third_party/harfbuzz-ng/src/hb-cache-private.hh

   1 /*
   2  * Copyright © 2012  Google, Inc.
   3  *
   4  *  This is part of HarfBuzz, a text shaping library.
   5  *
   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.
  11  *
  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
  16  * DAMAGE.
  17  *
  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.
  23  *
  24  * Google Author(s): Behdad Esfahbod
  25  */
  26
  27 #ifndef HB_CACHE_PRIVATE_HH
  28 #define HB_CACHE_PRIVATE_HH
  29
  30 #include "hb-private.hh"
  31
  32
  33 /* Implements a lock-free cache for int->int functions. */
  34
  35 template <unsigned int key_bits, unsigned int value_bits, unsigned int cache_bits>
  36 struct hb_cache_t
  37 {
  38   ASSERT_STATIC (key_bits >= cache_bits);
  39   ASSERT_STATIC (key_bits + value_bits - cache_bits < 8 * sizeof (unsigned int));
  40
  41   inline void clear (void)
  42   {
  43     memset (values, 255, sizeof (values));
  44   }
  45
  46   inline bool get (unsigned int key, unsigned int *value)
  47   {
  48     unsigned int k = key & ((1<<cache_bits)-1);
  49     unsigned int v = values[k];
  50     if ((v >> value_bits) != (key >> cache_bits))
  51       return false;
  52     *value = v & ((1<<value_bits)-1);
  53     return true;
  54   }
  55
  56   inline bool set (unsigned int key, unsigned int value)
  57   {
  58     if (unlikely ((key >> key_bits) || (value >> value_bits)))
  59       return false; /* Overflows */
  60     unsigned int k = key & ((1<<cache_bits)-1);
  61     unsigned int v = ((key>>cache_bits)<<value_bits) | value;
  62     values[k] = v;
  63     return true;
  64   }
  65
  66   private:
  67   unsigned int values[1<<cache_bits];
  68 };
  69
  70 typedef hb_cache_t<21, 16, 8> hb_cmap_cache_t;
  71 typedef hb_cache_t<16, 24, 8> hb_advance_cache_t;
  72
  73
  74 #endif /* HB_CACHE_PRIVATE_HH */