Struct Rewriter

pub struct Rewriter<'a, W: ?Sized + 'a> { /* private fields */ }

A lightweight adapter from std::io::Write to core::fmt::Write.

Since Rust encodes strings and string slices in UTF-8, forwarding core::fmt::Write::write_str to std::io::Write::write_all is straight-forward. The challenge is that std::io::Error covers many different error conditions, whereas core::fmt::Error is a unit-like struct. The primary benefit of this adapter is that it tracks the most recent I/O error. Hence, if the rewriter fails with a format error, code using this struct can recover the underlying I/O error.

Example

The match below illustrates how to do just that:

let mut cursor = Cursor::new(vec![0; 10]);
let mut writer = Rewriter::new(&mut cursor);

match writer.write_str("Hello!") {
    Ok(()) => (),
    Err(_) => return Err(writer.into_err()),
}

assert_eq!(&cursor.get_ref()[0..5], b"Hello");

Implementations

impl<'a, W: ?Sized + 'a> Rewriter<'a, W>

pub fn new(writer: &'a mut W) -> Self

Create a new rewriter.

pub fn into_err(self) -> Error

Consume the rewriter to get its error.

If the code using this rewriter produced a fmt::Error, this method produces the underlying I/O error.

Panics

If the rewriter didn’t record an error.

Trait Implementations

impl<W: Write + ?Sized> Write for Rewriter<'_, W>

fn write_str(&mut self, s: &str) -> Result

Writes a string slice into this writer, returning whether the write succeeded.

fn write_char(&mut self, c: char) -> Result<(), Error>

Writes a char into this writer, returning whether the write succeeded.

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

Glue for usage of the write! macro with implementors of this trait.