text: /*
  
  Copyright (c) 2014-2020, Arvid Norberg
  Copyright (c) 2015, Thomas Yuan
  Copyright (c) 2016-2018, Alden Torres
  Copyright (c) 2017, Steven Siloti
  Copyright (c) 2017, Andrei Kurushin
  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 the author 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.
  
  */
  
  #include "libtorrent/config.hpp"
  #include "libtorrent/assert.hpp"
  #include "libtorrent/settings_pack.hpp"
  #include "libtorrent/aux_/session_impl.hpp"
  #include "libtorrent/aux_/array.hpp"
  #include "libtorrent/aux_/session_settings.hpp"
  
  #include <algorithm>
  
  namespace {
  
  	template <class T>
  	bool compare_first(std::pair<std::uint16_t, T> const& lhs
  		, std::pair<std::uint16_t, T> const& rhs)
  	{
  		return lhs.first < rhs.first;
  	}
  
  	template <class T>
  	void insort_replace(std::vector<std::pair<std::uint16_t, T>>& c, std::pair<std::uint16_t, T> v)
  	{
  		auto i = std::lower_bound(c.begin(), c.end(), v, &compare_first<T>);
  		if (i != c.end() && i->first == v.first) i->second = std::move(v.second);
  		else c.emplace(i, std::move(v));
  	}
  
  	// return the string, unless it's null, in which case the empty string is
  	// returned
  	char const* ensure_string(char const* str)
  	{ return str == nullptr ? "" : str; }
  }
  
  namespace libtorrent {
  
  	struct str_setting_entry_t
  	{
  		// the name of this setting. used for serialization and deserialization
  		char const* name;
  		// if present, this function is called when the setting is changed
  		void (aux::session_impl::*fun)();
  		char const *default_value;
  	};
  
  	struct int_setting_entry_t
  	{
  		// the name of this setting. used for serialization and deserialization
  		char const* name;
  		// if present, this function is called when the setting is changed
  		void (aux::session_impl::*fun)();
  		int default_value;
  	};
  
  	struct bool_setting_entry_t
  	{
  		// the name of this setting. used for serialization and deserialization
  		char const* name;
  		// if present, this function is called when the setting is changed
  		void (aux::session_impl::*fun)();
  		bool default_value;
  	};
  
  
  #define SET(name, default_value, fun) { #name, fun, default_value }
  
  #if TORRENT_ABI_VERSION == 1
  #define DEPRECATED_SET(name, default_value, fun) { #name, fun, default_value }
  #define DEPRECATED_SET_STR(name, default_value, fun) { #name, fun, default_value }
  #else
  #define DEPRECATED_SET(name, default_value, fun) { "", nullptr, 0 }
  #define DEPRECATED_SET_STR(name, default_value, fun) { "", nullptr, nullptr }
  #endif
  
  #ifdef TORRENT_WINDOWS
  constexpr int CLOSE_FILE_INTERVAL = 240;
  #else
  constexpr int CLOSE_FILE_INTERVAL = 0;
  #endif
  
  		// tested to fail with _MSC_VER <= 1916. The actual version condition
  #if !defined _MSC_VER
  #define CONSTEXPR_SETTINGS constexpr
  #else
  #define CONSTEXPR_SETTINGS
  #endif
  
  	namespace {
  
  	using aux::session_impl;
  
  	CONSTEXPR_SETTINGS
  	aux::array<str_setting_entry_t, settings_pack::num_string_settings> const str_settings
  	({{
  		SET(user_agent, "libtorrent/" LIBTORRENT_VERSION, &session_impl::update_user_agent),
  		SET(announce_ip, nullptr, nullptr),
  		DEPRECATED_SET_STR(mmap_cache, nullptr, nullptr),
  		SET(handshake_client_version, nullptr, nullptr),
  		SET(outgoing_interfaces, "", &session_impl::update_outgoing_interfaces),
  		SET(listen_interfaces, "0.0.0.0:6881,[::]:6881", &session_impl::update_listen_interfaces),
  		SET(proxy_hostname, "", &session_impl::update_proxy),
  		SET(proxy_username, "", &session_impl::update_proxy),
  		SET(proxy_password, "", &session_impl::update_proxy),
  		SET(i2p_hostname, "", &session_impl::update_i2p_bridge),
  		SET(peer_fingerprint, "-LT2050-", nullptr),
  		SET(dht_bootstrap_nodes, "dht.libtorrent.org:25401", &session_impl::update_dht_bootstrap_nodes)
  	}});
  
  	CONSTEXPR_SETTINGS
  	aux::array<bool_setting_entry_t, settings_pack::num_bool_settings> const bool_settings
  	({{
  		SET(allow_multiple_connections_per_ip, false, nullptr),
  		DEPRECATED_SET(ignore_limits_on_local_network, true, &session_impl::update_ignore_rate_limits_on_local_network),
  		SET(send_redundant_have, true, nullptr),
  		DEPRECATED_SET(lazy_bitfields, false, nullptr),
  		SET(use_dht_as_fallback, false, nullptr),
  		SET(upnp_ignore_nonrouters, false, nullptr),
  		SET(use_parole_mode, true, nullptr),
  		DEPRECATED_SET(use_read_cache, true, nullptr),
  		DEPRECATED_SET(use_write_cache, true, nullptr),
  		DEPRECATED_SET(dont_flush_write_cache, false, nullptr),
  		DEPRECATED_SET(coalesce_reads, false, nullptr),
  		DEPRECATED_SET(coalesce_writes, false, nullptr),
  		SET(auto_manage_prefer_seeds, false, nullptr),
  		SET(dont_count_slow_torrents, true, &session_impl::update_count_slow),
  		SET(close_redundant_connections, true, nullptr),
  		SET(prioritize_partial_pieces, false, nullptr),
  		SET(rate_limit_ip_overhead, true, nullptr),
  		SET(announce_to_all_trackers, false, nullptr),
  		SET(announce_to_all_tiers, false, nullptr),
  		SET(prefer_udp_trackers, true, nullptr),
  		DEPRECATED_SET(strict_super_seeding, false, nullptr),
  		DEPRECATED_SET(lock_disk_cache, false, nullptr),
  		SET(disable_hash_checks, false, nullptr),
  		SET(allow_i2p_mixed, false, nullptr),
  		DEPRECATED_SET(low_prio_disk, true, nullptr),
  		SET(volatile_read_cache, false, nullptr),
  		DEPRECATED_SET(guided_read_cache, false, nullptr),
  		SET(no_atime_storage, true, nullptr),
  		SET(incoming_starts_queued_torrents, false, nullptr),
  		SET(report_true_downloaded, false, nullptr),
  		SET(strict_end_game_mode, true, nullptr),
  		DEPRECATED_SET(broadcast_lsd, true, nullptr),
  		SET(enable_outgoing_utp, true, nullptr),
  		SET(enable_incoming_utp, true, nullptr),
  		SET(enable_outgoing_tcp, true, nullptr),
  		SET(enable_incoming_tcp, true, nullptr),
  		SET(ignore_resume_timestamps, false, nullptr),
  		SET(no_recheck_incomplete_resume, false, nullptr),
  		SET(anonymous_mode, false, nullptr),
  		SET(report_web_seed_downloads, true, &session_impl::update_report_web_seed_downloads),
  		DEPRECATED_SET(rate_limit_utp, true, &session_impl::update_rate_limit_utp),
  		DEPRECATED_SET(announce_double_nat, false, nullptr),
  		SET(seeding_outgoing_connections, true, nullptr),
  		SET(no_connect_privileged_ports, false, &session_impl::update_privileged_ports),
  		SET(smooth_connects, true, nullptr),
  		SET(always_send_user_agent, false, nullptr),
  		SET(apply_ip_filter_to_trackers, true, nullptr),
  		DEPRECATED_SET(use_disk_read_ahead, true, nullptr),
  		DEPRECATED_SET(lock_files, false, nullptr),
  		DEPRECATED_SET(contiguous_recv_buffer, true, nullptr),
  		SET(ban_web_seeds, true, nullptr),
  		SET(allow_partial_disk_writes, true, nullptr),
  		DEPRECATED_SET(force_proxy, false, nullptr),
  		SET(support_share_mode, true, nullptr),
  		DEPRECATED_SET(support_merkle_torrents, false, nullptr),
  		SET(report_redundant_bytes, true, nullptr),
  		SET(listen_system_port_fallback, true, nullptr),
  		DEPRECATED_SET(use_disk_cache_pool, false, nullptr),
  		SET(announce_crypto_support, true, nullptr),
  		SET(enable_upnp, true, &session_impl::update_upnp),
  		SET(enable_natpmp, true, &session_impl::update_natpmp),
  		SET(enable_lsd, true, &session_impl::update_lsd),
  		SET(enable_dht, true, &session_impl::update_dht),
  		SET(prefer_rc4, false, nullptr),
  		SET(proxy_hostnames, true, nullptr),
  		SET(proxy_peer_connections, true, nullptr),
  		SET(auto_sequential, true, &session_impl::update_auto_sequential),
  		SET(proxy_tracker_connections, true, nullptr),
  		SET(enable_ip_notifier, true, &session_impl::update_ip_notifier),
  		SET(dht_prefer_verified_node_ids, true, nullptr),
  		SET(dht_restrict_routing_ips, true, nullptr),
  		SET(dht_restrict_search_ips, true, nullptr),
  		SET(dht_extended_routing_table, true, nullptr),
  		SET(dht_aggressive_lookups, true, nullptr),
  		SET(dht_privacy_lookups, false, nullptr),
  		SET(dht_enforce_node_id, false, nullptr),
  		SET(dht_ignore_dark_internet, true, nullptr),
  		SET(dht_read_only, false, nullptr),
  		SET(piece_extent_affinity, false, nullptr),
  		SET(validate_https_trackers, true, &session_impl::update_validate_https),
  		SET(ssrf_mitigation, true, nullptr),
  		SET(allow_idna, false, nullptr),
  		SET(enable_set_file_valid_data, false, nullptr),
  		SET(socks5_udp_send_local_ep, false, nullptr),
  	}});
  
  	CONSTEXPR_SETTINGS
  	aux::array<int_setting_entry_t, settings_pack::num_int_settings> const int_settings
  	({{
  		SET(tracker_completion_timeout, 30, nullptr),
  		SET(tracker_receive_timeout, 10, nullptr),
  		SET(stop_tracker_timeout, 5, nullptr),
  		SET(tracker_maximum_response_length, 1024*1024, nullptr),
  		SET(piece_timeout, 20, nullptr),
  		SET(request_timeout, 60, nullptr),
  		SET(request_queue_time, 3, nullptr),
  		SET(max_allowed_in_request_queue, 2000, nullptr),
  		SET(max_out_request_queue, 500, nullptr),
  		SET(whole_pieces_threshold, 20, nullptr),
  		SET(peer_timeout, 120, nullptr),
  		SET(urlseed_timeout, 20, nullptr),
  		SET(urlseed_pipeline_size, 5, nullptr),
  		SET(urlseed_wait_retry, 30, nullptr),
  		SET(file_pool_size, 40, nullptr),
  		SET(max_failcount, 3, &session_impl::update_max_failcount),
  		SET(min_reconnect_time, 60, nullptr),
  		SET(peer_connect_timeout, 15, nullptr),
  		SET(connection_speed, 30, &session_impl::update_connection_speed),
  		SET(inactivity_timeout, 600, nullptr),
  		SET(unchoke_interval, 15, nullptr),
  		SET(optimistic_unchoke_interval, 30, nullptr),
  		SET(num_want, 200, nullptr),
  		SET(initial_picker_threshold, 4, nullptr),
  		SET(allowed_fast_set_size, 5, nullptr),
  		SET(suggest_mode, settings_pack::no_piece_suggestions, nullptr),
  		SET(max_queued_disk_bytes, 1024 * 1024, nullptr),
  		SET(handshake_timeout, 10, nullptr),
  		SET(send_buffer_low_watermark, 10 * 1024, nullptr),
  		SET(send_buffer_watermark, 500 * 1024, nullptr),
  		SET(send_buffer_watermark_factor, 50, nullptr),
  		SET(choking_algorithm, settings_pack::fixed_slots_choker, nullptr),
  		SET(seed_choking_algorithm, settings_pack::round_robin, nullptr),
  		DEPRECATED_SET(cache_size, 2048, nullptr),
  		DEPRECATED_SET(cache_buffer_chunk_size, 0, nullptr),
  		DEPRECATED_SET(cache_expiry, 300, nullptr),
  		SET(disk_io_write_mode, settings_pack::enable_os_cache, nullptr),
  		SET(disk_io_read_mode, settings_pack::enable_os_cache, nullptr),
  		SET(outgoing_port, 0, nullptr),
  		SET(num_outgoing_ports, 0, nullptr),
  		SET(peer_tos, 0x04, &session_impl::update_peer_tos),
  		SET(active_downloads, 3, &session_impl::trigger_auto_manage),
  		SET(active_seeds, 5, &session_impl::trigger_auto_manage),
  		SET(active_checking, 1, &session_impl::trigger_auto_manage),
  		SET(active_dht_limit, 88, nullptr),
  		SET(active_tracker_limit, 1600, nullptr),
  		SET(active_lsd_limit, 60, nullptr),
  		SET(active_limit, 500, &session_impl::trigger_auto_manage),
  		DEPRECATED_SET(active_loaded_limit, 0, &session_impl::trigger_auto_manage),
  		SET(auto_manage_interval, 30, nullptr),
  		SET(seed_time_limit, 24 * 60 * 60, nullptr),
  		SET(auto_scrape_interval, 1800, nullptr),
  		SET(auto_scrape_min_interval, 300, nullptr),
  		SET(max_peerlist_size, 3000, nullptr),
  		SET(max_paused_peerlist_size, 1000, nullptr),
  		SET(min_announce_interval, 5 * 60, nullptr),
  		SET(auto_manage_startup, 60, nullptr),
  		SET(seeding_piece_quota, 20, nullptr),
  		// TODO: deprecate this
  		SET(max_rejects, 50, nullptr),
  		SET(recv_socket_buffer_size, 0, &session_impl::update_socket_buffer_size),
  		SET(send_socket_buffer_size, 0, &session_impl::update_socket_buffer_size),
  		SET(max_peer_recv_buffer_size, 2 * 1024 * 1024, nullptr),
  		DEPRECATED_SET(file_checks_delay_per_block, 0, nullptr),
  		SET(read_cache_line_size, 32, nullptr),
  		SET(write_cache_line_size, 16, nullptr),
  		SET(optimistic_disk_retry, 10 * 60, nullptr),
  		SET(max_suggest_pieces, 16, nullptr),
  		SET(local_service_announce_interval, 5 * 60, nullptr),
  		SET(dht_announce_interval, 15 * 60, &session_impl::update_dht_announce_interval),
  		SET(udp_tracker_token_expiry, 60, nullptr),
  		DEPRECATED_SET(default_cache_min_age, 1, nullptr),
  		SET(num_optimistic_unchoke_slots, 0, nullptr),
  		SET(default_est_reciprocation_rate, 16000, nullptr),
  		SET(increase_est_reciprocation_rate, 20, nullptr),
  		SET(decrease_est_reciprocation_rate, 3, nullptr),
  		SET(max_pex_peers, 50, nullptr),
  		SET(tick_interval, 500, nullptr),
  		SET(share_mode_target, 3, nullptr),
  		SET(upload_rate_limit, 0, &session_impl::update_upload_rate),
  		SET(download_rate_limit, 0, &session_impl::update_download_rate),
  		DEPRECATED_SET(local_upload_rate_limit, 0, &session_impl::update_local_upload_rate),
  		DEPRECATED_SET(local_download_rate_limit, 0, &session_impl::update_local_download_rate),
  		SET(dht_upload_rate_limit, 8000, &session_impl::update_dht_upload_rate_limit),
  		SET(unchoke_slots_limit, 8, &session_impl::update_unchoke_limit),
  		DEPRECATED_SET(half_open_limit, 0, nullptr),
  		SET(connections_limit, 200, &session_impl::update_connections_limit),
  		SET(connections_slack, 10, nullptr),
  		SET(utp_target_delay, 100, nullptr),
  		SET(utp_gain_factor, 3000, nullptr),
  		SET(utp_min_timeout, 500, nullptr),
  		SET(utp_syn_resends, 2, nullptr),
  		SET(utp_fin_resends, 2, nullptr),
  		SET(utp_num_resends, 3, nullptr),
  		SET(utp_connect_timeout, 3000, nullptr),
  		SET(utp_delayed_ack, 0, nullptr),
  		SET(utp_loss_multiplier, 50, nullptr),
  		SET(mixed_mode_algorithm, settings_pack::peer_proportional, nullptr),
  		SET(listen_queue_size, 5, nullptr),
  		SET(torrent_connect_boost, 30, nullptr),
  		SET(alert_queue_size, 2000, &session_impl::update_alert_queue_size),
  		SET(max_metadata_size, 3 * 1024 * 10240, nullptr),
  		SET(hashing_threads, 2, &session_impl::update_disk_threads),
  		SET(checking_mem_usage, 256, nullptr),
  		SET(predictive_piece_announce, 0, nullptr),
  		SET(aio_threads, 10, &session_impl::update_disk_threads),
  		DEPRECATED_SET(aio_max, 300, nullptr),
  		DEPRECATED_SET(network_threads, 0, nullptr),
  		DEPRECATED_SET(ssl_listen, 0, &session_impl::update_ssl_listen),
  		SET(tracker_backoff, 250, nullptr),
  		SET(share_ratio_limit, 200, nullptr),
  		SET(seed_time_ratio_limit, 700, nullptr),
  		SET(peer_turnover, 4, nullptr),
  		SET(peer_turnover_cutoff, 90, nullptr),
  		SET(peer_turnover_interval, 300, nullptr),
  		SET(connect_seed_every_n_download, 10, nullptr),
  		SET(max_http_recv_buffer_size, 4*1024*204, nullptr),
  		SET(max_retry_port_bind, 10, nullptr),
  		SET(alert_mask, int(static_cast<std::uint32_t>(alert_category::error)), &session_impl::update_alert_mask),
  		SET(out_enc_policy, settings_pack::pe_enabled, nullptr),
  		SET(in_enc_policy, settings_pack::pe_enabled, nullptr),
  		SET(allowed_enc_level, settings_pack::pe_both, nullptr),
  		SET(inactive_down_rate, 2048, nullptr),
  		SET(inactive_up_rate, 2048, nullptr),
  		SET(proxy_type, settings_pack::none, &session_impl::update_proxy),
  		SET(proxy_port, 0, &session_impl::update_proxy),
  		SET(i2p_port, 0, &session_impl::update_i2p_bridge),
  		DEPRECATED_SET(cache_size_volatile, 256, nullptr),
  		SET(urlseed_max_request_bytes, 16 * 1024 * 1024, nullptr),
  		SET(web_seed_name_lookup_retry, 1800, nullptr),
  		SET(close_file_interval, CLOSE_FILE_INTERVAL, nullptr),
  		SET(utp_cwnd_reduce_timer, 100, nullptr),
  		SET(max_web_seed_connections, 3, nullptr),
  		SET(resolver_cache_timeout, 1200, &session_impl::update_resolver_cache_timeout),
  		SET(send_not_sent_low_watermark, 16384, nullptr),
  		SET(rate_choker_initial_threshold, 1024, nullptr),
  		SET(upnp_lease_duration, 3600, nullptr),
  		SET(max_concurrent_http_announces, 50, nullptr),
  		SET(dht_max_peers_reply, 100, nullptr),
  		SET(dht_search_branching, 5, nullptr),
  		SET(dht_max_fail_count, 20, nullptr),
  		SET(dht_max_torrents, 2000, nullptr),
  		SET(dht_max_dht_items, 700, nullptr),
  		SET(dht_max_peers, 500, nullptr),
  		SET(dht_max_torrent_search_reply, 20, nullptr),
  		SET(dht_block_timeout, 5 * 60, nullptr),
  		SET(dht_block_ratelimit, 5, nullptr),
  		SET(dht_item_lifetime, 0, nullptr),
  		SET(dht_sample_infohashes_interval, 21600, nullptr),
  		SET(dht_max_infohashes_sample_count, 20, nullptr),
  		SET(max_piece_count, 0x200000, nullptr),
  		SET(metadata_token_limit, 2500000, nullptr),
  	}});
  
  #undef SET
  #undef DEPRECATED_SET
  #undef CONSTEXPR_SETTINGS
  
  	} // anonymous namespace
  
  	int setting_by_name(string_view const key)
  	{
  		for (int k = 0; k < str_settings.end_index(); ++k)
  		{
  			if (key != str_settings[k].name) continue;
  			return settings_pack::string_type_base + k;
  		}
  		for (int k = 0; k < int_settings.end_index(); ++k)
  		{
  			if (key != int_settings[k].name) continue;
  			return settings_pack::int_type_base + k;
  		}
  		for (int k = 0; k < bool_settings.end_index(); ++k)
  		{
  			if (key != bool_settings[k].name) continue;
  			return settings_pack::bool_type_base + k;
  		}
  		return -1;
  	}
  
  	char const* name_for_setting(int s)
  	{
  		switch (s & settings_pack::type_mask)
  		{
  			case settings_pack::string_type_base:
  				return str_settings[s - settings_pack::string_type_base].name;
  			case settings_pack::int_type_base:
  				return int_settings[s - settings_pack::int_type_base].name;
  			case settings_pack::bool_type_base:
  				return bool_settings[s - settings_pack::bool_type_base].name;
  		}
  		return "";
  	}
  
  	settings_pack load_pack_from_dict(bdecode_node const& settings)
  	{
  		settings_pack pack;
  
  		for (int i = 0; i < settings.dict_size(); ++i)
  		{
  			string_view key;
  			bdecode_node val;
  			std::tie(key, val) = settings.dict_at(i);
  			switch (val.type())
  			{
  				case bdecode_node::dict_t:
  				case bdecode_node::list_t:
  					continue;
  				case bdecode_node::int_t:
  				{
  					bool found = false;
  					for (int k = 0; k < int_settings.end_index(); ++k)
  					{
  						if (key != int_settings[k].name) continue;
  						pack.set_int(settings_pack::int_type_base | k, int(val.int_value()));
  						found = true;
  						break;
  					}
  					if (found) continue;
  					for (int k = 0; k < bool_settings.end_index(); ++k)
  					{
  						if (key != bool_settings[k].name) continue;
  						pack.set_bool(settings_pack::bool_type_base | k, val.int_value() != 0);
  						break;
  					}
  				}
  				break;
  			case bdecode_node::string_t:
  				for (int k = 0; k < str_settings.end_index(); ++k)
  				{
  					if (key != str_settings[k].name) continue;
  					pack.set_str(settings_pack::string_type_base + k, val.string_value().to_string());
  					break;
  				}
  				break;
  			case bdecode_node::none_t:
  				break;
  			}
  		}
  		return pack;
  	}
  
  	settings_pack non_default_settings(aux::session_settings const& sett)
  	{
  		settings_pack ret;
  		sett.bulk_get([&ret](aux::session_settings_single_thread const& s)
  		{
  		// loop over all settings that differ from default
  			for (std::uint16_t i = 0; i < settings_pack::num_string_settings; ++i)
  			{
  				std::uint16_t const n = i | settings_pack::string_type_base;
  				if (ensure_string(str_settings[i].default_value) == s.get_str(n)) continue;
  				ret.set_str(n, s.get_str(n));
  			}
  
  			for (std::uint16_t i = 0; i < settings_pack::num_int_settings; ++i)
  			{
  				std::uint16_t const n = i | settings_pack::int_type_base;
  				if (int_settings[i].default_value == s.get_int(n)) continue;
  				ret.set_int(n, s.get_int(n));
  			}
  
  			for (std::uint16_t i = 0; i < settings_pack::num_bool_settings; ++i)
  			{
  				std::uint16_t const n = i | settings_pack::bool_type_base;
  				if (bool_settings[i].default_value == s.get_bool(n)) continue;
  				ret.set_bool(n, s.get_bool(n));
  			}
  		});
  		return ret;
  	}
  
  	void save_settings_to_dict(settings_pack const& sett, entry::dictionary_type& out)
  	{
  		struct visitor
  		{
  			void operator()(std::uint16_t i, std::string const& str) { out[str_settings[i & settings_pack::index_mask].name] = str; }
  			void operator()(std::uint16_t i, int val) { out[int_settings[i & settings_pack::index_mask].name] = val; }
  			void operator()(std::uint16_t i, bool val) { out[bool_settings[i & settings_pack::index_mask].name] = val; }
  			entry::dictionary_type& out;
  		};
  		sett.for_each(visitor{out});
  	}
  
  	void run_all_updates(aux::session_impl& ses)
  	{
  		using fun_t = void (aux::session_impl::*)();
  		for (int i = 0; i < settings_pack::num_string_settings; ++i)
  		{
  			fun_t const& f = str_settings[i].fun;
  			if (f) (ses.*f)();
  		}
  
  		for (int i = 0; i < settings_pack::num_int_settings; ++i)
  		{
  			fun_t const& f = int_settings[i].fun;
  			if (f) (ses.*f)();
  		}
  
  		for (int i = 0; i < settings_pack::num_bool_settings; ++i)
  		{
  			fun_t const& f = bool_settings[i].fun;
  			if (f) (ses.*f)();
  		}
  	}
  
  	void initialize_default_settings(aux::session_settings_single_thread& s)
  	{
  		for (int i = 0; i < settings_pack::num_string_settings; ++i)
  		{
  			if (str_settings[i].default_value == nullptr) continue;
  			s.set_str(settings_pack::string_type_base | i, str_settings[i].default_value);
  			TORRENT_ASSERT(s.get_str(settings_pack::string_type_base + i) == str_settings[i].default_value);
  		}
  
  		for (int i = 0; i < settings_pack::num_int_settings; ++i)
  		{
  			s.set_int(settings_pack::int_type_base | i, int_settings[i].default_value);
  			TORRENT_ASSERT(s.get_int(settings_pack::int_type_base + i) == int_settings[i].default_value);
  		}
  
  		for (int i = 0; i < settings_pack::num_bool_settings; ++i)
  		{
  			s.set_bool(settings_pack::bool_type_base | i, bool_settings[i].default_value);
  			TORRENT_ASSERT(s.get_bool(settings_pack::bool_type_base + i) == bool_settings[i].default_value);
  		}
  	}
  
  	settings_pack default_settings()
  	{
  		settings_pack ret;
  		// TODO: it would be nice to reserve() these vectors up front
  		for (int i = 0; i < settings_pack::num_string_settings; ++i)
  		{
  			if (str_settings[i].default_value == nullptr) continue;
  			ret.set_str(settings_pack::string_type_base + i, str_settings[i].default_value);
  		}
  
  		for (int i = 0; i < settings_pack::num_int_settings; ++i)
  		{
  			ret.set_int(settings_pack::int_type_base + i, int_settings[i].default_value);
  		}
  
  		for (int i = 0; i < settings_pack::num_bool_settings; ++i)
  		{
  			ret.set_bool(settings_pack::bool_type_base + i, bool_settings[i].default_value);
  		}
  		return ret;
  	}
  
  	void apply_pack(settings_pack const* pack, aux::session_settings& sett
  		, aux::session_impl* ses)
  	{
  		using fun_t = void (aux::session_impl::*)();
  		std::vector<fun_t> callbacks;
  
  		sett.bulk_set([&](aux::session_settings_single_thread& s)
  		{
  			apply_pack_impl(pack, s, ses ? &callbacks : nullptr);
  		});
  
  		// call the callbacks once all the settings have been applied, and
  		// only once per callback
  		for (auto const& f : callbacks)
  		{
  			(ses->*f)();
  		}
  	}
  
  	void apply_pack_impl(settings_pack const* pack, aux::session_settings_single_thread& sett
  		, std::vector<void(aux::session_impl::*)()>* callbacks)
  	{
  		for (auto const& p : pack->m_strings)
  		{
  			// disregard setting indices that are not string types
  			if ((p.first & settings_pack::type_mask) != settings_pack::string_type_base)
  				continue;
  
  			// ignore settings that are out of bounds
  			int const index = p.first & settings_pack::index_mask;
  			TORRENT_ASSERT_PRECOND(index >= 0 && index < settings_pack::num_string_settings);
  			if (index < 0 || index >= settings_pack::num_string_settings)
  				continue;
  
  			// if the value did not change, don't call the update callback
  			if (sett.get_str(p.first) == p.second) continue;
  
  			sett.set_str(p.first, p.second);
  			str_setting_entry_t const& sa = str_settings[index];
  
  			if (sa.fun && callbacks
  				&& std::find(callbacks->begin(), callbacks->end(), sa.fun) == callbacks->end())
  				callbacks->push_back(sa.fun);
  		}
  
  		for (auto const& p : pack->m_ints)
  		{
  			// disregard setting indices that are not int types
  			if ((p.first & settings_pack::type_mask) != settings_pack::int_type_base)
  				continue;
  
  			// ignore settings that are out of bounds
  			int const index = p.first & settings_pack::index_mask;
  			TORRENT_ASSERT_PRECOND(index >= 0 && index < settings_pack::num_int_settings);
  			if (index < 0 || index >= settings_pack::num_int_settings)
  				continue;
  
  			// if the value did not change, don't call the update callback
  			if (sett.get_int(p.first) == p.second) continue;
  
  			sett.set_int(p.first, p.second);
  			int_setting_entry_t const& sa = int_settings[index];
  			if (sa.fun && callbacks
  				&& std::find(callbacks->begin(), callbacks->end(), sa.fun) == callbacks->end())
  				callbacks->push_back(sa.fun);
  		}
  
  		for (auto const& p : pack->m_bools)
  		{
  			// disregard setting indices that are not bool types
  			if ((p.first & settings_pack::type_mask) != settings_pack::bool_type_base)
  				continue;
  
  			// ignore settings that are out of bounds
  			int const index = p.first & settings_pack::index_mask;
  			TORRENT_ASSERT_PRECOND(index >= 0 && index < settings_pack::num_bool_settings);
  			if (index < 0 || index >= settings_pack::num_bool_settings)
  				continue;
  
  			// if the value did not change, don't call the update callback
  			if (sett.get_bool(p.first) == p.second) continue;
  
  			sett.set_bool(p.first, p.second);
  			bool_setting_entry_t const& sa = bool_settings[index];
  			if (sa.fun && callbacks
  				&& std::find(callbacks->begin(), callbacks->end(), sa.fun) == callbacks->end())
  				callbacks->push_back(sa.fun);
  		}
  	}
  
  	void settings_pack::set_str(int const name, std::string val)
  	{
  		TORRENT_ASSERT((name & type_mask) == string_type_base);
  		if ((name & type_mask) != string_type_base) return;
  		std::pair<std::uint16_t, std::string> v(aux::numeric_cast<std::uint16_t>(name), std::move(val));
  		insort_replace(m_strings, std::move(v));
  	}
  
  	void settings_pack::set_int(int const name, int const val)
  	{
  		TORRENT_ASSERT((name & type_mask) == int_type_base);
  		if ((name & type_mask) != int_type_base) return;
  		std::pair<std::uint16_t, int> v(aux::numeric_cast<std::uint16_t>(name), val);
  		insort_replace(m_ints, v);
  	}
  
  	void settings_pack::set_bool(int const name, bool const val)
  	{
  		TORRENT_ASSERT((name & type_mask) == bool_type_base);
  		if ((name & type_mask) != bool_type_base) return;
  		std::pair<std::uint16_t, bool> v(aux::numeric_cast<std::uint16_t>(name), val);
  		insort_replace(m_bools, v);
  	}
  
  	bool settings_pack::has_val(int const name) const
  	{
  		switch (name & type_mask)
  		{
  			case string_type_base:
  			{
  				// this is an optimization. If the settings pack is complete,
  				// i.e. has every key, we don't need to search, it's just a lookup
  				if (m_strings.size() == settings_pack::num_string_settings)
  					return true;
  				std::pair<std::uint16_t, std::string> v(aux::numeric_cast<std::uint16_t>(name), std::string());
  				auto i = std::lower_bound(m_strings.begin(), m_strings.end(), v
  						, &compare_first<std::string>);
  				return i != m_strings.end() && i->first == name;
  			}
  			case int_type_base:
  			{
  				// this is an optimization. If the settings pack is complete,
  				// i.e. has every key, we don't need to search, it's just a lookup
  				if (m_ints.size() == settings_pack::num_int_settings)
  					return true;
  				std::pair<std::uint16_t, int> v(aux::numeric_cast<std::uint16_t>(name), 0);
  				auto i = std::lower_bound(m_ints.begin(), m_ints.end(), v
  						, &compare_first<int>);
  				return i != m_ints.end() && i->first == name;
  			}
  			case bool_type_base:
  			{
  				// this is an optimization. If the settings pack is complete,
  				// i.e. has every key, we don't need to search, it's just a lookup
  				if (m_bools.size() == settings_pack::num_bool_settings)
  					return true;
  				std::pair<std::uint16_t, bool> v(aux::numeric_cast<std::uint16_t>(name), false);
  				auto i = std::lower_bound(m_bools.begin(), m_bools.end(), v
  						, &compare_first<bool>);
  				return i != m_bools.end() && i->first == name;
  			}
  		}
  		TORRENT_ASSERT_FAIL();
  		return false;
  	}
  
  	std::string const& settings_pack::get_str(int name) const
  	{
  		static std::string const empty;
  		TORRENT_ASSERT_PRECOND((name & type_mask) == string_type_base);
  		if ((name & type_mask) != string_type_base) return empty;
  
  		// this is an optimization. If the settings pack is complete,
  		// i.e. has every key, we don't need to search, it's just a lookup
  		if (m_strings.size() == settings_pack::num_string_settings)
  		{
  			TORRENT_ASSERT(m_strings[name & index_mask].first == name);
  			return m_strings[name & index_mask].second;
  		}
  		std::pair<std::uint16_t, std::string> v(aux::numeric_cast<std::uint16_t>(name), std::string());
  		auto i = std::lower_bound(m_strings.begin(), m_strings.end(), v
  				, &compare_first<std::string>);
  		if (i != m_strings.end() && i->first == name) return i->second;
  		return empty;
  	}
  
  	int settings_pack::get_int(int name) const
  	{
  		TORRENT_ASSERT_PRECOND((name & type_mask) == int_type_base);
  		if ((name & type_mask) != int_type_base) return 0;
  
  		// this is an optimization. If the settings pack is complete,
  		// i.e. has every key, we don't need to search, it's just a lookup
  		if (m_ints.size() == settings_pack::num_int_settings)
  		{
  			TORRENT_ASSERT(m_ints[name & index_mask].first == name);
  			return m_ints[name & index_mask].second;
  		}
  		std::pair<std::uint16_t, int> v(aux::numeric_cast<std::uint16_t>(name), 0);
  		auto i = std::lower_bound(m_ints.begin(), m_ints.end(), v
  				, &compare_first<int>);
  		if (i != m_ints.end() && i->first == name) return i->second;
  		return 0;
  	}
  
  	bool settings_pack::get_bool(int name) const
  	{
  		TORRENT_ASSERT_PRECOND((name & type_mask) == bool_type_base);
  		if ((name & type_mask) != bool_type_base) return false;
  
  		// this is an optimization. If the settings pack is complete,
  		// i.e. has every key, we don't need to search, it's just a lookup
  		if (m_bools.size() == settings_pack::num_bool_settings)
  		{
  			TORRENT_ASSERT(m_bools[name & index_mask].first == name);
  			return m_bools[name & index_mask].second;
  		}
  		std::pair<std::uint16_t, bool> v(aux::numeric_cast<std::uint16_t>(name), false);
  		auto i = std::lower_bound(m_bools.begin(), m_bools.end(), v
  			, &compare_first<bool>);
  		if (i != m_bools.end() && i->first == name) return i->second;
  		return false;
  	}
  
  	void settings_pack::clear()
  	{
  		m_strings.clear();
  		m_ints.clear();
  		m_bools.clear();
  	}
  
  	void settings_pack::clear(int const name)
  	{
  		switch (name & type_mask)
  		{
  			case string_type_base:
  			{
  				std::pair<std::uint16_t, std::string> v(aux::numeric_cast<std::uint16_t>(name), std::string());
  				auto const i = std::lower_bound(m_strings.begin(), m_strings.end()
  					, v, &compare_first<std::string>);
  				if (i != m_strings.end() && i->first == name) m_strings.erase(i);
  				break;
  			}
  			case int_type_base:
  			{
  				std::pair<std::uint16_t, int> v(aux::numeric_cast<std::uint16_t>(name), 0);
  				auto const i = std::lower_bound(m_ints.begin(), m_ints.end()
  					, v, &compare_first<int>);
  				if (i != m_ints.end() && i->first == name) m_ints.erase(i);
  				break;
  			}
  			case bool_type_base:
  			{
  				std::pair<std::uint16_t, bool> v(aux::numeric_cast<std::uint16_t>(name), false);
  				auto const i = std::lower_bound(m_bools.begin(), m_bools.end()
  					, v, &compare_first<bool>);
  				if (i != m_bools.end() && i->first == name) m_bools.erase(i);
  				break;
  			}
  		}
  	}
  }
  