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 45 void free_static_shapers (void) 46 { 47 retry: 48 hb_shaper_pair_t *shapers = (hb_shaper_pair_t *) hb_atomic_ptr_get (&static_shapers); 49 if (!hb_atomic_ptr_cmpexch (&static_shapers, shapers, nullptr)) 50 goto retry; 51 52 if (unlikely (shapers != all_shapers)) 53 free ((void *) shapers); 54 } 55 #endif 56 57 const hb_shaper_pair_t * 58 _hb_shapers_get (void) 59 { 60 retry: 61 hb_shaper_pair_t *shapers = (hb_shaper_pair_t *) hb_atomic_ptr_get (&static_shapers); 62 63 if (unlikely (!shapers)) 64 { 65 char *env = getenv ("HB_SHAPER_LIST"); 66 if (!env || !*env) { 67 (void) hb_atomic_ptr_cmpexch (&static_shapers, nullptr, &all_shapers[0]); 68 return (const hb_shaper_pair_t *) all_shapers; 69 } 70 71 /* Not found; allocate one. */ 72 shapers = (hb_shaper_pair_t *) calloc (1, sizeof (all_shapers)); 73 if (unlikely (!shapers)) { 74 (void) hb_atomic_ptr_cmpexch (&static_shapers, nullptr, &all_shapers[0]); 75 return (const hb_shaper_pair_t *) all_shapers; 76 } 77 78 memcpy (shapers, all_shapers, sizeof (all_shapers)); 79 80 /* Reorder shaper list to prefer requested shapers. */ 81 unsigned int i = 0; 82 char *end, *p = env; 83 for (;;) { 84 end = strchr (p, ','); 85 if (!end) 86 end = p + strlen (p); 87 88 for (unsigned int j = i; j < ARRAY_LENGTH (all_shapers); j++) 89 if (end - p == (int) strlen (shapers[j].name) && 90 0 == strncmp (shapers[j].name, p, end - p)) 91 { 92 /* Reorder this shaper to position i */ 93 struct hb_shaper_pair_t t = shapers[j]; 94 memmove (&shapers[i + 1], &shapers[i], sizeof (shapers[i]) * (j - i)); 95 shapers[i] = t; 96 i++; 97 } 98 99 if (!*end) 100 break; 101 else 102 p = end + 1; 103 } 104 105 if (!hb_atomic_ptr_cmpexch (&static_shapers, nullptr, shapers)) { 106 free (shapers); 107 goto retry; 108 } 109 110 #ifdef HB_USE_ATEXIT 111 atexit (free_static_shapers); /* First person registers atexit() callback. */ 112 #endif 113 } 114 115 return shapers; 116 }