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119 lines
3.4 KiB
C++
119 lines
3.4 KiB
C++
//
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// TapeParser.hpp
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// Clock Signal
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//
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// Created by Thomas Harte on 05/09/2016.
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// Copyright © 2016 Thomas Harte. All rights reserved.
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//
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#ifndef TapeParser_hpp
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#define TapeParser_hpp
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#include "../Tape.hpp"
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#include <memory>
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#include <vector>
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namespace Storage {
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namespace Tape {
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/*!
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A partly-abstract base class to help in the authorship of tape format parsers;
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provides hooks for pulse classification from pulses to waves and for symbol identification from
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waves.
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Very optional, not intended to box in the approaches taken for analysis.
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*/
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template <typename WaveType, typename SymbolType> class Parser {
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public:
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/// Instantiates a new parser with the supplied @c tape.
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Parser() : _has_next_symbol(false), _error_flag(false) {}
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/// Resets the error flag.
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void reset_error_flag() { _error_flag = false; }
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/// @returns @c true if an error has occurred since the error flag was last reset; @c false otherwise.
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bool get_error_flag() { return _error_flag; }
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/*!
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Asks the parser to continue taking pulses from the tape until either the subclass next declares a symbol
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or the tape runs out, returning the most-recently declared symbol.
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*/
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SymbolType get_next_symbol(const std::shared_ptr<Storage::Tape::Tape> &tape)
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{
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while(!_has_next_symbol && !tape->is_at_end())
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{
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process_pulse(tape->get_next_pulse());
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}
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_has_next_symbol = false;
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return _next_symbol;
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}
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/*!
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Should be implemented by subclasses. Consumes @c pulse. Is likely either to call @c push_wave
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or to take no action.
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*/
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virtual void process_pulse(Storage::Tape::Tape::Pulse pulse) = 0;
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protected:
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/*!
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Adds @c wave to the back of the list of recognised waves and calls @c inspect_waves to check for a new symbol.
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Expected to be called by subclasses from @c process_pulse as and when recognised waves arise.
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*/
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void push_wave(WaveType wave)
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{
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_wave_queue.push_back(wave);
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inspect_waves(_wave_queue);
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}
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/*!
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Removes @c nunber_of_waves waves from the front of the list.
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Expected to be called by subclasses from @c process_pulse if it is recognised that the first set of waves
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do not form a valid symbol.
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*/
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void remove_waves(int number_of_waves)
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{
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_wave_queue.erase(_wave_queue.begin(), _wave_queue.begin()+number_of_waves);
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}
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/*!
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Sets @c symbol as the newly-recognised symbol and removes @c nunber_of_waves waves from the front of the list.
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Expected to be called by subclasses from @c process_pulse when it recognises that the first @c number_of_waves
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waves together represent @c symbol.
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*/
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void push_symbol(SymbolType symbol, int number_of_waves)
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{
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_has_next_symbol = true;
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_next_symbol = symbol;
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remove_waves(number_of_waves);
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}
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void set_error_flag()
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{
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_error_flag = true;
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}
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private:
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bool _error_flag;
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/*!
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Should be implemented by subclasses. Inspects @c waves for a potential new symbol. If one is
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found should call @c push_symbol. May wish alternatively to call @c remove_waves to have entries
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removed from the start of @c waves that cannot form a valid symbol. Need not do anything while
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the waves at the start of @c waves may end up forming a symbol but the symbol is not yet complete.
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*/
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virtual void inspect_waves(const std::vector<WaveType> &waves) = 0;
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std::vector<WaveType> _wave_queue;
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SymbolType _next_symbol;
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bool _has_next_symbol;
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};
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}
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}
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#endif /* TapeParser_hpp */
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