michael@0: /*
michael@0:  * Copyright © 2012  Google, Inc.
michael@0:  *
michael@0:  *  This is part of HarfBuzz, a text shaping library.
michael@0:  *
michael@0:  * Permission is hereby granted, without written agreement and without
michael@0:  * license or royalty fees, to use, copy, modify, and distribute this
michael@0:  * software and its documentation for any purpose, provided that the
michael@0:  * above copyright notice and the following two paragraphs appear in
michael@0:  * all copies of this software.
michael@0:  *
michael@0:  * IN NO EVENT SHALL THE COPYRIGHT HOLDER BE LIABLE TO ANY PARTY FOR
michael@0:  * DIRECT, INDIRECT, SPECIAL, INCIDENTAL, OR CONSEQUENTIAL DAMAGES
michael@0:  * ARISING OUT OF THE USE OF THIS SOFTWARE AND ITS DOCUMENTATION, EVEN
michael@0:  * IF THE COPYRIGHT HOLDER HAS BEEN ADVISED OF THE POSSIBILITY OF SUCH
michael@0:  * DAMAGE.
michael@0:  *
michael@0:  * THE COPYRIGHT HOLDER SPECIFICALLY DISCLAIMS ANY WARRANTIES, INCLUDING,
michael@0:  * BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND
michael@0:  * FITNESS FOR A PARTICULAR PURPOSE.  THE SOFTWARE PROVIDED HEREUNDER IS
michael@0:  * ON AN "AS IS" BASIS, AND THE COPYRIGHT HOLDER HAS NO OBLIGATION TO
michael@0:  * PROVIDE MAINTENANCE, SUPPORT, UPDATES, ENHANCEMENTS, OR MODIFICATIONS.
michael@0:  *
michael@0:  * Google Author(s): Behdad Esfahbod
michael@0:  */
michael@0: 
michael@0: #ifndef HB_CACHE_PRIVATE_HH
michael@0: #define HB_CACHE_PRIVATE_HH
michael@0: 
michael@0: #include "hb-private.hh"
michael@0: 
michael@0: 
michael@0: /* Implements a lock-free cache for int->int functions. */
michael@0: 
michael@0: template <unsigned int key_bits, unsigned int value_bits, unsigned int cache_bits>
michael@0: struct hb_cache_t
michael@0: {
michael@0:   ASSERT_STATIC (key_bits >= cache_bits);
michael@0:   ASSERT_STATIC (key_bits + value_bits - cache_bits < 8 * sizeof (unsigned int));
michael@0: 
michael@0:   inline void clear (void)
michael@0:   {
michael@0:     memset (values, 255, sizeof (values));
michael@0:   }
michael@0: 
michael@0:   inline bool get (unsigned int key, unsigned int *value)
michael@0:   {
michael@0:     unsigned int k = key & ((1<<cache_bits)-1);
michael@0:     unsigned int v = values[k];
michael@0:     if ((v >> value_bits) != (key >> cache_bits))
michael@0:       return false;
michael@0:     *value = v & ((1<<value_bits)-1);
michael@0:     return true;
michael@0:   }
michael@0: 
michael@0:   inline bool set (unsigned int key, unsigned int value)
michael@0:   {
michael@0:     if (unlikely ((key >> key_bits) || (value >> value_bits)))
michael@0:       return false; /* Overflows */
michael@0:     unsigned int k = key & ((1<<cache_bits)-1);
michael@0:     unsigned int v = ((key>>cache_bits)<<value_bits) | value;
michael@0:     values[k] = v;
michael@0:     return true;
michael@0:   }
michael@0: 
michael@0:   private:
michael@0:   unsigned int values[1<<cache_bits];
michael@0: };
michael@0: 
michael@0: typedef hb_cache_t<21, 16, 8> hb_cmap_cache_t;
michael@0: typedef hb_cache_t<16, 24, 8> hb_advance_cache_t;
michael@0: 
michael@0: 
michael@0: #endif /* HB_CACHE_PRIVATE_HH */