| /* |
| * 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> |
| 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 */ |