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b5406b90cd
Increasing independence of format-specific stuff and generic caching without mangling them into a common namespace, and allowing in some cases for a decrease in read/write blocking.
136 lines
3.0 KiB
C++
136 lines
3.0 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 <cstdio>
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#include <cstdint>
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#include <mutex>
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#include <string>
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namespace Storage {
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class FileHolder {
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public:
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enum {
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ErrorCantOpen = -1
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};
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virtual ~FileHolder();
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protected:
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FileHolder(const std::string &file_name);
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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 up to and 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, size_t length);
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/*!
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Performs @c fgetc 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 fgetc32le();
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/*!
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Performs @c fgetc 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 fgetc24le();
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/*!
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Performs @c fgetc 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 fgetc16le();
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/*!
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Performs @c fgetc 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 fgetc32be();
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/*!
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Performs @c fgetc 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 fgetc16be();
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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_file_is_at_least_length(long length);
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class BitStream {
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public:
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BitStream(FILE *f, bool lsb_first) :
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file_(f),
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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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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 = (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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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_ = (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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FILE *file_;
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struct stat file_stats_;
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bool is_read_only_;
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std::mutex file_access_mutex_;
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const std::string name_;
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};
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}
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#endif /* FileHolder_hpp */
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