Enum Backing 

pub enum Backing {
    File(File),
    Sub {
        file: Arc<File>,
        base: u64,
        len: u64,
    },
    Mem(Arc<[u8]>),
}

A positioned, cursor-free reader over one VHDX container’s bytes.

read_at(buf, offset) fills buf from logical offset within the container and returns the byte count (short only at end of container) — never touching a shared cursor, so it is safe to call concurrently through &self.

Variants

File(File)

A loose container file: positioned reads go straight to the OS handle.

Sub

A contiguous sub-range [base, base+len) of a larger shared file.

Fields

file: Arc<File>

The backing file (shared; positioned reads carry their own offset).

base: u64

Absolute file offset where this container’s bytes begin.

len: u64

Length of this container in bytes.

Mem(Arc<[u8]>)

An in-RAM container (e.g. the legacy from_bytes path or an inflated zip entry).

Implementations

impl Backing

pub fn sub(file: Arc<File>, base: u64, len: u64) -> Self

Construct a Backing::Sub over [base, base+len) of file.

pub fn from_bytes(bytes: impl Into<Arc<[u8]>>) -> Self

Construct an in-RAM Backing::Mem from owned bytes.

pub fn len(&self) -> u64

Total length of this container in bytes.

pub fn is_empty(&self) -> bool

Whether the container is empty.

pub fn read_at(&self, buf: &mut [u8], offset: u64) -> Result<usize>

Fill buf from logical offset within this container, returning the bytes read (short only at the container’s end). Cursor-free and thread-safe.

Errors

Propagates the underlying I/O error for Backing::File / Backing::Sub; Backing::Mem never fails.

pub fn read_exact_at(&self, offset: u64, len: usize) -> Result<Vec<u8>>

Read exactly len bytes starting at offset into a fresh Vec.

Used by the open/parse pass to pull a small, known-size structure (a header slot, the region table, the metadata region, the BAT) into a bounded buffer. The returned Vec is short only when the container ends before offset + len (so the caller still range-checks the parse).

Errors

Propagates the underlying positioned-read error.

Trait Implementations

impl Debug for Backing

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

Formats the value using the given formatter.