Struct DeferredWriter

pub struct DeferredWriter<'a> { /* private fields */ }

A buffered writer with deferred error checking.

This can be used like std::io::BufWriter, but like DeferredReader this performs deferred error checking. This means that any call to write, will always succeed. IO errors that occur during writing will be reported during the next call to flush or check_io_error. Any data written after an IO error occured, before it is eventually reported, will be discarded.

Deferring error checks like this can result in a significant speed up for some usage patterns.

Implementations

impl<'a> DeferredWriter<'a>

pub fn from_write(write: impl Write + 'a) -> Self

Creates a DeferredWriter writing data to a Write instance.

pub fn from_boxed_dyn_write(write: Box<dyn Write + 'a>) -> Self

Creates a DeferredWriter writing data to a boxed Write instance.

pub fn flush_defer_err(&mut self)

Flush the buffered data to the underlying Write instance, deferring IO errors.

pub fn write_all_defer_err(&mut self, buf: &[u8])

Write a slice of bytes, deferring IO errors.

Both, write and write_all directly call this method. Unlike them, this does not return a #[must_use] value, making it clear that this cannot return an error.

pub fn buf_write_ptr(&mut self, len: usize) -> *mut u8

Returns a pointer to the current write pointer within the internal buffer if sufficient space is available.

If only fewer than len bytes are available, this returns a null pointer.

Can be used in conjunction with advance_unchecked to construct output data directly within the output buffer, potentially avoiding a redundant copy.

pub unsafe fn advance_unchecked(&mut self, len: usize)

Advances the write pointer within the internal buffer.

Safety

This assumes that a) there is sufficient space left in the buffer and b) that the bytes the pointer is advanced over were initialized prior to calling this (via buf_write_ptr).

If either assumption does not hold calling this results in undefined behavior.

pub fn check_io_error(&mut self) -> Result<()>

Returns an encountered IO errors as Err(io_err).

This resets the stored IO error and returns Ok(()) if no IO error is stored.

Trait Implementations

impl<'a> Drop for DeferredWriter<'a>

fn drop(&mut self)

Executes the destructor for this type.

impl<'a> Write for DeferredWriter<'a>

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_all(&mut self, buf: &[u8]) -> Result<()>

Attempts to write an entire buffer into this writer.

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_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.