libtorrent/src/load_torrent.cpp

/*

Copyright (c) 2022, Arvid Norberg
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
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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
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*/

#include "libtorrent/load_torrent.hpp"
#include "libtorrent/torrent_info.hpp"
#include "libtorrent/file_storage.hpp"
#include "libtorrent/sha1_hash.hpp"
#include "libtorrent/aux_/merkle.hpp"
#include "libtorrent/aux_/throw.hpp"

namespace libtorrent {

namespace {
	void update_atp(add_torrent_params& atp)
	{
		auto const& ti = atp.ti;
		// This is a temporary measure until all non info-dict content is parsed
		// here, rather than the torrent_info constructor
		auto drained_state = ti->_internal_drain();
		for (auto const& ae : drained_state.urls)
		{
			atp.trackers.push_back(std::move(ae.url));
			atp.tracker_tiers.push_back(ae.tier);
		}
		if (ti->is_i2p())
			atp.flags |= torrent_flags::i2p_torrent;

		for (auto const& ws : drained_state.web_seeds)
		{
			if (ws.type == web_seed_entry::url_seed)
				atp.url_seeds.push_back(std::move(ws.url));
			else if (ws.type == web_seed_entry::http_seed)
				atp.http_seeds.push_back(std::move(ws.url));
		}

		atp.dht_nodes = std::move(drained_state.nodes);

		if (ti->v2_piece_hashes_verified())
		{
			int const blocks_per_piece = ti->files().blocks_per_piece();
			std::vector<sha256_hash> scratch;
			sha256_hash const pad = merkle_pad(blocks_per_piece, 1);
			file_storage const& fs = ti->files();
			atp.merkle_trees.resize(fs.num_files());
			atp.merkle_tree_mask.resize(fs.num_files());
			for (auto const f : fs.file_range())
			{
				if (fs.pad_file_at(f)) continue;
				if (fs.file_size(f) == 0) continue;
				auto const bytes = ti->piece_layer(f);
				auto& layer = atp.merkle_trees[f];
				layer.reserve(std::size_t(bytes.size() / sha256_hash::size()));
				for (int i = 0; i < bytes.size(); i += int(sha256_hash::size()))
					layer.emplace_back(bytes.data() + i);

				int const full_size = merkle_num_nodes(
					merkle_num_leafs(fs.file_num_blocks(f)));
				int const num_pieces = fs.file_num_pieces(f);
				int const piece_layer_size = merkle_num_leafs(num_pieces);

				if (!layer.empty())
				{
					sha256_hash const computed_root = merkle_root_scratch(layer
						, piece_layer_size
						, pad
						, scratch);
					if (computed_root != fs.root(f))
						aux::throw_ex<system_error>(errors::torrent_invalid_piece_layer);
				}

				auto& mask = atp.merkle_tree_mask[f];
				mask.resize(std::size_t(full_size), false);
				for (int i = merkle_first_leaf(piece_layer_size)
					, end = i + num_pieces; i < end; ++i)
				{
					mask[std::size_t(i)] = true;
				}
			}
			ti->free_piece_layers();
		}
		atp.info_hashes = atp.ti->info_hashes();
	}
}

	add_torrent_params load_torrent_file(std::string const& filename)
	{ return load_torrent_file(filename, load_torrent_limits{}); }
	add_torrent_params load_torrent_buffer(span<char const> buffer)
	{ return load_torrent_buffer(buffer, load_torrent_limits{}); }
	add_torrent_params load_torrent_parsed(bdecode_node const& torrent_file)
	{ return load_torrent_parsed(torrent_file, load_torrent_limits{}); }

	// TODO: move the loading logic from torrent_info constructor into here
	add_torrent_params load_torrent_file(std::string const& filename, load_torrent_limits const& cfg)
	{
		add_torrent_params ret;
		ret.ti = std::make_shared<torrent_info>(filename, cfg);
		update_atp(ret);
		return ret;
	}

	add_torrent_params load_torrent_buffer(span<char const> buffer, load_torrent_limits const& cfg)
	{
		add_torrent_params ret;
		ret.ti = std::make_shared<torrent_info>(buffer, cfg, from_span);
		update_atp(ret);
		return ret;
	}

	add_torrent_params load_torrent_parsed(bdecode_node const& torrent_file, load_torrent_limits const& cfg)
	{
		add_torrent_params ret;
		ret.ti = std::make_shared<torrent_info>(torrent_file, cfg);
		update_atp(ret);
		return ret;
	}

}