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fd89185461
rust-fatfs/src/fs.rs
Rafał Harabień fd89185461 Add more format_volume tests and simlify code
2018-12-05 22:31:59 +01:00

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#[cfg(all(not(feature = "std"), feature = "alloc"))]
use alloc::String;
use core::cell::{Cell, RefCell};
use core::char;
use core::cmp;
use core::fmt::Debug;
use core::iter::FromIterator;
use io;
use io::prelude::*;
use io::{Error, ErrorKind, SeekFrom};
use byteorder::LittleEndian;
use byteorder_ext::{ReadBytesExt, WriteBytesExt};
use dir::{Dir, DirRawStream};
use dir_entry::DIR_ENTRY_SIZE;
use file::File;
use table::{alloc_cluster, count_free_clusters, read_fat_flags, format_fat, ClusterIterator, RESERVED_FAT_ENTRIES};
use time::{TimeProvider, DEFAULT_TIME_PROVIDER};
// FAT implementation based on:
// http://wiki.osdev.org/FAT
// https://www.win.tue.nl/~aeb/linux/fs/fat/fat-1.html
/// A type of FAT filesystem.
///
/// `FatType` values are based on the size of File Allocation Table entry.
#[derive(Copy, Clone, Eq, PartialEq, Debug)]
pub enum FatType {
/// 12 bits per FAT entry
Fat12,
/// 16 bits per FAT entry
Fat16,
/// 32 bits per FAT entry
Fat32,
}
impl FatType {
fn from_clusters(total_clusters: u32) -> FatType {
if total_clusters < 4085 {
FatType::Fat12
} else if total_clusters < 65525 {
FatType::Fat16
} else {
FatType::Fat32
}
}
pub(crate) fn bits_per_fat_entry(&self) -> u32 {
match self {
&FatType::Fat12 => 12,
&FatType::Fat16 => 16,
&FatType::Fat32 => 32,
}
}
}
/// A FAT volume status flags retrived from the Boot Sector and the allocation table second entry.
#[derive(Copy, Clone, Eq, PartialEq, Debug)]
pub struct FsStatusFlags {
pub(crate) dirty: bool,
pub(crate) io_error: bool,
}
impl FsStatusFlags {
/// Checks if the volume is marked as dirty.
///
/// Dirty flag means volume has been suddenly ejected from filesystem without unmounting.
pub fn dirty(&self) -> bool {
self.dirty
}
/// Checks if the volume has the IO Error flag active.
pub fn io_error(&self) -> bool {
self.io_error
}
fn encode(&self) -> u8 {
let mut res = 0u8;
if self.dirty {
res |= 1;
}
if self.io_error {
res |= 2;
}
res
}
fn decode(flags: u8) -> Self {
FsStatusFlags {
dirty: flags & 1 != 0,
io_error: flags & 2 != 0,
}
}
}
/// A sum of `Read` and `Seek` traits.
pub trait ReadSeek: Read + Seek {}
impl<T: Read + Seek> ReadSeek for T {}
/// A sum of `Read`, `Write` and `Seek` traits.
pub trait ReadWriteSeek: Read + Write + Seek {}
impl<T: Read + Write + Seek> ReadWriteSeek for T {}
#[allow(dead_code)]
#[derive(Default, Debug, Clone)]
pub(crate) struct BiosParameterBlock {
bytes_per_sector: u16,
sectors_per_cluster: u8,
reserved_sectors: u16,
fats: u8,
root_entries: u16,
total_sectors_16: u16,
media: u8,
sectors_per_fat_16: u16,
sectors_per_track: u16,
heads: u16,
hidden_sectors: u32,
total_sectors_32: u32,
// Extended BIOS Parameter Block
sectors_per_fat_32: u32,
extended_flags: u16,
fs_version: u16,
root_dir_first_cluster: u32,
fs_info_sector: u16,
backup_boot_sector: u16,
reserved_0: [u8; 12],
drive_num: u8,
reserved_1: u8,
ext_sig: u8,
volume_id: u32,
volume_label: [u8; 11],
fs_type_label: [u8; 8],
}
impl BiosParameterBlock {
fn deserialize<T: Read>(rdr: &mut T) -> io::Result<BiosParameterBlock> {
let mut bpb: BiosParameterBlock = Default::default();
bpb.bytes_per_sector = rdr.read_u16::<LittleEndian>()?;
bpb.sectors_per_cluster = rdr.read_u8()?;
bpb.reserved_sectors = rdr.read_u16::<LittleEndian>()?;
bpb.fats = rdr.read_u8()?;
bpb.root_entries = rdr.read_u16::<LittleEndian>()?;
bpb.total_sectors_16 = rdr.read_u16::<LittleEndian>()?;
bpb.media = rdr.read_u8()?;
bpb.sectors_per_fat_16 = rdr.read_u16::<LittleEndian>()?;
bpb.sectors_per_track = rdr.read_u16::<LittleEndian>()?;
bpb.heads = rdr.read_u16::<LittleEndian>()?;
bpb.hidden_sectors = rdr.read_u32::<LittleEndian>()?;
bpb.total_sectors_32 = rdr.read_u32::<LittleEndian>()?;
if bpb.is_fat32() {
bpb.sectors_per_fat_32 = rdr.read_u32::<LittleEndian>()?;
bpb.extended_flags = rdr.read_u16::<LittleEndian>()?;
bpb.fs_version = rdr.read_u16::<LittleEndian>()?;
bpb.root_dir_first_cluster = rdr.read_u32::<LittleEndian>()?;
bpb.fs_info_sector = rdr.read_u16::<LittleEndian>()?;
bpb.backup_boot_sector = rdr.read_u16::<LittleEndian>()?;
rdr.read_exact(&mut bpb.reserved_0)?;
bpb.drive_num = rdr.read_u8()?;
bpb.reserved_1 = rdr.read_u8()?;
bpb.ext_sig = rdr.read_u8()?; // 0x29
bpb.volume_id = rdr.read_u32::<LittleEndian>()?;
rdr.read_exact(&mut bpb.volume_label)?;
rdr.read_exact(&mut bpb.fs_type_label)?;
} else {
bpb.drive_num = rdr.read_u8()?;
bpb.reserved_1 = rdr.read_u8()?;
bpb.ext_sig = rdr.read_u8()?; // 0x29
bpb.volume_id = rdr.read_u32::<LittleEndian>()?;
rdr.read_exact(&mut bpb.volume_label)?;
rdr.read_exact(&mut bpb.fs_type_label)?;
}
// when the extended boot signature is anything other than 0x29, the fields are invalid
if bpb.ext_sig != 0x29 {
// fields after ext_sig are not used - clean them
bpb.volume_id = 0;
bpb.volume_label = [0; 11];
bpb.fs_type_label = [0; 8];
}
Ok(bpb)
}
fn serialize<T: Write>(&self, mut wrt: T) -> io::Result<()> {
wrt.write_u16::<LittleEndian>(self.bytes_per_sector)?;
wrt.write_u8(self.sectors_per_cluster)?;
wrt.write_u16::<LittleEndian>(self.reserved_sectors)?;
wrt.write_u8(self.fats)?;
wrt.write_u16::<LittleEndian>(self.root_entries)?;
wrt.write_u16::<LittleEndian>(self.total_sectors_16)?;
wrt.write_u8(self.media)?;
wrt.write_u16::<LittleEndian>(self.sectors_per_fat_16)?;
wrt.write_u16::<LittleEndian>(self.sectors_per_track)?;
wrt.write_u16::<LittleEndian>(self.heads)?;
wrt.write_u32::<LittleEndian>(self.hidden_sectors)?;
wrt.write_u32::<LittleEndian>(self.total_sectors_32)?;
if self.is_fat32() {
wrt.write_u32::<LittleEndian>(self.sectors_per_fat_32)?;
wrt.write_u16::<LittleEndian>(self.extended_flags)?;
wrt.write_u16::<LittleEndian>(self.fs_version)?;
wrt.write_u32::<LittleEndian>(self.root_dir_first_cluster)?;
wrt.write_u16::<LittleEndian>(self.fs_info_sector)?;
wrt.write_u16::<LittleEndian>(self.backup_boot_sector)?;
wrt.write_all(&self.reserved_0)?;
wrt.write_u8(self.drive_num)?;
wrt.write_u8(self.reserved_1)?;
wrt.write_u8(self.ext_sig)?; // 0x29
wrt.write_u32::<LittleEndian>(self.volume_id)?;
wrt.write_all(&self.volume_label)?;
wrt.write_all(&self.fs_type_label)?;
} else {
wrt.write_u8(self.drive_num)?;
wrt.write_u8(self.reserved_1)?;
wrt.write_u8(self.ext_sig)?; // 0x29
wrt.write_u32::<LittleEndian>(self.volume_id)?;
wrt.write_all(&self.volume_label)?;
wrt.write_all(&self.fs_type_label)?;
}
Ok(())
}
fn validate(&self) -> io::Result<()> {
// sanity checks
if self.bytes_per_sector.count_ones() != 1 {
return Err(Error::new(
ErrorKind::Other,
"invalid bytes_per_sector value in BPB (not power of two)",
));
} else if self.bytes_per_sector < 512 {
return Err(Error::new(ErrorKind::Other, "invalid bytes_per_sector value in BPB (value < 512)"));
} else if self.bytes_per_sector > 4096 {
return Err(Error::new(ErrorKind::Other, "invalid bytes_per_sector value in BPB (value > 4096)"));
}
if self.sectors_per_cluster.count_ones() != 1 {
return Err(Error::new(
ErrorKind::Other,
"invalid sectors_per_cluster value in BPB (not power of two)",
));
} else if self.sectors_per_cluster < 1 {
return Err(Error::new(ErrorKind::Other, "invalid sectors_per_cluster value in BPB (value < 1)"));
} else if self.sectors_per_cluster > 128 {
return Err(Error::new(
ErrorKind::Other,
"invalid sectors_per_cluster value in BPB (value > 128)",
));
}
// bytes per sector is u16, sectors per cluster is u8, so guaranteed no overflow in multiplication
let bytes_per_cluster = self.bytes_per_sector as u32 * self.sectors_per_cluster as u32;
let maximum_compatibility_bytes_per_cluster: u32 = 32 * 1024;
if bytes_per_cluster > maximum_compatibility_bytes_per_cluster {
// 32k is the largest value to maintain greatest compatibility
// Many implementations appear to support 64k per cluster, and some may support 128k or larger
// However, >32k is not as thoroughly tested...
warn!("fs compatibility: bytes_per_cluster value '{}' in BPB exceeds '{}', and thus may be incompatible with some implementations",
bytes_per_cluster, maximum_compatibility_bytes_per_cluster);
}
let is_fat32 = self.is_fat32();
if self.reserved_sectors < 1 {
return Err(Error::new(ErrorKind::Other, "invalid reserved_sectors value in BPB"));
} else if !is_fat32 && self.reserved_sectors != 1 {
// Microsoft document indicates fat12 and fat16 code exists that presume this value is 1
warn!(
"fs compatibility: reserved_sectors value '{}' in BPB is not '1', and thus is incompatible with some implementations",
self.reserved_sectors
);
}
if self.fats == 0 {
return Err(Error::new(ErrorKind::Other, "invalid fats value in BPB"));
} else if self.fats > 2 {
// Microsoft document indicates that few implementations support any values other than 1 or 2
warn!(
"fs compatibility: numbers of FATs '{}' in BPB is greater than '2', and thus is incompatible with some implementations",
self.fats
);
}
if is_fat32 && self.root_entries != 0 {
return Err(Error::new(
ErrorKind::Other,
"Invalid root_entries value in BPB (should be zero for FAT32)",
));
}
if is_fat32 && self.total_sectors_16 != 0 {
return Err(Error::new(
ErrorKind::Other,
"Invalid total_sectors_16 value in BPB (should be zero for FAT32)",
));
}
if (self.total_sectors_16 == 0) == (self.total_sectors_32 == 0) {
return Err(Error::new(
ErrorKind::Other,
"Invalid BPB (total_sectors_16 or total_sectors_32 should be non-zero)",
));
}
if is_fat32 && self.sectors_per_fat_32 == 0 {
return Err(Error::new(
ErrorKind::Other,
"Invalid sectors_per_fat_32 value in BPB (should be non-zero for FAT32)",
));
}
if self.fs_version != 0 {
return Err(Error::new(ErrorKind::Other, "Unknown FS version"));
}
if self.total_sectors() <= self.first_data_sector() {
return Err(Error::new(
ErrorKind::Other,
"Invalid BPB (total_sectors field value is too small)",
));
}
let total_clusters = self.total_clusters();
let fat_type = FatType::from_clusters(total_clusters);
if is_fat32 != (fat_type == FatType::Fat32) {
return Err(Error::new(
ErrorKind::Other,
"Invalid BPB (result of FAT32 determination from total number of clusters and sectors_per_fat_16 field differs)",
));
}
let bits_per_fat_entry = fat_type.bits_per_fat_entry();
let total_fat_entries = self.sectors_per_fat() * self.bytes_per_sector as u32 * 8 / bits_per_fat_entry as u32;
if total_fat_entries - RESERVED_FAT_ENTRIES < total_clusters {
warn!("FAT is too small to compared to total number of clusters");
}
Ok(())
}
fn mirroring_enabled(&self) -> bool {
self.extended_flags & 0x80 == 0
}
fn active_fat(&self) -> u16 {
// The zero-based number of the active FAT is only valid if mirroring is disabled.
if self.mirroring_enabled() {
0
} else {
self.extended_flags & 0x0F
}
}
fn status_flags(&self) -> FsStatusFlags {
FsStatusFlags::decode(self.reserved_1)
}
fn is_fat32(&self) -> bool {
// because this field must be zero on FAT32, and
// because it must be non-zero on FAT12/FAT16,
// this provides a simple way to detect FAT32
self.sectors_per_fat_16 == 0
}
fn sectors_per_fat(&self) -> u32 {
if self.is_fat32() {
self.sectors_per_fat_32
} else {
self.sectors_per_fat_16 as u32
}
}
fn total_sectors(&self) -> u32 {
if self.total_sectors_16 == 0 {
self.total_sectors_32
} else {
self.total_sectors_16 as u32
}
}
fn root_dir_sectors(&self) -> u32 {
let root_dir_bytes = self.root_entries as u32 * DIR_ENTRY_SIZE as u32;
(root_dir_bytes + self.bytes_per_sector as u32 - 1) / self.bytes_per_sector as u32
}
fn sectors_per_all_fats(&self) -> u32 {
self.fats as u32 * self.sectors_per_fat()
}
fn first_data_sector(&self) -> u32 {
let root_dir_sectors = self.root_dir_sectors();
let fat_sectors = self.sectors_per_all_fats();
self.reserved_sectors as u32 + fat_sectors + root_dir_sectors
}
fn total_clusters(&self) -> u32 {
let total_sectors = self.total_sectors();
let first_data_sector = self.first_data_sector();
let data_sectors = total_sectors - first_data_sector;
data_sectors / self.sectors_per_cluster as u32
}
}
#[allow(dead_code)]
struct BootRecord {
bootjmp: [u8; 3],
oem_name: [u8; 8],
bpb: BiosParameterBlock,
boot_code: [u8; 448],
boot_sig: [u8; 2],
}
impl BootRecord {
fn deserialize<T: Read>(rdr: &mut T) -> io::Result<BootRecord> {
let mut boot: BootRecord = Default::default();
rdr.read_exact(&mut boot.bootjmp)?;
rdr.read_exact(&mut boot.oem_name)?;
boot.bpb = BiosParameterBlock::deserialize(rdr)?;
if boot.bpb.is_fat32() {
rdr.read_exact(&mut boot.boot_code[0..420])?;
} else {
rdr.read_exact(&mut boot.boot_code[0..448])?;
}
rdr.read_exact(&mut boot.boot_sig)?;
Ok(boot)
}
fn serialize<T: Write>(&self, mut wrt: T) -> io::Result<()> {
wrt.write_all(&self.bootjmp)?;
wrt.write_all(&self.oem_name)?;
self.bpb.serialize(&mut wrt)?;
if self.bpb.is_fat32() {
wrt.write_all(&self.boot_code[0..420])?;
} else {
wrt.write_all(&self.boot_code[0..448])?;
}
wrt.write_all(&self.boot_sig)?;
Ok(())
}
fn validate(&self) -> io::Result<()> {
if self.boot_sig != [0x55, 0xAA] {
return Err(Error::new(ErrorKind::Other, "Invalid boot sector signature"));
}
if self.bootjmp[0] != 0xEB && self.bootjmp[0] != 0xE9 {
warn!("Unknown opcode {:x} in bootjmp boot sector field", self.bootjmp[0]);
}
self.bpb.validate()?;
Ok(())
}
}
impl Default for BootRecord {
fn default() -> BootRecord {
BootRecord {
bootjmp: Default::default(),
oem_name: Default::default(),
bpb: Default::default(),
boot_code: [0; 448],
boot_sig: Default::default(),
}
}
}
#[derive(Clone, Default, Debug)]
struct FsInfoSector {
free_cluster_count: Option<u32>,
next_free_cluster: Option<u32>,
dirty: bool,
}
impl FsInfoSector {
const LEAD_SIG: u32 = 0x41615252;
const STRUC_SIG: u32 = 0x61417272;
const TRAIL_SIG: u32 = 0xAA550000;
fn deserialize<T: Read>(rdr: &mut T) -> io::Result<FsInfoSector> {
let lead_sig = rdr.read_u32::<LittleEndian>()?;
if lead_sig != Self::LEAD_SIG {
return Err(Error::new(ErrorKind::Other, "invalid lead_sig in FsInfo sector"));
}
let mut reserved = [0u8; 480];
rdr.read_exact(&mut reserved)?;
let struc_sig = rdr.read_u32::<LittleEndian>()?;
if struc_sig != Self::STRUC_SIG {
return Err(Error::new(ErrorKind::Other, "invalid struc_sig in FsInfo sector"));
}
let free_cluster_count = match rdr.read_u32::<LittleEndian>()? {
0xFFFFFFFF => None,
// Note: value is validated in FileSystem::new function using values from BPB
n => Some(n),
};
let next_free_cluster = match rdr.read_u32::<LittleEndian>()? {
0xFFFFFFFF => None,
0 | 1 => {
warn!("invalid next_free_cluster in FsInfo sector (values 0 and 1 are reserved)");
None
},
// Note: other values are validated in FileSystem::new function using values from BPB
n => Some(n),
};
let mut reserved2 = [0u8; 12];
rdr.read_exact(&mut reserved2)?;
let trail_sig = rdr.read_u32::<LittleEndian>()?;
if trail_sig != Self::TRAIL_SIG {
return Err(Error::new(ErrorKind::Other, "invalid trail_sig in FsInfo sector"));
}
Ok(FsInfoSector {
free_cluster_count,
next_free_cluster,
dirty: false,
})
}
fn serialize<T: Write>(&self, wrt: &mut T) -> io::Result<()> {
wrt.write_u32::<LittleEndian>(Self::LEAD_SIG)?;
let reserved = [0u8; 480];
wrt.write(&reserved)?;
wrt.write_u32::<LittleEndian>(Self::STRUC_SIG)?;
wrt.write_u32::<LittleEndian>(self.free_cluster_count.unwrap_or(0xFFFFFFFF))?;
wrt.write_u32::<LittleEndian>(self.next_free_cluster.unwrap_or(0xFFFFFFFF))?;
let reserved2 = [0u8; 12];
wrt.write(&reserved2)?;
wrt.write_u32::<LittleEndian>(Self::TRAIL_SIG)?;
Ok(())
}
fn validate_and_fix(&mut self, total_clusters: u32) {
let max_valid_cluster_number = total_clusters + RESERVED_FAT_ENTRIES;
if let Some(n) = self.free_cluster_count {
if n > total_clusters {
warn!(
"invalid free_cluster_count ({}) in fs_info exceeds total cluster count ({})",
n, total_clusters
);
self.free_cluster_count = None;
}
}
if let Some(n) = self.next_free_cluster {
if n > max_valid_cluster_number {
warn!(
"invalid free_cluster_count ({}) in fs_info exceeds maximum cluster number ({})",
n, max_valid_cluster_number
);
self.next_free_cluster = None;
}
}
}
fn add_free_clusters(&mut self, free_clusters: i32) {
if let Some(n) = self.free_cluster_count {
self.free_cluster_count = Some((n as i32 + free_clusters) as u32);
self.dirty = true;
}
}
fn set_next_free_cluster(&mut self, cluster: u32) {
self.next_free_cluster = Some(cluster);
self.dirty = true;
}
fn set_free_cluster_count(&mut self, free_cluster_count: u32) {
self.free_cluster_count = Some(free_cluster_count);
self.dirty = true;
}
}
/// A FAT filesystem mount options.
///
/// Options are specified as an argument for `FileSystem::new` method.
#[derive(Copy, Clone, Debug)]
pub struct FsOptions {
pub(crate) update_accessed_date: bool,
pub(crate) oem_cp_converter: &'static OemCpConverter,
pub(crate) time_provider: &'static TimeProvider,
}
impl FsOptions {
/// Creates a `FsOptions` struct with default options.
pub fn new() -> Self {
FsOptions {
update_accessed_date: false,
oem_cp_converter: &LOSSY_OEM_CP_CONVERTER,
time_provider: &DEFAULT_TIME_PROVIDER,
}
}
/// If enabled accessed date field in directory entry is updated when reading or writing a file.
pub fn update_accessed_date(mut self, enabled: bool) -> Self {
self.update_accessed_date = enabled;
self
}
/// Changes default OEM code page encoder-decoder.
pub fn oem_cp_converter(mut self, oem_cp_converter: &'static OemCpConverter) -> Self {
self.oem_cp_converter = oem_cp_converter;
self
}
/// Changes default time provider.
pub fn time_provider(mut self, time_provider: &'static TimeProvider) -> Self {
self.time_provider = time_provider;
self
}
}
/// A FAT volume statistics.
#[derive(Copy, Clone, Eq, PartialEq, Debug)]
pub struct FileSystemStats {
cluster_size: u32,
total_clusters: u32,
free_clusters: u32,
}
impl FileSystemStats {
/// Cluster size in bytes
pub fn cluster_size(&self) -> u32 {
self.cluster_size
}
/// Number of total clusters in filesystem usable for file allocation
pub fn total_clusters(&self) -> u32 {
self.total_clusters
}
/// Number of free clusters
pub fn free_clusters(&self) -> u32 {
self.free_clusters
}
}
/// A FAT filesystem object.
///
/// `FileSystem` struct is representing a state of a mounted FAT volume.
pub struct FileSystem<T: ReadWriteSeek> {
pub(crate) disk: RefCell<T>,
pub(crate) options: FsOptions,
fat_type: FatType,
bpb: BiosParameterBlock,
first_data_sector: u32,
root_dir_sectors: u32,
total_clusters: u32,
fs_info: RefCell<FsInfoSector>,
current_status_flags: Cell<FsStatusFlags>,
}
impl<T: ReadWriteSeek> FileSystem<T> {
/// Creates a new filesystem object instance.
///
/// Supplied `disk` parameter cannot be seeked. If there is a need to read a fragment of disk
/// image (e.g. partition) library user should wrap the file handle in a struct limiting
/// access to partition bytes only e.g. `fscommon::StreamSlice`.
///
/// Note: creating multiple filesystem objects with one underlying device/disk image can
/// cause a filesystem corruption.
pub fn new(mut disk: T, options: FsOptions) -> io::Result<Self> {
// Make sure given image is not seeked
debug_assert!(disk.seek(SeekFrom::Current(0))? == 0);
// read boot sector
let bpb = {
let boot = BootRecord::deserialize(&mut disk)?;
boot.validate()?;
boot.bpb
};
let root_dir_sectors = bpb.root_dir_sectors();
let first_data_sector = bpb.first_data_sector();
let total_clusters = bpb.total_clusters();
let fat_type = FatType::from_clusters(total_clusters);
// read FSInfo sector if this is FAT32
let mut fs_info = if fat_type == FatType::Fat32 {
disk.seek(SeekFrom::Start(bpb.fs_info_sector as u64 * bpb.bytes_per_sector as u64))?;
FsInfoSector::deserialize(&mut disk)?
} else {
FsInfoSector::default()
};
// if dirty flag is set completly ignore free_cluster_count in FSInfo
if bpb.status_flags().dirty {
fs_info.free_cluster_count = None;
}
// Validate the numbers stored in the free_cluster_count and next_free_cluster are within bounds for volume
fs_info.validate_and_fix(total_clusters);
// return FileSystem struct
let status_flags = bpb.status_flags();
Ok(FileSystem {
disk: RefCell::new(disk),
options,
fat_type,
bpb,
first_data_sector,
root_dir_sectors,
total_clusters,
fs_info: RefCell::new(fs_info),
current_status_flags: Cell::new(status_flags),
})
}
/// Returns a type of File Allocation Table (FAT) used by this filesystem.
pub fn fat_type(&self) -> FatType {
self.fat_type
}
/// Returns a volume identifier read from BPB in the Boot Sector.
pub fn volume_id(&self) -> u32 {
self.bpb.volume_id
}
/// Returns a volume label from BPB in the Boot Sector as `String`.
///
/// Non-ASCII characters are replaced by the replacement character (U+FFFD).
/// Note: File with `VOLUME_ID` attribute in root directory is ignored by this library.
/// Only label from BPB is used.
#[cfg(feature = "alloc")]
pub fn volume_label(&self) -> String {
// Decode volume label from OEM codepage
let volume_label_iter = self.volume_label_as_bytes().iter().cloned();
let char_iter = volume_label_iter.map(|c| self.options.oem_cp_converter.decode(c));
// Build string from character iterator
String::from_iter(char_iter)
}
/// Returns a volume label from BPB in the Boot Sector as byte array slice.
///
/// Label is encoded in the OEM codepage.
/// Note: File with `VOLUME_ID` attribute in root directory is ignored by this library.
/// Only label from BPB is used.
pub fn volume_label_as_bytes(&self) -> &[u8] {
const PADDING: u8 = 0x20;
let full_label_slice = &self.bpb.volume_label;
let len = full_label_slice.iter().rposition(|b| *b != PADDING).map(|p| p + 1).unwrap_or(0);
&full_label_slice[..len]
}
/// Returns a volume label from root directory as `String`.
///
/// It finds file with `VOLUME_ID` attribute and returns its short name.
#[cfg(feature = "alloc")]
pub fn read_volume_label_from_root_dir(&self) -> io::Result<Option<String>> {
// Note: DirEntry::file_short_name() cannot be used because it interprets name as 8.3
// (adds dot before an extension)
let volume_label_opt = self.read_volume_label_from_root_dir_as_bytes()?;
if let Some(volume_label) = volume_label_opt {
const PADDING: u8 = 0x20;
// Strip label padding
let len = volume_label.iter().rposition(|b| *b != PADDING).map(|p| p + 1).unwrap_or(0);
let label_slice = &volume_label[..len];
// Decode volume label from OEM codepage
let volume_label_iter = label_slice.iter().cloned();
let char_iter = volume_label_iter.map(|c| self.options.oem_cp_converter.decode(c));
// Build string from character iterator
Ok(Some(String::from_iter(char_iter)))
} else {
Ok(None)
}
}
/// Returns a volume label from root directory as byte array.
///
/// Label is encoded in the OEM codepage.
/// It finds file with `VOLUME_ID` attribute and returns its short name.
pub fn read_volume_label_from_root_dir_as_bytes(&self) -> io::Result<Option<[u8; 11]>> {
let entry_opt = self.root_dir().find_volume_entry()?;
Ok(entry_opt.map(|e| *e.raw_short_name()))
}
/// Returns a root directory object allowing for futher penetration of a filesystem structure.
pub fn root_dir<'b>(&'b self) -> Dir<'b, T> {
let root_rdr = {
match self.fat_type {
FatType::Fat12 | FatType::Fat16 => DirRawStream::Root(DiskSlice::from_sectors(
self.first_data_sector - self.root_dir_sectors,
self.root_dir_sectors,
1,
&self.bpb,
FsIoAdapter { fs: self },
)),
_ => DirRawStream::File(File::new(Some(self.bpb.root_dir_first_cluster), None, self)),
}
};
Dir::new(root_rdr, self)
}
fn offset_from_sector(&self, sector: u32) -> u64 {
(sector as u64) * self.bpb.bytes_per_sector as u64
}
fn sector_from_cluster(&self, cluster: u32) -> u32 {
((cluster - 2) * self.bpb.sectors_per_cluster as u32) + self.first_data_sector
}
pub(crate) fn cluster_size(&self) -> u32 {
self.bpb.sectors_per_cluster as u32 * self.bpb.bytes_per_sector as u32
}
pub(crate) fn offset_from_cluster(&self, cluser: u32) -> u64 {
self.offset_from_sector(self.sector_from_cluster(cluser))
}
fn fat_slice<'b>(&'b self) -> DiskSlice<FsIoAdapter<'b, T>> {
let io = FsIoAdapter {
fs: self,
};
fat_slice(io, &self.bpb)
}
pub(crate) fn cluster_iter<'b>(&'b self, cluster: u32) -> ClusterIterator<DiskSlice<FsIoAdapter<'b, T>>> {
let disk_slice = self.fat_slice();
ClusterIterator::new(disk_slice, self.fat_type, cluster)
}
pub(crate) fn truncate_cluster_chain(&self, cluster: u32) -> io::Result<()> {
let mut iter = self.cluster_iter(cluster);
let num_free = iter.truncate()?;
let mut fs_info = self.fs_info.borrow_mut();
fs_info.add_free_clusters(num_free as i32);
Ok(())
}
pub(crate) fn free_cluster_chain(&self, cluster: u32) -> io::Result<()> {
let mut iter = self.cluster_iter(cluster);
let num_free = iter.free()?;
let mut fs_info = self.fs_info.borrow_mut();
fs_info.add_free_clusters(num_free as i32);
Ok(())
}
pub(crate) fn alloc_cluster(&self, prev_cluster: Option<u32>) -> io::Result<u32> {
let hint = self.fs_info.borrow().next_free_cluster;
let mut fat = self.fat_slice();
let cluster = alloc_cluster(&mut fat, self.fat_type, prev_cluster, hint, self.total_clusters)?;
let mut fs_info = self.fs_info.borrow_mut();
fs_info.set_next_free_cluster(cluster + 1);
fs_info.add_free_clusters(-1);
Ok(cluster)
}
/// Returns status flags for this volume.
pub fn read_status_flags(&self) -> io::Result<FsStatusFlags> {
let bpb_status = self.bpb.status_flags();
let fat_status = read_fat_flags(&mut self.fat_slice(), self.fat_type)?;
Ok(FsStatusFlags {
dirty: bpb_status.dirty || fat_status.dirty,
io_error: bpb_status.io_error || fat_status.io_error,
})
}
/// Returns filesystem statistics like number of total and free clusters.
///
/// For FAT32 volumes number of free clusters from FSInfo sector is returned (may be incorrect).
/// For other FAT variants number is computed on the first call to this method and cached for later use.
pub fn stats(&self) -> io::Result<FileSystemStats> {
let free_clusters_option = self.fs_info.borrow().free_cluster_count;
let free_clusters = match free_clusters_option {
Some(n) => n,
_ => self.recalc_free_clusters()?,
};
Ok(FileSystemStats {
cluster_size: self.cluster_size(),
total_clusters: self.total_clusters,
free_clusters,
})
}
/// Forces free clusters recalculation.
fn recalc_free_clusters(&self) -> io::Result<u32> {
let mut fat = self.fat_slice();
let free_cluster_count = count_free_clusters(&mut fat, self.fat_type, self.total_clusters)?;
self.fs_info.borrow_mut().set_free_cluster_count(free_cluster_count);
Ok(free_cluster_count)
}
/// Unmounts the filesystem.
///
/// Updates FSInfo sector if needed.
pub fn unmount(self) -> io::Result<()> {
self.unmount_internal()
}
fn unmount_internal(&self) -> io::Result<()> {
self.flush_fs_info()?;
self.set_dirty_flag(false)?;
Ok(())
}
fn flush_fs_info(&self) -> io::Result<()> {
let mut fs_info = self.fs_info.borrow_mut();
if self.fat_type == FatType::Fat32 && fs_info.dirty {
let mut disk = self.disk.borrow_mut();
disk.seek(SeekFrom::Start(self.offset_from_sector(self.bpb.fs_info_sector as u32)))?;
fs_info.serialize(&mut *disk)?;
fs_info.dirty = false;
}
Ok(())
}
pub(crate) fn set_dirty_flag(&self, dirty: bool) -> io::Result<()> {
// Do not overwrite flags read from BPB on mount
let mut flags = self.bpb.status_flags();
flags.dirty |= dirty;
// Check if flags has changed
let current_flags = self.current_status_flags.get();
if flags == current_flags {
// Nothing to do
return Ok(());
}
let encoded = flags.encode();
// Note: only one field is written to avoid rewriting entire boot-sector which could be dangerous
// Compute reserver_1 field offset and write new flags
let offset = if self.fat_type() == FatType::Fat32 { 0x041 } else { 0x025 };
let mut disk = self.disk.borrow_mut();
disk.seek(io::SeekFrom::Start(offset))?;
disk.write_u8(encoded)?;
self.current_status_flags.set(flags);
Ok(())
}
}
/// `Drop` implementation tries to unmount the filesystem when dropping.
impl<T: ReadWriteSeek> Drop for FileSystem<T> {
fn drop(&mut self) {
if let Err(err) = self.unmount_internal() {
error!("unmount failed {}", err);
}
}
}
pub(crate) struct FsIoAdapter<'a, T: ReadWriteSeek + 'a> {
fs: &'a FileSystem<T>,
}
impl<'a, T: ReadWriteSeek> Read for FsIoAdapter<'a, T> {
fn read(&mut self, buf: &mut [u8]) -> io::Result<usize> {
self.fs.disk.borrow_mut().read(buf)
}
}
impl<'a, T: ReadWriteSeek> Write for FsIoAdapter<'a, T> {
fn write(&mut self, buf: &[u8]) -> io::Result<usize> {
let size = self.fs.disk.borrow_mut().write(buf)?;
if size > 0 {
self.fs.set_dirty_flag(true)?;
}
Ok(size)
}
fn flush(&mut self) -> io::Result<()> {
self.fs.disk.borrow_mut().flush()
}
}
impl<'a, T: ReadWriteSeek> Seek for FsIoAdapter<'a, T> {
fn seek(&mut self, pos: SeekFrom) -> io::Result<u64> {
self.fs.disk.borrow_mut().seek(pos)
}
}
// Note: derive cannot be used because of invalid bounds. See: https://github.com/rust-lang/rust/issues/26925
impl<'a, T: ReadWriteSeek> Clone for FsIoAdapter<'a, T> {
fn clone(&self) -> Self {
FsIoAdapter {
fs: self.fs,
}
}
}
fn fat_slice<T: ReadWriteSeek>(io: T, bpb: &BiosParameterBlock) -> DiskSlice<T> {
let sectors_per_fat = bpb.sectors_per_fat();
let mirroring_enabled = bpb.mirroring_enabled();
let (fat_first_sector, mirrors) = if mirroring_enabled {
(bpb.reserved_sectors as u32, bpb.fats)
} else {
let active_fat = bpb.active_fat() as u32;
let fat_first_sector = (bpb.reserved_sectors as u32) + active_fat * sectors_per_fat;
(fat_first_sector, 1)
};
DiskSlice::from_sectors(fat_first_sector, sectors_per_fat, mirrors, bpb, io)
}
pub(crate) struct DiskSlice<T> {
begin: u64,
size: u64,
offset: u64,
mirrors: u8,
inner: T,
}
impl<T> DiskSlice<T> {
pub(crate) fn new(begin: u64, size: u64, mirrors: u8, inner: T) -> Self {
DiskSlice {
begin,
size,
mirrors,
inner,
offset: 0,
}
}
fn from_sectors(first_sector: u32, sector_count: u32, mirrors: u8, bpb: &BiosParameterBlock, inner: T) -> Self {
let bytes_per_sector = bpb.bytes_per_sector as u64;
Self::new(
first_sector as u64 * bytes_per_sector,
sector_count as u64 * bytes_per_sector,
mirrors,
inner,
)
}
pub(crate) fn abs_pos(&self) -> u64 {
self.begin + self.offset
}
}
// Note: derive cannot be used because of invalid bounds. See: https://github.com/rust-lang/rust/issues/26925
impl<T: Clone> Clone for DiskSlice<T> {
fn clone(&self) -> Self {
DiskSlice {
begin: self.begin,
size: self.size,
offset: self.offset,
mirrors: self.mirrors,
inner: self.inner.clone(),
}
}
}
impl<'a, T: Read + Seek> Read for DiskSlice<T> {
fn read(&mut self, buf: &mut [u8]) -> io::Result<usize> {
let offset = self.begin + self.offset;
let read_size = cmp::min((self.size - self.offset) as usize, buf.len());
self.inner.seek(SeekFrom::Start(offset))?;
let size = self.inner.read(&mut buf[..read_size])?;
self.offset += size as u64;
Ok(size)
}
}
impl<'a, T: Write + Seek> Write for DiskSlice<T> {
fn write(&mut self, buf: &[u8]) -> io::Result<usize> {
let offset = self.begin + self.offset;
let write_size = cmp::min((self.size - self.offset) as usize, buf.len());
if write_size == 0 {
return Ok(0);
}
// Write data
for i in 0..self.mirrors {
self.inner.seek(SeekFrom::Start(offset + i as u64 * self.size))?;
self.inner.write_all(&buf[..write_size])?;
}
self.offset += write_size as u64;
Ok(write_size)
}
fn flush(&mut self) -> io::Result<()> {
self.inner.flush()
}
}
impl<'a, T> Seek for DiskSlice<T> {
fn seek(&mut self, pos: SeekFrom) -> io::Result<u64> {
let new_offset = match pos {
SeekFrom::Current(x) => self.offset as i64 + x,
SeekFrom::Start(x) => x as i64,
SeekFrom::End(x) => self.size as i64 + x,
};
if new_offset < 0 || new_offset as u64 > self.size {
Err(io::Error::new(ErrorKind::InvalidInput, "Seek to a negative offset"))
} else {
self.offset = new_offset as u64;
Ok(self.offset)
}
}
}
/// An OEM code page encoder/decoder.
///
/// Provides a custom implementation for a short name encoding/decoding.
/// Default implementation changes all non-ASCII characters to the replacement character (U+FFFD).
/// `OemCpConverter` is specified by the `oem_cp_converter` property in `FsOptions` struct.
pub trait OemCpConverter: Debug {
fn decode(&self, oem_char: u8) -> char;
fn encode(&self, uni_char: char) -> Option<u8>;
}
#[derive(Debug)]
pub(crate) struct LossyOemCpConverter {
_dummy: (),
}
impl OemCpConverter for LossyOemCpConverter {
fn decode(&self, oem_char: u8) -> char {
if oem_char <= 0x7F {
oem_char as char
} else {
'\u{FFFD}'
}
}
fn encode(&self, uni_char: char) -> Option<u8> {
if uni_char <= '\x7F' {
Some(uni_char as u8)
} else {
None
}
}
}
pub(crate) static LOSSY_OEM_CP_CONVERTER: LossyOemCpConverter = LossyOemCpConverter { _dummy: () };
#[derive(Default, Debug, Clone)]
pub struct FormatOptions {
pub bytes_per_sector: Option<u16>,
pub total_sectors: u32,
pub bytes_per_cluster: Option<u32>,
pub fat_type: Option<FatType>,
pub root_entries: Option<u16>,
pub media: Option<u8>,
pub sectors_per_track: Option<u16>,
pub heads: Option<u16>,
pub drive_num: Option<u8>,
pub volume_id: Option<u32>,
pub volume_label: Option<[u8; 11]>,
// force usage of Default trait by struct users
_end: [u8;0],
}
const KB: u64 = 1024;
const MB: u64 = KB * 1024;
const GB: u64 = MB * 1024;
fn determine_fat_type(total_bytes: u64) -> FatType {
if total_bytes < 4 * MB {
FatType::Fat12
} else if total_bytes < 512 * MB {
FatType::Fat16
} else {
FatType::Fat32
}
}
fn determine_bytes_per_cluster(total_bytes: u64, fat_type: FatType, bytes_per_sector: u16) -> u32 {
let bytes_per_cluster = match fat_type {
FatType::Fat12 => (total_bytes.next_power_of_two() / MB * 512) as u32,
FatType::Fat16 => {
if total_bytes <= 16 * MB {
1 * KB as u32
} else if total_bytes <= 128 * MB {
2 * KB as u32
} else {
(total_bytes.next_power_of_two() / (64 * MB) * KB) as u32
}
},
FatType::Fat32 => {
if total_bytes <= 260 * MB {
512
} else if total_bytes <= 8 * GB {
4 * KB as u32
} else {
(total_bytes.next_power_of_two() / (2 * GB) * KB) as u32
}
},
};
const MAX_CLUSTER_SIZE: u32 = 32 * KB as u32;
debug_assert!(bytes_per_cluster.is_power_of_two());
cmp::min(cmp::max(bytes_per_cluster, bytes_per_sector as u32), MAX_CLUSTER_SIZE)
}
fn determine_sectors_per_fat(total_sectors: u32, reserved_sectors: u16, fats: u8, root_dir_sectors: u32,
sectors_per_cluster: u8, fat_type: FatType) -> u32 {
// TODO: use _fat_entries_per_sector
// FIXME: this is for FAT16/32
let tmp_val1 = total_sectors - (reserved_sectors as u32 + root_dir_sectors as u32);
let mut tmp_val2 = (256 * sectors_per_cluster as u32) + fats as u32;
if fat_type == FatType::Fat32 {
tmp_val2 = tmp_val2 / 2;
} else if fat_type == FatType::Fat12 {
tmp_val2 = tmp_val2 / 3 * 4
}
let sectors_per_fat = (tmp_val1 + (tmp_val2 - 1)) / tmp_val2;
// total_sectors = reserved_sectors + sectors_per_fat * fats + data_sectors
// sectors_per_fat >= data_sectors / sectors_per_cluster / fat_entries_per_sector
//
// sectors_per_fat >= (total_sectors - reserved_sectors - sectors_per_fat * fats) / sectors_per_cluster / fat_entries_per_sector
// sectors_per_fat + sectors_per_fat * fats / sectors_per_cluster / fat_entries_per_sector >= (total_sectors - reserved_sectors) / sectors_per_cluster / fat_entries_per_sector
// sectors_per_fat * (1 + fats / sectors_per_cluster / fat_entries_per_sector) >= (total_sectors - reserved_sectors) / sectors_per_cluster / fat_entries_per_sector
// sectors_per_fat >= (total_sectors - reserved_sectors) / sectors_per_cluster / fat_entries_per_sector / (1 + fats / sectors_per_cluster / fat_entries_per_sector)
// fat_entries_per_sector = bytes_per_sector / bytes_per_fat_entry = fat16: 512/2
sectors_per_fat
}
fn format_bpb(options: &FormatOptions) -> io::Result<(BiosParameterBlock, FatType)> {
// TODO: maybe total_sectors could be optional?
let bytes_per_sector = options.bytes_per_sector.unwrap_or(512);
let total_sectors = options.total_sectors;
let total_bytes = total_sectors as u64 * bytes_per_sector as u64;
let fat_type = options.fat_type.unwrap_or_else(|| determine_fat_type(total_bytes));
let bytes_per_cluster = options.bytes_per_cluster
.unwrap_or_else(|| determine_bytes_per_cluster(total_bytes, fat_type, bytes_per_sector));
let sectors_per_cluster = (bytes_per_cluster / bytes_per_sector as u32) as u8;
// Note: most of implementations use 32 reserved sectors for FAT32 but it's wasting of space
let reserved_sectors: u16 = if fat_type == FatType::Fat32 { 4 } else { 1 };
let fats = 2u8;
let is_fat32 = fat_type == FatType::Fat32;
let root_entries = if is_fat32 { 0 } else { options.root_entries.unwrap_or(512) };
let root_dir_bytes = root_entries as u32 * DIR_ENTRY_SIZE as u32;
let root_dir_sectors = (root_dir_bytes + bytes_per_sector as u32 - 1) / bytes_per_sector as u32;
if total_sectors <= reserved_sectors as u32 + root_dir_sectors as u32 + 16 {
return Err(Error::new(ErrorKind::Other, "Volume is too small",));
}
//let fat_entries_per_sector = bytes_per_sector * 8 / fat_type.bits_per_fat_entry() as u16;
let sectors_per_fat = determine_sectors_per_fat(total_sectors, reserved_sectors, fats, root_dir_sectors,
sectors_per_cluster, fat_type);
// drive_num should be 0 for floppy disks and 0x80 for hard disks - determine it using FAT type
let drive_num = options.drive_num.unwrap_or_else(|| if fat_type == FatType::Fat12 { 0 } else { 0x80 });
let reserved_0 = [0u8; 12];
let mut volume_label = [0u8; 11];
if let Some(volume_label_from_opts) = options.volume_label {
volume_label.copy_from_slice(&volume_label_from_opts);
} else {
volume_label.copy_from_slice("NO NAME ".as_bytes());
}
let mut fs_type_label = [0u8; 8];
let fs_type_label_str = match fat_type {
FatType::Fat12 => "FAT12 ",
FatType::Fat16 => "FAT16 ",
FatType::Fat32 => "FAT32 ",
};
fs_type_label.copy_from_slice(fs_type_label_str.as_bytes());
let bpb = BiosParameterBlock {
bytes_per_sector,
sectors_per_cluster,
reserved_sectors,
fats,
root_entries,
total_sectors_16: if total_sectors < 0x10000 { total_sectors as u16 } else { 0 },
media: options.media.unwrap_or(0xF8),
sectors_per_fat_16: if is_fat32 { 0 } else { sectors_per_fat as u16 },
sectors_per_track: options.sectors_per_track.unwrap_or(0x20),
heads: options.heads.unwrap_or(0x40),
hidden_sectors: 0,
total_sectors_32: if total_sectors >= 0x10000 { total_sectors } else { 0 },
// FAT32 fields start
sectors_per_fat_32: if is_fat32 { sectors_per_fat } else { 0 },
extended_flags: 0, // mirroring enabled
fs_version: 0,
root_dir_first_cluster: if is_fat32 { 2 } else { 0 },
fs_info_sector: if is_fat32 { 1 } else { 0 },
backup_boot_sector: if is_fat32 { 6 } else { 0 },
reserved_0,
// FAT32 fields end
drive_num,
reserved_1: 0,
ext_sig: 0x29,
volume_id: options.volume_id.unwrap_or(0x12345678),
volume_label,
fs_type_label,
};
if FatType::from_clusters(bpb.total_clusters()) != fat_type {
return Err(Error::new(ErrorKind::Other, "Total number of clusters and FAT type does not match. Try other volume size"));
}
Ok((bpb, fat_type))
}
fn write_zeros<T: ReadWriteSeek>(mut disk: T, mut len: usize) -> io::Result<()> {
const ZEROS: [u8; 512] = [0u8; 512];
while len > 0 {
let write_size = cmp::min(len, ZEROS.len());
disk.write_all(&ZEROS[..write_size])?;
len -= write_size;
}
Ok(())
}
fn write_zeros_until_end_of_sector<T: ReadWriteSeek>(mut disk: T, bytes_per_sector: u16) -> io::Result<()> {
let pos = disk.seek(SeekFrom::Current(0))?;
let total_bytes_to_write = bytes_per_sector as usize - (pos % bytes_per_sector as u64) as usize;
if total_bytes_to_write != bytes_per_sector as usize {
write_zeros(disk, total_bytes_to_write)?;
}
Ok(())
}
fn format_boot_sector(options: &FormatOptions) -> io::Result<(BootRecord, FatType)> {
let mut boot: BootRecord = Default::default();
let (bpb, fat_type) = format_bpb(options)?;
boot.bpb = bpb;
boot.oem_name.copy_from_slice("MSWIN4.1".as_bytes());
// Boot code copied from FAT32 boot sector initialized by mkfs.fat
boot.bootjmp = [0xEB, 0x58, 0x90];
let boot_code: [u8; 129] = [
0x0E, 0x1F, 0xBE, 0x77, 0x7C, 0xAC, 0x22, 0xC0, 0x74, 0x0B, 0x56, 0xB4, 0x0E, 0xBB, 0x07, 0x00,
0xCD, 0x10, 0x5E, 0xEB, 0xF0, 0x32, 0xE4, 0xCD, 0x16, 0xCD, 0x19, 0xEB, 0xFE, 0x54, 0x68, 0x69,
0x73, 0x20, 0x69, 0x73, 0x20, 0x6E, 0x6F, 0x74, 0x20, 0x61, 0x20, 0x62, 0x6F, 0x6F, 0x74, 0x61,
0x62, 0x6C, 0x65, 0x20, 0x64, 0x69, 0x73, 0x6B, 0x2E, 0x20, 0x20, 0x50, 0x6C, 0x65, 0x61, 0x73,
0x65, 0x20, 0x69, 0x6E, 0x73, 0x65, 0x72, 0x74, 0x20, 0x61, 0x20, 0x62, 0x6F, 0x6F, 0x74, 0x61,
0x62, 0x6C, 0x65, 0x20, 0x66, 0x6C, 0x6F, 0x70, 0x70, 0x79, 0x20, 0x61, 0x6E, 0x64, 0x0D, 0x0A,
0x70, 0x72, 0x65, 0x73, 0x73, 0x20, 0x61, 0x6E, 0x79, 0x20, 0x6B, 0x65, 0x79, 0x20, 0x74, 0x6F,
0x20, 0x74, 0x72, 0x79, 0x20, 0x61, 0x67, 0x61, 0x69, 0x6E, 0x20, 0x2E, 0x2E, 0x2E, 0x20, 0x0D,
0x0A];
boot.boot_code[..boot_code.len()].copy_from_slice(&boot_code);
boot.boot_sig = [0x55, 0xAA];
// fix offsets in bootjmp and boot code for non-FAT32 filesystems (bootcode is on a different offset)
if fat_type != FatType::Fat32 {
// offset of boot code
let boot_code_offset = 0x36 + 8;
boot.bootjmp[1] = (boot_code_offset - 2) as u8;
// offset of message
const MESSAGE_OFFSET: u32 = 29;
let message_offset_in_sector = boot_code_offset + MESSAGE_OFFSET + 0x7c00;
boot.boot_code[3] = (message_offset_in_sector & 0xff) as u8;
boot.boot_code[4] = (message_offset_in_sector >> 8) as u8;
}
Ok((boot, fat_type))
}
// alternative names: create_filesystem, init_filesystem, prepare_fs
pub fn format_volume<T: ReadWriteSeek>(mut disk: T, options: FormatOptions) -> io::Result<()> {
let (boot, fat_type) = format_boot_sector(&options)?;
boot.serialize(&mut disk)?;
let bytes_per_sector = boot.bpb.bytes_per_sector;
write_zeros_until_end_of_sector(&mut disk, bytes_per_sector)?;
if boot.bpb.is_fat32() {
// FSInfo sector
let fs_info_sector = FsInfoSector {
free_cluster_count: None,
next_free_cluster: None,
dirty: false,
};
disk.seek(SeekFrom::Start(boot.bpb.fs_info_sector as u64 * bytes_per_sector as u64))?;
fs_info_sector.serialize(&mut disk)?;
write_zeros_until_end_of_sector(&mut disk, bytes_per_sector)?;
// backup boot sector
disk.seek(SeekFrom::Start(boot.bpb.backup_boot_sector as u64 * bytes_per_sector as u64))?;
boot.serialize(&mut disk)?;
write_zeros_until_end_of_sector(&mut disk, bytes_per_sector)?;
}
// FATs
let sectors_per_fat: u32 = boot.bpb.sectors_per_fat();
let bytes_per_fat: u32 = sectors_per_fat * bytes_per_sector as u32;
let reserved_sectors = boot.bpb.reserved_sectors;
let fat_pos = reserved_sectors as u64 * bytes_per_sector as u64;
disk.seek(SeekFrom::Start(fat_pos))?;
write_zeros(&mut disk, bytes_per_fat as usize * boot.bpb.fats as usize)?;
{
let mut fat_slice = fat_slice(&mut disk, &boot.bpb);
format_fat(&mut fat_slice, fat_type, boot.bpb.media, bytes_per_fat, boot.bpb.total_clusters())?;
}
// Root directory
let root_dir_pos = fat_pos + bytes_per_fat as u64 * boot.bpb.fats as u64;
disk.seek(SeekFrom::Start(root_dir_pos))?;
let root_dir_sectors: u32 = boot.bpb.root_dir_sectors();
write_zeros(&mut disk, root_dir_sectors as usize * bytes_per_sector as usize)?;
if fat_type == FatType::Fat32 {
let root_dir_first_cluster = {
let mut fat_slice = fat_slice(&mut disk, &boot.bpb);
alloc_cluster(&mut fat_slice, fat_type, None, None, 1)?
};
assert!(root_dir_first_cluster == boot.bpb.root_dir_first_cluster);
let first_data_sector = reserved_sectors as u32 + sectors_per_fat + root_dir_sectors;
let sectors_per_cluster = boot.bpb.sectors_per_cluster;
let root_dir_first_sector =
((root_dir_first_cluster - RESERVED_FAT_ENTRIES) * sectors_per_cluster as u32) + first_data_sector;
let root_dir_pos = root_dir_first_sector as u64 * bytes_per_sector as u64;
disk.seek(SeekFrom::Start(root_dir_pos))?;
write_zeros(&mut disk, sectors_per_cluster as usize * bytes_per_sector as usize)?;
}
// TODO: create volume label dir entry if volume label is set
disk.seek(SeekFrom::Start(0))?;
Ok(())
}
#[cfg(test)]
mod tests {
use super::*;
#[test]
fn test_determine_fat_type() {
assert_eq!(determine_fat_type(3 * MB), FatType::Fat12);
assert_eq!(determine_fat_type(4 * MB), FatType::Fat16);
assert_eq!(determine_fat_type(511 * MB), FatType::Fat16);
assert_eq!(determine_fat_type(512 * MB), FatType::Fat32);
}
#[test]
fn test_determine_bytes_per_cluster_fat12() {
assert_eq!(determine_bytes_per_cluster(1 * MB + 0, FatType::Fat12, 512), 512);
assert_eq!(determine_bytes_per_cluster(1 * MB + 1, FatType::Fat12, 512), 1024);
assert_eq!(determine_bytes_per_cluster(1 * MB, FatType::Fat12, 4096), 4096);
}
#[test]
fn test_determine_bytes_per_cluster_fat16() {
assert_eq!(determine_bytes_per_cluster(1 * MB, FatType::Fat16, 512), 1 * KB as u32);
assert_eq!(determine_bytes_per_cluster(1 * MB, FatType::Fat16, 4 * KB as u16), 4 * KB as u32);
assert_eq!(determine_bytes_per_cluster(16 * MB + 0, FatType::Fat16, 512), 1 * KB as u32);
assert_eq!(determine_bytes_per_cluster(16 * MB + 1, FatType::Fat16, 512), 2 * KB as u32);
assert_eq!(determine_bytes_per_cluster(128 * MB + 0, FatType::Fat16, 512), 2 * KB as u32);
assert_eq!(determine_bytes_per_cluster(128 * MB + 1, FatType::Fat16, 512), 4 * KB as u32);
assert_eq!(determine_bytes_per_cluster(256 * MB + 0, FatType::Fat16, 512), 4 * KB as u32);
assert_eq!(determine_bytes_per_cluster(256 * MB + 1, FatType::Fat16, 512), 8 * KB as u32);
assert_eq!(determine_bytes_per_cluster(512 * MB + 0, FatType::Fat16, 512), 8 * KB as u32);
assert_eq!(determine_bytes_per_cluster(512 * MB + 1, FatType::Fat16, 512), 16 * KB as u32);
assert_eq!(determine_bytes_per_cluster(1024 * MB + 0, FatType::Fat16, 512), 16 * KB as u32);
assert_eq!(determine_bytes_per_cluster(1024 * MB + 1, FatType::Fat16, 512), 32 * KB as u32);
assert_eq!(determine_bytes_per_cluster(99999 * MB, FatType::Fat16, 512), 32 * KB as u32);
}
#[test]
fn test_determine_bytes_per_cluster_fat32() {
assert_eq!(determine_bytes_per_cluster(260 * MB as u64, FatType::Fat32, 512), 512);
assert_eq!(determine_bytes_per_cluster(260 * MB as u64, FatType::Fat32, 4 * KB as u16), 4 * KB as u32);
assert_eq!(determine_bytes_per_cluster(260 * MB as u64 + 1, FatType::Fat32, 512), 4 * KB as u32);
assert_eq!(determine_bytes_per_cluster(8 * GB as u64, FatType::Fat32, 512), 4 * KB as u32);
assert_eq!(determine_bytes_per_cluster(8 * GB as u64 + 1, FatType::Fat32, 512), 8 * KB as u32);
assert_eq!(determine_bytes_per_cluster(16 * GB as u64 + 0, FatType::Fat32, 512), 8 * KB as u32);
assert_eq!(determine_bytes_per_cluster(16 * GB as u64 + 1, FatType::Fat32, 512), 16 * KB as u32);
assert_eq!(determine_bytes_per_cluster(32 * GB as u64, FatType::Fat32, 512), 16 * KB as u32);
assert_eq!(determine_bytes_per_cluster(32 * GB as u64 + 1, FatType::Fat32, 512), 32 * KB as u32);
assert_eq!(determine_bytes_per_cluster(999 * GB as u64, FatType::Fat32, 512), 32 * KB as u32);
}
#[test]
fn test_determine_sectors_per_fat() {
assert_eq!(determine_sectors_per_fat(1 * MB as u32 / 512, 1, 2, 32, 1, FatType::Fat12), 6);
}
}
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