Method new

block/src/vhdx/vhdx_metadata.rs:105–245

Parse all metadata from the provided file and store info in DiskSpec structure.

(f: &mut File, metadata_region: &RegionTableEntry)

    /// Parse all metadata from the provided file and store info in DiskSpec
    /// structure.
    pub fn new(f: &mut File, metadata_region: &RegionTableEntry) -> Result<DiskSpec> {
        let mut disk_spec = DiskSpec::default();
        let mut metadata_presence: u16 = 0;
        let mut offset = 0;
        let metadata = f.metadata().map_err(VhdxMetadataError::ReadMetadata)?;
        disk_spec.image_size = metadata.len();

        let mut buffer = [0u8; METADATA_TABLE_MAX_SIZE];
        f.seek(SeekFrom::Start(metadata_region.file_offset))
            .map_err(VhdxMetadataError::ReadMetadata)?;
        f.read_exact(&mut buffer)
            .map_err(VhdxMetadataError::ReadMetadata)?;

        let metadata_header =
            MetadataTableHeader::new(&buffer[0..size_of::<MetadataTableHeader>()])?;

        offset += size_of::<MetadataTableHeader>();
        for _ in 0..metadata_header.entry_count {
            let metadata_entry =
                MetadataTableEntry::new(&buffer[offset..offset + size_of::<MetadataTableEntry>()])?;

            f.seek(SeekFrom::Start(
                metadata_region.file_offset + metadata_entry.offset as u64,
            ))
            .map_err(VhdxMetadataError::ReadMetadata)?;

            if metadata_entry.item_id
                == Uuid::parse_str(METADATA_FILE_PARAMETER)
                    .map_err(VhdxMetadataError::InvalidUuid)?
            {
                disk_spec.block_size = f
                    .read_u32::<LittleEndian>()
                    .map_err(VhdxMetadataError::ReadMetadata)?;

                // MUST be at least 1 MiB and not greater than 256 MiB
                if disk_spec.block_size < BLOCK_SIZE_MIN || disk_spec.block_size > BLOCK_SIZE_MAX {
                    return Err(VhdxMetadataError::InvalidBlockSize);
                }

                // MUST be power of 2
                if !disk_spec.block_size.is_power_of_two() {
                    return Err(VhdxMetadataError::InvalidBlockSize);
                }

                let bits = f
                    .read_u32::<LittleEndian>()
                    .map_err(VhdxMetadataError::ReadMetadata)?;
                disk_spec.has_parent = bits & BLOCK_HAS_PARENT != 0;

                metadata_presence |= METADATA_FILE_PARAMETER_PRESENT;
            } else if metadata_entry.item_id
                == Uuid::parse_str(METADATA_VIRTUAL_DISK_SIZE)
                    .map_err(VhdxMetadataError::InvalidUuid)?
            {
                disk_spec.virtual_disk_size = f
                    .read_u64::<LittleEndian>()
                    .map_err(VhdxMetadataError::ReadMetadata)?;