98 lines
2.8 KiB
C++
98 lines
2.8 KiB
C++
#include <boost/thread/shared_mutex.hpp>
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#include <functional>
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#include <list>
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#include <memory>
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#include <mutex>
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#include <utility>
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#include <vector>
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template <typename Key, typename Value, typename Hash = std::hash<Key>>
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class threadsafe_lookup_table {
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private:
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class bucket_type {
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private:
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typedef std::pair<Key, Value> bucket_value;
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typedef std::list<bucket_value> bucket_data;
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typedef typename bucket_data::iterator bucket_iterator;
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bucket_data data;
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mutable boost::shared_mutex mutex;
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bucket_iterator find_entry_for(Key const& key) const
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{
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return std::find_if(
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data.begin(), data.end(), [&](bucket_value const& item) {
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return item.first == key;
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});
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}
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public:
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Value value_for(Key const& key, Value const& default_value) const
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{
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boost::shared_lock<boost::shared_mutex> lock(mutex);
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bucket_iterator const found_entry = find_entry_for(key);
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return (found_entry == data.end()) ? default_value : found_entry->second;
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}
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void add_or_update_mapping(Key const& key, Value const& value)
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{
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std::unique_lock<boost::shared_mutex> lock(mutex);
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bucket_iterator const found_entry = find_entry_for(key);
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if (found_entry == data.end()) {
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data.push_back(bucket_value(key, value));
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}
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else {
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found_entry->second = value;
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}
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}
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void remove_mapping(Key const& key)
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{
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std::unique_lock<boost::shared_mutex> lock(mutex);
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bucket_iterator const found_entry = find_entry_for(key);
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if (found_entry != data.end()) {
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data.erase(found_entry);
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}
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}
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};
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std::vector<std::unique_ptr<bucket_type>> buckets;
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Hash hasher;
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bucket_type& get_bucket(Key const& key) const
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{
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std::size_t const bucket_index = hasher(key) % buckets.size();
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return *buckets[bucket_index];
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}
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public:
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typedef Key key_type;
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typedef Value mapped_type;
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typedef Hash hash_type;
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threadsafe_lookup_table(unsigned num_buckets = 19,
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Hash const& hasher_ = Hash())
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: buckets(num_buckets), hasher(hasher_)
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{
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for (unsigned i = 0; i < num_buckets; ++i) {
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buckets[i].reset(new bucket_type);
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}
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}
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threadsafe_lookup_table(threadsafe_lookup_table const& other) = delete;
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threadsafe_lookup_table& operator=(threadsafe_lookup_table const& other) =
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delete;
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Value value_for(Key const& key, Value const& default_value = Value()) const
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{
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return get_bucket(key).value_for(key, default_value);
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}
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void add_or_update_mapping(Key const& key, Value const& value)
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{
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get_bucket(key).add_or_update_mapping(key, value);
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}
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void remove_mapping(Key const& key) { get_bucket(key).remove_mapping(key); }
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};
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