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254 lines
6.3 KiB
C++
254 lines
6.3 KiB
C++
//
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// FileHolder.hpp
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// Clock Signal
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//
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// Created by Thomas Harte on 21/11/2016.
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// Copyright 2016 Thomas Harte. All rights reserved.
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//
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#ifndef FileHolder_hpp
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#define FileHolder_hpp
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#include <sys/stat.h>
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#include <array>
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#include <cstdio>
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#include <cstdint>
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#include <mutex>
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#include <string>
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#include <vector>
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namespace Storage {
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class FileHolder final {
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public:
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enum class Error {
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CantOpen = -1
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};
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enum class FileMode {
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ReadWrite,
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Read,
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Rewrite
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};
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~FileHolder();
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/*!
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Attempts to open the file indicated by @c file_name. @c ideal_mode nominates how the file would
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most ideally be opened. It can be one of:
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ReadWrite attempt to open this file for random access reading and writing. If that fails,
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will attept to open in Read mode.
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Read attempts to open this file for reading only.
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Rewrite opens the file for rewriting; none of the original content is preserved; whatever
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the caller outputs will replace the existing file.
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@raises ErrorCantOpen if the file cannot be opened.
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*/
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FileHolder(const std::string &file_name, FileMode ideal_mode = FileMode::ReadWrite);
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/*!
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Performs @c get8 four times on @c file, casting each result to a @c uint32_t
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and returning the four assembled in little endian order.
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*/
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uint32_t get32le();
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/*!
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Writes @c value using successive @c put8s, in little endian order.
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*/
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template <typename T> void put_le(T value) {
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auto bytes = sizeof(T);
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while(bytes--) {
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put8(value&0xff);
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value >>= 8;
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}
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}
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/*!
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Writes @c value using successive @c put8s, in big endian order.
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*/
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template <typename T> void put_be(T value) {
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auto shift = sizeof(T) * 8;
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while(shift) {
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shift -= 8;
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put8((value >> shift)&0xff);
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}
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}
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/*!
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Performs @c get8 four times on @c file, casting each result to a @c uint32_t
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and returning the four assembled in big endian order.
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*/
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uint32_t get32be();
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/*!
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Performs @c get8 three times on @c file, casting each result to a @c uint32_t
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and returning the three assembled in little endian order.
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*/
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uint32_t get24le();
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/*!
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Performs @c get8 three times on @c file, casting each result to a @c uint32_t
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and returning the three assembled in big endian order.
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*/
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uint32_t get24be();
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/*!
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Performs @c get8 two times on @c file, casting each result to a @c uint32_t
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and returning the two assembled in little endian order.
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*/
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uint16_t get16le();
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/*!
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Writes @c value using two successive @c put8s, in little endian order.
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*/
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void put16le(uint16_t value);
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/*!
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Performs @c get8 two times on @c file, casting each result to a @c uint32_t
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and returning the two assembled in big endian order.
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*/
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uint16_t get16be();
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/*!
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Writes @c value using two successive @c put8s, in big endian order.
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*/
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void put16be(uint16_t value);
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/*! Reads a single byte from @c file. */
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uint8_t get8();
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/*! Writes a single byte from @c file. */
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void put8(uint8_t value);
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/*! Writes @c value a total of @c repeats times. */
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void putn(std::size_t repeats, uint8_t value);
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/*! Reads @c size bytes and returns them as a vector. */
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std::vector<uint8_t> read(std::size_t size);
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/*! Reads @c a.size() bytes into @c a.data(). */
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template <size_t size> std::size_t read(std::array<uint8_t, size> &a) {
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return read(a.data(), a.size());
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}
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/*! Reads @c size bytes and writes them to @c buffer. */
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std::size_t read(uint8_t *buffer, std::size_t size);
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/*! Writes @c buffer one byte at a time in order. */
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std::size_t write(const std::vector<uint8_t> &buffer);
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/*! Writes @c buffer one byte at a time in order, writing @c size bytes in total. */
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std::size_t write(const uint8_t *buffer, std::size_t size);
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/*! Moves @c bytes from the anchor indicated by @c whence: SEEK_SET, SEEK_CUR or SEEK_END. */
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void seek(long offset, int whence);
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/*! @returns The current cursor position within this file. */
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long tell();
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/*! Flushes any queued content that has not yet been written to disk. */
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void flush();
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/*! @returns @c true if the end-of-file indicator is set, @c false otherwise. */
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bool eof();
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class BitStream {
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public:
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uint8_t get_bits(int q) {
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uint8_t result = 0;
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while(q--) {
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result = static_cast<uint8_t>((result << 1) | get_bit());
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}
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return result;
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}
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private:
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BitStream(FILE *file, bool lsb_first) :
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file_(file),
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lsb_first_(lsb_first),
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next_value_(0),
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bits_remaining_(0) {}
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friend FileHolder;
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FILE *file_;
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bool lsb_first_;
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uint8_t next_value_;
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int bits_remaining_;
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uint8_t get_bit() {
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if(!bits_remaining_) {
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bits_remaining_ = 8;
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next_value_ = static_cast<uint8_t>(fgetc(file_));
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}
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uint8_t bit;
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if(lsb_first_) {
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bit = next_value_ & 1;
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next_value_ >>= 1;
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} else {
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bit = next_value_ >> 7;
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next_value_ <<= 1;
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}
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bits_remaining_--;
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return bit;
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}
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};
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/*!
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Obtains a BitStream for reading from the file from the current reading cursor.
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*/
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BitStream get_bitstream(bool lsb_first);
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/*!
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Reads @c length bytes from the file and compares them to the first
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@c length bytes of @c signature. If @c length is 0, it is computed
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as the length of @c signature not including the terminating null.
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@returns @c true if the bytes read match the signature; @c false otherwise.
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*/
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bool check_signature(const char *signature, std::size_t length = 0);
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/*!
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Determines and returns the file extension: everything from the final character
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back to the first dot. The string is converted to lowercase before being returned.
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*/
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std::string extension();
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/*!
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Ensures the file is at least @c length bytes long, appending 0s until it is
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if necessary.
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*/
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void ensure_is_at_least_length(long length);
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/*!
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@returns @c true if an attempt was made to read this file in ReadWrite mode but it could be opened only for reading; @c false otherwise.
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*/
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bool get_is_known_read_only();
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/*!
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@returns the stat struct describing this file.
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*/
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struct stat &stats();
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/*!
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@returns a mutex owned by the file that can be used to serialise file access.
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*/
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std::mutex &get_file_access_mutex();
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private:
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FILE *file_ = nullptr;
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const std::string name_;
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struct stat file_stats_;
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bool is_read_only_ = false;
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std::mutex file_access_mutex_;
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};
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}
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#endif /* FileHolder_hpp */
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