Struct Writer 

pub struct Writer<W> { /* private fields */ }

Stateful MP4 writer that can backfill container sizes after payload bytes are written.

This wrapper is designed for rewrite-style flows that need to stream payload bytes, nest container boxes, and then patch final sizes back into previously written headers.

Implementations

impl<W> Writer<W>

pub fn new(writer: W) -> Self

Wraps writer with box-start and box-end tracking.

pub const fn get_ref(&self) -> &W

Returns a shared view of the underlying writer.

pub fn get_mut(&mut self) -> &mut W

Returns a mutable view of the underlying writer.

pub fn into_inner(self) -> W

Consumes the wrapper and returns the underlying writer.

impl<W> Writer<W>

where W: Write + Seek,

pub fn start_box_type( &mut self, box_type: FourCc, ) -> Result<BoxInfo, WriterError>

Starts a new box using box_type and an empty small-header placeholder.

The final size is written later by Writer::end_box.

pub fn start_box(&mut self, info: BoxInfo) -> Result<BoxInfo, WriterError>

Writes info as the next box header and pushes it onto the open-box stack.

Callers typically pass either a small-header placeholder or a header copied from an existing box when preserving layout details.

pub fn end_box(&mut self) -> Result<BoxInfo, WriterError>

Rewrites the most recently opened box header with its final size.

The returned BoxInfo reflects the finalized on-disk size after the rewrite completes.

pub fn copy_box<R>( &mut self, reader: &mut R, info: &BoxInfo, ) -> Result<(), WriterError>

where R: Read + Seek,

Copies the exact byte range described by info into the current output position.

impl<W> Writer<W>

where W: AsyncWriteSeek,

pub async fn start_box_type_async( &mut self, box_type: FourCc, ) -> Result<BoxInfo, WriterError>

Available on crate feature async only.

Starts a new box through the additive Tokio-based async library surface using box_type and an empty small-header placeholder.

The final size is written later by Writer::end_box_async.

pub async fn start_box_async( &mut self, info: BoxInfo, ) -> Result<BoxInfo, WriterError>

Available on crate feature async only.

Writes info as the next box header through the additive Tokio-based async library surface and pushes it onto the open-box stack.

pub async fn end_box_async(&mut self) -> Result<BoxInfo, WriterError>

Available on crate feature async only.

Rewrites the most recently opened box header with its final size through the additive Tokio-based async library surface.

The returned BoxInfo reflects the finalized on-disk size after the rewrite completes.

pub async fn copy_box_async<R>( &mut self, reader: &mut R, info: &BoxInfo, ) -> Result<(), WriterError>

where R: AsyncReadSeek,

Available on crate feature async only.

Copies the exact byte range described by info into the current output position through the additive Tokio-based async library surface.

Trait Implementations

impl<W> AsyncSeek for Writer<W>

where W: AsyncSeek + Unpin,

Available on crate feature async only.

fn start_seek(self: Pin<&mut Self>, position: SeekFrom) -> Result<()>

Attempts to seek to an offset, in bytes, in a stream.

fn poll_complete( self: Pin<&mut Self>, cx: &mut Context<'_>, ) -> Poll<Result<u64>>

Waits for a seek operation to complete.

impl<W> AsyncWrite for Writer<W>

where W: AsyncWrite + Unpin,

Available on crate feature async only.

fn poll_write( self: Pin<&mut Self>, cx: &mut Context<'_>, buf: &[u8], ) -> Poll<Result<usize>>

Attempt to write bytes from buf into the object.

fn poll_flush(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Result<()>>

Attempts to flush the object, ensuring that any buffered data reach their destination.

fn poll_shutdown(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Result<()>>

Initiates or attempts to shut down this writer, returning success when the I/O connection has completely shut down.

fn poll_write_vectored( self: Pin<&mut Self>, cx: &mut Context<'_>, bufs: &[IoSlice<'_>], ) -> Poll<Result<usize, Error>>

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

fn is_write_vectored(&self) -> bool

Determines if this writer has an efficient poll_write_vectored implementation.

impl<W> Seek for Writer<W>

where W: Seek,

fn seek(&mut self, pos: SeekFrom) -> Result<u64>

Seek to an offset, in bytes, in a stream.

fn rewind(&mut self) -> Result<(), Error>

Rewind to the beginning of a stream.

fn stream_len(&mut self) -> Result<u64, Error>

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

Returns the length of this stream (in bytes).

fn stream_position(&mut self) -> Result<u64, Error>

Returns the current seek position from the start of the stream.

fn seek_relative(&mut self, offset: i64) -> Result<(), Error>

Seeks relative to the current position.

impl<W> Write for Writer<W>

where W: Write,

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.