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140 lines
4.2 KiB
C++
140 lines
4.2 KiB
C++
//
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// ZX8081.cpp
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// Clock Signal
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//
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// Created by Thomas Harte on 07/06/2017.
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// Copyright 2017 Thomas Harte. All rights reserved.
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//
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#include "ZX8081.hpp"
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using namespace Storage::Tape::ZX8081;
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Parser::Parser() : pulse_was_high_(false), pulse_time_(0) {}
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void Parser::process_pulse(const Storage::Tape::Tape::Pulse &pulse) {
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// If this is anything other than a transition from low to high, just add it to the
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// count of time.
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const bool pulse_is_high = pulse.type == Storage::Tape::Tape::Pulse::High;
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const bool pulse_did_change = pulse_is_high != pulse_was_high_;
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pulse_was_high_ = pulse_is_high;
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if(!pulse_did_change || !pulse_is_high) {
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pulse_time_ += pulse.length;
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return;
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}
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// Otherwise post a new pulse.
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post_pulse();
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pulse_time_ = pulse.length;
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}
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void Parser::post_pulse() {
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constexpr float expected_pulse_length = 300.0f / 1000000.0f;
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constexpr float expected_gap_length = 1300.0f / 1000000.0f;
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const auto pulse_time = pulse_time_.get<float>();
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if(pulse_time > expected_gap_length * 1.25f) {
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push_wave(WaveType::LongGap);
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} else if(pulse_time > expected_pulse_length * 1.25f) {
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push_wave(WaveType::Gap);
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} else if(pulse_time >= expected_pulse_length * 0.75f && pulse_time <= expected_pulse_length * 1.25f) {
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push_wave(WaveType::Pulse);
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} else {
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push_wave(WaveType::Unrecognised);
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}
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}
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void Parser::mark_end() {
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// Post a long gap to cap any bit that's in the process of recognition.
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push_wave(WaveType::LongGap);
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}
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void Parser::inspect_waves(const std::vector<WaveType> &waves) {
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// A long gap is a file gap.
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if(waves[0] == WaveType::LongGap) {
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push_symbol(SymbolType::FileGap, 1);
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return;
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}
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if(waves[0] == WaveType::Unrecognised) {
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push_symbol(SymbolType::Unrecognised, 1);
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return;
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}
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if(waves.size() >= 4) {
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std::size_t wave_offset = 0;
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// If the very first thing is a gap, swallow it.
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if(waves[0] == WaveType::Gap) {
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wave_offset = 1;
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}
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// Count the number of pulses at the start of this vector
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std::size_t number_of_pulses = 0;
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while(number_of_pulses + wave_offset < waves.size() && waves[number_of_pulses + wave_offset] == WaveType::Pulse) {
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number_of_pulses++;
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}
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// If those pulses were followed by something not recognised as a pulse, check for a bit
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if(number_of_pulses + wave_offset < waves.size()) {
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// A 1 is 9 waves, a 0 is 4. Counting upward zero transitions, the first in either group will
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// act simply to terminate the gap beforehand and won't be logged as a pulse. So counts to
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// check are 8 and 3.
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std::size_t gaps_to_swallow = wave_offset + ((waves[number_of_pulses + wave_offset] == WaveType::Gap) ? 1 : 0);
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switch(number_of_pulses) {
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case 8: push_symbol(SymbolType::One, int(number_of_pulses + gaps_to_swallow)); break;
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case 3: push_symbol(SymbolType::Zero, int(number_of_pulses + gaps_to_swallow)); break;
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default: push_symbol(SymbolType::Unrecognised, 1); break;
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}
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}
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}
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}
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int Parser::get_next_byte(const std::shared_ptr<Storage::Tape::Tape> &tape) {
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int c = 8;
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int result = 0;
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while(c) {
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if(is_at_end(tape)) return -1;
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SymbolType symbol = get_next_symbol(tape);
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if(symbol != SymbolType::One && symbol != SymbolType::Zero) {
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if(c == 8) continue;
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return_symbol(symbol);
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return -1;
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}
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result = (result << 1) | (symbol == SymbolType::One ? 1 : 0);
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c--;
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}
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return result;
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}
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std::shared_ptr<std::vector<uint8_t>> Parser::get_next_file_data(const std::shared_ptr<Storage::Tape::Tape> &tape) {
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if(is_at_end(tape)) return nullptr;
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SymbolType symbol = get_next_symbol(tape);
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if(symbol != SymbolType::FileGap) {
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return nullptr;
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}
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while((symbol == SymbolType::FileGap || symbol == SymbolType::Unrecognised) && !is_at_end(tape)) {
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symbol = get_next_symbol(tape);
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}
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if(is_at_end(tape)) return nullptr;
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return_symbol(symbol);
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auto result = std::make_shared<std::vector<uint8_t>>();
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int byte;
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while(!is_at_end(tape)) {
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byte = get_next_byte(tape);
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if(byte == -1) return result;
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result->push_back(uint8_t(byte));
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}
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return result;
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}
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std::shared_ptr<Storage::Data::ZX8081::File> Parser::get_next_file(const std::shared_ptr<Storage::Tape::Tape> &tape) {
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std::shared_ptr<std::vector<uint8_t>> file_data = get_next_file_data(tape);
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if(!file_data) {
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return nullptr;
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}
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return Storage::Data::ZX8081::FileFromData(*file_data);
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}
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