mkfs-ext2 0.1.0

Read or write ext2 file systems (in no_std environments).
Documentation 
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use alloc::string::{FromUtf8Error, String};
use core::fmt::{Debug, Display, Formatter};

use bitflags::bitflags;

#[derive(Debug, Eq, PartialEq)]
pub struct Superblock {
    pub num_inodes: u32,
    pub num_blocks: u32,
    pub num_superuser_reserved_blocks: u32,
    pub num_unallocated_blocks: u32,
    pub num_unallocated_inodes: u32,
    pub superblock_block_number: u32,
    pub block_size: u32,
    pub fragment_size: u32,
    pub blocks_per_group: u32,
    pub fragments_per_group: u32,
    pub inodes_per_group: u32,
    pub last_mount_time: u32,
    pub last_written_time: u32,
    pub mounts_since_fsck: u16,
    pub mounts_allowed_before_fsck: u16,
    pub magic_number: u16,
    pub state: State,
    pub error_policy: ErrorPolicy,
    pub version_minor: u16,
    pub last_fsck: u32,
    pub fsck_force_interval: u32,
    pub os_id: u32,
    pub version_major: u32,
    pub uid_for_reserved_blocks: u16,
    pub gid_for_reserved_blocks: u16,
    pub extended: Option<SuperblockExtended>,
}

#[derive(Debug, Copy, Clone, Eq, PartialEq)]
pub enum SuperblockDecodeError {
    InvalidMagicNumber,
    /// Indicates, that more bytes were expected than provided.
    /// This is an internal error.
    ShortRead,
    InvalidBlockSize,
    InvalidFragmentSize,
    InvalidData,
}

impl Display for SuperblockDecodeError {
    fn fmt(&self, f: &mut Formatter<'_>) -> core::fmt::Result {
        Debug::fmt(&self, f)
    }
}

impl core::error::Error for SuperblockDecodeError {}

impl From<ShortReadError> for SuperblockDecodeError {
    fn from(_: ShortReadError) -> Self {
        Self::ShortRead
    }
}

impl From<FromUtf8Error> for SuperblockDecodeError {
    fn from(_: FromUtf8Error) -> Self {
        Self::InvalidData
    }
}

impl TryFrom<[u8; 1024]> for Superblock {
    type Error = SuperblockDecodeError;

    fn try_from(value: [u8; 1024]) -> Result<Self, Self::Error> {
        let num_inodes = read_u32_le(&value[0..4])?;
        let num_blocks = read_u32_le(&value[4..8])?;
        let num_superuser_reserved_blocks = read_u32_le(&value[8..12])?;
        let num_unallocated_blocks = read_u32_le(&value[12..16])?;
        let num_unallocated_inodes = read_u32_le(&value[16..20])?;
        let superblock_block_number = read_u32_le(&value[20..24])?;
        let log2_block_size = read_u32_le(&value[24..28])?;
        let block_size = u32::checked_shl(1024, log2_block_size)
            .ok_or(SuperblockDecodeError::InvalidBlockSize)?;
        let log2_fragment_size = read_u32_le(&value[28..32])?;
        let fragment_size = u32::checked_shl(1024, log2_fragment_size)
            .ok_or(SuperblockDecodeError::InvalidFragmentSize)?;
        let blocks_per_group = read_u32_le(&value[32..36])?;
        let fragments_per_group = read_u32_le(&value[36..40])?;
        let inodes_per_group = read_u32_le(&value[40..44])?;
        let last_mount_time = read_u32_le(&value[44..48])?;
        let last_written_time = read_u32_le(&value[48..52])?;
        let mounts_since_fsck = read_u16_le(&value[52..54])?;
        let mounts_allowed_before_fsck = read_u16_le(&value[54..56])?;
        let magic_number = read_u16_le(&value[56..58])?;
        let state = State::from_bits_truncate(read_u16_le(&value[58..60])?);
        let error_policy = ErrorPolicy::from_bits_truncate(read_u16_le(&value[60..62])?);
        let version_minor = read_u16_le(&value[62..64])?;
        let last_fsck = read_u32_le(&value[64..68])?;
        let fsck_force_interval = read_u32_le(&value[68..72])?;
        let os_id = read_u32_le(&value[72..76])?;
        let version_major = read_u32_le(&value[76..80])?;
        let uid_for_reserved_blocks = read_u16_le(&value[80..82])?;
        let gid_for_reserved_blocks = read_u16_le(&value[82..84])?;

        // validation

        if blocks_per_group < 1 || inodes_per_group < 1 {
            return Err(SuperblockDecodeError::InvalidData);
        }
        let check1 = (num_blocks + blocks_per_group - 1) / blocks_per_group;
        let check2 = (num_inodes + inodes_per_group - 1) / inodes_per_group;
        if check1 != check2 {
            return Err(SuperblockDecodeError::InvalidData);
        }

        if magic_number != 0xEF53 {
            return Err(SuperblockDecodeError::InvalidMagicNumber);
        }

        let extended = if version_major >= 1 {
            Some(SuperblockExtended::try_from(value)?)
        } else {
            None
        };

        Ok(Self {
            num_inodes,
            num_blocks,
            num_superuser_reserved_blocks,
            num_unallocated_blocks,
            num_unallocated_inodes,
            superblock_block_number,
            block_size,
            fragment_size,
            blocks_per_group,
            fragments_per_group,
            inodes_per_group,
            last_mount_time,
            last_written_time,
            mounts_since_fsck,
            mounts_allowed_before_fsck,
            magic_number,
            state,
            error_policy,
            version_minor,
            last_fsck,
            fsck_force_interval,
            os_id,
            version_major,
            uid_for_reserved_blocks,
            gid_for_reserved_blocks,
            extended,
        })
    }
}

#[derive(Debug, Eq, PartialEq)]
pub struct Ext2FsId([u8; 16]);

#[derive(Debug, Eq, PartialEq)]
pub struct SuperblockExtended {
    pub first_non_reserved_inode: u32,
    pub inode_size: u16,
    pub this_superblock_block_group: u16,
    pub optional_features: OptionalFeatures,
    pub required_features: RequiredFeatures,
    pub write_required_features: ReadOnlyFeatures,
    pub fsid: Ext2FsId,
    pub volume_name: String,
    pub last_mount_path: String,
    pub compression: u32,
    pub num_preallocate_blocks_file: u8,
    pub num_preallocate_blocks_directory: u8,
}

impl TryFrom<[u8; 1024]> for SuperblockExtended {
    type Error = SuperblockDecodeError;

    fn try_from(value: [u8; 1024]) -> Result<Self, Self::Error> {
        let first_non_reserved_inode = read_u32_le(&value[84..88])?;
        let inode_size = read_u16_le(&value[88..90])?;
        let this_superblock_block_group = read_u16_le(&value[90..92])?;
        let optional_features = read_u32_le(&value[92..96])?;
        let required_features = read_u32_le(&value[96..100])?;
        let write_required_features = read_u32_le(&value[100..104])?;
        let mut fsid = [0_u8; 16];
        fsid.copy_from_slice(&value[104..120]);
        let volume_name = read_c_str(&value[120..136])?;
        let last_mount_path = read_c_str(&value[136..200])?;
        let compression = read_u32_le(&value[200..204])?;
        let num_preallocate_blocks_file = value[204];
        let num_preallocate_blocks_directory = value[205];

        Ok(Self {
            first_non_reserved_inode,
            inode_size,
            this_superblock_block_group,
            optional_features: OptionalFeatures::from_bits_truncate(optional_features),
            required_features: RequiredFeatures::from_bits_truncate(required_features),
            write_required_features: ReadOnlyFeatures::from_bits_truncate(write_required_features),
            fsid: Ext2FsId(fsid),
            volume_name,
            last_mount_path,
            compression,
            num_preallocate_blocks_file,
            num_preallocate_blocks_directory,
        })
    }
}

bitflags! {
    #[derive(Debug, Copy, Clone, Eq, PartialEq)]
    pub struct OptionalFeatures: u32 {
        const PREALLOCATE_FOR_DIRECTORY = 0x0001;
        const AFS_SERVER_INODES_EXIST = 0x0002;
        const HAS_JOURNAL = 0x0004;
        const INODES_EXTENDED_ATTRIBUTES = 0x0008;
        const CAN_RESIZE = 0x0010;
        const DIRECTORIES_USE_HASH_INDEX = 0x0020;
    }
}

bitflags! {
    #[derive(Debug, Copy, Clone, Eq, PartialEq)]
    pub struct RequiredFeatures: u32 {
        const COMPRESSION_USED = 0x0001;
        const DIRECTORY_ENTRIES_HAVE_TYPE = 0x0002;
        const NEEDS_JOURNAL_REPLAY = 0x0004;
        const USES_JOURNAL_DEVICE = 0x0008;
    }
}

bitflags! {
    #[derive(Debug, Copy, Clone, Eq, PartialEq)]
    pub struct ReadOnlyFeatures: u32 {
        const SPARSE_SUPERBLOCK_AND_GDTS = 0x0001;
        const USE_64BIT_FILE_SIZE = 0x0002;
        const DIRS_STORED_AS_BINARY_TREE = 0x0004;
    }
}

bitflags! {
    #[derive(Debug, Copy, Clone, Eq, PartialEq)]
    pub struct State: u16 {
        const CLEAN = 1;
        const ERRONOUS = 2;
    }
}

bitflags! {
    #[derive(Debug, Copy, Clone, Eq, PartialEq)]
    pub struct ErrorPolicy: u16 {
        const IGNORE = 1;
        const REMOUNT_READ_ONLY = 2;
        const KERNEL_PANIC = 3;
    }
}

#[derive(Debug)]
struct ShortReadError;

fn read_u32_le(data: &[u8]) -> Result<u32, ShortReadError> {
    if data.len() < 4 {
        return Err(ShortReadError);
    }
    Ok(u32::from_le_bytes(data[0..4].try_into().unwrap()))
}

fn read_u16_le(data: &[u8]) -> Result<u16, ShortReadError> {
    if data.len() < 2 {
        return Err(ShortReadError);
    }
    Ok(u16::from_le_bytes(data[0..2].try_into().unwrap()))
}

fn read_c_str(data: &[u8]) -> Result<String, FromUtf8Error> {
    let termination_index = data.iter().position(|&b| b == 0).unwrap_or(data.len() + 1);
    String::from_utf8(data[0..termination_index].into())
}

#[cfg(test)]
mod tests {
    use super::*;
    use alloc::string::ToString;

    #[test]
    fn test_superblock_try_from() {
        // bytes of a superblock generated by `mkfs.ext2`
        let data = [
            0x80, 0x00, 0x00, 0x00, 0x00, 0x04, 0x00, 0x00, 0x33, 0x00, 0x00, 0x00, 0xca, 0x03,
            0x00, 0x00, 0x75, 0x00, 0x00, 0x00, 0x01, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
            0x00, 0x00, 0x00, 0x00, 0x00, 0x20, 0x00, 0x00, 0x00, 0x20, 0x00, 0x00, 0x80, 0x00,
            0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0xc6, 0x5d, 0x7f, 0x64, 0x00, 0x00, 0xff, 0xff,
            0x53, 0xef, 0x01, 0x00, 0x01, 0x00, 0x00, 0x00, 0xc5, 0x5d, 0x7f, 0x64, 0x00, 0x00,
            0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x01, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
            0x0b, 0x00, 0x00, 0x00, 0x00, 0x01, 0x00, 0x00, 0x38, 0x00, 0x00, 0x00, 0x02, 0x00,
            0x00, 0x00, 0x03, 0x00, 0x00, 0x00, 0x77, 0x4b, 0x94, 0xce, 0x3d, 0x05, 0x4b, 0x71,
            0x98, 0xfc, 0xfc, 0xf6, 0x37, 0xfd, 0x2b, 0x48, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
            0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
            0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
            0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
            0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
            0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
            0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x03, 0x00, 0x00, 0x00,
            0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
            0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0xe3, 0x38,
            0x05, 0x06, 0x72, 0xb2, 0x44, 0xcd, 0xbb, 0x20, 0x4e, 0xa1, 0xcb, 0x69, 0xa6, 0x1d,
            0x01, 0x00, 0x00, 0x00, 0x0c, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0xc5, 0x5d,
            0x7f, 0x64, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
            0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
            0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
            0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
            0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
            0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x20, 0x00,
            0x20, 0x00, 0x01, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
            0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
            0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
            0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
            0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
            0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
            0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
            0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
            0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
            0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
            0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
            0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
            0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
            0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
            0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
            0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
            0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x28, 0x00, 0x00, 0x00,
            0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
            0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
            0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
            0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
            0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
            0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
            0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
            0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
            0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
            0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
            0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
            0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
            0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
            0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
            0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
            0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
            0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
            0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
            0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
            0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
            0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
            0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
            0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
            0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
            0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
            0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
            0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
            0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
            0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
            0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
            0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
            0x00, 0x00,
        ];
        let sb = Superblock::try_from(data).unwrap();

        // result manually validated via `debugfs`
        assert_eq!(
            Superblock {
                num_inodes: 128,
                num_blocks: 1024,
                num_superuser_reserved_blocks: 51,
                num_unallocated_blocks: 970,
                num_unallocated_inodes: 117,
                superblock_block_number: 1,
                block_size: 1024,
                fragment_size: 1024,
                blocks_per_group: 8192,
                fragments_per_group: 8192,
                inodes_per_group: 128,
                last_mount_time: 0,
                last_written_time: 1686068678,
                mounts_since_fsck: 0,
                mounts_allowed_before_fsck: 65535,
                magic_number: 61267,
                state: State::CLEAN,
                error_policy: ErrorPolicy::IGNORE,
                version_minor: 0,
                last_fsck: 1686068677,
                fsck_force_interval: 0,
                os_id: 0,
                version_major: 1,
                uid_for_reserved_blocks: 0,
                gid_for_reserved_blocks: 0,
                extended: Some(SuperblockExtended {
                    first_non_reserved_inode: 11,
                    inode_size: 256,
                    this_superblock_block_group: 0,
                    optional_features: OptionalFeatures::INODES_EXTENDED_ATTRIBUTES
                        | OptionalFeatures::CAN_RESIZE
                        | OptionalFeatures::DIRECTORIES_USE_HASH_INDEX,
                    required_features: RequiredFeatures::DIRECTORY_ENTRIES_HAVE_TYPE,
                    write_required_features: ReadOnlyFeatures::SPARSE_SUPERBLOCK_AND_GDTS
                        | ReadOnlyFeatures::USE_64BIT_FILE_SIZE,
                    fsid: Ext2FsId([
                        119, 75, 148, 206, 61, 5, 75, 113, 152, 252, 252, 246, 55, 253, 43, 72,
                    ],),
                    volume_name: "".to_string(),
                    last_mount_path: "".to_string(),
                    compression: 0,
                    num_preallocate_blocks_file: 0,
                    num_preallocate_blocks_directory: 0,
                },),
            },
            sb
        );
    }

    #[test]
    fn test_read_u32_le() {
        for (expected, data) in [
            (1, [0x01, 0x00, 0x00, 0x00]),
            (2, [0x02, 0x00, 0x00, 0x00]),
            (255, [0xFF, 0x00, 0x00, 0x00]),
            (65280, [0x00, 0xFF, 0x00, 0x00]),
            (4294967040, [0x00, 0xFF, 0xFF, 0xFF]),
            (4294967295, [0xFF, 0xFF, 0xFF, 0xFF]),
        ] {
            let actual = read_u32_le(&data).unwrap();
            assert_eq!(expected, actual);
        }
    }

    #[test]
    fn test_read_u32_le_short() {
        assert!(read_u32_le(&[]).is_err());
        assert!(read_u32_le(&[0]).is_err());
        assert!(read_u32_le(&[0, 0]).is_err());
        assert!(read_u32_le(&[0, 0, 0]).is_err());
        assert!(read_u32_le(&[0, 0, 0, 0]).is_ok_and(|i| i == 0));
    }

    #[test]
    fn test_read_u16_le() {
        for (expected, data) in [
            (1, [0x01, 0x00]),
            (2, [0x02, 0x00]),
            (255, [0xFF, 0x00]),
            (65280, [0x00, 0xFF]),
            (65535, [0xFF, 0xFF]),
        ] {
            let actual = read_u16_le(&data).unwrap();
            assert_eq!(expected, actual);
        }
    }

    #[test]
    fn test_read_u16_le_short() {
        assert!(read_u16_le(&[]).is_err());
        assert!(read_u16_le(&[0]).is_err());
        assert!(read_u16_le(&[0, 0]).is_ok_and(|i| i == 0));
    }
}