81 lines
2.5 KiB
C++
81 lines
2.5 KiB
C++
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/*
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* Copyright © 2012 Google, Inc.
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*
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* This is part of HarfBuzz, a text shaping library.
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*
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* Permission is hereby granted, without written agreement and without
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* license or royalty fees, to use, copy, modify, and distribute this
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* software and its documentation for any purpose, provided that the
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* above copyright notice and the following two paragraphs appear in
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* all copies of this software.
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*
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* IN NO EVENT SHALL THE COPYRIGHT HOLDER BE LIABLE TO ANY PARTY FOR
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* DIRECT, INDIRECT, SPECIAL, INCIDENTAL, OR CONSEQUENTIAL DAMAGES
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* ARISING OUT OF THE USE OF THIS SOFTWARE AND ITS DOCUMENTATION, EVEN
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* IF THE COPYRIGHT HOLDER HAS BEEN ADVISED OF THE POSSIBILITY OF SUCH
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* DAMAGE.
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*
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* THE COPYRIGHT HOLDER SPECIFICALLY DISCLAIMS ANY WARRANTIES, INCLUDING,
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* BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND
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* FITNESS FOR A PARTICULAR PURPOSE. THE SOFTWARE PROVIDED HEREUNDER IS
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* ON AN "AS IS" BASIS, AND THE COPYRIGHT HOLDER HAS NO OBLIGATION TO
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* PROVIDE MAINTENANCE, SUPPORT, UPDATES, ENHANCEMENTS, OR MODIFICATIONS.
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*
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* Google Author(s): Behdad Esfahbod
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*/
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#ifndef HB_CACHE_HH
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#define HB_CACHE_HH
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#include "hb.hh"
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/* Implements a lock-free cache for int->int functions. */
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template <unsigned int key_bits, unsigned int value_bits, unsigned int cache_bits>
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struct hb_cache_t
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{
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static_assert ((key_bits >= cache_bits), "");
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static_assert ((key_bits + value_bits - cache_bits <= 8 * sizeof (hb_atomic_int_t)), "");
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static_assert (sizeof (hb_atomic_int_t) == sizeof (unsigned int), "");
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void init () { clear (); }
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void fini () {}
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void clear ()
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{
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for (unsigned i = 0; i < ARRAY_LENGTH (values); i++)
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values[i].set_relaxed (-1);
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}
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bool get (unsigned int key, unsigned int *value) const
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{
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unsigned int k = key & ((1u<<cache_bits)-1);
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unsigned int v = values[k].get_relaxed ();
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if ((key_bits + value_bits - cache_bits == 8 * sizeof (hb_atomic_int_t) && v == (unsigned int) -1) ||
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(v >> value_bits) != (key >> cache_bits))
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return false;
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*value = v & ((1u<<value_bits)-1);
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return true;
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}
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bool set (unsigned int key, unsigned int value)
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{
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if (unlikely ((key >> key_bits) || (value >> value_bits)))
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return false; /* Overflows */
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unsigned int k = key & ((1u<<cache_bits)-1);
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unsigned int v = ((key>>cache_bits)<<value_bits) | value;
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values[k].set_relaxed (v);
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return true;
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}
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private:
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hb_atomic_int_t values[1u<<cache_bits];
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};
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typedef hb_cache_t<21, 16, 8> hb_cmap_cache_t;
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typedef hb_cache_t<16, 24, 8> hb_advance_cache_t;
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#endif /* HB_CACHE_HH */
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