271 lines
7.5 KiB
C++
271 lines
7.5 KiB
C++
// This file Copyright 2010-2022 Mnemosyne LLC.
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// It may be used under GPLv2 (SPDX: GPL-2.0-only), GPLv3 (SPDX: GPL-3.0-only),
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// or any future license endorsed by Mnemosyne LLC.
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// License text can be found in the licenses/ folder.
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#include <algorithm>
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#include <cstdlib> // std::lldiv()
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#include <iterator> // std::distance(), std::next(), std::prev()
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#include <memory>
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#include <numeric> // std::accumulate()
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#include <utility> // std::make_pair()
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#include <vector>
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#include <fmt/core.h>
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#include "libtransmission/transmission.h"
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#include "libtransmission/cache.h"
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#include "libtransmission/inout.h"
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#include "libtransmission/log.h"
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#include "libtransmission/torrent.h"
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#include "libtransmission/torrents.h"
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#include "libtransmission/tr-assert.h"
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#include "libtransmission/utils.h" // tr_formatter
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Cache::Key Cache::make_key(tr_torrent const* torrent, tr_block_info::Location loc) noexcept
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{
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return std::make_pair(torrent->id(), loc.block);
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}
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Cache::CIter Cache::find_span_end(CIter span_begin, CIter end) noexcept
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{
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static constexpr auto NotAdjacent = [](CacheBlock const& block1, CacheBlock const& block2)
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{
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return block1.key.first != block2.key.first || block1.key.second + 1 != block2.key.second;
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};
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auto const span_end = std::adjacent_find(span_begin, end, NotAdjacent);
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return span_end == end ? end : std::next(span_end);
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}
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std::pair<Cache::CIter, Cache::CIter> Cache::find_biggest_span(CIter const begin, CIter const end) noexcept
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{
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auto biggest_begin = begin;
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auto biggest_end = begin;
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auto biggest_len = std::distance(biggest_begin, biggest_end);
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for (auto span_begin = begin; span_begin < end;)
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{
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auto span_end = find_span_end(span_begin, end);
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auto const len = std::distance(span_begin, span_end);
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if (len > biggest_len)
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{
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biggest_begin = span_begin;
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biggest_end = span_end;
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biggest_len = len;
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}
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std::advance(span_begin, len);
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}
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return { biggest_begin, biggest_end };
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}
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int Cache::write_contiguous(CIter const begin, CIter const end) const
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{
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// The most common case without an extra data copy.
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auto const* out = std::data(*begin->buf);
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auto outlen = std::size(*begin->buf);
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// Contiguous area to join more than one block, if any.
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auto buf = std::vector<uint8_t>{};
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if (end - begin > 1)
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{
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// copy blocks into contiguous memory
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auto const buflen = std::accumulate(
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begin,
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end,
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size_t{},
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[](size_t sum, auto const& block) { return sum + std::size(*block.buf); });
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buf.resize(buflen);
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auto* walk = std::data(buf);
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for (auto iter = begin; iter != end; ++iter)
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{
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TR_ASSERT(begin->key.first == iter->key.first);
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TR_ASSERT(begin->key.second + std::distance(begin, iter) == iter->key.second);
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walk = std::copy_n(std::data(*iter->buf), std::size(*iter->buf), walk);
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}
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TR_ASSERT(std::data(buf) + std::size(buf) == walk);
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out = std::data(buf);
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outlen = std::size(buf);
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}
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// save it
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auto const& [torrent_id, block] = begin->key;
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auto* const tor = torrents_.get(torrent_id);
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if (tor == nullptr)
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{
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return EINVAL;
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}
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auto const loc = tor->block_loc(block);
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if (auto const err = tr_ioWrite(tor, loc, outlen, out); err != 0)
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{
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return err;
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}
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++disk_writes_;
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disk_write_bytes_ += outlen;
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return {};
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}
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size_t Cache::get_max_blocks(size_t max_bytes) noexcept
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{
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return max_bytes / tr_block_info::BlockSize;
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}
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int Cache::set_limit(size_t new_limit)
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{
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max_blocks_ = get_max_blocks(new_limit);
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tr_logAddDebug(fmt::format("Maximum cache size set to {} ({} blocks)", tr_formatter_mem_B(new_limit), max_blocks_));
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return cache_trim();
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}
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Cache::Cache(tr_torrents& torrents, size_t max_bytes)
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: torrents_{ torrents }
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, max_blocks_(get_max_blocks(max_bytes))
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{
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}
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// ---
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int Cache::write_block(tr_torrent_id_t tor_id, tr_block_index_t block, std::unique_ptr<BlockData> writeme)
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{
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if (max_blocks_ == 0U)
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{
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TR_ASSERT(std::empty(blocks_));
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// Bypass cache. This may be helpful for those whose filesystem
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// already has a cache layer for the very purpose of this cache
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// https://github.com/transmission/transmission/pull/5668
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auto* const tor = torrents_.get(tor_id);
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return tr_ioWrite(tor, tor->block_loc(block), std::size(*writeme), std::data(*writeme));
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}
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auto const key = Key{ tor_id, block };
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auto iter = std::lower_bound(std::begin(blocks_), std::end(blocks_), key, CompareCacheBlockByKey);
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if (iter == std::end(blocks_) || iter->key != key)
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{
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iter = blocks_.emplace(iter);
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iter->key = key;
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}
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iter->buf = std::move(writeme);
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++cache_writes_;
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cache_write_bytes_ += std::size(*iter->buf);
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return cache_trim();
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}
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Cache::CIter Cache::get_block(tr_torrent const* torrent, tr_block_info::Location const& loc) noexcept
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{
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if (auto const [begin, end] = std::equal_range(
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std::begin(blocks_),
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std::end(blocks_),
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make_key(torrent, loc),
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CompareCacheBlockByKey);
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begin < end)
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{
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return begin;
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}
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return std::end(blocks_);
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}
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int Cache::read_block(tr_torrent* torrent, tr_block_info::Location const& loc, uint32_t len, uint8_t* setme)
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{
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if (auto const iter = get_block(torrent, loc); iter != std::end(blocks_))
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{
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std::copy_n(std::begin(*iter->buf), len, setme);
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return {};
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}
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return tr_ioRead(torrent, loc, len, setme);
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}
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int Cache::prefetch_block(tr_torrent* torrent, tr_block_info::Location const& loc, uint32_t len)
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{
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if (auto const iter = get_block(torrent, loc); iter != std::end(blocks_))
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{
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return {}; // already have it
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}
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return tr_ioPrefetch(torrent, loc, len);
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}
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// ---
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int Cache::flush_span(CIter const begin, CIter const end)
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{
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for (auto span_begin = begin; span_begin < end;)
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{
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auto const span_end = find_span_end(span_begin, end);
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if (auto const err = write_contiguous(span_begin, span_end); err != 0)
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{
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return err;
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}
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span_begin = span_end;
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}
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blocks_.erase(begin, end);
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return {};
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}
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int Cache::flush_file(tr_torrent const* torrent, tr_file_index_t file)
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{
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auto const tor_id = torrent->id();
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auto const [block_begin, block_end] = tr_torGetFileBlockSpan(torrent, file);
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return flush_span(
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std::lower_bound(std::begin(blocks_), std::end(blocks_), std::make_pair(tor_id, block_begin), CompareCacheBlockByKey),
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std::lower_bound(std::begin(blocks_), std::end(blocks_), std::make_pair(tor_id, block_end), CompareCacheBlockByKey));
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}
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int Cache::flush_torrent(tr_torrent const* torrent)
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{
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auto const tor_id = torrent->id();
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return flush_span(
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std::lower_bound(std::begin(blocks_), std::end(blocks_), std::make_pair(tor_id, 0), CompareCacheBlockByKey),
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std::lower_bound(std::begin(blocks_), std::end(blocks_), std::make_pair(tor_id + 1, 0), CompareCacheBlockByKey));
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}
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int Cache::flush_biggest()
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{
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auto const [begin, end] = find_biggest_span(std::begin(blocks_), std::end(blocks_));
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if (begin == end) // nothing to flush
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{
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return 0;
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}
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if (auto const err = write_contiguous(begin, end); err != 0)
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{
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return err;
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}
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blocks_.erase(begin, end);
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return 0;
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}
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int Cache::cache_trim()
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{
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while (std::size(blocks_) > max_blocks_)
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{
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if (auto const err = flush_biggest(); err != 0)
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{
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return err;
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}
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}
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return 0;
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}
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