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81 lines
2.6 KiB
C++
81 lines
2.6 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 "../../Encodings/AppleGCR.hpp"
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using namespace Storage::Disk;
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namespace {
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const int number_of_tracks = 35;
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const 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_ = static_cast<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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int AppleDSK::get_head_position_count() {
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return number_of_tracks * 4;
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}
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std::shared_ptr<Track> AppleDSK::get_track_at_position(Track::Address address) {
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const long file_offset = (address.position >> 2) * bytes_per_sector * sectors_per_track_;
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file_.seek(file_offset, SEEK_SET);
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const std::vector<uint8_t> track_data = file_.read(static_cast<size_t>(bytes_per_sector * sectors_per_track_));
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std::vector<Storage::Disk::PCMSegment> segments;
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const uint8_t track = static_cast<uint8_t>(address.position >> 2);
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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 the sectors.
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uint8_t sector_number_ = 0;
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for(std::size_t c = 0; c < 16; ++c) {
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segments.push_back(Encodings::AppleGCR::six_and_two_sync(10));
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segments.push_back(Encodings::AppleGCR::header(0, track, sector_number_));
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segments.push_back(Encodings::AppleGCR::six_and_two_sync(10));
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segments.push_back(Encodings::AppleGCR::six_and_two_data(&track_data[c * 256]));
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segments.push_back(Encodings::AppleGCR::six_and_two_sync(10));
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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. So that skew needs to be applied here.
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sector_number_ += is_prodos_ ? 8 : 7;
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if(sector_number_ > 0xf) sector_number_ %= 15;
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}
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// Pad if necessary.
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int encoded_length = (80 + 112 + 80 + 2848 + 80) * sectors_per_track_;
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if(encoded_length < 50000) {
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segments.push_back(Encodings::AppleGCR::six_and_two_sync((50000 - encoded_length) >> 3));
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}
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} else {
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}
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return std::shared_ptr<PCMTrack>(new PCMTrack(segments));
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}
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