90 lines
2.7 KiB
C++
90 lines
2.7 KiB
C++
/*
|
|
* 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 lockfree cache for int->int functions. */
|
|
|
|
template <unsigned int key_bits=16,
|
|
unsigned int value_bits=8 + 32 - key_bits,
|
|
unsigned int cache_bits=8,
|
|
bool thread_safe=true>
|
|
struct hb_cache_t
|
|
{
|
|
using item_t = typename std::conditional<thread_safe,
|
|
typename std::conditional<key_bits + value_bits - cache_bits <= 16,
|
|
hb_atomic_short_t,
|
|
hb_atomic_int_t>::type,
|
|
typename std::conditional<key_bits + value_bits - cache_bits <= 16,
|
|
short,
|
|
int>::type
|
|
>::type;
|
|
|
|
static_assert ((key_bits >= cache_bits), "");
|
|
static_assert ((key_bits + value_bits <= cache_bits + 8 * sizeof (item_t)), "");
|
|
|
|
hb_cache_t () { init (); }
|
|
|
|
void init () { clear (); }
|
|
|
|
void clear ()
|
|
{
|
|
for (unsigned i = 0; i < ARRAY_LENGTH (values); i++)
|
|
values[i] = -1;
|
|
}
|
|
|
|
bool get (unsigned int key, unsigned int *value) const
|
|
{
|
|
unsigned int k = key & ((1u<<cache_bits)-1);
|
|
unsigned int v = values[k];
|
|
if ((key_bits + value_bits - cache_bits == 8 * sizeof (item_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] = v;
|
|
return true;
|
|
}
|
|
|
|
private:
|
|
item_t values[1u<<cache_bits];
|
|
};
|
|
|
|
|
|
#endif /* HB_CACHE_HH */
|