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214 lines
5.7 KiB
C++
214 lines
5.7 KiB
C++
//
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// MFM.cpp
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// Clock Signal
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//
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// Created by Thomas Harte on 18/09/2016.
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// Copyright © 2016 Thomas Harte. All rights reserved.
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//
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#include "MFM.hpp"
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#include "../PCMTrack.hpp"
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#include "../../../NumberTheory/CRC.hpp"
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using namespace Storage::Encodings::MFM;
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class MFMEncoder: public Encoder {
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public:
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MFMEncoder(std::vector<uint8_t> &target) : Encoder(target) {}
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void add_byte(uint8_t input) {
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uint16_t spread_value =
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(uint16_t)(
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((input & 0x01) << 0) |
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((input & 0x02) << 1) |
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((input & 0x04) << 2) |
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((input & 0x08) << 3) |
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((input & 0x10) << 4) |
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((input & 0x20) << 5) |
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((input & 0x40) << 6) |
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((input & 0x80) << 7)
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);
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uint16_t or_bits = (uint16_t)((spread_value << 1) | (spread_value >> 1) | (output_ << 15));
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output_ = spread_value | ((~or_bits) & 0xaaaa);
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output_short(output_);
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}
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void add_index_address_mark() {
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output_short(output_ = MFMIndexAddressMark);
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add_byte(MFMIndexAddressByte);
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}
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void add_ID_address_mark() {
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output_short(output_ = MFMAddressMark);
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add_byte(MFMIDAddressByte);
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}
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void add_data_address_mark() {
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output_short(output_ = MFMAddressMark);
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add_byte(MFMDataAddressByte);
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}
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void add_deleted_data_address_mark() {
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output_short(output_ = MFMAddressMark);
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add_byte(MFMDeletedDataAddressByte);
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}
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private:
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uint16_t output_;
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};
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class FMEncoder: public Encoder {
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// encodes each 16-bit part as clock, data, clock, data [...]
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public:
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FMEncoder(std::vector<uint8_t> &target) : Encoder(target) {}
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void add_byte(uint8_t input) {
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output_short(
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(uint16_t)(
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((input & 0x01) << 0) |
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((input & 0x02) << 1) |
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((input & 0x04) << 2) |
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((input & 0x08) << 3) |
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((input & 0x10) << 4) |
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((input & 0x20) << 5) |
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((input & 0x40) << 6) |
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((input & 0x80) << 7) |
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0xaaaa
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));
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}
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void add_index_address_mark() { output_short(FMIndexAddressMark); }
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void add_ID_address_mark() { output_short(FMIDAddressMark); }
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void add_data_address_mark() { output_short(FMDataAddressMark); }
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void add_deleted_data_address_mark() { output_short(FMDeletedDataAddressMark); }
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};
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static uint8_t logarithmic_size_for_size(size_t size)
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{
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switch(size)
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{
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default: return 0;
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case 256: return 1;
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case 512: return 2;
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case 1024: return 3;
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case 2048: return 4;
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case 4196: return 5;
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}
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}
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template<class T> std::shared_ptr<Storage::Disk::Track>
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GetTrackWithSectors(
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const std::vector<Sector> §ors,
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size_t post_index_address_mark_bytes, uint8_t post_index_address_mark_value,
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size_t pre_address_mark_bytes, size_t post_address_mark_bytes,
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size_t pre_data_mark_bytes, size_t post_data_bytes,
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size_t inter_sector_gap,
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size_t expected_track_bytes)
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{
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Storage::Disk::PCMSegment segment;
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segment.data.reserve(expected_track_bytes);
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T shifter(segment.data);
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NumberTheory::CRC16 crc_generator(0x1021, 0xffff);
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// output the index mark
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shifter.add_index_address_mark();
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// add the post-index mark
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for(int c = 0; c < post_index_address_mark_bytes; c++) shifter.add_byte(post_index_address_mark_value);
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// add sectors
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for(const Sector §or : sectors)
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{
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// gap
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for(int c = 0; c < pre_address_mark_bytes; c++) shifter.add_byte(0x00);
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// sector header
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shifter.add_ID_address_mark();
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shifter.add_byte(sector.track);
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shifter.add_byte(sector.side);
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shifter.add_byte(sector.sector);
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uint8_t size = logarithmic_size_for_size(sector.data.size());
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shifter.add_byte(size);
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// header CRC
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crc_generator.reset();
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crc_generator.add(sector.track);
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crc_generator.add(sector.side);
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crc_generator.add(sector.sector);
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crc_generator.add(size);
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uint16_t crc_value = crc_generator.get_value();
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shifter.add_byte(crc_value >> 8);
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shifter.add_byte(crc_value & 0xff);
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// gap
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for(int c = 0; c < post_address_mark_bytes; c++) shifter.add_byte(0x4e);
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for(int c = 0; c < pre_data_mark_bytes; c++) shifter.add_byte(0x00);
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// data
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shifter.add_data_address_mark();
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crc_generator.reset();
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for(size_t c = 0; c < sector.data.size(); c++)
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{
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shifter.add_byte(sector.data[c]);
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crc_generator.add(sector.data[c]);
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}
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// data CRC
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crc_value = crc_generator.get_value();
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shifter.add_byte(crc_value >> 8);
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shifter.add_byte(crc_value & 0xff);
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// gap
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for(int c = 0; c < post_data_bytes; c++) shifter.add_byte(0x00);
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for(int c = 0; c < inter_sector_gap; c++) shifter.add_byte(0x4e);
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}
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while(segment.data.size() < expected_track_bytes) shifter.add_byte(0x00);
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segment.number_of_bits = (unsigned int)(segment.data.size() * 8);
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return std::shared_ptr<Storage::Disk::Track>(new Storage::Disk::PCMTrack(std::move(segment)));
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}
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Encoder::Encoder(std::vector<uint8_t> &target) :
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target_(target)
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{}
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void Encoder::output_short(uint16_t value)
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{
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target_.push_back(value >> 8);
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target_.push_back(value & 0xff);
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}
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std::shared_ptr<Storage::Disk::Track> Storage::Encodings::MFM::GetFMTrackWithSectors(const std::vector<Sector> §ors)
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{
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return GetTrackWithSectors<FMEncoder>(
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sectors,
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16, 0x00,
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6, 0,
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17, 14,
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0,
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6250); // i.e. 250kbps (including clocks) * 60 = 15000kpm, at 300 rpm => 50 kbits/rotation => 6250 bytes/rotation
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}
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std::shared_ptr<Storage::Disk::Track> Storage::Encodings::MFM::GetMFMTrackWithSectors(const std::vector<Sector> §ors)
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{
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return GetTrackWithSectors<MFMEncoder>(
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sectors,
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50, 0x4e,
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12, 22,
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12, 18,
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32,
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12500); // unintelligently: double the single-density bytes/rotation (or: 500kps @ 300 rpm)
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}
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std::unique_ptr<Encoder> Storage::Encodings::MFM::GetMFMEncoder(std::vector<uint8_t> &target)
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{
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return std::unique_ptr<Encoder>(new MFMEncoder(target));
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}
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std::unique_ptr<Encoder> Storage::Encodings::MFM::GetFMEncoder(std::vector<uint8_t> &target)
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{
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return std::unique_ptr<Encoder>(new FMEncoder(target));
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}
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