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// Copyright (c) 2019 GeometryFactory Sarl (France)
// All rights reserved.
//
// This file is part of CGAL (www.cgal.org)
//
// $URL: https://github.com/CGAL/cgal/blob/v6.1/STL_Extension/include/CGAL/Small_unordered_map.h $
// $Id: include/CGAL/Small_unordered_map.h b26b07a1242 $
// SPDX-License-Identifier: LGPL-3.0-or-later OR LicenseRef-Commercial
//
// Author(s) : Andreas Fabri
#ifndef CGAL_SMALL_UNORDERED_MAP_H
#define CGAL_SMALL_UNORDERED_MAP_H
#include <array>
#include <iostream>
//#define CGAL_SMALL_UNORDERED_MAP_STATS
namespace CGAL {
template <typename K, typename T, typename H, unsigned int M>
class Small_unordered_map{
#ifdef CGAL_SMALL_UNORDERED_MAP_STATS
std::array<int,20> collisions = { 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0};
#endif
int head = -2;
mutable std::array<int, M> occupied;
std::array<int, M> unfreelist;
std::array<std::pair<K,T>, M> data;
const H hash = {};
public:
Small_unordered_map()
{
occupied.fill(-1);
}
#ifdef CGAL_SMALL_UNORDERED_MAP_STATS
~Small_unordered_map()
{
int total = 0;
std::cout << "0 " << collisions[0] << std::endl;
for(int i = 1; i < 20; i++){
total += collisions[i];
if(collisions[i] != 0){
std::cout << i << " " << collisions[i] << std::endl;
}
}
std::cout << "Total: " << total << " " << 100 * (double(total) / double(total + collisions[0])) << "%" << std::endl;
}
#endif
/// Set only once for a key and not more than N
void set(const K& k, const T& t)
{
unsigned int h = hash(k)%M;
unsigned i = h;
#ifdef CGAL_SMALL_UNORDERED_MAP_STATS
int collision = 0;
#endif
do {
if(occupied[i]== -1){
occupied[i] = 1;
data[i].first = k;
data[i].second = t;
unfreelist[i] = head;
head = i;
#ifdef CGAL_SMALL_UNORDERED_MAP_STATS
if(collision>19){
std::cerr << collision << " collisions" << std::endl;
}else{
++collisions[collision];
}
#endif
return;
}
i = (i+1)%M;
#ifdef CGAL_SMALL_UNORDERED_MAP_STATS
++collision;
#endif
}while(i != h);
CGAL_error();
}
// et only once as it is erased
const T& get_and_erase(const K& k) const
{
unsigned int h = hash(k)%M;
unsigned int i = h;
do{
if((occupied[i] == 1) && (data[i].first == k)){
occupied[i] = -1;
return data[i].second;
}
i = (i+1)%M;
}while(i != h);
CGAL_error();
}
void clear()
{
head = -2;
// without erase we would have to call occupied.fill(-1); which is costly
}
struct iterator {
const Small_unordered_map& map;
int pos;
iterator(const Small_unordered_map& map)
: map(map),pos(-2)
{}
iterator(const Small_unordered_map& map, int pos)
: map(map), pos(pos)
{}
bool operator==(const iterator& other) const
{
return pos == other.pos;
}
bool operator!=(const iterator& other) const
{
return pos != other.pos;
}
iterator operator++()
{
pos = map.unfreelist[pos];
return *this;
}
const std::pair<K,T>& operator*()const
{
return map.data[pos];
}
};
iterator begin() const
{
return iterator(*this,head);
}
iterator end() const
{
return iterator(*this);
}
void clear(const iterator it)
{
occupied[it.pos] = -1;
}
friend struct iterator;
};
} // namespace CGAL
#endif // CGAL_SMALL_UNORDERED_MAP_H
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