transmission/libtransmission/cache.h

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// This file Copyright © 2010-2022 Mnemosyne LLC.
// It may be used under GPLv2 (SPDX: GPL-2.0), GPLv3 (SPDX: GPL-3.0),
// or any future license endorsed by Mnemosyne LLC.
// License text can be found in the licenses/ folder.
#pragma once
#ifndef __TRANSMISSION__
#error only libtransmission should #include this header.
#endif
#include <cstdint> // intX_t, uintX_t
#include <memory> // std::unique_ptr
#include <utility> // std::pair
#include <vector>
#include "transmission.h"
#include "block-info.h"
class tr_torrents;
struct evbuffer;
struct tr_torrent;
class Cache
{
public:
Cache(tr_torrents& torrents, int64_t max_bytes);
int setLimit(int64_t new_limit);
[[nodiscard]] constexpr auto getLimit() const noexcept
{
return max_bytes_;
}
void writeBlock(tr_torrent_id_t tor, tr_block_index_t block, std::unique_ptr<std::vector<uint8_t>>& writeme);
int readBlock(tr_torrent* torrent, tr_block_info::Location loc, uint32_t len, uint8_t* setme);
int prefetchBlock(tr_torrent* torrent, tr_block_info::Location loc, uint32_t len);
int flushTorrent(tr_torrent* torrent);
int flushFile(tr_torrent* torrent, tr_file_index_t file);
private:
using Key = std::pair<tr_torrent_id_t, tr_block_index_t>;
struct CacheBlock
{
Key key;
std::unique_ptr<std::vector<uint8_t>> buf;
time_t time_added = {};
};
using Blocks = std::vector<CacheBlock>;
using CIter = Blocks::const_iterator;
struct CompareCacheBlockByKey
{
[[nodiscard]] constexpr bool operator()(Key const& key, CacheBlock const& block)
{
return key < block.key;
}
[[nodiscard]] constexpr bool operator()(CacheBlock const& block, Key const& key)
{
return block.key < key;
}
};
[[nodiscard]] static Key makeKey(tr_torrent const* torrent, tr_block_info::Location loc) noexcept;
[[nodiscard]] static std::pair<CIter, CIter> findContiguous(CIter const begin, CIter const end, CIter const iter) noexcept;
// @return any error code from tr_ioWrite()
[[nodiscard]] int writeContiguous(CIter const begin, CIter const end) const;
// @return any error code from writeContiguous()
[[nodiscard]] int flushSpan(CIter const begin, CIter const end);
// @return any error code from writeContiguous()
[[nodiscard]] int flushOldest();
// @return any error code from writeContiguous()
[[nodiscard]] int cacheTrim();
[[nodiscard]] static size_t getMaxBlocks(int64_t max_bytes) noexcept;
[[nodiscard]] CIter getBlock(tr_torrent const* torrent, tr_block_info::Location loc) noexcept;
tr_torrents& torrents_;
Blocks blocks_ = {};
size_t max_blocks_ = 0;
size_t max_bytes_ = 0;
mutable size_t disk_writes_ = 0;
mutable size_t disk_write_bytes_ = 0;
mutable size_t cache_writes_ = 0;
mutable size_t cache_write_bytes_ = 0;
};