1 /*
   2  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   3  *
   4  * This code is free software; you can redistribute it and/or modify it
   5  * under the terms of the GNU General Public License version 2 only, as
   6  * published by the Free Software Foundation.  Oracle designates this
   7  * particular file as subject to the "Classpath" exception as provided
   8  * by Oracle in the LICENSE file that accompanied this code.
   9  *
  10  * This code is distributed in the hope that it will be useful, but WITHOUT
  11  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  12  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  13  * version 2 for more details (a copy is included in the LICENSE file that
  14  * accompanied this code).
  15  *
  16  * You should have received a copy of the GNU General Public License version
  17  * 2 along with this work; if not, write to the Free Software Foundation,
  18  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  19  *
  20  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  21  * or visit www.oracle.com if you need additional information or have any
  22  * questions.
  23  */
  24 
  25 // This file is available under and governed by the GNU General Public
  26 // License version 2 only, as published by the Free Software Foundation.
  27 // However, the following notice accompanied the original version of this
  28 // file:
  29 //
  30 /*
  31  * Copyright © 2012  Google, Inc.
  32  *
  33  *  This is part of HarfBuzz, a text shaping library.
  34  *
  35  * Permission is hereby granted, without written agreement and without
  36  * license or royalty fees, to use, copy, modify, and distribute this
  37  * software and its documentation for any purpose, provided that the
  38  * above copyright notice and the following two paragraphs appear in
  39  * all copies of this software.
  40  *
  41  * IN NO EVENT SHALL THE COPYRIGHT HOLDER BE LIABLE TO ANY PARTY FOR
  42  * DIRECT, INDIRECT, SPECIAL, INCIDENTAL, OR CONSEQUENTIAL DAMAGES
  43  * ARISING OUT OF THE USE OF THIS SOFTWARE AND ITS DOCUMENTATION, EVEN
  44  * IF THE COPYRIGHT HOLDER HAS BEEN ADVISED OF THE POSSIBILITY OF SUCH
  45  * DAMAGE.
  46  *
  47  * THE COPYRIGHT HOLDER SPECIFICALLY DISCLAIMS ANY WARRANTIES, INCLUDING,
  48  * BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND
  49  * FITNESS FOR A PARTICULAR PURPOSE.  THE SOFTWARE PROVIDED HEREUNDER IS
  50  * ON AN "AS IS" BASIS, AND THE COPYRIGHT HOLDER HAS NO OBLIGATION TO
  51  * PROVIDE MAINTENANCE, SUPPORT, UPDATES, ENHANCEMENTS, OR MODIFICATIONS.
  52  *
  53  * Google Author(s): Behdad Esfahbod
  54  */
  55 
  56 #ifndef HB_CACHE_PRIVATE_HH
  57 #define HB_CACHE_PRIVATE_HH
  58 
  59 #include "hb-private.hh"
  60 
  61 
  62 /* Implements a lock-free cache for int->int functions. */
  63 
  64 template <unsigned int key_bits, unsigned int value_bits, unsigned int cache_bits>
  65 struct hb_cache_t
  66 {
  67   ASSERT_STATIC (key_bits >= cache_bits);
  68   ASSERT_STATIC (key_bits + value_bits - cache_bits < 8 * sizeof (unsigned int));
  69 
  70   inline void clear (void)
  71   {
  72     memset (values, 255, sizeof (values));
  73   }
  74 
  75   inline bool get (unsigned int key, unsigned int *value)
  76   {
  77     unsigned int k = key & ((1<<cache_bits)-1);
  78     unsigned int v = values[k];
  79     if ((v >> value_bits) != (key >> cache_bits))
  80       return false;
  81     *value = v & ((1<<value_bits)-1);
  82     return true;
  83   }
  84 
  85   inline bool set (unsigned int key, unsigned int value)
  86   {
  87     if (unlikely ((key >> key_bits) || (value >> value_bits)))
  88       return false; /* Overflows */
  89     unsigned int k = key & ((1<<cache_bits)-1);
  90     unsigned int v = ((key>>cache_bits)<<value_bits) | value;
  91     values[k] = v;
  92     return true;
  93   }
  94 
  95   private:
  96   unsigned int values[1<<cache_bits];
  97 };
  98 
  99 typedef hb_cache_t<21, 16, 8> hb_cmap_cache_t;
 100 typedef hb_cache_t<16, 24, 8> hb_advance_cache_t;
 101 
 102 
 103 #endif /* HB_CACHE_PRIVATE_HH */