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94 lines
2.9 KiB
C++
94 lines
2.9 KiB
C++
// Copyright (c) 2009-2010 Satoshi Nakamoto
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// Copyright (c) 2009-2019 The Bitcoin Core developers
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// Distributed under the MIT software license, see the accompanying
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// file COPYING or http://www.opensource.org/licenses/mit-license.php.
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#ifndef BITCOIN_FLATFILE_H
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#define BITCOIN_FLATFILE_H
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#include <string>
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#include <fs.h>
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#include <serialize.h>
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struct FlatFilePos
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{
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int nFile;
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unsigned int nPos;
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SERIALIZE_METHODS(FlatFilePos, obj)
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{
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READWRITE(VARINT(obj.nFile, VarIntMode::NONNEGATIVE_SIGNED), VARINT(obj.nPos));
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}
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FlatFilePos() : nFile(-1), nPos(0) {}
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FlatFilePos(int nFileIn, unsigned int nPosIn) :
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nFile(nFileIn),
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nPos(nPosIn)
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{}
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friend bool operator==(const FlatFilePos &a, const FlatFilePos &b) {
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return (a.nFile == b.nFile && a.nPos == b.nPos);
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}
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friend bool operator!=(const FlatFilePos &a, const FlatFilePos &b) {
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return !(a == b);
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}
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void SetNull() { nFile = -1; nPos = 0; }
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bool IsNull() const { return (nFile == -1); }
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std::string ToString() const;
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};
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/**
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* FlatFileSeq represents a sequence of numbered files storing raw data. This class facilitates
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* access to and efficient management of these files.
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*/
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class FlatFileSeq
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{
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private:
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const fs::path m_dir;
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const char* const m_prefix;
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const size_t m_chunk_size;
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public:
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/**
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* Constructor
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*
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* @param dir The base directory that all files live in.
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* @param prefix A short prefix given to all file names.
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* @param chunk_size Disk space is pre-allocated in multiples of this amount.
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*/
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FlatFileSeq(fs::path dir, const char* prefix, size_t chunk_size);
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/** Get the name of the file at the given position. */
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fs::path FileName(const FlatFilePos& pos) const;
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/** Open a handle to the file at the given position. */
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FILE* Open(const FlatFilePos& pos, bool read_only = false);
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/**
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* Allocate additional space in a file after the given starting position. The amount allocated
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* will be the minimum multiple of the sequence chunk size greater than add_size.
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*
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* @param[in] pos The starting position that bytes will be allocated after.
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* @param[in] add_size The minimum number of bytes to be allocated.
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* @param[out] out_of_space Whether the allocation failed due to insufficient disk space.
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* @return The number of bytes successfully allocated.
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*/
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size_t Allocate(const FlatFilePos& pos, size_t add_size, bool& out_of_space);
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/**
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* Commit a file to disk, and optionally truncate off extra pre-allocated bytes if final.
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*
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* @param[in] pos The first unwritten position in the file to be flushed.
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* @param[in] finalize True if no more data will be written to this file.
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* @return true on success, false on failure.
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*/
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bool Flush(const FlatFilePos& pos, bool finalize = false);
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};
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#endif // BITCOIN_FLATFILE_H
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