101 lines
2.4 KiB
C++
101 lines
2.4 KiB
C++
/*
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* Copyright © 2019 Facebook, Inc.
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*
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* This is part of HarfBuzz, a text shaping library.
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*
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* Permission is hereby granted, without written agreement and without
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* license or royalty fees, to use, copy, modify, and distribute this
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* software and its documentation for any purpose, provided that the
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* above copyright notice and the following two paragraphs appear in
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* all copies of this software.
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*
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* IN NO EVENT SHALL THE COPYRIGHT HOLDER BE LIABLE TO ANY PARTY FOR
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* DIRECT, INDIRECT, SPECIAL, INCIDENTAL, OR CONSEQUENTIAL DAMAGES
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* ARISING OUT OF THE USE OF THIS SOFTWARE AND ITS DOCUMENTATION, EVEN
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* IF THE COPYRIGHT HOLDER HAS BEEN ADVISED OF THE POSSIBILITY OF SUCH
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* DAMAGE.
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*
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* THE COPYRIGHT HOLDER SPECIFICALLY DISCLAIMS ANY WARRANTIES, INCLUDING,
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* BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND
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* FITNESS FOR A PARTICULAR PURPOSE. THE SOFTWARE PROVIDED HEREUNDER IS
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* ON AN "AS IS" BASIS, AND THE COPYRIGHT HOLDER HAS NO OBLIGATION TO
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* PROVIDE MAINTENANCE, SUPPORT, UPDATES, ENHANCEMENTS, OR MODIFICATIONS.
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*
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* Facebook Author(s): Behdad Esfahbod
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*/
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#ifndef HB_POOL_HH
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#define HB_POOL_HH
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#include "hb.hh"
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/* Memory pool for persistent allocation of small objects. */
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template <typename T, unsigned ChunkLen = 16>
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struct hb_pool_t
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{
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hb_pool_t () : next (nullptr) {}
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~hb_pool_t () { fini (); }
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void fini ()
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{
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next = nullptr;
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for (chunk_t *_ : chunks) ::free (_);
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chunks.fini ();
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}
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T* alloc ()
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{
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if (unlikely (!next))
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{
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if (unlikely (!chunks.alloc (chunks.length + 1))) return nullptr;
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chunk_t *chunk = (chunk_t *) calloc (1, sizeof (chunk_t));
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if (unlikely (!chunk)) return nullptr;
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chunks.push (chunk);
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next = chunk->thread ();
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}
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T* obj = next;
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next = * ((T**) next);
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memset (obj, 0, sizeof (T));
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return obj;
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}
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void free (T* obj)
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{
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* (T**) obj = next;
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next = obj;
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}
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private:
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static_assert (ChunkLen > 1, "");
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static_assert (sizeof (T) >= sizeof (void *), "");
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static_assert (alignof (T) % alignof (void *) == 0, "");
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struct chunk_t
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{
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T* thread ()
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{
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for (unsigned i = 0; i < ARRAY_LENGTH (arrayZ) - 1; i++)
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* (T**) &arrayZ[i] = &arrayZ[i + 1];
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* (T**) &arrayZ[ARRAY_LENGTH (arrayZ) - 1] = nullptr;
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return arrayZ;
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}
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T arrayZ[ChunkLen];
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};
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T* next;
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hb_vector_t<chunk_t *> chunks;
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};
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#endif /* HB_POOL_HH */
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