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CLK/Storage/Disk/Encodings/MFM/Shifter.cpp

121 lines
3.2 KiB
C++

//
// Shifter.cpp
// Clock Signal
//
// Created by Thomas Harte on 24/09/2017.
// Copyright 2017 Thomas Harte. All rights reserved.
//
#include "Shifter.hpp"
#include "Constants.hpp"
using namespace Storage::Encodings::MFM;
Shifter::Shifter() : owned_crc_generator_(new CRC::CCITT()), crc_generator_(owned_crc_generator_.get()) {}
Shifter::Shifter(CRC::CCITT *crc_generator) : crc_generator_(crc_generator) {}
void Shifter::set_is_double_density(bool is_double_density) {
is_double_density_ = is_double_density;
if(!is_double_density) is_awaiting_marker_value_ = false;
}
void Shifter::set_should_obey_syncs(bool should_obey_syncs) {
should_obey_syncs_ = should_obey_syncs;
}
void Shifter::add_input_bit(int value) {
shift_register_ = (shift_register_ << 1) | static_cast<unsigned int>(value);
bits_since_token_++;
token_ = Token::None;
if(should_obey_syncs_) {
if(!is_double_density_) {
switch(shift_register_ & 0xffff) {
case Storage::Encodings::MFM::FMIndexAddressMark:
token_ = Token::Index;
crc_generator_->reset();
crc_generator_->add(Storage::Encodings::MFM::IndexAddressByte);
break;
case Storage::Encodings::MFM::FMIDAddressMark:
token_ = Token::ID;
crc_generator_->reset();
crc_generator_->add(Storage::Encodings::MFM::IDAddressByte);
break;
case Storage::Encodings::MFM::FMDataAddressMark:
token_ = Token::Data;
crc_generator_->reset();
crc_generator_->add(Storage::Encodings::MFM::DataAddressByte);
break;
case Storage::Encodings::MFM::FMDeletedDataAddressMark:
token_ = Token::DeletedData;
crc_generator_->reset();
crc_generator_->add(Storage::Encodings::MFM::DeletedDataAddressByte);
break;
default:
break;
}
} else {
switch(shift_register_ & 0xffff) {
case Storage::Encodings::MFM::MFMIndexSync:
bits_since_token_ = 0;
is_awaiting_marker_value_ = true;
token_ = Token::Sync;
break;
case Storage::Encodings::MFM::MFMSync:
bits_since_token_ = 0;
is_awaiting_marker_value_ = true;
crc_generator_->set_value(Storage::Encodings::MFM::MFMPostSyncCRCValue);
token_ = Token::Sync;
break;
default:
break;
}
}
if(token_ != Token::None) {
bits_since_token_ = 0;
return;
}
}
if(bits_since_token_ == 16) {
token_ = Token::Byte;
bits_since_token_ = 0;
if(is_awaiting_marker_value_ && is_double_density_) {
is_awaiting_marker_value_ = false;
switch(get_byte()) {
case Storage::Encodings::MFM::IndexAddressByte:
token_ = Token::Index;
break;
case Storage::Encodings::MFM::IDAddressByte:
token_ = Token::ID;
break;
case Storage::Encodings::MFM::DataAddressByte:
token_ = Token::Data;
break;
case Storage::Encodings::MFM::DeletedDataAddressByte:
token_ = Token::DeletedData;
break;
default: break;
}
}
crc_generator_->add(get_byte());
}
}
uint8_t Shifter::get_byte() const {
return static_cast<uint8_t>(
((shift_register_ & 0x0001) >> 0) |
((shift_register_ & 0x0004) >> 1) |
((shift_register_ & 0x0010) >> 2) |
((shift_register_ & 0x0040) >> 3) |
((shift_register_ & 0x0100) >> 4) |
((shift_register_ & 0x0400) >> 5) |
((shift_register_ & 0x1000) >> 6) |
((shift_register_ & 0x4000) >> 7));
}