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#ifndef HB_CACHE_PRIVATE_HH
28#define HB_CACHE_PRIVATE_HH
29
30#include "hb-private.hh"
31
32
33/* Implements a lock-free cache for int->int functions. */
34
35template <unsigned int key_bits, unsigned int value_bits, unsigned int cache_bits>
36struct hb_cache_t
37{
38  ASSERT_STATIC (key_bits >= cache_bits);
39  ASSERT_STATIC (key_bits + value_bits - cache_bits < 8 * sizeof (unsigned int));
40
41  inline void clear (void)
42  {
43    memset (values, 255, sizeof (values));
44  }
45
46  inline bool get (unsigned int key, unsigned int *value)
47  {
48    unsigned int k = key & ((1<<cache_bits)-1);
49    unsigned int v = values[k];
50    if ((v >> value_bits) != (key >> cache_bits))
51      return false;
52    *value = v & ((1<<value_bits)-1);
53    return true;
54  }
55
56  inline bool set (unsigned int key, unsigned int value)
57  {
58    if (unlikely ((key >> key_bits) || (value >> value_bits)))
59      return false; /* Overflows */
60    unsigned int k = key & ((1<<cache_bits)-1);
61    unsigned int v = ((key>>cache_bits)<<value_bits) | value;
62    values[k] = v;
63    return true;
64  }
65
66  private:
67  unsigned int values[1<<cache_bits];
68};
69
70typedef hb_cache_t<21, 16, 8> hb_cmap_cache_t;
71typedef hb_cache_t<16, 24, 8> hb_advance_cache_t;
72
73
74#endif /* HB_CACHE_PRIVATE_HH */
75