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/*
* Copyright © 2012 Google, 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.
*
* Google Author(s): Behdad Esfahbod
*/
#ifndef HB_CACHE_HH
#define HB_CACHE_HH
#include "hb.hh"
/* Implements a lock-free cache for int->int functions. */
template <unsigned int key_bits, unsigned int value_bits, unsigned int cache_bits>
struct hb_cache_t
{
static_assert ((key_bits >= cache_bits), "");
static_assert ((key_bits + value_bits - cache_bits <= 8 * sizeof (hb_atomic_int_t)), "");
static_assert (sizeof (hb_atomic_int_t) == sizeof (unsigned int), "");
void init () { clear (); }
void fini () {}
void clear ()
{
for (unsigned i = 0; i < ARRAY_LENGTH (values); i++)
values[i].set_relaxed (-1);
}
bool get (unsigned int key, unsigned int *value) const
{
unsigned int k = key & ((1u<<cache_bits)-1);
unsigned int v = values[k].get_relaxed ();
if ((key_bits + value_bits - cache_bits == 8 * sizeof (hb_atomic_int_t) && v == (unsigned int) -1) ||
(v >> value_bits) != (key >> cache_bits))
return false;
*value = v & ((1u<<value_bits)-1);
return true;
}
bool set (unsigned int key, unsigned int value)
{
if (unlikely ((key >> key_bits) || (value >> value_bits)))
return false; /* Overflows */
unsigned int k = key & ((1u<<cache_bits)-1);
unsigned int v = ((key>>cache_bits)<<value_bits) | value;
values[k].set_relaxed (v);
return true;
}
private:
hb_atomic_int_t values[1u<<cache_bits];
};
typedef hb_cache_t<21, 16, 8> hb_cmap_cache_t;
typedef hb_cache_t<16, 24, 8> hb_advance_cache_t;
#endif /* HB_CACHE_HH */
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