1 /*
2 * Copyright © 2012 Google, Inc.
3 *
4 * This is part of HarfBuzz, a text shaping library.
5 *
6 * Permission is hereby granted, without written agreement and without
7 * license or royalty fees, to use, copy, modify, and distribute this
8 * software and its documentation for any purpose, provided that the
9 * above copyright notice and the following two paragraphs appear in
10 * all copies of this software.
11 *
12 * IN NO EVENT SHALL THE COPYRIGHT HOLDER BE LIABLE TO ANY PARTY FOR
13 * DIRECT, INDIRECT, SPECIAL, INCIDENTAL, OR CONSEQUENTIAL DAMAGES
14 * ARISING OUT OF THE USE OF THIS SOFTWARE AND ITS DOCUMENTATION, EVEN
15 * IF THE COPYRIGHT HOLDER HAS BEEN ADVISED OF THE POSSIBILITY OF SUCH
16 * DAMAGE.
17 *
18 * THE COPYRIGHT HOLDER SPECIFICALLY DISCLAIMS ANY WARRANTIES, INCLUDING,
19 * BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND
20 * FITNESS FOR A PARTICULAR PURPOSE. THE SOFTWARE PROVIDED HEREUNDER IS
21 * ON AN "AS IS" BASIS, AND THE COPYRIGHT HOLDER HAS NO OBLIGATION TO
22 * PROVIDE MAINTENANCE, SUPPORT, UPDATES, ENHANCEMENTS, OR MODIFICATIONS.
23 *
24 * Google Author(s): Behdad Esfahbod
25 */
26
27 #include "hb-private.hh"
28 #include "hb-shaper-private.hh"
29 #include "hb-atomic-private.hh"
30
31
32 static const hb_shaper_pair_t all_shapers[] = {
33 #define HB_SHAPER_IMPLEMENT(name) {#name, _hb_##name##_shape},
34 #include "hb-shaper-list.hh"
35 #undef HB_SHAPER_IMPLEMENT
36 };
37
38
39 /* Thread-safe, lock-free, shapers */
40
41 static const hb_shaper_pair_t *static_shapers;
42
43 #ifdef HB_USE_ATEXIT
44 static
free_static_shapers(void)45 void free_static_shapers (void)
46 {
47 if (unlikely (static_shapers != all_shapers))
48 free ((void *) static_shapers);
49 }
50 #endif
51
52 const hb_shaper_pair_t *
_hb_shapers_get(void)53 _hb_shapers_get (void)
54 {
55 retry:
56 hb_shaper_pair_t *shapers = (hb_shaper_pair_t *) hb_atomic_ptr_get (&static_shapers);
57
58 if (unlikely (!shapers))
59 {
60 char *env = getenv ("HB_SHAPER_LIST");
61 if (!env || !*env) {
62 (void) hb_atomic_ptr_cmpexch (&static_shapers, nullptr, &all_shapers[0]);
63 return (const hb_shaper_pair_t *) all_shapers;
64 }
65
66 /* Not found; allocate one. */
67 shapers = (hb_shaper_pair_t *) calloc (1, sizeof (all_shapers));
68 if (unlikely (!shapers)) {
69 (void) hb_atomic_ptr_cmpexch (&static_shapers, nullptr, &all_shapers[0]);
70 return (const hb_shaper_pair_t *) all_shapers;
71 }
72
73 memcpy (shapers, all_shapers, sizeof (all_shapers));
74
75 /* Reorder shaper list to prefer requested shapers. */
76 unsigned int i = 0;
77 char *end, *p = env;
78 for (;;) {
79 end = strchr (p, ',');
80 if (!end)
81 end = p + strlen (p);
82
83 for (unsigned int j = i; j < ARRAY_LENGTH (all_shapers); j++)
84 if (end - p == (int) strlen (shapers[j].name) &&
85 0 == strncmp (shapers[j].name, p, end - p))
86 {
87 /* Reorder this shaper to position i */
88 struct hb_shaper_pair_t t = shapers[j];
89 memmove (&shapers[i + 1], &shapers[i], sizeof (shapers[i]) * (j - i));
90 shapers[i] = t;
91 i++;
92 }
93
94 if (!*end)
95 break;
96 else
97 p = end + 1;
98 }
99
100 if (!hb_atomic_ptr_cmpexch (&static_shapers, nullptr, shapers)) {
101 free (shapers);
102 goto retry;
103 }
104
105 #ifdef HB_USE_ATEXIT
106 atexit (free_static_shapers); /* First person registers atexit() callback. */
107 #endif
108 }
109
110 return shapers;
111 }
112