Home - News ( United States | United Kingdom | Italy | Germany ) - Football scores

Showing content from https://doc.rust-lang.org/std/io/trait.Write.html below:

Write in std::io - Rust

pub trait Write {
    // Required methods
    fn write(&mut self, buf: &[u8]) -> Result<usize>;
    fn flush(&mut self) -> Result<()>;

    // Provided methods
    fn write_vectored(&mut self, bufs: &[IoSlice<'_>]) -> Result<usize> { ... }
    fn is_write_vectored(&self) -> bool { ... }
    fn write_all(&mut self, buf: &[u8]) -> Result<()> { ... }
    fn write_all_vectored(&mut self, bufs: &mut [IoSlice<'_>]) -> Result<()> { ... }
    fn write_fmt(&mut self, args: Arguments<'_>) -> Result<()> { ... }
    fn by_ref(&mut self) -> &mut Self
       where Self: Sized { ... }
}

A trait for objects which are byte-oriented sinks.

Implementors of the Write trait are sometimes called ‘writers’.

Writers are defined by two required methods, write and flush:

• The write method will attempt to write some data into the object, returning how many bytes were successfully written.

• The flush method is useful for adapters and explicit buffers themselves for ensuring that all buffered data has been pushed out to the ‘true sink’.

Writers are intended to be composable with one another. Many implementors throughout std::io take and provide types which implement the Write trait.

use std::io::prelude::*;
use std::fs::File;

fn main() -> std::io::Result<()> {
    let data = b"some bytes";

    let mut pos = 0;
    let mut buffer = File::create("foo.txt")?;

    while pos < data.len() {
        let bytes_written = buffer.write(&data[pos..])?;
        pos += bytes_written;
    }
    Ok(())
}

The trait also provides convenience methods like write_all, which calls write in a loop until its entire input has been written.

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

This function will attempt to write the entire contents of buf, but the entire write might not succeed, or the write may also generate an error. Typically, a call to write represents one attempt to write to any wrapped object.

Calls to write are not guaranteed to block waiting for data to be written, and a write which would otherwise block can be indicated through an Err variant.

If this method consumed n > 0 bytes of buf it must return Ok(n). If the return value is Ok(n) then n must satisfy n <= buf.len(). A return value of Ok(0) typically means that the underlying object is no longer able to accept bytes and will likely not be able to in the future as well, or that the buffer provided is empty.

Each call to write may generate an I/O error indicating that the operation could not be completed. If an error is returned then no bytes in the buffer were written to this writer.

It is not considered an error if the entire buffer could not be written to this writer.

An error of the ErrorKind::Interrupted kind is non-fatal and the write operation should be retried if there is nothing else to do.

use std::io::prelude::*;
use std::fs::File;

fn main() -> std::io::Result<()> {
    let mut buffer = File::create("foo.txt")?;

    buffer.write(b"some bytes")?;
    Ok(())
}

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

It is considered an error if not all bytes could be written due to I/O errors or EOF being reached.

use std::io::prelude::*;
use std::io::BufWriter;
use std::fs::File;

fn main() -> std::io::Result<()> {
    let mut buffer = BufWriter::new(File::create("foo.txt")?);

    buffer.write_all(b"some bytes")?;
    buffer.flush()?;
    Ok(())
}

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

Data is copied from each buffer in order, with the final buffer read from possibly being only partially consumed. This method must behave as a call to write with the buffers concatenated would.

The default implementation calls write with either the first nonempty buffer provided, or an empty one if none exists.

use std::io::IoSlice;
use std::io::prelude::*;
use std::fs::File;

fn main() -> std::io::Result<()> {
    let data1 = [1; 8];
    let data2 = [15; 8];
    let io_slice1 = IoSlice::new(&data1);
    let io_slice2 = IoSlice::new(&data2);

    let mut buffer = File::create("foo.txt")?;

    buffer.write_vectored(&[io_slice1, io_slice2])?;
    Ok(())
}

Determines if this Writer has an efficient write_vectored implementation.

If a Writer does not override the default write_vectored implementation, code using it may want to avoid the method all together and coalesce writes into a single buffer for higher performance.

The default implementation returns false.

Attempts to write an entire buffer into this writer.

This method will continuously call write until there is no more data to be written or an error of non-ErrorKind::Interrupted kind is returned. This method will not return until the entire buffer has been successfully written or such an error occurs. The first error that is not of ErrorKind::Interrupted kind generated from this method will be returned.

If the buffer contains no data, this will never call write.

This function will return the first error of non-ErrorKind::Interrupted kind that write returns.

use std::io::prelude::*;
use std::fs::File;

fn main() -> std::io::Result<()> {
    let mut buffer = File::create("foo.txt")?;

    buffer.write_all(b"some bytes")?;
    Ok(())
}

Attempts to write multiple buffers into this writer.

This method will continuously call write_vectored until there is no more data to be written or an error of non-ErrorKind::Interrupted kind is returned. This method will not return until all buffers have been successfully written or such an error occurs. The first error that is not of ErrorKind::Interrupted kind generated from this method will be returned.

If the buffer contains no data, this will never call write_vectored.

Unlike write_vectored, this takes a mutable reference to a slice of IoSlices, not an immutable one. That’s because we need to modify the slice to keep track of the bytes already written.

Once this function returns, the contents of bufs are unspecified, as this depends on how many calls to write_vectored were necessary. It is best to understand this function as taking ownership of bufs and to not use bufs afterwards. The underlying buffers, to which the IoSlices point (but not the IoSlices themselves), are unchanged and can be reused.

#![feature(write_all_vectored)]

use std::io::{Write, IoSlice};

let mut writer = Vec::new();
let bufs = &mut [
    IoSlice::new(&[1]),
    IoSlice::new(&[2, 3]),
    IoSlice::new(&[4, 5, 6]),
];

writer.write_all_vectored(bufs)?;
assert_eq!(writer, &[1, 2, 3, 4, 5, 6]);

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

This method is primarily used to interface with the format_args!() macro, and it is rare that this should explicitly be called. The write!() macro should be favored to invoke this method instead.

This function internally uses the write_all method on this trait and hence will continuously write data so long as no errors are received. This also means that partial writes are not indicated in this signature.

This function will return any I/O error reported while formatting.

use std::io::prelude::*;
use std::fs::File;

fn main() -> std::io::Result<()> {
    let mut buffer = File::create("foo.txt")?;

    write!(buffer, "{:.*}", 2, 1.234567)?;
    buffer.write_fmt(format_args!("{:.*}", 2, 1.234567))?;
    Ok(())
}

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

The returned adapter also implements Write and will simply borrow this current writer.

use std::io::Write;
use std::fs::File;

fn main() -> std::io::Result<()> {
    let mut buffer = File::create("foo.txt")?;

    let reference = buffer.by_ref();

    reference.write_all(b"some bytes")?;
    Ok(())
}

RetroSearch is an open source project built by @garambo | Open a GitHub Issue

Search and Browse the WWW like it's 1997 | Search results from DuckDuckGo

HTML: 3.2 | Encoding: UTF-8 | Version: 0.7.4