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CLK/Storage/Disk/DiskImage/Formats/MSA.cpp
2023-12-10 22:17:23 -05:00

97 lines
2.6 KiB
C++

//
// MSA.cpp
// Clock Signal
//
// Created by Thomas Harte on 03/10/2019.
// Copyright © 2019 Thomas Harte. All rights reserved.
//
#include "MSA.hpp"
#include "Utility/ImplicitSectors.hpp"
#include <cassert>
using namespace Storage::Disk;
MSA::MSA(const std::string &file_name) :
file_(file_name) {
const auto signature = file_.get16be();
if(signature != 0x0e0f) throw Error::InvalidFormat;
sectors_per_track_ = file_.get16be();
sides_ = 1 + file_.get16be();
starting_track_ = file_.get16be();
ending_track_ = file_.get16be();
// Create the uncompressed track list.
while(true) {
const auto data_length = file_.get16be();
if(file_.eof()) break;
if(data_length == sectors_per_track_ * 512) {
// This is an uncompressed track.
uncompressed_tracks_.push_back(file_.read(data_length));
} else {
#ifndef NDEBUG
const auto start_of_track = file_.tell();
#endif
// This is an RLE-compressed track.
std::vector<uint8_t> track;
track.reserve(sectors_per_track_ * 512);
uint16_t pointer = 0;
while(pointer < data_length) {
const auto byte = file_.get8();
// Compression scheme: if the byte E5 is encountered, an RLE run follows.
// An RLE run is encoded as the byte to repeat plus a 16-bit repeat count.
if(byte != 0xe5) {
track.push_back(byte);
++pointer;
continue;
}
pointer += 4;
if(pointer > data_length) break;
const auto value = file_.get8();
auto count = file_.get16be();
while(count--) {
track.push_back(value);
}
}
#ifndef NDEBUG
assert(file_.tell() - start_of_track == pointer);
#endif
if(pointer != data_length || track.size() != sectors_per_track_ * 512)
throw Error::InvalidFormat;
uncompressed_tracks_.push_back(std::move(track));
}
}
if(uncompressed_tracks_.size() != size_t((ending_track_ - starting_track_ + 1)*sides_))
throw Error::InvalidFormat;
}
std::shared_ptr<::Storage::Disk::Track> MSA::get_track_at_position(::Storage::Disk::Track::Address address) {
if(address.head >= sides_) return nullptr;
const auto position = address.position.as_int();
if(position < starting_track_) return nullptr;
if(position > ending_track_) return nullptr;
const auto &track = uncompressed_tracks_[size_t(position - starting_track_) * size_t(sides_) + size_t(address.head)];
assert(!track.empty());
return track_for_sectors(track.data(), sectors_per_track_, uint8_t(position), uint8_t(address.head), 1, 2, Storage::Encodings::MFM::Density::Double);
}
HeadPosition MSA::get_maximum_head_position() {
return HeadPosition(ending_track_ + 1);
}
int MSA::get_head_count() {
return sides_;
}