hb-shaper.c

   1 // C99 port from c++ is protected by a GNU Lesser GPLv3
   2 // Copyright © 2013 Sylvain BERTRAND <sylvain.bertrand@gmail.com>
   3 //                                   <sylware@legeek.net>
   4 #include <string.h>
   5 #include <stdlib.h>
   6
   7 #include "hb.h"
   8 #include "hb-private.h"
   9 #include "hb-atomic-private.h"
  10 #include "hb-shaper-private.h"
  11
  12 static struct hb_shaper_pair_t all_shapers[] = {
  13 #ifdef HAVE_GRAPHITE2
  14   {"graphite2", hb_graphite2_shape},
  15 #endif
  16 #ifdef HAVE_OT
  17   {"ot", hb_ot_shape},
  18 #endif
  19   {"fallback", hb_fallback_shape}
  20 };
  21
  22 //Thread-safe, lock-free, shapers
  23
  24 static struct hb_shaper_pair_t *static_shapers = NULL;
  25
  26 struct hb_shaper_pair_t *
  27 hb_shapers_get(void)
  28 {
  29   while (1) {
  30     struct hb_shaper_pair_t *shapers = hb_atomic_ptr_get(&static_shapers);
  31     if (shapers)
  32       return shapers;
  33
  34     char *env = getenv("HB_SHAPER_LIST");
  35     if (!env || !*env) {
  36       void *expected = NULL;
  37       void *desired = &all_shapers[0];
  38       hb_atomic_ptr_cmpexch(&static_shapers, &expected, &desired);
  39       return all_shapers;
  40     }
  41
  42     //Not found; allocate one
  43     shapers = malloc(sizeof(all_shapers));
  44     if (!shapers) {
  45       void *expected = NULL;
  46       void *desired = &all_shapers[0];
  47       hb_atomic_ptr_cmpexch(&static_shapers, &expected, &desired);
  48       return all_shapers;
  49     }
  50
  51     memcpy(shapers, all_shapers, sizeof(all_shapers));
  52
  53     //Reorder shaper list to prefer requested shapers.
  54     unsigned i = 0;
  55     char *end, *p = env;
  56     for (;;) {
  57       end = strchr(p, ',');
  58       if (!end)
  59         end = p + strlen(p);
  60
  61       for (unsigned j = i; j < ARRAY_LENGTH(all_shapers); ++j)
  62         if (end - p == (int)strlen(shapers[j].name) &&
  63                                     0 == strncmp(shapers[j].name, p, end - p)) {
  64          //Reorder this shaper to position i
  65          struct hb_shaper_pair_t t = shapers[j];
  66          memmove(&shapers[i + 1], &shapers[i], sizeof (shapers[i]) * (j - i));
  67          shapers[i] = t;
  68          i++;
  69         }
  70
  71       if (!*end)
  72         break;
  73       else
  74         p = end + 1;
  75     }
  76
  77     void *expected = NULL;
  78     if (hb_atomic_ptr_cmpexch(&static_shapers, &expected, &shapers)) {
  79       return shapers;
  80     }
  81     free(shapers);
  82   }
  83 }