danicoin/external/google/sparsehash/hashtable-common.h

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2014-08-13 10:51:37 +00:00
// Copyright (c) 2005, Google Inc.
// All rights reserved.
//
// Redistribution and use in source and binary forms, with or without
// modification, are permitted provided that the following conditions are
// met:
//
// * Redistributions of source code must retain the above copyright
// notice, this list of conditions and the following disclaimer.
// * Redistributions in binary form must reproduce the above
// copyright notice, this list of conditions and the following disclaimer
// in the documentation and/or other materials provided with the
// distribution.
// * Neither the name of Google Inc. nor the names of its
// contributors may be used to endorse or promote products derived from
// this software without specific prior written permission.
//
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
// ---
// Author: Giao Nguyen
#ifndef UTIL_GTL_HASHTABLE_COMMON_H_
#define UTIL_GTL_HASHTABLE_COMMON_H_
#include <assert.h>
// Settings contains parameters for growing and shrinking the table.
// It also packages zero-size functor (ie. hasher).
template<typename Key, typename HashFunc,
typename SizeType, int HT_MIN_BUCKETS>
class sh_hashtable_settings : public HashFunc {
public:
typedef Key key_type;
typedef HashFunc hasher;
typedef SizeType size_type;
public:
sh_hashtable_settings(const hasher& hf,
const float ht_occupancy_flt,
const float ht_empty_flt)
: hasher(hf),
enlarge_threshold_(0),
shrink_threshold_(0),
consider_shrink_(false),
use_empty_(false),
use_deleted_(false),
num_ht_copies_(0) {
set_enlarge_factor(ht_occupancy_flt);
set_shrink_factor(ht_empty_flt);
}
size_type hash(const key_type& v) const {
return hasher::operator()(v);
}
float enlarge_factor() const {
return enlarge_factor_;
}
void set_enlarge_factor(float f) {
enlarge_factor_ = f;
}
float shrink_factor() const {
return shrink_factor_;
}
void set_shrink_factor(float f) {
shrink_factor_ = f;
}
size_type enlarge_threshold() const {
return enlarge_threshold_;
}
void set_enlarge_threshold(size_type t) {
enlarge_threshold_ = t;
}
size_type shrink_threshold() const {
return shrink_threshold_;
}
void set_shrink_threshold(size_type t) {
shrink_threshold_ = t;
}
size_type enlarge_size(size_type x) const {
return static_cast<size_type>(x * enlarge_factor_);
}
size_type shrink_size(size_type x) const {
return static_cast<size_type>(x * shrink_factor_);
}
bool consider_shrink() const {
return consider_shrink_;
}
void set_consider_shrink(bool t) {
consider_shrink_ = t;
}
bool use_empty() const {
return use_empty_;
}
void set_use_empty(bool t) {
use_empty_ = t;
}
bool use_deleted() const {
return use_deleted_;
}
void set_use_deleted(bool t) {
use_deleted_ = t;
}
size_type num_ht_copies() const {
return static_cast<size_type>(num_ht_copies_);
}
void inc_num_ht_copies() {
++num_ht_copies_;
}
// Reset the enlarge and shrink thresholds
void reset_thresholds(size_type num_buckets) {
set_enlarge_threshold(enlarge_size(num_buckets));
set_shrink_threshold(shrink_size(num_buckets));
// whatever caused us to reset already considered
set_consider_shrink(false);
}
// Caller is resposible for calling reset_threshold right after
// set_resizing_parameters.
void set_resizing_parameters(float shrink, float grow) {
assert(shrink >= 0.0);
assert(grow <= 1.0);
if (shrink > grow/2.0f)
shrink = grow / 2.0f; // otherwise we thrash hashtable size
set_shrink_factor(shrink);
set_enlarge_factor(grow);
}
// This is the smallest size a hashtable can be without being too crowded
// If you like, you can give a min #buckets as well as a min #elts
size_type min_buckets(size_type num_elts, size_type min_buckets_wanted) {
float enlarge = enlarge_factor();
size_type sz = HT_MIN_BUCKETS; // min buckets allowed
while ( sz < min_buckets_wanted ||
num_elts >= static_cast<size_type>(sz * enlarge) ) {
// This just prevents overflowing size_type, since sz can exceed
// max_size() here.
if (static_cast<size_type>(sz * 2) < sz) {
throw std::length_error("resize overflow"); // protect against overflow
}
sz *= 2;
}
return sz;
}
private:
size_type enlarge_threshold_; // table.size() * enlarge_factor
size_type shrink_threshold_; // table.size() * shrink_factor
float enlarge_factor_; // how full before resize
float shrink_factor_; // how empty before resize
// consider_shrink=true if we should try to shrink before next insert
bool consider_shrink_;
bool use_empty_; // used only by densehashtable, not sparsehashtable
bool use_deleted_; // false until delkey has been set
// num_ht_copies is a counter incremented every Copy/Move
unsigned int num_ht_copies_;
};
#endif // UTIL_GTL_HASHTABLE_COMMON_H_