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58 lines
1.6 KiB
C++
58 lines
1.6 KiB
C++
//
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// FAT12.cpp
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// Clock Signal
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//
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// Created by Thomas Harte on 07/01/2018.
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// Copyright 2018 Thomas Harte. All rights reserved.
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//
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#include "FAT12.hpp"
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#include "Utility/ImplicitSectors.hpp"
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using namespace Storage::Disk;
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FAT12::FAT12(const std::string &file_name) :
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MFMSectorDump(file_name) {
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// The only sanity check here is whether a sensible
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// geometry is encoded in the first sector, or can be guessed.
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off_t file_size = file_.stats().st_size;
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if(file_size < 512) throw Error::InvalidFormat;
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// Inspect the FAT.
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file_.seek(11, SEEK_SET);
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sector_size_ = file_.get16le();
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file_.seek(19, SEEK_SET);
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const uint16_t total_sectors = file_.get16le();
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file_.seek(24, SEEK_SET);
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sector_count_ = file_.get16le();
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head_count_ = file_.get16le();
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// Throw if there would seemingly be an incomplete track.
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if(file_size != total_sectors*sector_size_) throw Error::InvalidFormat;
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if(total_sectors % (head_count_ * sector_count_)) throw Error::InvalidFormat;
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track_count_ = int(total_sectors / (head_count_ * sector_count_));
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// Check that there is a valid power-of-two sector size.
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uint8_t log_sector_size = 2;
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while(log_sector_size < 5 && (1 << (7+log_sector_size)) != sector_size_) {
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++log_sector_size;
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}
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if(log_sector_size >= 5) throw Error::InvalidFormat;
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set_geometry(sector_count_, log_sector_size, 1, true);
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}
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HeadPosition FAT12::get_maximum_head_position() {
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return HeadPosition(track_count_);
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}
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int FAT12::get_head_count() {
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return head_count_;
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}
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long FAT12::get_file_offset_for_position(Track::Address address) {
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return (address.position.as_int()*head_count_ + address.head) * sector_size_ * sector_count_;
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}
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