third_party/harfbuzz-ng/src/hb-shaper.cc

   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
  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 *
  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 HAVE_ATEXIT
 104     atexit (free_static_shapers); /* First person registers atexit() callback. */
 105 #endif
 106   }
 107
 108   return shapers;
 109 }