pub trait AsyncSeek {
    // Required method
    fn poll_seek(
        self: Pin<&mut Self>,
        cx: &mut Context<'_>,
        pos: SeekFrom
    ) -> Poll<Result<u64, Error>>;
}
Expand description

Seek bytes asynchronously.

This trait is analogous to the std::io::Seek trait, but integrates with the asynchronous task system. In particular, the poll_seek method, unlike Seek::seek, will automatically queue the current task for wakeup and return if data is not yet available, rather than blocking the calling thread.

Required Methods§

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

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

A seek beyond the end of a stream is allowed, but behavior is defined by the implementation.

If the seek operation completed successfully, this method returns the new position from the start of the stream. That position can be used later with SeekFrom::Start.

Errors

Seeking to a negative offset is considered an error.

Implementation

This function may not return errors of kind WouldBlock or Interrupted. Implementations must convert WouldBlock into Poll::Pending and either internally retry or convert Interrupted into another error kind.

Implementations on Foreign Types§

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impl AsyncSeek for File

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fn poll_seek( self: Pin<&mut File>, cx: &mut Context<'_>, pos: SeekFrom ) -> Poll<Result<u64, Error>>

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impl AsyncSeek for File

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fn poll_seek( self: Pin<&mut File>, cx: &mut Context<'_>, pos: SeekFrom ) -> Poll<Result<u64, Error>>

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impl<A, B> AsyncSeek for Either<A, B>
where A: AsyncSeek, B: AsyncSeek,

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fn poll_seek( self: Pin<&mut Either<A, B>>, cx: &mut Context<'_>, pos: SeekFrom ) -> Poll<Result<u64, Error>>

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impl<P> AsyncSeek for Pin<P>
where P: DerefMut + Unpin, <P as Deref>::Target: AsyncSeek,

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fn poll_seek( self: Pin<&mut Pin<P>>, cx: &mut Context<'_>, pos: SeekFrom ) -> Poll<Result<u64, Error>>

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impl<R> AsyncSeek for BufReader<R>
where R: AsyncRead + AsyncSeek,

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fn poll_seek( self: Pin<&mut BufReader<R>>, cx: &mut Context<'_>, pos: SeekFrom ) -> Poll<Result<u64, Error>>

Seek to an offset, in bytes, in the underlying reader.

The position used for seeking with SeekFrom::Current(_) is the position the underlying reader would be at if the BufReader had no internal buffer.

Seeking always discards the internal buffer, even if the seek position would otherwise fall within it. This guarantees that calling .into_inner() immediately after a seek yields the underlying reader at the same position.

To seek without discarding the internal buffer, use BufReader::seek_relative or BufReader::poll_seek_relative.

See AsyncSeek for more details.

Note: In the edge case where you’re seeking with SeekFrom::Current(n) where n minus the internal buffer length overflows an i64, two seeks will be performed instead of one. If the second seek returns Err, the underlying reader will be left at the same position it would have if you called seek with SeekFrom::Current(0).

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impl<R> AsyncSeek for BufReader<R>
where R: AsyncSeek,

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fn poll_seek( self: Pin<&mut BufReader<R>>, cx: &mut Context<'_>, pos: SeekFrom ) -> Poll<Result<u64, Error>>

Seeks to an offset, in bytes, in the underlying reader.

The position used for seeking with SeekFrom::Current is the position the underlying reader would be at if the [BufReader] had no internal buffer.

Seeking always discards the internal buffer, even if the seek position would otherwise fall within it. This guarantees that calling [into_inner()][BufReader::into_inner()] immediately after a seek yields the underlying reader at the same position.

See AsyncSeek for more details.

Note: In the edge case where you’re seeking with SeekFrom::Current(n) where n minus the internal buffer length overflows an i64, two seeks will be performed instead of one. If the second seek returns Err, the underlying reader will be left at the same position it would have if you called [seek()][AsyncSeekExt::seek()] with SeekFrom::Current(0).

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impl<T> AsyncSeek for &mut T
where T: AsyncSeek + Unpin + ?Sized,

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fn poll_seek( self: Pin<&mut &mut T>, cx: &mut Context<'_>, pos: SeekFrom ) -> Poll<Result<u64, Error>>

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impl<T> AsyncSeek for AllowStdIo<T>
where T: Seek,

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fn poll_seek( self: Pin<&mut AllowStdIo<T>>, _: &mut Context<'_>, pos: SeekFrom ) -> Poll<Result<u64, Error>>

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impl<T> AsyncSeek for AssertAsync<T>
where T: Seek,

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fn poll_seek( self: Pin<&mut AssertAsync<T>>, _: &mut Context<'_>, pos: SeekFrom ) -> Poll<Result<u64, Error>>

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impl<T> AsyncSeek for Cursor<T>
where T: AsRef<[u8]> + Unpin,

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fn poll_seek( self: Pin<&mut Cursor<T>>, _: &mut Context<'_>, pos: SeekFrom ) -> Poll<Result<u64, Error>>

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impl<T> AsyncSeek for Cursor<T>
where T: AsRef<[u8]> + Unpin,

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fn poll_seek( self: Pin<&mut Cursor<T>>, _: &mut Context<'_>, pos: SeekFrom ) -> Poll<Result<u64, Error>>

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impl<T> AsyncSeek for Unblock<T>
where T: Seek + Send + 'static,

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fn poll_seek( self: Pin<&mut Unblock<T>>, cx: &mut Context<'_>, pos: SeekFrom ) -> Poll<Result<u64, Error>>

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impl<W> AsyncSeek for BufWriter<W>
where W: AsyncWrite + AsyncSeek,

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fn poll_seek( self: Pin<&mut BufWriter<W>>, cx: &mut Context<'_>, pos: SeekFrom ) -> Poll<Result<u64, Error>>

Seek to the offset, in bytes, in the underlying writer.

Seeking always writes out the internal buffer before seeking.

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impl<W> AsyncSeek for BufWriter<W>
where W: AsyncWrite + AsyncSeek,

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fn poll_seek( self: Pin<&mut BufWriter<W>>, cx: &mut Context<'_>, pos: SeekFrom ) -> Poll<Result<u64, Error>>

Seek to the offset, in bytes, in the underlying writer.

Seeking always writes out the internal buffer before seeking.

Implementors§

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impl<R> AsyncSeek for bevy::tasks::futures_lite::io::BufReader<R>
where R: AsyncSeek,

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impl<T> AsyncSeek for Box<T>
where T: AsyncSeek + Unpin + ?Sized,

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impl<T> AsyncSeek for bevy::tasks::futures_lite::io::AssertAsync<T>
where T: Seek,

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impl<T> AsyncSeek for bevy::tasks::futures_lite::io::Cursor<T>
where T: AsRef<[u8]> + Unpin,

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impl<W> AsyncSeek for bevy::tasks::futures_lite::io::BufWriter<W>
where W: AsyncWrite + AsyncSeek,