Struct SuperBlock 

#[repr(C)]
pub struct SuperBlock {

    pub magic: U32,
    pub checksum: U32,
    pub feature_compat: U32,
    pub block_size_bits: u8,
    pub sb_ext_slots: u8,
    pub root_nid: U16,
    pub inode_count: U64,
    pub epoch: U64,
    pub fixed_nsec: U32,
    pub blocks: U32,
    pub meta_block_addr: U32,
    pub xattr_block_addr: U32,
    pub uuid: [u8; 16],
    pub volume_name: [u8; 16],
    pub feature_incompat: U32,
    pub available_compr_algs: U16,
    pub extra_devices: U32,
    pub dirblkbits: u8,
    pub reserved: [u8; 37],
}

The on-disk format of an erofs superblock.

Fields

magic: U32

Magic number. Should be equal to EROFS_MAGIC.

checksum: U32

CRC-32 checksum of the block containing the superblock. This field is set to zero in the checksummed version.

feature_compat: U32

Feature flags. If any flags in here are not recognized the filesystem can still mount without a loss of correctness.

block_size_bits: u8

Block size stored as a power of two.

sb_ext_slots: u8

Number of 16-byte superblock extension slots.

root_nid: U16

Node ID of the root directory.

inode_count: U64

Total number of inodes - primarily for statfs. Can potentially be set to zero, don’t rely on it for validation.

epoch: U64

UNIX timestamp of when the filesystem was created, used as mtime for compact inodes.

fixed_nsec: U32

Fixed nanosecond timestamp used as mtime for compact inodes.

blocks: U32

Total number of blocks - primarily for statfs. Can potentially be set to zero, don’t rely on it for validation.

meta_block_addr: U32

Start block address of inode metadata zone. This is essentially an offset for node id calculations, not a guarantee that the inode data actually starts at this offset.

xattr_block_addr: U32

Start block address of the xattr zone. Similar to meta_block_addr.

uuid: [u8; 16]

128-bit UUID for this volume.

volume_name: [u8; 16]

The volume name, zero-padded.

feature_incompat: U32

Feature flags. If any flags here are not recognized, the filesystem can not be mounted.

available_compr_algs: U16

Info about compression algorithms. Set to zero if image is not compressed.

extra_devices: U32

External device support, ignored in core format.

dirblkbits: u8

Set to zero in the core format. This can be used to make directory blocks larger than regular blocks (it modifies the block_size_bits field).

reserved: [u8; 37]

There are some other fields we will care about when we implement xattr and compression support, but for now with the core format we don’t care about the rest of the superblock.

Trait Implementations

impl Debug for SuperBlock

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl FromBytes for SuperBlock

where LEU32: FromBytes, u8: FromBytes, LEU16: FromBytes, LEU64: FromBytes, [u8; 16]: FromBytes, [u8; 37]: FromBytes,

fn ref_from_bytes( source: &[u8], ) -> Result<&Self, ConvertError<AlignmentError<&[u8], Self>, SizeError<&[u8], Self>, Infallible>>

where Self: KnownLayout + Immutable,

Interprets the given source as a &Self.

fn ref_from_prefix( source: &[u8], ) -> Result<(&Self, &[u8]), ConvertError<AlignmentError<&[u8], Self>, SizeError<&[u8], Self>, Infallible>>

where Self: KnownLayout + Immutable,

Interprets the prefix of the given source as a &Self without copying.

fn ref_from_suffix( source: &[u8], ) -> Result<(&[u8], &Self), ConvertError<AlignmentError<&[u8], Self>, SizeError<&[u8], Self>, Infallible>>

where Self: Immutable + KnownLayout,

Interprets the suffix of the given bytes as a &Self.

fn mut_from_bytes( source: &mut [u8], ) -> Result<&mut Self, ConvertError<AlignmentError<&mut [u8], Self>, SizeError<&mut [u8], Self>, Infallible>>

where Self: IntoBytes + KnownLayout,

Interprets the given source as a &mut Self.

fn mut_from_prefix( source: &mut [u8], ) -> Result<(&mut Self, &mut [u8]), ConvertError<AlignmentError<&mut [u8], Self>, SizeError<&mut [u8], Self>, Infallible>>

where Self: IntoBytes + KnownLayout,

Interprets the prefix of the given source as a &mut Self without copying.

fn mut_from_suffix( source: &mut [u8], ) -> Result<(&mut [u8], &mut Self), ConvertError<AlignmentError<&mut [u8], Self>, SizeError<&mut [u8], Self>, Infallible>>

where Self: IntoBytes + KnownLayout,

Interprets the suffix of the given source as a &mut Self without copying.

fn ref_from_bytes_with_elems( source: &[u8], count: usize, ) -> Result<&Self, ConvertError<AlignmentError<&[u8], Self>, SizeError<&[u8], Self>, Infallible>>

where Self: KnownLayout<PointerMetadata = usize> + Immutable,

Interprets the given source as a &Self with a DST length equal to count.

fn ref_from_prefix_with_elems( source: &[u8], count: usize, ) -> Result<(&Self, &[u8]), ConvertError<AlignmentError<&[u8], Self>, SizeError<&[u8], Self>, Infallible>>

where Self: KnownLayout<PointerMetadata = usize> + Immutable,

Interprets the prefix of the given source as a DST &Self with length equal to count.

fn ref_from_suffix_with_elems( source: &[u8], count: usize, ) -> Result<(&[u8], &Self), ConvertError<AlignmentError<&[u8], Self>, SizeError<&[u8], Self>, Infallible>>

where Self: KnownLayout<PointerMetadata = usize> + Immutable,

Interprets the suffix of the given source as a DST &Self with length equal to count.

fn mut_from_bytes_with_elems( source: &mut [u8], count: usize, ) -> Result<&mut Self, ConvertError<AlignmentError<&mut [u8], Self>, SizeError<&mut [u8], Self>, Infallible>>

where Self: IntoBytes + KnownLayout<PointerMetadata = usize> + Immutable,

Interprets the given source as a &mut Self with a DST length equal to count.

fn mut_from_prefix_with_elems( source: &mut [u8], count: usize, ) -> Result<(&mut Self, &mut [u8]), ConvertError<AlignmentError<&mut [u8], Self>, SizeError<&mut [u8], Self>, Infallible>>

where Self: IntoBytes + KnownLayout<PointerMetadata = usize>,

Interprets the prefix of the given source as a &mut Self with DST length equal to count.

fn mut_from_suffix_with_elems( source: &mut [u8], count: usize, ) -> Result<(&mut [u8], &mut Self), ConvertError<AlignmentError<&mut [u8], Self>, SizeError<&mut [u8], Self>, Infallible>>

where Self: IntoBytes + KnownLayout<PointerMetadata = usize>,

Interprets the suffix of the given source as a &mut Self with DST length equal to count.

fn read_from_bytes(source: &[u8]) -> Result<Self, SizeError<&[u8], Self>>

where Self: Sized,

Reads a copy of Self from the given source.

fn read_from_prefix( source: &[u8], ) -> Result<(Self, &[u8]), SizeError<&[u8], Self>>

where Self: Sized,

Reads a copy of Self from the prefix of the given source.

fn read_from_suffix( source: &[u8], ) -> Result<(&[u8], Self), SizeError<&[u8], Self>>

where Self: Sized,

Reads a copy of Self from the suffix of the given source.

impl FromZeros for SuperBlock

where LEU32: FromZeros, u8: FromZeros, LEU16: FromZeros, LEU64: FromZeros, [u8; 16]: FromZeros, [u8; 37]: FromZeros,

fn zero(&mut self)

Overwrites self with zeros.

fn new_zeroed() -> Self

where Self: Sized,

Creates an instance of Self from zeroed bytes.

fn new_box_zeroed() -> Result<Box<Self>, AllocError>

where Self: Sized,

Creates a Box<Self> from zeroed bytes.

fn new_box_zeroed_with_elems(count: usize) -> Result<Box<Self>, AllocError>

where Self: KnownLayout<PointerMetadata = usize>,

Creates a Box<[Self]> (a boxed slice) from zeroed bytes.

fn new_vec_zeroed(len: usize) -> Result<Vec<Self>, AllocError>

where Self: Sized,

Creates a Vec<Self> from zeroed bytes.

fn extend_vec_zeroed( v: &mut Vec<Self>, additional: usize, ) -> Result<(), AllocError>

where Self: Sized,

Extends a Vec<Self> by pushing additional new items onto the end of the vector. The new items are initialized with zeros.

fn insert_vec_zeroed( v: &mut Vec<Self>, position: usize, additional: usize, ) -> Result<(), AllocError>

where Self: Sized,

Inserts additional new items into Vec<Self> at position. The new items are initialized with zeros.

impl IntoBytes for SuperBlock

where LEU32: IntoBytes, u8: IntoBytes, LEU16: IntoBytes, LEU64: IntoBytes, [u8; 16]: IntoBytes, [u8; 37]: IntoBytes, (): PaddingFree<Self, { _ }>,

fn as_bytes(&self) -> &[u8]

where Self: Immutable,

Gets the bytes of this value.

fn as_mut_bytes(&mut self) -> &mut [u8]

where Self: FromBytes,

Gets the bytes of this value mutably.

fn write_to(&self, dst: &mut [u8]) -> Result<(), SizeError<&Self, &mut [u8]>>

where Self: Immutable,

Writes a copy of self to dst.

fn write_to_prefix( &self, dst: &mut [u8], ) -> Result<(), SizeError<&Self, &mut [u8]>>

where Self: Immutable,

Writes a copy of self to the prefix of dst.

fn write_to_suffix( &self, dst: &mut [u8], ) -> Result<(), SizeError<&Self, &mut [u8]>>

where Self: Immutable,

Writes a copy of self to the suffix of dst.

impl KnownLayout for SuperBlock

where [u8; 37]: KnownLayout,

type PointerMetadata = <[u8; 37] as KnownLayout>::PointerMetadata

The type of metadata stored in a pointer to Self.

fn size_for_metadata(meta: Self::PointerMetadata) -> Option<usize>

Computes the size of an object of type Self with the given pointer metadata.

impl TryFromBytes for SuperBlock

where LEU32: TryFromBytes, u8: TryFromBytes, LEU16: TryFromBytes, LEU64: TryFromBytes, [u8; 16]: TryFromBytes, [u8; 37]: TryFromBytes,

fn try_ref_from_bytes( source: &[u8], ) -> Result<&Self, ConvertError<AlignmentError<&[u8], Self>, SizeError<&[u8], Self>, ValidityError<&[u8], Self>>>

where Self: KnownLayout + Immutable,

Attempts to interpret the given source as a &Self.

fn try_ref_from_prefix( source: &[u8], ) -> Result<(&Self, &[u8]), ConvertError<AlignmentError<&[u8], Self>, SizeError<&[u8], Self>, ValidityError<&[u8], Self>>>

where Self: KnownLayout + Immutable,

Attempts to interpret the prefix of the given source as a &Self.

fn try_ref_from_suffix( source: &[u8], ) -> Result<(&[u8], &Self), ConvertError<AlignmentError<&[u8], Self>, SizeError<&[u8], Self>, ValidityError<&[u8], Self>>>

where Self: KnownLayout + Immutable,

Attempts to interpret the suffix of the given source as a &Self.

fn try_mut_from_bytes( bytes: &mut [u8], ) -> Result<&mut Self, ConvertError<AlignmentError<&mut [u8], Self>, SizeError<&mut [u8], Self>, ValidityError<&mut [u8], Self>>>

where Self: KnownLayout + IntoBytes,

Attempts to interpret the given source as a &mut Self without copying.

fn try_mut_from_prefix( source: &mut [u8], ) -> Result<(&mut Self, &mut [u8]), ConvertError<AlignmentError<&mut [u8], Self>, SizeError<&mut [u8], Self>, ValidityError<&mut [u8], Self>>>

where Self: KnownLayout + IntoBytes,

Attempts to interpret the prefix of the given source as a &mut Self.

fn try_mut_from_suffix( source: &mut [u8], ) -> Result<(&mut [u8], &mut Self), ConvertError<AlignmentError<&mut [u8], Self>, SizeError<&mut [u8], Self>, ValidityError<&mut [u8], Self>>>

where Self: KnownLayout + IntoBytes,

Attempts to interpret the suffix of the given source as a &mut Self.

fn try_ref_from_bytes_with_elems( source: &[u8], count: usize, ) -> Result<&Self, ConvertError<AlignmentError<&[u8], Self>, SizeError<&[u8], Self>, ValidityError<&[u8], Self>>>

where Self: KnownLayout<PointerMetadata = usize> + Immutable,

Attempts to interpret the given source as a &Self with a DST length equal to count.

fn try_ref_from_prefix_with_elems( source: &[u8], count: usize, ) -> Result<(&Self, &[u8]), ConvertError<AlignmentError<&[u8], Self>, SizeError<&[u8], Self>, ValidityError<&[u8], Self>>>

where Self: KnownLayout<PointerMetadata = usize> + Immutable,

Attempts to interpret the prefix of the given source as a &Self with a DST length equal to count.

fn try_ref_from_suffix_with_elems( source: &[u8], count: usize, ) -> Result<(&[u8], &Self), ConvertError<AlignmentError<&[u8], Self>, SizeError<&[u8], Self>, ValidityError<&[u8], Self>>>

where Self: KnownLayout<PointerMetadata = usize> + Immutable,

Attempts to interpret the suffix of the given source as a &Self with a DST length equal to count.

fn try_mut_from_bytes_with_elems( source: &mut [u8], count: usize, ) -> Result<&mut Self, ConvertError<AlignmentError<&mut [u8], Self>, SizeError<&mut [u8], Self>, ValidityError<&mut [u8], Self>>>

where Self: KnownLayout<PointerMetadata = usize> + IntoBytes,

Attempts to interpret the given source as a &mut Self with a DST length equal to count.

fn try_mut_from_prefix_with_elems( source: &mut [u8], count: usize, ) -> Result<(&mut Self, &mut [u8]), ConvertError<AlignmentError<&mut [u8], Self>, SizeError<&mut [u8], Self>, ValidityError<&mut [u8], Self>>>

where Self: KnownLayout<PointerMetadata = usize> + IntoBytes,

Attempts to interpret the prefix of the given source as a &mut Self with a DST length equal to count.

fn try_mut_from_suffix_with_elems( source: &mut [u8], count: usize, ) -> Result<(&mut [u8], &mut Self), ConvertError<AlignmentError<&mut [u8], Self>, SizeError<&mut [u8], Self>, ValidityError<&mut [u8], Self>>>

where Self: KnownLayout<PointerMetadata = usize> + IntoBytes,

Attempts to interpret the suffix of the given source as a &mut Self with a DST length equal to count.

fn try_read_from_bytes( source: &[u8], ) -> Result<Self, ConvertError<Infallible, SizeError<&[u8], Self>, ValidityError<&[u8], Self>>>

where Self: Sized,

Attempts to read the given source as a Self.

fn try_read_from_prefix( source: &[u8], ) -> Result<(Self, &[u8]), ConvertError<Infallible, SizeError<&[u8], Self>, ValidityError<&[u8], Self>>>

where Self: Sized,

Attempts to read a Self from the prefix of the given source.

fn try_read_from_suffix( source: &[u8], ) -> Result<(&[u8], Self), ConvertError<Infallible, SizeError<&[u8], Self>, ValidityError<&[u8], Self>>>

where Self: Sized,

Attempts to read a Self from the suffix of the given source.

impl Immutable for SuperBlock

where LEU32: Immutable, u8: Immutable, LEU16: Immutable, LEU64: Immutable, [u8; 16]: Immutable, [u8; 37]: Immutable,

impl Unaligned for SuperBlock

where LEU32: Unaligned, u8: Unaligned, LEU16: Unaligned, LEU64: Unaligned, [u8; 16]: Unaligned, [u8; 37]: Unaligned,