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83 lines
2.5 KiB
C++
83 lines
2.5 KiB
C++
//
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// PCMTrack.cpp
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// Clock Signal
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//
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// Created by Thomas Harte on 10/07/2016.
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// Copyright © 2016 Thomas Harte. All rights reserved.
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//
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#include "PCMTrack.hpp"
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#include "../../NumberTheory/Factors.hpp"
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using namespace Storage;
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PCMTrack::PCMTrack(std::vector<PCMSegment> segments)
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{
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_segments = std::move(segments);
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fix_length();
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}
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PCMTrack::PCMTrack(PCMSegment segment)
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{
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segment.length_of_a_bit.length = 1;
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segment.length_of_a_bit.clock_rate = 1;
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_segments.push_back(std::move(segment));
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fix_length();
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}
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PCMTrack::Event PCMTrack::get_next_event()
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{
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// find the next 1 in the input stream, keeping count of length as we go, and assuming it's going
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// to be a flux transition
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_next_event.type = Track::Event::FluxTransition;
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_next_event.length.length = 0;
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while(_segment_pointer < _segments.size())
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{
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unsigned int clock_multiplier = _track_clock_rate / _segments[_segment_pointer].length_of_a_bit.clock_rate;
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unsigned int bit_length = clock_multiplier * _segments[_segment_pointer].length_of_a_bit.length;
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const uint8_t *segment_data = _segments[_segment_pointer].data.get();
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while(_bit_pointer < _segments[_segment_pointer].number_of_bits)
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{
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// for timing simplicity, bits are modelled as happening at the end of their window
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// TODO: should I account for the converse bit ordering? Or can I assume MSB first?
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int bit = segment_data[_bit_pointer >> 3] & (0x80 >> (_bit_pointer&7));
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_bit_pointer++;
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_next_event.length.length += bit_length;
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if(bit) return _next_event;
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}
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_bit_pointer = 0;
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_segment_pointer++;
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}
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// check whether we actually reached the index hole
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if(_segment_pointer == _segments.size())
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{
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_segment_pointer = 0;
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_next_event.type = Track::Event::IndexHole;
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}
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return _next_event;
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}
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void PCMTrack::fix_length()
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{
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// find the least common multiple of all segment clock rates
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_track_clock_rate = _segments[0].length_of_a_bit.clock_rate;
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for(size_t c = 1; c < _segments.size(); c++)
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{
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_track_clock_rate = NumberTheory::least_common_multiple(_track_clock_rate, _segments[c].length_of_a_bit.clock_rate);
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}
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// thereby determine the total length, storing it to next_event as the track-total divisor
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_next_event.length.clock_rate = 0;
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for(size_t c = 0; c < _segments.size(); c++)
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{
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unsigned int multiplier = _track_clock_rate / _segments[c].length_of_a_bit.clock_rate;
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_next_event.length.clock_rate += _segments[c].length_of_a_bit.length * _segments[c].number_of_bits * multiplier;
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}
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_segment_pointer = _bit_pointer = 0;
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}
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