1
0
mirror of https://github.com/TomHarte/CLK.git synced 2024-12-13 00:29:14 +00:00
CLK/Storage/Disk/Parsers/FAT.cpp

180 lines
6.4 KiB
C++
Raw Normal View History

2021-07-02 22:56:43 +00:00
//
// FAT.cpp
// Clock Signal
//
// Created by Thomas Harte on 02/07/2021.
// Copyright © 2021 Thomas Harte. All rights reserved.
//
#include "FAT.hpp"
#include "../Encodings/MFM/Parser.hpp"
#include <iostream>
using namespace Storage::Disk;
FAT::Volume::CHS FAT::Volume::chs_for_sector(int sector) const {
2021-07-02 23:28:13 +00:00
const auto track = sector / sectors_per_track;
2021-07-02 22:56:43 +00:00
2021-07-02 23:28:13 +00:00
// Sides are interleaved.
2021-07-02 22:56:43 +00:00
return CHS{
2021-07-02 23:28:13 +00:00
track / head_count,
track % head_count,
2021-07-02 22:56:43 +00:00
1 + (sector % sectors_per_track)
};
}
2021-07-02 23:28:13 +00:00
int FAT::Volume::sector_for_cluster(uint16_t cluster) const {
// The first cluster in the data area is numbered as 2.
return ((cluster - 2) * sectors_per_cluster) + first_data_sector;
2021-07-02 22:56:43 +00:00
}
namespace {
template <typename CharT> std::string trim(CharT start, CharT end) {
std::string result(start, end);
result.erase(std::find_if(result.rbegin(), result.rend(), [](unsigned char ch) {
return !std::isspace(ch);
}).base(), result.end());
return result;
}
2021-07-02 22:56:43 +00:00
FAT::Directory directory_from(const std::vector<uint8_t> &contents) {
FAT::Directory result;
2021-07-02 23:28:13 +00:00
// Worst case: parse until the amount of data supplied is fully consumed.
2021-07-02 22:56:43 +00:00
for(size_t base = 0; base < contents.size(); base += 32) {
// An entry starting with byte 0 indicates end-of-directory.
if(!contents[base]) {
break;
}
// An entry starting in 0xe5 is merely deleted.
if(contents[base] == 0xe5) {
continue;
}
// Otherwise create and populate a new entry.
result.emplace_back();
result.back().name = trim(&contents[base], &contents[base+8]);
result.back().extension = trim(&contents[base+8], &contents[base+11]);
2021-07-02 22:56:43 +00:00
result.back().attributes = contents[base + 11];
result.back().time = uint16_t(contents[base+22] | (contents[base+23] << 8));
result.back().date = uint16_t(contents[base+24] | (contents[base+25] << 8));
result.back().starting_cluster = uint16_t(contents[base+26] | (contents[base+27] << 8));
result.back().size = uint32_t(
contents[base+28] |
(contents[base+29] << 8) |
(contents[base+30] << 16) |
(contents[base+31] << 24)
);
}
return result;
}
}
std::optional<FAT::Volume> FAT::GetVolume(const std::shared_ptr<Storage::Disk::Disk> &disk) {
2023-12-11 03:17:23 +00:00
Storage::Encodings::MFM::Parser parser(Storage::Encodings::MFM::Density::Double, disk);
2021-07-02 22:56:43 +00:00
// Grab the boot sector; that'll be enough to establish the volume.
2023-12-11 14:58:24 +00:00
const Storage::Encodings::MFM::Sector *const boot_sector = parser.sector(0, 0, 1);
2021-07-02 22:56:43 +00:00
if(!boot_sector || boot_sector->samples.empty() || boot_sector->samples[0].size() < 512) {
return std::nullopt;
}
// Obtain volume details.
const auto &data = boot_sector->samples[0];
FAT::Volume volume;
volume.bytes_per_sector = uint16_t(data[11] | (data[12] << 8));
volume.sectors_per_cluster = data[13];
2021-07-02 23:28:13 +00:00
volume.reserved_sectors = uint16_t(data[14] | (data[15] << 8));
2021-07-02 22:56:43 +00:00
volume.fat_copies = data[16];
const uint16_t root_directory_entries = uint16_t(data[17] | (data[18] << 8));
volume.total_sectors = uint16_t(data[19] | (data[20] << 8));
volume.sectors_per_fat = uint16_t(data[22] | (data[23] << 8));
volume.sectors_per_track = uint16_t(data[24] | (data[25] << 8));
volume.head_count = uint16_t(data[26] | (data[27] << 8));
volume.correct_signature = data[510] == 0x55 && data[511] == 0xaa;
const size_t root_directory_sectors = (root_directory_entries*32 + volume.bytes_per_sector - 1) / volume.bytes_per_sector;
volume.first_data_sector = int(volume.reserved_sectors + volume.sectors_per_fat*volume.fat_copies + root_directory_sectors);
// Grab the FAT.
std::vector<uint8_t> source_fat;
for(int c = 0; c < volume.sectors_per_fat; c++) {
const int sector_number = volume.reserved_sectors + c;
const auto address = volume.chs_for_sector(sector_number);
2023-12-11 14:58:24 +00:00
const Storage::Encodings::MFM::Sector *const fat_sector =
parser.sector(address.head, address.cylinder, uint8_t(address.sector));
2021-07-02 22:56:43 +00:00
if(!fat_sector || fat_sector->samples.empty() || fat_sector->samples[0].size() != volume.bytes_per_sector) {
return std::nullopt;
}
std::copy(fat_sector->samples[0].begin(), fat_sector->samples[0].end(), std::back_inserter(source_fat));
}
// Decode the FAT.
// TODO: stop assuming FAT12 here.
for(size_t c = 0; c < source_fat.size(); c += 3) {
const uint32_t double_cluster = uint32_t(source_fat[c] + (source_fat[c + 1] << 8) + (source_fat[c + 2] << 16));
2021-07-02 23:28:13 +00:00
volume.fat.push_back(uint16_t(double_cluster & 0xfff));
volume.fat.push_back(uint16_t(double_cluster >> 12));
2021-07-02 22:56:43 +00:00
}
// Grab the root directory.
std::vector<uint8_t> root_directory;
for(size_t c = 0; c < root_directory_sectors; c++) {
2021-07-02 23:28:13 +00:00
const auto sector_number = int(volume.reserved_sectors + c + volume.sectors_per_fat*volume.fat_copies);
2021-07-02 22:56:43 +00:00
const auto address = volume.chs_for_sector(sector_number);
2023-12-11 14:58:24 +00:00
const Storage::Encodings::MFM::Sector *const sector =
parser.sector(address.head, address.cylinder, uint8_t(address.sector));
2021-07-02 22:56:43 +00:00
if(!sector || sector->samples.empty() || sector->samples[0].size() != volume.bytes_per_sector) {
return std::nullopt;
}
std::copy(sector->samples[0].begin(), sector->samples[0].end(), std::back_inserter(root_directory));
}
volume.root_directory = directory_from(root_directory);
return volume;
}
std::optional<std::vector<uint8_t>> FAT::GetFile(const std::shared_ptr<Storage::Disk::Disk> &disk, const Volume &volume, const File &file) {
2023-12-11 03:17:23 +00:00
Storage::Encodings::MFM::Parser parser(Storage::Encodings::MFM::Density::Double, disk);
2021-07-02 22:56:43 +00:00
std::vector<uint8_t> contents;
2021-07-02 23:28:13 +00:00
// In FAT cluster numbers describe a linked list via the FAT table, with values above $FF0 being reserved
// (relevantly: FF7 means bad cluster; FF8FFF mean end-of-file).
2021-07-02 22:56:43 +00:00
uint16_t cluster = file.starting_cluster;
2021-07-02 23:28:13 +00:00
do {
const int sector = volume.sector_for_cluster(cluster);
2021-07-02 22:56:43 +00:00
for(int c = 0; c < volume.sectors_per_cluster; c++) {
2021-07-02 23:28:13 +00:00
const auto address = volume.chs_for_sector(sector + c);
2021-07-02 22:56:43 +00:00
2023-12-11 14:58:24 +00:00
const Storage::Encodings::MFM::Sector *const sector_contents =
parser.sector(address.head, address.cylinder, uint8_t(address.sector));
2021-07-02 22:56:43 +00:00
if(!sector_contents || sector_contents->samples.empty() || sector_contents->samples[0].size() != volume.bytes_per_sector) {
return std::nullopt;
}
std::copy(sector_contents->samples[0].begin(), sector_contents->samples[0].end(), std::back_inserter(contents));
}
2021-07-02 23:28:13 +00:00
cluster = volume.fat[cluster];
} while(cluster < 0xff0);
2021-07-02 22:56:43 +00:00
return contents;
}
std::optional<FAT::Directory> FAT::GetDirectory(const std::shared_ptr<Storage::Disk::Disk> &disk, const Volume &volume, const File &file) {
const auto contents = GetFile(disk, volume, file);
if(!contents) {
return std::nullopt;
}
return directory_from(*contents);
}