| 1 | # A simple FAT16 driver that is used to test the `vvfat` driver in QEMU. |
| 2 | # |
| 3 | # Copyright (C) 2024 Amjad Alsharafi <amjadsharafi10@gmail.com> |
| 4 | # |
| 5 | # This program is free software; you can redistribute it and/or modify |
| 6 | # it under the terms of the GNU General Public License as published by |
| 7 | # the Free Software Foundation; either version 2 of the License, or |
| 8 | # (at your option) any later version. |
| 9 | # |
| 10 | # This program is distributed in the hope that it will be useful, |
| 11 | # but WITHOUT ANY WARRANTY; without even the implied warranty of |
| 12 | # MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
| 13 | # GNU General Public License for more details. |
| 14 | # |
| 15 | # You should have received a copy of the GNU General Public License |
| 16 | # along with this program. If not, see <http://www.gnu.org/licenses/>. |
| 17 | |
| 18 | from typing import Callable, List, Optional, Protocol, Set |
| 19 | import string |
| 20 | |
| 21 | SECTOR_SIZE = 512 |
| 22 | DIRENTRY_SIZE = 32 |
| 23 | ALLOWED_FILE_CHARS = set( |
| 24 | "!#$%&'()-@^_`{}~" + string.digits + string.ascii_uppercase |
| 25 | ) |
| 26 | |
| 27 | |
| 28 | class MBR: |
| 29 | def __init__(self, data: bytes): |
| 30 | assert len(data) == 512 |
| 31 | self.partition_table = [] |
| 32 | for i in range(4): |
| 33 | partition = data[446 + i * 16 : 446 + (i + 1) * 16] |
| 34 | self.partition_table.append( |
| 35 | { |
| 36 | "status": partition[0], |
| 37 | "start_head": partition[1], |
| 38 | "start_sector": partition[2] & 0x3F, |
| 39 | "start_cylinder": ((partition[2] & 0xC0) << 2) |
| 40 | | partition[3], |
| 41 | "type": partition[4], |
| 42 | "end_head": partition[5], |
| 43 | "end_sector": partition[6] & 0x3F, |
| 44 | "end_cylinder": ((partition[6] & 0xC0) << 2) |
| 45 | | partition[7], |
| 46 | "start_lba": int.from_bytes(partition[8:12], "little"), |
| 47 | "size": int.from_bytes(partition[12:16], "little"), |
| 48 | } |
| 49 | ) |
| 50 | |
| 51 | def __str__(self): |
| 52 | return "\n".join( |
| 53 | [ |
| 54 | f"{i}: {partition}" |
| 55 | for i, partition in enumerate(self.partition_table) |
| 56 | ] |
| 57 | ) |
| 58 | |
| 59 | |
| 60 | class FatBootSector: |
| 61 | # pylint: disable=too-many-instance-attributes |
| 62 | def __init__(self, data: bytes): |
| 63 | assert len(data) == 512 |
| 64 | self.bytes_per_sector = int.from_bytes(data[11:13], "little") |
| 65 | self.sectors_per_cluster = data[13] |
| 66 | self.reserved_sectors = int.from_bytes(data[14:16], "little") |
| 67 | self.fat_count = data[16] |
| 68 | self.root_entries = int.from_bytes(data[17:19], "little") |
| 69 | total_sectors_16 = int.from_bytes(data[19:21], "little") |
| 70 | self.media_descriptor = data[21] |
| 71 | self.sectors_per_fat = int.from_bytes(data[22:24], "little") |
| 72 | self.sectors_per_track = int.from_bytes(data[24:26], "little") |
| 73 | self.heads = int.from_bytes(data[26:28], "little") |
| 74 | self.hidden_sectors = int.from_bytes(data[28:32], "little") |
| 75 | total_sectors_32 = int.from_bytes(data[32:36], "little") |
| 76 | assert ( |
| 77 | total_sectors_16 == 0 or total_sectors_32 == 0 |
| 78 | ), "Both total sectors (16 and 32) fields are non-zero" |
| 79 | self.total_sectors = total_sectors_16 or total_sectors_32 |
| 80 | self.drive_number = data[36] |
| 81 | self.volume_id = int.from_bytes(data[39:43], "little") |
| 82 | self.volume_label = data[43:54].decode("ascii").strip() |
| 83 | self.fs_type = data[54:62].decode("ascii").strip() |
| 84 | |
| 85 | def root_dir_start(self): |
| 86 | """ |
| 87 | Calculate the start sector of the root directory. |
| 88 | """ |
| 89 | return self.reserved_sectors + self.fat_count * self.sectors_per_fat |
| 90 | |
| 91 | def root_dir_size(self): |
| 92 | """ |
| 93 | Calculate the size of the root directory in sectors. |
| 94 | """ |
| 95 | return ( |
| 96 | self.root_entries * DIRENTRY_SIZE + self.bytes_per_sector - 1 |
| 97 | ) // self.bytes_per_sector |
| 98 | |
| 99 | def data_sector_start(self): |
| 100 | """ |
| 101 | Calculate the start sector of the data region. |
| 102 | """ |
| 103 | return self.root_dir_start() + self.root_dir_size() |
| 104 | |
| 105 | def first_sector_of_cluster(self, cluster: int) -> int: |
| 106 | """ |
| 107 | Calculate the first sector of the given cluster. |
| 108 | """ |
| 109 | return ( |
| 110 | self.data_sector_start() + (cluster - 2) * self.sectors_per_cluster |
| 111 | ) |
| 112 | |
| 113 | def cluster_bytes(self): |
| 114 | """ |
| 115 | Calculate the number of bytes in a cluster. |
| 116 | """ |
| 117 | return self.bytes_per_sector * self.sectors_per_cluster |
| 118 | |
| 119 | def __str__(self): |
| 120 | return ( |
| 121 | f"Bytes per sector: {self.bytes_per_sector}\n" |
| 122 | f"Sectors per cluster: {self.sectors_per_cluster}\n" |
| 123 | f"Reserved sectors: {self.reserved_sectors}\n" |
| 124 | f"FAT count: {self.fat_count}\n" |
| 125 | f"Root entries: {self.root_entries}\n" |
| 126 | f"Total sectors: {self.total_sectors}\n" |
| 127 | f"Media descriptor: {self.media_descriptor}\n" |
| 128 | f"Sectors per FAT: {self.sectors_per_fat}\n" |
| 129 | f"Sectors per track: {self.sectors_per_track}\n" |
| 130 | f"Heads: {self.heads}\n" |
| 131 | f"Hidden sectors: {self.hidden_sectors}\n" |
| 132 | f"Drive number: {self.drive_number}\n" |
| 133 | f"Volume ID: {self.volume_id}\n" |
| 134 | f"Volume label: {self.volume_label}\n" |
| 135 | f"FS type: {self.fs_type}\n" |
| 136 | ) |
| 137 | |
| 138 | |
| 139 | class FatDirectoryEntry: |
| 140 | # pylint: disable=too-many-instance-attributes |
| 141 | def __init__(self, data: bytes, sector: int, offset: int): |
| 142 | self.name = data[0:8].decode("ascii").strip() |
| 143 | self.ext = data[8:11].decode("ascii").strip() |
| 144 | self.attributes = data[11] |
| 145 | self.reserved = data[12] |
| 146 | self.create_time_tenth = data[13] |
| 147 | self.create_time = int.from_bytes(data[14:16], "little") |
| 148 | self.create_date = int.from_bytes(data[16:18], "little") |
| 149 | self.last_access_date = int.from_bytes(data[18:20], "little") |
| 150 | high_cluster = int.from_bytes(data[20:22], "little") |
| 151 | self.last_mod_time = int.from_bytes(data[22:24], "little") |
| 152 | self.last_mod_date = int.from_bytes(data[24:26], "little") |
| 153 | low_cluster = int.from_bytes(data[26:28], "little") |
| 154 | self.cluster = (high_cluster << 16) | low_cluster |
| 155 | self.size_bytes = int.from_bytes(data[28:32], "little") |
| 156 | |
| 157 | # extra (to help write back to disk) |
| 158 | self.sector = sector |
| 159 | self.offset = offset |
| 160 | |
| 161 | def as_bytes(self) -> bytes: |
| 162 | return ( |
| 163 | self.name.ljust(8, " ").encode("ascii") |
| 164 | + self.ext.ljust(3, " ").encode("ascii") |
| 165 | + self.attributes.to_bytes(1, "little") |
| 166 | + self.reserved.to_bytes(1, "little") |
| 167 | + self.create_time_tenth.to_bytes(1, "little") |
| 168 | + self.create_time.to_bytes(2, "little") |
| 169 | + self.create_date.to_bytes(2, "little") |
| 170 | + self.last_access_date.to_bytes(2, "little") |
| 171 | + (self.cluster >> 16).to_bytes(2, "little") |
| 172 | + self.last_mod_time.to_bytes(2, "little") |
| 173 | + self.last_mod_date.to_bytes(2, "little") |
| 174 | + (self.cluster & 0xFFFF).to_bytes(2, "little") |
| 175 | + self.size_bytes.to_bytes(4, "little") |
| 176 | ) |
| 177 | |
| 178 | def whole_name(self): |
| 179 | if self.ext: |
| 180 | return f"{self.name}.{self.ext}" |
| 181 | else: |
| 182 | return self.name |
| 183 | |
| 184 | def __str__(self): |
| 185 | return ( |
| 186 | f"Name: {self.name}\n" |
| 187 | f"Ext: {self.ext}\n" |
| 188 | f"Attributes: {self.attributes}\n" |
| 189 | f"Reserved: {self.reserved}\n" |
| 190 | f"Create time tenth: {self.create_time_tenth}\n" |
| 191 | f"Create time: {self.create_time}\n" |
| 192 | f"Create date: {self.create_date}\n" |
| 193 | f"Last access date: {self.last_access_date}\n" |
| 194 | f"Last mod time: {self.last_mod_time}\n" |
| 195 | f"Last mod date: {self.last_mod_date}\n" |
| 196 | f"Cluster: {self.cluster}\n" |
| 197 | f"Size: {self.size_bytes}\n" |
| 198 | ) |
| 199 | |
| 200 | def __repr__(self): |
| 201 | # convert to dict |
| 202 | return str(vars(self)) |
| 203 | |
| 204 | |
| 205 | class SectorReader(Protocol): |
| 206 | def __call__(self, start_sector: int, num_sectors: int = 1) -> bytes: ... |
| 207 | |
| 208 | # pylint: disable=broad-exception-raised |
| 209 | class Fat16: |
| 210 | def __init__( |
| 211 | self, |
| 212 | start_sector: int, |
| 213 | size: int, |
| 214 | sector_reader: SectorReader, |
| 215 | sector_writer: Callable[[int, bytes], None] |
| 216 | ): |
| 217 | self.start_sector = start_sector |
| 218 | self.size_in_sectors = size |
| 219 | self.sector_reader = sector_reader |
| 220 | self.sector_writer = sector_writer |
| 221 | |
| 222 | self.boot_sector = FatBootSector(self.sector_reader(start_sector, 1)) |
| 223 | |
| 224 | fat_size_in_sectors = ( |
| 225 | self.boot_sector.sectors_per_fat * self.boot_sector.fat_count |
| 226 | ) |
| 227 | self.fats = self.read_sectors( |
| 228 | self.boot_sector.reserved_sectors, fat_size_in_sectors |
| 229 | ) |
| 230 | self.fats_dirty_sectors: Set[int] = set() |
| 231 | |
| 232 | def read_sectors(self, start_sector: int, num_sectors: int) -> bytes: |
| 233 | return self.sector_reader(start_sector + self.start_sector, |
| 234 | num_sectors) |
| 235 | |
| 236 | def write_sectors(self, start_sector: int, data: bytes) -> None: |
| 237 | return self.sector_writer(start_sector + self.start_sector, data) |
| 238 | |
| 239 | def directory_from_bytes( |
| 240 | self, data: bytes, start_sector: int |
| 241 | ) -> List[FatDirectoryEntry]: |
| 242 | """ |
| 243 | Convert `bytes` into a list of `FatDirectoryEntry` objects. |
| 244 | Will ignore long file names. |
| 245 | Will stop when it encounters a 0x00 byte. |
| 246 | """ |
| 247 | |
| 248 | entries = [] |
| 249 | for i in range(0, len(data), DIRENTRY_SIZE): |
| 250 | entry = data[i : i + DIRENTRY_SIZE] |
| 251 | |
| 252 | current_sector = start_sector + (i // SECTOR_SIZE) |
| 253 | current_offset = i % SECTOR_SIZE |
| 254 | |
| 255 | if entry[0] == 0: |
| 256 | break |
| 257 | |
| 258 | if entry[0] == 0xE5: |
| 259 | # Deleted file |
| 260 | continue |
| 261 | |
| 262 | if entry[11] & 0xF == 0xF: |
| 263 | # Long file name |
| 264 | continue |
| 265 | |
| 266 | entries.append( |
| 267 | FatDirectoryEntry(entry, current_sector, current_offset) |
| 268 | ) |
| 269 | return entries |
| 270 | |
| 271 | def read_root_directory(self) -> List[FatDirectoryEntry]: |
| 272 | root_dir = self.read_sectors( |
| 273 | self.boot_sector.root_dir_start(), self.boot_sector.root_dir_size() |
| 274 | ) |
| 275 | return self.directory_from_bytes( |
| 276 | root_dir, self.boot_sector.root_dir_start() |
| 277 | ) |
| 278 | |
| 279 | def read_fat_entry(self, cluster: int) -> int: |
| 280 | """ |
| 281 | Read the FAT entry for the given cluster. |
| 282 | """ |
| 283 | fat_offset = cluster * 2 # FAT16 |
| 284 | return int.from_bytes(self.fats[fat_offset : fat_offset + 2], "little") |
| 285 | |
| 286 | def write_fat_entry(self, cluster: int, value: int) -> None: |
| 287 | """ |
| 288 | Write the FAT entry for the given cluster. |
| 289 | """ |
| 290 | fat_offset = cluster * 2 |
| 291 | self.fats = ( |
| 292 | self.fats[:fat_offset] |
| 293 | + value.to_bytes(2, "little") |
| 294 | + self.fats[fat_offset + 2 :] |
| 295 | ) |
| 296 | self.fats_dirty_sectors.add(fat_offset // SECTOR_SIZE) |
| 297 | |
| 298 | def flush_fats(self) -> None: |
| 299 | """ |
| 300 | Write the FATs back to the disk. |
| 301 | """ |
| 302 | for sector in self.fats_dirty_sectors: |
| 303 | data = self.fats[sector * SECTOR_SIZE : (sector + 1) * SECTOR_SIZE] |
| 304 | sector = self.boot_sector.reserved_sectors + sector |
| 305 | self.write_sectors(sector, data) |
| 306 | self.fats_dirty_sectors = set() |
| 307 | |
| 308 | def next_cluster(self, cluster: int) -> Optional[int]: |
| 309 | """ |
| 310 | Get the next cluster in the chain. |
| 311 | If its `None`, then its the last cluster. |
| 312 | The function will crash if the next cluster |
| 313 | is `FREE` (unexpected) or invalid entry. |
| 314 | """ |
| 315 | fat_entry = self.read_fat_entry(cluster) |
| 316 | if fat_entry == 0: |
| 317 | raise Exception("Unexpected: FREE cluster") |
| 318 | if fat_entry == 1: |
| 319 | raise Exception("Unexpected: RESERVED cluster") |
| 320 | if fat_entry >= 0xFFF8: |
| 321 | return None |
| 322 | if fat_entry >= 0xFFF7: |
| 323 | raise Exception("Invalid FAT entry") |
| 324 | |
| 325 | return fat_entry |
| 326 | |
| 327 | def next_free_cluster(self) -> int: |
| 328 | """ |
| 329 | Find the next free cluster. |
| 330 | """ |
| 331 | # simple linear search |
| 332 | for i in range(2, 0xFFFF): |
| 333 | if self.read_fat_entry(i) == 0: |
| 334 | return i |
| 335 | raise Exception("No free clusters") |
| 336 | |
| 337 | def next_free_cluster_non_continuous(self) -> int: |
| 338 | """ |
| 339 | Find the next free cluster, but makes sure |
| 340 | that the cluster before and after it are not allocated. |
| 341 | """ |
| 342 | # simple linear search |
| 343 | before = False |
| 344 | for i in range(2, 0xFFFF): |
| 345 | if self.read_fat_entry(i) == 0: |
| 346 | if before and self.read_fat_entry(i + 1) == 0: |
| 347 | return i |
| 348 | else: |
| 349 | before = True |
| 350 | else: |
| 351 | before = False |
| 352 | |
| 353 | raise Exception("No free clusters") |
| 354 | |
| 355 | def read_cluster(self, cluster: int) -> bytes: |
| 356 | """ |
| 357 | Read the cluster at the given cluster. |
| 358 | """ |
| 359 | return self.read_sectors( |
| 360 | self.boot_sector.first_sector_of_cluster(cluster), |
| 361 | self.boot_sector.sectors_per_cluster, |
| 362 | ) |
| 363 | |
| 364 | def write_cluster(self, cluster: int, data: bytes) -> None: |
| 365 | """ |
| 366 | Write the cluster at the given cluster. |
| 367 | """ |
| 368 | assert len(data) == self.boot_sector.cluster_bytes() |
| 369 | self.write_sectors( |
| 370 | self.boot_sector.first_sector_of_cluster(cluster), |
| 371 | data, |
| 372 | ) |
| 373 | |
| 374 | def read_directory( |
| 375 | self, cluster: Optional[int] |
| 376 | ) -> List[FatDirectoryEntry]: |
| 377 | """ |
| 378 | Read the directory at the given cluster. |
| 379 | """ |
| 380 | entries = [] |
| 381 | while cluster is not None: |
| 382 | data = self.read_cluster(cluster) |
| 383 | entries.extend( |
| 384 | self.directory_from_bytes( |
| 385 | data, self.boot_sector.first_sector_of_cluster(cluster) |
| 386 | ) |
| 387 | ) |
| 388 | cluster = self.next_cluster(cluster) |
| 389 | return entries |
| 390 | |
| 391 | def add_direntry( |
| 392 | self, cluster: Optional[int], name: str, ext: str, attributes: int |
| 393 | ) -> FatDirectoryEntry: |
| 394 | """ |
| 395 | Add a new directory entry to the given cluster. |
| 396 | If the cluster is `None`, then it will be added to the root directory. |
| 397 | """ |
| 398 | |
| 399 | def find_free_entry(data: bytes) -> Optional[int]: |
| 400 | for i in range(0, len(data), DIRENTRY_SIZE): |
| 401 | entry = data[i : i + DIRENTRY_SIZE] |
| 402 | if entry[0] == 0 or entry[0] == 0xE5: |
| 403 | return i |
| 404 | return None |
| 405 | |
| 406 | assert len(name) <= 8, "Name must be 8 characters or less" |
| 407 | assert len(ext) <= 3, "Ext must be 3 characters or less" |
| 408 | assert attributes % 0x15 != 0x15, "Invalid attributes" |
| 409 | |
| 410 | # initial dummy data |
| 411 | new_entry = FatDirectoryEntry(b"\0" * 32, 0, 0) |
| 412 | new_entry.name = name.ljust(8, " ") |
| 413 | new_entry.ext = ext.ljust(3, " ") |
| 414 | new_entry.attributes = attributes |
| 415 | new_entry.reserved = 0 |
| 416 | new_entry.create_time_tenth = 0 |
| 417 | new_entry.create_time = 0 |
| 418 | new_entry.create_date = 0 |
| 419 | new_entry.last_access_date = 0 |
| 420 | new_entry.last_mod_time = 0 |
| 421 | new_entry.last_mod_date = 0 |
| 422 | new_entry.cluster = self.next_free_cluster() |
| 423 | new_entry.size_bytes = 0 |
| 424 | |
| 425 | # mark as EOF |
| 426 | self.write_fat_entry(new_entry.cluster, 0xFFFF) |
| 427 | |
| 428 | if cluster is None: |
| 429 | for i in range(self.boot_sector.root_dir_size()): |
| 430 | sector_data = self.read_sectors( |
| 431 | self.boot_sector.root_dir_start() + i, 1 |
| 432 | ) |
| 433 | offset = find_free_entry(sector_data) |
| 434 | if offset is not None: |
| 435 | new_entry.sector = self.boot_sector.root_dir_start() + i |
| 436 | new_entry.offset = offset |
| 437 | self.update_direntry(new_entry) |
| 438 | return new_entry |
| 439 | else: |
| 440 | while cluster is not None: |
| 441 | data = self.read_cluster(cluster) |
| 442 | offset = find_free_entry(data) |
| 443 | if offset is not None: |
| 444 | new_entry.sector = ( |
| 445 | self.boot_sector.first_sector_of_cluster(cluster) |
| 446 | + (offset // SECTOR_SIZE)) |
| 447 | new_entry.offset = offset % SECTOR_SIZE |
| 448 | self.update_direntry(new_entry) |
| 449 | return new_entry |
| 450 | cluster = self.next_cluster(cluster) |
| 451 | |
| 452 | raise Exception("No free directory entries") |
| 453 | |
| 454 | def update_direntry(self, entry: FatDirectoryEntry) -> None: |
| 455 | """ |
| 456 | Write the directory entry back to the disk. |
| 457 | """ |
| 458 | sector = self.read_sectors(entry.sector, 1) |
| 459 | sector = ( |
| 460 | sector[: entry.offset] |
| 461 | + entry.as_bytes() |
| 462 | + sector[entry.offset + DIRENTRY_SIZE :] |
| 463 | ) |
| 464 | self.write_sectors(entry.sector, sector) |
| 465 | |
| 466 | def find_direntry(self, path: str) -> Optional[FatDirectoryEntry]: |
| 467 | """ |
| 468 | Find the directory entry for the given path. |
| 469 | """ |
| 470 | assert path[0] == "/", "Path must start with /" |
| 471 | |
| 472 | path = path[1:] # remove the leading / |
| 473 | parts = path.split("/") |
| 474 | directory = self.read_root_directory() |
| 475 | |
| 476 | current_entry = None |
| 477 | |
| 478 | for i, part in enumerate(parts): |
| 479 | is_last = i == len(parts) - 1 |
| 480 | |
| 481 | for entry in directory: |
| 482 | if entry.whole_name() == part: |
| 483 | current_entry = entry |
| 484 | break |
| 485 | if current_entry is None: |
| 486 | return None |
| 487 | |
| 488 | if is_last: |
| 489 | return current_entry |
| 490 | |
| 491 | if current_entry.attributes & 0x10 == 0: |
| 492 | raise Exception( |
| 493 | f"{current_entry.whole_name()} is not a directory" |
| 494 | ) |
| 495 | |
| 496 | directory = self.read_directory(current_entry.cluster) |
| 497 | |
| 498 | assert False, "Exited loop with is_last == False" |
| 499 | |
| 500 | def read_file(self, entry: Optional[FatDirectoryEntry]) -> Optional[bytes]: |
| 501 | """ |
| 502 | Read the content of the file at the given path. |
| 503 | """ |
| 504 | if entry is None: |
| 505 | return None |
| 506 | if entry.attributes & 0x10 != 0: |
| 507 | raise Exception(f"{entry.whole_name()} is a directory") |
| 508 | |
| 509 | data = b"" |
| 510 | cluster: Optional[int] = entry.cluster |
| 511 | while cluster is not None and len(data) <= entry.size_bytes: |
| 512 | data += self.read_cluster(cluster) |
| 513 | cluster = self.next_cluster(cluster) |
| 514 | return data[: entry.size_bytes] |
| 515 | |
| 516 | def truncate_file( |
| 517 | self, |
| 518 | entry: FatDirectoryEntry, |
| 519 | new_size: int, |
| 520 | allocate_non_continuous: bool = False, |
| 521 | ) -> None: |
| 522 | """ |
| 523 | Truncate the file at the given path to the new size. |
| 524 | """ |
| 525 | if entry is None: |
| 526 | raise Exception("entry is None") |
| 527 | if entry.attributes & 0x10 != 0: |
| 528 | raise Exception(f"{entry.whole_name()} is a directory") |
| 529 | |
| 530 | def clusters_from_size(size: int) -> int: |
| 531 | return ( |
| 532 | size + self.boot_sector.cluster_bytes() - 1 |
| 533 | ) // self.boot_sector.cluster_bytes() |
| 534 | |
| 535 | # First, allocate new FATs if we need to |
| 536 | required_clusters = clusters_from_size(new_size) |
| 537 | current_clusters = clusters_from_size(entry.size_bytes) |
| 538 | |
| 539 | affected_clusters = set() |
| 540 | |
| 541 | # Keep at least one cluster, easier to manage this way |
| 542 | if required_clusters == 0: |
| 543 | required_clusters = 1 |
| 544 | if current_clusters == 0: |
| 545 | current_clusters = 1 |
| 546 | |
| 547 | cluster: Optional[int] |
| 548 | |
| 549 | if required_clusters > current_clusters: |
| 550 | # Allocate new clusters |
| 551 | cluster = entry.cluster |
| 552 | to_add = required_clusters |
| 553 | for _ in range(current_clusters - 1): |
| 554 | to_add -= 1 |
| 555 | assert cluster is not None, "Cluster is None" |
| 556 | affected_clusters.add(cluster) |
| 557 | cluster = self.next_cluster(cluster) |
| 558 | assert required_clusters > 0, "No new clusters to allocate" |
| 559 | assert cluster is not None, "Cluster is None" |
| 560 | assert ( |
| 561 | self.next_cluster(cluster) is None |
| 562 | ), "Cluster is not the last cluster" |
| 563 | |
| 564 | # Allocate new clusters |
| 565 | for _ in range(to_add - 1): |
| 566 | if allocate_non_continuous: |
| 567 | new_cluster = self.next_free_cluster_non_continuous() |
| 568 | else: |
| 569 | new_cluster = self.next_free_cluster() |
| 570 | self.write_fat_entry(cluster, new_cluster) |
| 571 | self.write_fat_entry(new_cluster, 0xFFFF) |
| 572 | cluster = new_cluster |
| 573 | |
| 574 | elif required_clusters < current_clusters: |
| 575 | # Truncate the file |
| 576 | cluster = entry.cluster |
| 577 | for _ in range(required_clusters - 1): |
| 578 | assert cluster is not None, "Cluster is None" |
| 579 | cluster = self.next_cluster(cluster) |
| 580 | assert cluster is not None, "Cluster is None" |
| 581 | |
| 582 | next_cluster = self.next_cluster(cluster) |
| 583 | # mark last as EOF |
| 584 | self.write_fat_entry(cluster, 0xFFFF) |
| 585 | # free the rest |
| 586 | while next_cluster is not None: |
| 587 | cluster = next_cluster |
| 588 | next_cluster = self.next_cluster(next_cluster) |
| 589 | self.write_fat_entry(cluster, 0) |
| 590 | |
| 591 | self.flush_fats() |
| 592 | |
| 593 | # verify number of clusters |
| 594 | cluster = entry.cluster |
| 595 | count = 0 |
| 596 | while cluster is not None: |
| 597 | count += 1 |
| 598 | affected_clusters.add(cluster) |
| 599 | cluster = self.next_cluster(cluster) |
| 600 | assert ( |
| 601 | count == required_clusters |
| 602 | ), f"Expected {required_clusters} clusters, got {count}" |
| 603 | |
| 604 | # update the size |
| 605 | entry.size_bytes = new_size |
| 606 | self.update_direntry(entry) |
| 607 | |
| 608 | # trigger every affected cluster |
| 609 | for cluster in affected_clusters: |
| 610 | first_sector = self.boot_sector.first_sector_of_cluster(cluster) |
| 611 | first_sector_data = self.read_sectors(first_sector, 1) |
| 612 | self.write_sectors(first_sector, first_sector_data) |
| 613 | |
| 614 | def write_file(self, entry: FatDirectoryEntry, data: bytes) -> None: |
| 615 | """ |
| 616 | Write the content of the file at the given path. |
| 617 | """ |
| 618 | if entry is None: |
| 619 | raise Exception("entry is None") |
| 620 | if entry.attributes & 0x10 != 0: |
| 621 | raise Exception(f"{entry.whole_name()} is a directory") |
| 622 | |
| 623 | data_len = len(data) |
| 624 | |
| 625 | self.truncate_file(entry, data_len) |
| 626 | |
| 627 | cluster: Optional[int] = entry.cluster |
| 628 | while cluster is not None: |
| 629 | data_to_write = data[: self.boot_sector.cluster_bytes()] |
| 630 | if len(data_to_write) < self.boot_sector.cluster_bytes(): |
| 631 | old_data = self.read_cluster(cluster) |
| 632 | data_to_write += old_data[len(data_to_write) :] |
| 633 | |
| 634 | self.write_cluster(cluster, data_to_write) |
| 635 | data = data[self.boot_sector.cluster_bytes() :] |
| 636 | if len(data) == 0: |
| 637 | break |
| 638 | cluster = self.next_cluster(cluster) |
| 639 | |
| 640 | assert ( |
| 641 | len(data) == 0 |
| 642 | ), "Data was not written completely, clusters missing" |
| 643 | |
| 644 | def create_file(self, path: str) -> Optional[FatDirectoryEntry]: |
| 645 | """ |
| 646 | Create a new file at the given path. |
| 647 | """ |
| 648 | assert path[0] == "/", "Path must start with /" |
| 649 | |
| 650 | path = path[1:] # remove the leading / |
| 651 | |
| 652 | parts = path.split("/") |
| 653 | |
| 654 | directory_cluster = None |
| 655 | directory = self.read_root_directory() |
| 656 | |
| 657 | parts, filename = parts[:-1], parts[-1] |
| 658 | |
| 659 | for _, part in enumerate(parts): |
| 660 | current_entry = None |
| 661 | for entry in directory: |
| 662 | if entry.whole_name() == part: |
| 663 | current_entry = entry |
| 664 | break |
| 665 | if current_entry is None: |
| 666 | return None |
| 667 | |
| 668 | if current_entry.attributes & 0x10 == 0: |
| 669 | raise Exception( |
| 670 | f"{current_entry.whole_name()} is not a directory" |
| 671 | ) |
| 672 | |
| 673 | directory = self.read_directory(current_entry.cluster) |
| 674 | directory_cluster = current_entry.cluster |
| 675 | |
| 676 | # add new entry to the directory |
| 677 | |
| 678 | filename, ext = filename.split(".") |
| 679 | |
| 680 | if len(ext) > 3: |
| 681 | raise Exception("Ext must be 3 characters or less") |
| 682 | if len(filename) > 8: |
| 683 | raise Exception("Name must be 8 characters or less") |
| 684 | |
| 685 | for c in filename + ext: |
| 686 | |
| 687 | if c not in ALLOWED_FILE_CHARS: |
| 688 | raise Exception("Invalid character in filename") |
| 689 | |
| 690 | return self.add_direntry(directory_cluster, filename, ext, 0) |