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/***************************************************************************
* examples/containers/unordered_map1.cpp
*
* Part of the STXXL. See http://stxxl.sourceforge.net
*
* Copyright (C) 2013 Daniel Feist <daniel.feist@student.kit.edu>
* Copyright (C) 2014 Timo Bingmann <tb@panthema.net>
*
* Distributed under the Boost Software License, Version 1.0.
* (See accompanying file LICENSE_1_0.txt or copy at
* http://www.boost.org/LICENSE_1_0.txt)
**************************************************************************/
//! [example]
#include <stxxl/unordered_map>
#include <iostream>
//! [hash]
struct HashFunctor
{
size_t operator () (int key) const
{
// a simple integer hash function
return (size_t)(key * 2654435761u);
}
};
//! [hash]
//! [comparator]
struct CompareLess
{
bool operator () (const int& a, const int& b) const
{ return a < b; }
static int min_value() { return std::numeric_limits<int>::min(); }
static int max_value() { return std::numeric_limits<int>::max(); }
};
//! [comparator]
int main()
{
//! [construction]
#define SUB_BLOCK_SIZE 8192
#define SUB_BLOCKS_PER_BLOCK 256
// template parameter <KeyType, MappedType, HashType, CompareType, SubBlockSize, SubBlocksPerBlock>
typedef stxxl::unordered_map<
int, char, HashFunctor, CompareLess, SUB_BLOCK_SIZE, SUB_BLOCKS_PER_BLOCK
> unordered_map_type;
// constructor: use defaults for all parameters
unordered_map_type my_map;
//! [construction]
// insert some items and delete one
my_map.insert(std::make_pair(1, 'a'));
my_map.insert(std::make_pair(2, 'b'));
my_map.insert(std::make_pair(3, 'c'));
my_map.insert(std::make_pair(4, 'd'));
my_map.erase(3);
// iterate over all items in the unordered_map
unordered_map_type::iterator iter;
std::cout << "my_map contains:\n";
for (iter = my_map.begin(); iter != my_map.end(); ++iter)
{
std::cout << iter->first << " => " << iter->second << std::endl;
}
// direct operator[] access to items
std::cout << "my_map[2] = " << my_map[2] << std::endl;
// efficient bulk-insert into hash map by sorting by hash keys
std::vector<unordered_map_type::value_type> value_array;
for (int i = 0; i < 128; ++i)
value_array.push_back(std::make_pair(i, (char)i));
my_map.insert(value_array.begin(), value_array.end(), 8 * 1024 * 1024);
// check results of insertion
std::cout << "my_map[42] = " << my_map[42] << std::endl;
std::cout << "my_map.size() = " << my_map.size() << std::endl;
return 0;
}
//! [example]
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