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feat: Make sector size and total sectors optional for format_volume

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* moved bytes_per_sector and total_sectors from FormatVolumeOptions::new
to a dedicated methods (it is optional now)
* calculate total number of sectors using seek() to disk end if not provided
* added more doc comments
* added assertions about disk handle position being zero
This commit is contained in:
Rafał Harabień 2018-12-20 01:47:34 +01:00
parent c372429951
commit 8502edb7b8
3 changed files with 98 additions and 35 deletions
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42
src/boot_sector.rs
View File

@ -258,6 +258,9 @@ impl BiosParameterBlock {
"Invalid BPB (result of FAT32 determination from total number of clusters and sectors_per_fat_16 field differs)",
));
}
if fat_type == FatType::Fat32 && total_clusters > 0x0FFF_FFFF {
return Err(Error::new(ErrorKind::Other, "Invalid BPB (too many clusters)"));
}
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;
@ -517,10 +520,9 @@ fn determine_sectors_per_fat(
sectors_per_fat as u32
}
fn format_bpb(options: &FormatVolumeOptions) -> io::Result<(BiosParameterBlock, FatType)> {
let bytes_per_sector = options.bytes_per_sector;
let total_sectors = options.total_sectors;
let total_bytes = total_sectors as u64 * bytes_per_sector as u64;
fn format_bpb(options: &FormatVolumeOptions, total_sectors: u32, bytes_per_sector: u16) -> io::Result<(BiosParameterBlock, FatType)> {
let total_bytes = u64::from(total_sectors) * u64::from(bytes_per_sector);
// FIXME: determine FAT type from cluster size because it can be modified by user
let fat_type = options.fat_type.unwrap_or_else(|| determine_fat_type(total_bytes));
let bytes_per_cluster = options
.bytes_per_cluster
@ -622,9 +624,9 @@ fn format_bpb(options: &FormatVolumeOptions) -> io::Result<(BiosParameterBlock,
Ok((bpb, fat_type))
}
pub(crate) fn format_boot_sector(options: &FormatVolumeOptions) -> io::Result<(BootSector, FatType)> {
pub(crate) fn format_boot_sector(options: &FormatVolumeOptions, total_sectors: u32, bytes_per_sector: u16) -> io::Result<(BootSector, FatType)> {
let mut boot: BootSector = Default::default();
let (bpb, fat_type) = format_bpb(options)?;
let (bpb, fat_type) = format_bpb(options, total_sectors, bytes_per_sector)?;
boot.bpb = bpb;
boot.oem_name.copy_from_slice(b"MSWIN4.1");
// Boot code copied from FAT32 boot sector initialized by mkfs.fat
@ -717,7 +719,7 @@ mod tests {
root_dir_entries: u32,
) {
let total_sectors = total_bytes / u64::from(bytes_per_sector);
debug_assert!(total_sectors < u64::from(core::u32::MAX));
debug_assert!(total_sectors <= u64::from(core::u32::MAX), "{:x}", total_sectors);
let total_sectors = total_sectors as u32;
let sectors_per_cluster = (bytes_per_cluster / u32::from(bytes_per_sector)) as u8;
@ -762,7 +764,7 @@ mod tests {
let mut bytes_per_cluster = u32::from(bytes_per_sector);
while bytes_per_cluster <= 64 * KB as u32 {
let mut size = 1 * MB;
while size <= 2048 * GB {
while size < 2048 * GB {
test_determine_sectors_per_fat_single(
size,
bytes_per_sector,
@ -774,6 +776,16 @@ mod tests {
);
size = size + size / 7;
}
size = 2048 * GB - 1;
test_determine_sectors_per_fat_single(
size,
bytes_per_sector,
bytes_per_cluster,
fat_type,
reserved_sectors,
fats,
root_dir_entries,
);
bytes_per_cluster *= 2;
}
}
@ -796,4 +808,18 @@ mod tests {
test_determine_sectors_per_fat_for_multiple_sizes(512, FatType::Fat32, 32, 1, 0);
test_determine_sectors_per_fat_for_multiple_sizes(4096, FatType::Fat32, 32, 2, 0);
}
#[test]
fn test_format_boot_sector_large_partition() {
let _ = env_logger::try_init();
let bytes_per_sector = 512;
let bytes_per_cluster = 4 * 4096;
let total_sectors = core::u32::MAX;
let (boot, _) = format_boot_sector(&FormatVolumeOptions::new()
.total_sectors(total_sectors)
.bytes_per_sector(bytes_per_sector)
.bytes_per_cluster(bytes_per_cluster), total_sectors, bytes_per_sector)
.expect("format_boot_sector");
boot.validate().expect("validate");
}
}

76
src/fs.rs
View File

@ -789,8 +789,8 @@ fn write_zeros_until_end_of_sector<T: ReadWriteSeek>(mut disk: T, bytes_per_sect
/// Options are specified as an argument for `format_volume` function.
#[derive(Default, Debug, Clone)]
pub struct FormatVolumeOptions {
pub(crate) bytes_per_sector: u16,
pub(crate) total_sectors: u32,
pub(crate) bytes_per_sector: Option<u16>,
pub(crate) total_sectors: Option<u32>,
pub(crate) bytes_per_cluster: Option<u32>,
pub(crate) fat_type: Option<FatType>,
pub(crate) root_entries: Option<u16>,
@ -803,21 +803,21 @@ pub struct FormatVolumeOptions {
}
impl FormatVolumeOptions {
/// Create options struct
/// Create options struct for `format_volume` function
///
/// `total_sectors` is size of partition in sectors.
/// `bytes_per_sector` is size of a logical sector (usually 512).
/// Other options can be optionally specified by calling adequate methods.
/// If not specified suitable defaults will be used based on partition size.
pub fn new(total_sectors: u32, bytes_per_sector: u16) -> Self {
/// Allows to overwrite many filesystem parameters.
/// In normal use-case defaults should suffice.
pub fn new() -> Self {
FormatVolumeOptions {
total_sectors,
bytes_per_sector,
..Default::default()
}
}
/// Set size of cluster in bytes (must be dividable by sector size)
///
/// Cluster size must be a power of two and be greater or equal to sector size.
/// If option is not specified optimal cluster size is selected based on partition size and
/// optionally FAT type override (if specified using `fat_type` method).
pub fn bytes_per_cluster(mut self, bytes_per_cluster: u32) -> Self {
self.bytes_per_cluster = Some(bytes_per_cluster);
self
@ -825,14 +825,37 @@ impl FormatVolumeOptions {
/// Set File Allocation Table type
///
/// Note: FAT type is defined by total number of clusters so changing this option
/// can cause formatting to fail if volume size is incompatible.
/// Option allows to override File Allocation Table (FAT) entry size.
/// It is unrecommended to set this option unless you know what you are doing.
/// Note: FAT type is determined from total number of clusters. Changing this option can cause formatting to fail
/// if the volume cannot be divided into proper number of clusters for selected FAT type.
pub fn fat_type(mut self, fat_type: FatType) -> Self {
self.fat_type = Some(fat_type);
self
}
/// Set sector size in bytes
///
/// Sector size must be a power of two and be in range 512 - 4096.
/// Default is `512`.
pub fn bytes_per_sector(mut self, bytes_per_sector: u16) -> Self {
self.bytes_per_sector = Some(bytes_per_sector);
self
}
/// Set total number of sectors
///
/// If option is not specified total number of sectors is calculated as storage device size divided by sector size.
pub fn total_sectors(mut self, total_sectors: u32) -> Self {
self.total_sectors = Some(total_sectors);
self
}
/// Set maximal numer of entries in root directory for FAT12/FAT16 volumes
///
/// Total root directory size should be dividable by sectors size so keep it a multiple of 16 (for default sector
/// size).
/// Default is `512`.
pub fn root_entries(mut self, root_entries: u16) -> Self {
self.root_entries = Some(root_entries);
self
@ -879,6 +902,8 @@ impl FormatVolumeOptions {
}
/// Set volume label
///
/// Default is empty label.
pub fn volume_label(mut self, volume_label: [u8; 11]) -> Self {
self.volume_label = Some(volume_label);
self
@ -887,14 +912,31 @@ impl FormatVolumeOptions {
/// Create FAT filesystem on a disk or partition (format a volume)
///
/// Supplied `disk` parameter cannot be seeked. If there is a need to format a fragment of a disk
/// image (e.g. partition) library user should wrap the file struct in a struct limiting
/// access to partition bytes only e.g. `fscommon::StreamSlice`.
/// Warning: this function overrides internal FAT filesystem structures and causes a loss of all data on provided
/// partition. Please use it with caution.
/// Only quick formatting is supported. To achieve a full format zero entire partition before calling this function.
/// Supplied `disk` parameter cannot be seeked (internal pointer must be on position 0).
/// To format a fragment of a disk image (e.g. partition) library user should wrap the file struct in a struct
/// limiting access to partition bytes only e.g. `fscommon::StreamSlice`.
pub fn format_volume<T: ReadWriteSeek>(mut disk: T, options: FormatVolumeOptions) -> io::Result<()> {
trace!("format_volume");
disk.seek(SeekFrom::Start(0))?;
debug_assert!(disk.seek(SeekFrom::Current(0))? == 0);
let bytes_per_sector = options.bytes_per_sector.unwrap_or(512);
let total_sectors = if options.total_sectors.is_none() {
let total_bytes: u64 = disk.seek(SeekFrom::End(0))?;
let total_sectors_64 = total_bytes / u64::from(bytes_per_sector);
disk.seek(SeekFrom::Start(0))?;
if total_sectors_64 > u64::from(core::u32::MAX) {
return Err(Error::new(ErrorKind::Other, "Volume has too many sectors"));
}
total_sectors_64 as u32
} else {
options.total_sectors.unwrap() // SAFE: checked above
};
// Create boot sector, validate and write to storage device
let (boot, fat_type) = format_boot_sector(&options)?;
let (boot, fat_type) = format_boot_sector(&options, total_sectors, bytes_per_sector)?;
boot.validate()?;
boot.serialize(&mut disk)?;
// Make sure entire logical sector is updated (serialize method always writes 512 bytes)

15
tests/format.rs
View File

@ -74,7 +74,7 @@ fn test_format_fs(opts: fatfs::FormatVolumeOptions, total_bytes: u64) -> FileSys
#[test]
fn test_format_1mb() {
let total_bytes = 1 * MB;
let opts = fatfs::FormatVolumeOptions::new((total_bytes / 512) as u32, 512);
let opts = fatfs::FormatVolumeOptions::new();
let fs = test_format_fs(opts, total_bytes);
assert_eq!(fs.fat_type(), fatfs::FatType::Fat12);
}
@ -82,7 +82,7 @@ fn test_format_1mb() {
#[test]
fn test_format_8mb() {
let total_bytes = 8 * MB;
let opts = fatfs::FormatVolumeOptions::new((total_bytes / 512) as u32, 512);
let opts = fatfs::FormatVolumeOptions::new();
let fs = test_format_fs(opts, total_bytes);
assert_eq!(fs.fat_type(), fatfs::FatType::Fat16);
}
@ -90,7 +90,7 @@ fn test_format_8mb() {
#[test]
fn test_format_50mb() {
let total_bytes = 50 * MB;
let opts = fatfs::FormatVolumeOptions::new((total_bytes / 512) as u32, 512);
let opts = fatfs::FormatVolumeOptions::new();
let fs = test_format_fs(opts, total_bytes);
assert_eq!(fs.fat_type(), fatfs::FatType::Fat16);
}
@ -98,20 +98,15 @@ fn test_format_50mb() {
#[test]
fn test_format_512mb_512sec() {
let total_bytes = 2 * 1024 * MB;
let opts = fatfs::FormatVolumeOptions::new((total_bytes / 512) as u32, 512);
let opts = fatfs::FormatVolumeOptions::new();
let fs = test_format_fs(opts, total_bytes);
assert_eq!(fs.fat_type(), fatfs::FatType::Fat32);
}
fn create_format_options(total_bytes: u64, bytes_per_sector: Option<u16>) -> fatfs::FormatVolumeOptions {
let total_sectors = (total_bytes / bytes_per_sector.unwrap_or(512) as u64) as u32;
fatfs::FormatVolumeOptions::new(total_sectors, bytes_per_sector.unwrap_or(512))
}
#[test]
fn test_format_512mb_4096sec() {
let total_bytes = 1 * 1024 * MB;
let opts = create_format_options(total_bytes, Some(1024));
let opts = fatfs::FormatVolumeOptions::new().bytes_per_sector(4096);
let fs = test_format_fs(opts, total_bytes);
assert_eq!(fs.fat_type(), fatfs::FatType::Fat32);
}