1/*
2 * Copyright © 2019 Facebook, 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 * Facebook Author(s): Behdad Esfahbod
25 */
26
27#ifndef HB_POOL_HH
28#define HB_POOL_HH
29
30#include "hb.hh"
31
32/* Memory pool for persistent allocation of small objects. */
33
34template <typename T, unsigned ChunkLen = 16>
35struct hb_pool_t
36{
37 hb_pool_t () : next (nullptr) {}
38 ~hb_pool_t () { fini (); }
39
40 void fini ()
41 {
42 next = nullptr;
43
44 + hb_iter (chunks)
45 | hb_apply ([] (chunk_t *_) { ::free (_); })
46 ;
47
48 chunks.fini ();
49 }
50
51 T* alloc ()
52 {
53 if (unlikely (!next))
54 {
55 if (unlikely (!chunks.alloc (chunks.length + 1))) return nullptr;
56 chunk_t *chunk = (chunk_t *) calloc (1, sizeof (chunk_t));
57 if (unlikely (!chunk)) return nullptr;
58 chunks.push (chunk);
59 next = chunk->thread ();
60 }
61
62 T* obj = next;
63 next = * ((T**) next);
64
65 memset (obj, 0, sizeof (T));
66
67 return obj;
68 }
69
70 void free (T* obj)
71 {
72 * (T**) obj = next;
73 next = obj;
74 }
75
76 private:
77
78 static_assert (ChunkLen > 1, "");
79 static_assert (sizeof (T) >= sizeof (void *), "");
80 static_assert (alignof (T) % alignof (void *) == 0, "");
81
82 struct chunk_t
83 {
84 T* thread ()
85 {
86 for (unsigned i = 0; i < ARRAY_LENGTH (arrayZ) - 1; i++)
87 * (T**) &arrayZ[i] = &arrayZ[i + 1];
88
89 * (T**) &arrayZ[ARRAY_LENGTH (arrayZ) - 1] = nullptr;
90
91 return arrayZ;
92 }
93
94 T arrayZ[ChunkLen];
95 };
96
97 T* next;
98 hb_vector_t<chunk_t *> chunks;
99};
100
101
102#endif /* HB_POOL_HH */
103