CLK/Storage/Disk/Formats/SSD.cpp

//
//  SSD.cpp
//  Clock Signal
//
//  Created by Thomas Harte on 18/09/2016.
//  Copyright © 2016 Thomas Harte. All rights reserved.
//

#include "SSD.hpp"

#include <sys/stat.h>
#include "../Encodings/MFM.hpp"

using namespace Storage::Disk;

SSD::SSD(const char *file_name) :
		Storage::FileHolder(file_name) {
	// very loose validation: the file needs to be a multiple of 256 bytes
	// and not ungainly large

	if(file_stats_.st_size & 255) throw ErrorNotSSD;
	if(file_stats_.st_size < 512) throw ErrorNotSSD;
	if(file_stats_.st_size > 800*256) throw ErrorNotSSD;

	// this has two heads if the suffix is .dsd, one if it's .ssd
	head_count_ = (tolower(file_name[strlen(file_name) - 3]) == 'd') ? 2 : 1;
	track_count_ = (unsigned int)(file_stats_.st_size / (256 * 10));
	if(track_count_ < 40) track_count_ = 40;
	else if(track_count_ < 80) track_count_ = 80;
}

SSD::~SSD() {
	flush_updates();
}

unsigned int SSD::get_head_position_count() {
	return track_count_;
}

unsigned int SSD::get_head_count() {
	return head_count_;
}

bool SSD::get_is_read_only() {
	return is_read_only_;
}

long SSD::get_file_offset_for_position(unsigned int head, unsigned int position) {
	return (position * head_count_ + head) * 256 * 10;
}

std::shared_ptr<Track> SSD::get_uncached_track_at_position(unsigned int head, unsigned int position) {
	std::shared_ptr<Track> track;

	if(head >= head_count_) return track;
	fseek(file_, get_file_offset_for_position(head, position), SEEK_SET);

	std::vector<Storage::Encodings::MFM::Sector> sectors;
	for(int sector = 0; sector < 10; sector++) {
		Storage::Encodings::MFM::Sector new_sector;
		new_sector.track = (uint8_t)position;
		new_sector.side = 0;
		new_sector.sector = (uint8_t)sector;

		new_sector.data.resize(256);
		fread(new_sector.data.data(), 1, 256, file_);

		// zero out if this wasn't present in the disk image; it's still appropriate to put a sector
		// on disk because one will have been placed during formatting, but there's no reason to leak
		// information from outside the emulated machine's world
		if(feof(file_)) memset(new_sector.data.data(), 0, 256);

		sectors.push_back(std::move(new_sector));
	}

	if(sectors.size()) return Storage::Encodings::MFM::GetFMTrackWithSectors(sectors);

	return track;
}

void SSD::store_updated_track_at_position(unsigned int head, unsigned int position, const std::shared_ptr<Track> &track, std::mutex &file_access_mutex) {
	std::vector<uint8_t> parsed_track;
	Storage::Encodings::MFM::Parser parser(false, track);
	for(unsigned int c = 0; c < 10; c++) {
		std::shared_ptr<Storage::Encodings::MFM::Sector> sector = parser.get_sector((uint8_t)position, (uint8_t)c);
		if(sector) {
			parsed_track.insert(parsed_track.end(), sector->data.begin(), sector->data.end());
		} else {
			// TODO: what's correct here? Warn the user that whatever has been written to the disk,
			// it can no longer be stored as an SSD? If so, warn them by what route?
			parsed_track.resize(parsed_track.size() + 256);
		}
	}

	std::lock_guard<std::mutex> lock_guard(file_access_mutex);
	long file_offset = get_file_offset_for_position(head, position);
	ensure_file_is_at_least_length(file_offset);
	fseek(file_, file_offset, SEEK_SET);
	fwrite(parsed_track.data(), 1, parsed_track.size(), file_);
}