/licenses/>. */
17
18 #include <kpathsea/config.h>
19
20 #include <kpathsea/str-llist.h>
21
22
23 /* Add the new string STR to the end of the list L. */
24
25 void
str_llist_add(str_llist_type * l,string str)26 str_llist_add (str_llist_type *l, string str)
27 {
28 str_llist_elt_type *e;
29 str_llist_elt_type *new_elt = XTALLOC1 (str_llist_elt_type);
30
31 /* The new element will be at the end of the list. */
32 STR_LLIST (*new_elt) = str;
33 STR_LLIST_MOVED (*new_elt) = false;
34 STR_LLIST_NEXT (*new_elt) = NULL;
35
36 /* Find the current end of the list. */
37 for (e = *l; e && STR_LLIST_NEXT (*e); e = STR_LLIST_NEXT (*e))
38 ;
39
40 if (!e)
41 *l = new_elt;
42 else
43 STR_LLIST_NEXT (*e) = new_elt;
44 }
45
46 /* Move an element towards the top. The idea is that when a file is
47 found in a given directory, later files will likely be in that same
48 directory, and looking for the file in all the directories in between
49 is thus a waste. */
50
51 void
str_llist_float(str_llist_type * l,str_llist_elt_type * mover)52 str_llist_float (str_llist_type *l, str_llist_elt_type *mover)
53 {
54 str_llist_elt_type *last_moved, *unmoved;
55
56 /* If we've already moved this element, never mind. */
57 if (STR_LLIST_MOVED (*mover))
58 return;
59
60 /* Find the first unmoved element (to insert before). We're
61 guaranteed this will terminate, since MOVER itself is currently
62 unmoved, and it must be in L (by hypothesis). */
63 for (last_moved = NULL, unmoved = *l; STR_LLIST_MOVED (*unmoved);
64 last_moved = unmoved, unmoved = STR_LLIST_NEXT (*unmoved))
65 ;
66
67 /* If we are the first unmoved element, nothing to relink. */
68 if (unmoved != mover)
69 { /* Remember `mover's current successor, so we can relink `mover's
70 predecessor to it. */
71 str_llist_elt_type *before_mover;
72 str_llist_elt_type *after_mover = STR_LLIST_NEXT (*mover);
73
74 /* Find `mover's predecessor. */
75 for (before_mover = unmoved; STR_LLIST_NEXT (*before_mover) != mover;
76 before_mover = STR_LLIST_NEXT (*before_mover))
77 ;
78
79 /* `before_mover' now links to `after_mover'. */
80 STR_LLIST_NEXT (*before_mover) = after_mover;
81
82 /* Insert `mover' before `unmoved' and after `last_moved' (or at
83 the head of the list). */
84 STR_LLIST_NEXT (*mover) = unmoved;
85 if (!last_moved)
86 *l = mover;
87 else
88 STR_LLIST_NEXT (*last_moved) = mover;
89 }
90
91 /* We've moved it. */
92 STR_LLIST_MOVED (*mover) = true;
93 }
94