transmission/libtransmission/cache.h

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// This file Copyright © 2010-2023 Mnemosyne LLC.
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// It may be used under GPLv2 (SPDX: GPL-2.0-only), GPLv3 (SPDX: GPL-3.0-only),
// 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 <cstddef> // for size_t
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#include <cstdint> // for intX_t, uintX_t
#include <memory> // for std::unique_ptr
#include <utility> // for std::pair
#include <vector>
#include <small/vector.hpp>
#include "transmission.h"
#include "block-info.h"
class tr_torrents;
struct tr_torrent;
class Cache
{
public:
using BlockData = small::max_size_vector<uint8_t, tr_block_info::BlockSize>;
Cache(tr_torrents& torrents, size_t max_bytes);
int set_limit(size_t new_limit);
// @return any error code from cacheTrim()
int write_block(tr_torrent_id_t tor, tr_block_index_t block, std::unique_ptr<BlockData> writeme);
int read_block(tr_torrent* torrent, tr_block_info::Location const& loc, uint32_t len, uint8_t* setme);
int prefetch_block(tr_torrent* torrent, tr_block_info::Location const& loc, uint32_t len);
int flush_torrent(tr_torrent const* torrent);
int flush_file(tr_torrent const* 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<BlockData> buf;
};
using Blocks = std::vector<CacheBlock>;
using CIter = Blocks::const_iterator;
[[nodiscard]] static Key make_key(tr_torrent const* torrent, tr_block_info::Location loc) noexcept;
[[nodiscard]] static std::pair<CIter, CIter> find_biggest_span(CIter begin, CIter end) noexcept;
[[nodiscard]] static CIter find_span_end(CIter span_begin, CIter end) noexcept;
// @return any error code from tr_ioWrite()
[[nodiscard]] int write_contiguous(CIter begin, CIter end) const;
// @return any error code from writeContiguous()
[[nodiscard]] int flush_span(CIter begin, CIter end);
// @return any error code from writeContiguous()
[[nodiscard]] int flush_biggest();
// @return any error code from writeContiguous()
[[nodiscard]] int cache_trim();
[[nodiscard]] static size_t get_max_blocks(size_t max_bytes) noexcept;
[[nodiscard]] CIter get_block(tr_torrent const* torrent, tr_block_info::Location const& loc) noexcept;
tr_torrents& torrents_;
Blocks blocks_ = {};
size_t max_blocks_ = 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;
static constexpr struct
{
[[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;
}
} CompareCacheBlockByKey{};
};