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CLK/Storage/Disk/DiskImage/Formats/MSXDSK.cpp

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//
// MSXDSK.cpp
// Clock Signal
//
// Created by Thomas Harte on 07/01/2018.
// Copyright 2018 Thomas Harte. All rights reserved.
//
#include "MSXDSK.hpp"
#include "Utility/ImplicitSectors.hpp"
namespace {
constexpr int sectors_per_track = 9;
constexpr int sector_size = 2;
constexpr off_t track_size = (128 << sector_size)*sectors_per_track;
}
using namespace Storage::Disk;
MSXDSK::MSXDSK(const std::string &file_name) :
MFMSectorDump(file_name) {
// The only sanity check here is whether a sensible
// geometry can be guessed.
off_t file_size = file_.stats().st_size;
// Throw if there would seemingly be an incomplete track.
if(file_size % track_size) throw Error::InvalidFormat;
track_count_ = int(file_size / track_size);
head_count_ = 1;
// Throw if too large or too small or too large for single sided and
// clearly not double sided.
if(track_count_ < 40) throw Error::InvalidFormat;
if(track_count_ > 82*2) throw Error::InvalidFormat;
if(track_count_ > 82 && track_count_&1) throw Error::InvalidFormat;
// The below effectively prefers the idea of a single-sided 80-track disk
// to a double-sided 40-track disk. Emulators have to guess.
if(track_count_ > 82) {
track_count_ /= 2;
head_count_ = 2;
}
set_geometry(sectors_per_track, sector_size, 1, true);
}
HeadPosition MSXDSK::get_maximum_head_position() {
return HeadPosition(track_count_);
}
int MSXDSK::get_head_count() {
return head_count_;
}
long MSXDSK::get_file_offset_for_position(Track::Address address) {
return (address.position.as_int()*head_count_ + address.head) * 512 * 9;
}