--- /dev/null
+/*
+ * Copyright © 2019 Facebook, 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.
+ *
+ * Facebook Author(s): Behdad Esfahbod
+ */
+
+#ifndef HB_POOL_HH
+#define HB_POOL_HH
+
+#include "hb.hh"
+
+/* Memory pool for persistent allocation of small objects. */
+
+template <typename T, unsigned ChunkLen = 16>
+struct hb_pool_t
+{
+ hb_pool_t () : next (nullptr) {}
+
+ ~hb_pool_t ()
+ {
+ next = nullptr;
+ + hb_iter (chunks)
+ | hb_apply ([] (chunk_t *_) { ::free (_); })
+ ;
+ }
+
+ T* alloc ()
+ {
+ if (unlikely (!next))
+ {
+ if (unlikely (!chunks.alloc (chunks.length + 1))) return nullptr;
+ chunk_t *chunk = (chunk_t *) malloc (sizeof (chunk_t));
+ if (unlikely (!chunk)) return nullptr;
+ chunks.push (chunk);
+ next = chunk->thread ();
+ }
+
+ T* obj = next;
+ next = * ((T**) next);
+
+ *obj = Null (T);
+
+ return obj;
+ }
+
+ void free (T* obj)
+ {
+ * (T**) obj = next;
+ next = obj;
+ }
+
+ private:
+
+ static_assert (ChunkLen > 1, "");
+ static_assert (sizeof (T) >= sizeof (void *), "");
+ static_assert (alignof (T) % sizeof (void *) == 0, "");
+
+ struct chunk_t
+ {
+ T* thread ()
+ {
+ for (unsigned i = 0; i < ARRAY_LENGTH (arrayZ) - 1; i++)
+ * (T**) &arrayZ[i] = &arrayZ[i + 1];
+
+ * (T**) &arrayZ[ARRAY_LENGTH (arrayZ) - 1] = nullptr;
+
+ return arrayZ;
+ }
+
+ T arrayZ[ChunkLen];
+ };
+
+ T* next;
+ hb_vector_t<chunk_t *> chunks;
+};
+
+
+#endif /* HB_POOL_HH */