Struct Writer

pub struct Writer<'a, B = ()> { /* private fields */ }

Provides high-level interface over the sequence of memory regions defined by writable descriptors in the descriptor chain.

Note that virtio spec requires driver to place any device-writable descriptors after any device-readable descriptors (2.6.4.2 in Virtio Spec v1.1). Writer will start iterating the descriptors from the first writable one and will assume that all following descriptors are writable.

Implementations

impl<'a, B: BitmapSlice> Writer<'a, B>

pub fn new<M, T>( mem: &'a M, desc_chain: DescriptorChain<T>, ) -> Result<Writer<'a, B>, Error>

where M: GuestMemory, <<M as GuestMemory>::R as GuestMemoryRegion>::B: WithBitmapSlice<'a, S = B>, T: Deref, T::Target: GuestMemory + Sized,

Construct a new Writer wrapper over desc_chain.

pub fn write_obj<T: ByteValued>(&mut self, val: T) -> Result<()>

Writes an object to the descriptor chain buffer.

pub fn available_bytes(&self) -> usize

Returns number of bytes available for writing. May return an error if the combined lengths of all the buffers in the DescriptorChain would cause an overflow.

pub fn bytes_written(&self) -> usize

Returns number of bytes already written to the descriptor chain buffer.

pub fn split_at(&mut self, offset: usize) -> Result<Writer<'a, B>, Error>

Splits this Writer into two at the given offset in the DescriptorChain buffer. After the split, self will be able to write up to offset bytes while the returned Writer can write up to available_bytes() - offset bytes. Returns an error if offset > self.available_bytes().

Trait Implementations

impl<'a, B: Clone> Clone for Writer<'a, B>

fn clone(&self) -> Writer<'a, B>

Returns a duplicate of the value.

const fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl<B: BitmapSlice> Write for Writer<'_, B>

fn write(&mut self, buf: &[u8]) -> Result<usize>

Writes a buffer into this writer, returning how many bytes were written.

fn flush(&mut self) -> Result<()>

Flushes this output stream, ensuring that all intermediately buffered contents reach their destination.

fn write_vectored(&mut self, bufs: &[IoSlice<'_>]) -> Result<usize, Error>

Like write, except that it writes from a slice of buffers.

fn is_write_vectored(&self) -> bool

🔬This is a nightly-only experimental API. (can_vector)

Determines if this Writer has an efficient write_vectored implementation.

fn write_all(&mut self, buf: &[u8]) -> Result<(), Error>

Attempts to write an entire buffer into this writer.

fn write_all_vectored(&mut self, bufs: &mut [IoSlice<'_>]) -> Result<(), Error>

🔬This is a nightly-only experimental API. (write_all_vectored)

Attempts to write multiple buffers into this writer.

fn write_fmt(&mut self, args: Arguments<'_>) -> Result<(), Error>

Writes a formatted string into this writer, returning any error encountered.

fn by_ref(&mut self) -> &mut Self

where Self: Sized,

Creates a “by reference” adapter for this instance of Write.