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/*
* Copyright © 2018 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_MAP_HH
#define HB_MAP_HH
#include "hb.hh"
template <typename T>
inline uint32_t Hash (const T &v)
{
/* Knuth's multiplicative method: */
return (uint32_t) v * 2654435761u;
}
/*
* hb_map_t
*/
struct hb_map_t
{
HB_NO_COPY_ASSIGN (hb_map_t);
hb_map_t () { init (); }
~hb_map_t () { fini (); }
struct item_t
{
hb_codepoint_t key;
hb_codepoint_t value;
bool is_unused () const { return key == INVALID; }
bool is_tombstone () const { return key != INVALID && value == INVALID; }
};
hb_object_header_t header;
bool successful; /* Allocations successful */
unsigned int population; /* Not including tombstones. */
unsigned int occupancy; /* Including tombstones. */
unsigned int mask;
unsigned int prime;
item_t *items;
void init_shallow ()
{
successful = true;
population = occupancy = 0;
mask = 0;
prime = 0;
items = nullptr;
}
void init ()
{
hb_object_init (this);
init_shallow ();
}
void fini_shallow ()
{
free (items);
items = nullptr;
}
void fini ()
{
population = occupancy = 0;
hb_object_fini (this);
fini_shallow ();
}
bool in_error () const { return !successful; }
bool resize ()
{
if (unlikely (!successful)) return false;
unsigned int power = hb_bit_storage (population * 2 + 8);
unsigned int new_size = 1u << power;
item_t *new_items = (item_t *) malloc ((size_t) new_size * sizeof (item_t));
if (unlikely (!new_items))
{
successful = false;
return false;
}
memset (new_items, 0xFF, (size_t) new_size * sizeof (item_t));
unsigned int old_size = mask + 1;
item_t *old_items = items;
/* Switch to new, empty, array. */
population = occupancy = 0;
mask = new_size - 1;
prime = prime_for (power);
items = new_items;
/* Insert back old items. */
if (old_items)
for (unsigned int i = 0; i < old_size; i++)
if (old_items[i].key != INVALID && old_items[i].value != INVALID)
set (old_items[i].key, old_items[i].value);
free (old_items);
return true;
}
void set (hb_codepoint_t key, hb_codepoint_t value)
{
if (unlikely (!successful)) return;
if (unlikely (key == INVALID)) return;
if ((occupancy + occupancy / 2) >= mask && !resize ()) return;
unsigned int i = bucket_for (key);
if (value == INVALID && items[i].key != key)
return; /* Trying to delete non-existent key. */
if (!items[i].is_unused ())
{
occupancy--;
if (items[i].is_tombstone ())
population--;
}
items[i].key = key;
items[i].value = value;
occupancy++;
if (!items[i].is_tombstone ())
population++;
}
hb_codepoint_t get (hb_codepoint_t key) const
{
if (unlikely (!items)) return INVALID;
unsigned int i = bucket_for (key);
return items[i].key == key ? items[i].value : INVALID;
}
void del (hb_codepoint_t key) { set (key, INVALID); }
bool has (hb_codepoint_t key) const
{ return get (key) != INVALID; }
hb_codepoint_t operator [] (unsigned int key) const
{ return get (key); }
static constexpr hb_codepoint_t INVALID = HB_MAP_VALUE_INVALID;
void clear ()
{
if (items) memset (items, 0xFF, ((size_t) mask + 1) * sizeof (item_t));
population = occupancy = 0;
}
bool is_empty () const { return population == 0; }
unsigned int get_population () const { return population; }
protected:
unsigned int bucket_for (hb_codepoint_t key) const
{
unsigned int i = Hash (key) % prime;
unsigned int step = 0;
unsigned int tombstone = INVALID;
while (!items[i].is_unused ())
{
if (items[i].key == key)
return i;
if (tombstone == INVALID && items[i].is_tombstone ())
tombstone = i;
i = (i + ++step) & mask;
}
return tombstone == INVALID ? i : tombstone;
}
static unsigned int prime_for (unsigned int shift)
{
/* Following comment and table copied from glib. */
/* Each table size has an associated prime modulo (the first prime
* lower than the table size) used to find the initial bucket. Probing
* then works modulo 2^n. The prime modulo is necessary to get a
* good distribution with poor hash functions.
*/
/* Not declaring static to make all kinds of compilers happy... */
/*static*/ const unsigned int prime_mod [32] =
{
1, /* For 1 << 0 */
2,
3,
7,
13,
31,
61,
127,
251,
509,
1021,
2039,
4093,
8191,
16381,
32749,
65521, /* For 1 << 16 */
131071,
262139,
524287,
1048573,
2097143,
4194301,
8388593,
16777213,
33554393,
67108859,
134217689,
268435399,
536870909,
1073741789,
2147483647 /* For 1 << 31 */
};
if (unlikely (shift >= ARRAY_LENGTH (prime_mod)))
return prime_mod[ARRAY_LENGTH (prime_mod) - 1];
return prime_mod[shift];
}
};
#endif /* HB_MAP_HH */
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