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 static inline
free_static_shapers(void)44 void free_static_shapers (void)
45 {
46 if (unlikely (static_shapers != all_shapers))
47 free ((void *) static_shapers);
48 }
49
50 const hb_shaper_pair_t *
_hb_shapers_get(void)51 _hb_shapers_get (void)
52 {
53 retry:
54 hb_shaper_pair_t *shapers = (hb_shaper_pair_t *) hb_atomic_ptr_get (&static_shapers);
55
56 if (unlikely (!shapers))
57 {
58 char *env = getenv ("HB_SHAPER_LIST");
59 if (!env || !*env) {
60 (void) hb_atomic_ptr_cmpexch (&static_shapers, NULL, &all_shapers[0]);
61 return (const hb_shaper_pair_t *) all_shapers;
62 }
63
64 /* Not found; allocate one. */
65 shapers = (hb_shaper_pair_t *) malloc (sizeof (all_shapers));
66 if (unlikely (!shapers)) {
67 (void) hb_atomic_ptr_cmpexch (&static_shapers, NULL, &all_shapers[0]);
68 return (const hb_shaper_pair_t *) all_shapers;
69 }
70
71 memcpy (shapers, all_shapers, sizeof (all_shapers));
72
73 /* Reorder shaper list to prefer requested shapers. */
74 unsigned int i = 0;
75 char *end, *p = env;
76 for (;;) {
77 end = strchr (p, ',');
78 if (!end)
79 end = p + strlen (p);
80
81 for (unsigned int j = i; j < ARRAY_LENGTH (all_shapers); j++)
82 if (end - p == (int) strlen (shapers[j].name) &&
83 0 == strncmp (shapers[j].name, p, end - p))
84 {
85 /* Reorder this shaper to position i */
86 struct hb_shaper_pair_t t = shapers[j];
87 memmove (&shapers[i + 1], &shapers[i], sizeof (shapers[i]) * (j - i));
88 shapers[i] = t;
89 i++;
90 }
91
92 if (!*end)
93 break;
94 else
95 p = end + 1;
96 }
97
98 if (!hb_atomic_ptr_cmpexch (&static_shapers, NULL, shapers)) {
99 free (shapers);
100 goto retry;
101 }
102
103 #ifdef HB_USE_ATEXIT
104 atexit (free_static_shapers); /* First person registers atexit() callback. */
105 #endif
106 }
107
108 return shapers;
109 }
110