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
32static 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
41static const hb_shaper_pair_t *static_shapers;
42
43static inline
44void free_static_shapers (void)
45{
46  if (unlikely (static_shapers != all_shapers))
47    free ((void *) static_shapers);
48}
49
50const hb_shaper_pair_t *
51_hb_shapers_get (void)
52{
53retry:
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 HAVE_ATEXIT
104    atexit (free_static_shapers); /* First person registers atexit() callback. */
105#endif
106  }
107
108  return shapers;
109}
110