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124 lines
4.2 KiB
C++
124 lines
4.2 KiB
C++
//
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// AppleDSK.cpp
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// Clock Signal
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//
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// Created by Thomas Harte on 27/04/2018.
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// Copyright 2018 Thomas Harte. All rights reserved.
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//
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#include "AppleDSK.hpp"
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#include "../../Track/PCMTrack.hpp"
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#include "../../Track/TrackSerialiser.hpp"
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#include "../../Encodings/AppleGCR/Encoder.hpp"
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#include "../../Encodings/AppleGCR/SegmentParser.hpp"
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#include <cstring>
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using namespace Storage::Disk;
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namespace {
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constexpr int number_of_tracks = 35;
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constexpr int bytes_per_sector = 256;
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}
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AppleDSK::AppleDSK(const std::string &file_name) :
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file_(file_name) {
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if(file_.stats().st_size % (number_of_tracks*bytes_per_sector)) throw Error::InvalidFormat;
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sectors_per_track_ = int(file_.stats().st_size / (number_of_tracks*bytes_per_sector));
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if(sectors_per_track_ != 13 && sectors_per_track_ != 16) throw Error::InvalidFormat;
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// Check whether this is a Pro DOS disk by inspecting the filename.
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if(sectors_per_track_ == 16) {
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size_t string_index = file_name.size()-1;
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while(file_name[string_index] != '.') {
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if(file_name[string_index] == 'p') {
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is_prodos_ = true;
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break;
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}
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--string_index;
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}
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}
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}
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HeadPosition AppleDSK::get_maximum_head_position() {
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return HeadPosition(number_of_tracks);
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}
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bool AppleDSK::get_is_read_only() {
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return file_.get_is_known_read_only();
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}
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long AppleDSK::file_offset(Track::Address address) {
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return address.position.as_int() * bytes_per_sector * sectors_per_track_;
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}
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size_t AppleDSK::logical_sector_for_physical_sector(size_t physical) {
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// DOS and Pro DOS interleave sectors on disk, and they're represented in a disk
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// image in physical order rather than logical.
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if(physical == 15) return 15;
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return (physical * (is_prodos_ ? 8 : 7)) % 15;
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}
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std::shared_ptr<Track> AppleDSK::get_track_at_position(Track::Address address) {
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std::vector<uint8_t> track_data;
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{
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std::lock_guard lock_guard(file_.get_file_access_mutex());
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file_.seek(file_offset(address), SEEK_SET);
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track_data = file_.read(size_t(bytes_per_sector * sectors_per_track_));
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}
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Storage::Disk::PCMSegment segment;
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const uint8_t track = uint8_t(address.position.as_int());
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// In either case below, the code aims for exactly 50,000 bits per track.
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if(sectors_per_track_ == 16) {
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// Write gap 1.
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segment += Encodings::AppleGCR::six_and_two_sync(24);
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// Write the sectors.
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for(uint8_t c = 0; c < 16; ++c) {
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segment += Encodings::AppleGCR::AppleII::header(is_prodos_ ? 0x01 : 0xfe, track, c); // Volume number is 0xfe for DOS 3.3, 0x01 for Pro-DOS.
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segment += Encodings::AppleGCR::six_and_two_sync(7); // Gap 2: 7 sync words.
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segment += Encodings::AppleGCR::AppleII::six_and_two_data(&track_data[logical_sector_for_physical_sector(c) * 256]);
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segment += Encodings::AppleGCR::six_and_two_sync(20); // Gap 3: 20 sync words.
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}
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} else {
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// TODO: 5 and 3, 13-sector format. If DSK actually supports it?
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}
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// Apply inter-track skew; skew is about 40ms between each track; assuming 300RPM that's
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// 1/5th of a revolution.
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const size_t offset_in_fifths = address.position.as_int() % 5;
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segment.rotate_right(offset_in_fifths * segment.data.size() / 5);
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return std::make_shared<PCMTrack>(segment);
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}
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void AppleDSK::set_tracks(const std::map<Track::Address, std::shared_ptr<Track>> &tracks) {
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std::map<Track::Address, std::vector<uint8_t>> tracks_by_address;
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for(const auto &pair: tracks) {
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// Decode the track.
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const auto sector_map = Storage::Encodings::AppleGCR::sectors_from_segment(
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Storage::Disk::track_serialisation(*pair.second, Storage::Time(1, 50000)));
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// Rearrange sectors into Apple DOS or Pro-DOS order.
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std::vector<uint8_t> track_contents(size_t(bytes_per_sector * sectors_per_track_));
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for(const auto §or_pair: sector_map) {
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const size_t target_address = logical_sector_for_physical_sector(sector_pair.second.address.sector);
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memcpy(&track_contents[target_address*256], sector_pair.second.data.data(), bytes_per_sector);
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}
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// Store for later.
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tracks_by_address[pair.first] = std::move(track_contents);
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}
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// Grab the file lock and write out the new tracks.
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std::lock_guard lock_guard(file_.get_file_access_mutex());
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for(const auto &pair: tracks_by_address) {
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file_.seek(file_offset(pair.first), SEEK_SET);
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file_.write(pair.second);
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}
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}
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