harfbuzz-ng roll

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

+/*
+ * Copyright © 2012  Google, Inc.
+ *
+ *  This is part of HarfBuzz, a text shaping library.
+ *
+ * Permission is hereby granted, without written agreement and without
+ * license or royalty fees, to use, copy, modify, and distribute this
+ * software and its documentation for any purpose, provided that the
+ * above copyright notice and the following two paragraphs appear in
+ * all copies of this software.
+ *
+ * IN NO EVENT SHALL THE COPYRIGHT HOLDER BE LIABLE TO ANY PARTY FOR
+ * DIRECT, INDIRECT, SPECIAL, INCIDENTAL, OR CONSEQUENTIAL DAMAGES
+ * ARISING OUT OF THE USE OF THIS SOFTWARE AND ITS DOCUMENTATION, EVEN
+ * IF THE COPYRIGHT HOLDER HAS BEEN ADVISED OF THE POSSIBILITY OF SUCH
+ * DAMAGE.
+ *
+ * THE COPYRIGHT HOLDER SPECIFICALLY DISCLAIMS ANY WARRANTIES, INCLUDING,
+ * BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND
+ * FITNESS FOR A PARTICULAR PURPOSE.  THE SOFTWARE PROVIDED HEREUNDER IS
+ * ON AN "AS IS" BASIS, AND THE COPYRIGHT HOLDER HAS NO OBLIGATION TO
+ * PROVIDE MAINTENANCE, SUPPORT, UPDATES, ENHANCEMENTS, OR MODIFICATIONS.
+ *
+ * Google Author(s): Behdad Esfahbod
+ */
+
+#include "hb-private.hh"
+
+#include "hb-shaper-private.hh"
+
+
+static const hb_shaper_pair_t all_shapers[] = {
+#define HB_SHAPER_IMPLEMENT(name) {#name, _hb_##name##_shape},
+#include "hb-shaper-list.hh"
+#undef HB_SHAPER_IMPLEMENT
+};
+
+
+/* Thread-safe, lock-free, shapers */
+
+static const hb_shaper_pair_t *static_shapers;
+
+static
+void free_static_shapers (void)
+{
+  if (unlikely (static_shapers != all_shapers))
+    free ((void *) static_shapers);
+}
+
+const hb_shaper_pair_t *
+_hb_shapers_get (void)
+{
+retry:
+  hb_shaper_pair_t *shapers = (hb_shaper_pair_t *) hb_atomic_ptr_get (&static_shapers);
+
+  if (unlikely (!shapers))
+  {
+    char *env = getenv ("HB_SHAPER_LIST");
+    if (!env || !*env) {
+      (void) hb_atomic_ptr_cmpexch (&static_shapers, NULL, &all_shapers[0]);
+      return (const hb_shaper_pair_t *) all_shapers;
+    }
+
+    /* Not found; allocate one. */
+    shapers = (hb_shaper_pair_t *) malloc (sizeof (all_shapers));
+    if (unlikely (!shapers)) {
+      (void) hb_atomic_ptr_cmpexch (&static_shapers, NULL, &all_shapers[0]);
+      return (const hb_shaper_pair_t *) all_shapers;
+    }
+
+    memcpy (shapers, all_shapers, sizeof (all_shapers));
+
+     /* Reorder shaper list to prefer requested shapers. */
+    unsigned int i = 0;
+    char *end, *p = env;
+    for (;;) {
+      end = strchr (p, ',');
+      if (!end)
+        end = p + strlen (p);
+
+      for (unsigned int j = i; j < ARRAY_LENGTH (all_shapers); j++)
+        if (end - p == (int) strlen (shapers[j].name) &&
+            0 == strncmp (shapers[j].name, p, end - p))
+        {
+          /* Reorder this shaper to position i */
+         struct hb_shaper_pair_t t = shapers[j];
+         memmove (&shapers[i + 1], &shapers[i], sizeof (shapers[i]) * (j - i));
+         shapers[i] = t;
+         i++;
+        }
+
+      if (!*end)
+        break;
+      else
+        p = end + 1;
+    }
+
+    if (!hb_atomic_ptr_cmpexch (&static_shapers, NULL, shapers)) {
+      free (shapers);
+      goto retry;
+    }
+
+#ifdef HAVE_ATEXIT
+    atexit (free_static_shapers); /* First person registers atexit() callback. */
+#endif
+  }
+
+  return shapers;
+}