2 * Copyright © 2012 Google, Inc.
4 * This is part of HarfBuzz, a text shaping library.
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.
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
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.
24 * Google Author(s): Behdad Esfahbod
33 /* Implements a lock-free cache for int->int functions. */
35 template <unsigned int key_bits, unsigned int value_bits, unsigned int cache_bits>
38 static_assert ((key_bits >= cache_bits), "");
39 static_assert ((key_bits + value_bits - cache_bits <= 8 * sizeof (hb_atomic_int_t)), "");
40 static_assert (sizeof (hb_atomic_int_t) == sizeof (unsigned int), "");
42 void init () { clear (); }
47 for (unsigned i = 0; i < ARRAY_LENGTH (values); i++)
48 values[i].set_relaxed (-1);
51 bool get (unsigned int key, unsigned int *value) const
53 unsigned int k = key & ((1u<<cache_bits)-1);
54 unsigned int v = values[k].get_relaxed ();
55 if ((key_bits + value_bits - cache_bits == 8 * sizeof (hb_atomic_int_t) && v == (unsigned int) -1) ||
56 (v >> value_bits) != (key >> cache_bits))
58 *value = v & ((1u<<value_bits)-1);
62 bool set (unsigned int key, unsigned int value)
64 if (unlikely ((key >> key_bits) || (value >> value_bits)))
65 return false; /* Overflows */
66 unsigned int k = key & ((1u<<cache_bits)-1);
67 unsigned int v = ((key>>cache_bits)<<value_bits) | value;
68 values[k].set_relaxed (v);
73 hb_atomic_int_t values[1u<<cache_bits];
76 typedef hb_cache_t<21, 16, 8> hb_cmap_cache_t;
77 typedef hb_cache_t<16, 24, 8> hb_advance_cache_t;
80 #endif /* HB_CACHE_HH */