itoa
====

[](https://github.com/dtolnay/itoa)
[](https://crates.io/crates/itoa)
[](https://docs.rs/itoa)
[](https://github.com/dtolnay/itoa/actions?query=branch%3Amaster)

This crate provides fast functions for printing integer primitives to an
[`io::Write`] or a [`fmt::Write`]. The implementation comes straight from
[libcore] but avoids the performance penalty of going through
[`fmt::Formatter`].

See also [`dtoa`] for printing floating point primitives.

*Version requirement: rustc 1.0+*

[`io::Write`]: https://doc.rust-lang.org/std/io/trait.Write.html
[`fmt::Write`]: https://doc.rust-lang.org/core/fmt/trait.Write.html
[libcore]: https://github.com/rust-lang/rust/blob/b8214dc6c6fc20d0a660fb5700dca9ebf51ebe89/src/libcore/fmt/num.rs#L201-L254
[`fmt::Formatter`]: https://doc.rust-lang.org/std/fmt/struct.Formatter.html
[`dtoa`]: https://github.com/dtolnay/dtoa

```toml
[dependencies]
itoa = "0.4"
```




## Performance (lower is better)

![performance](https://raw.githubusercontent.com/dtolnay/itoa/master/performance.png)




## Examples

```rust
use std::{fmt, io};

fn demo_itoa_write() -> io::Result<()> {
    // Write to a vector or other io::Write.
    let mut buf = Vec::new();
    itoa::write(&mut buf, 128u64)?;
    println!("{:?}", buf);

    // Write to a stack buffer.
    let mut bytes = [0u8; 20];
    let n = itoa::write(&mut bytes[..], 128u64)?;
    println!("{:?}", &bytes[..n]);

    Ok(())
}

fn demo_itoa_fmt() -> fmt::Result {
    // Write to a string.
    let mut s = String::new();
    itoa::fmt(&mut s, 128u64)?;
    println!("{}", s);

    Ok(())
}
```

The function signatures are:

```rust
fn write(writer: W, value: V) -> io::Result;

fn fmt(writer: W, value: V) -> fmt::Result;
```

where `itoa::Integer` is implemented for i8, u8, i16, u16, i32, u32, i64, u64,
i128, u128, isize and usize. 128-bit integer support requires rustc 1.26+ and
the `i128` feature of this crate enabled.

The `write` function is only available when the `std` feature is enabled
(default is enabled). The return value gives the number of bytes written.




#### License


Licensed under either of Apache License, Version
2.0 or MIT license at your option.






Unless you explicitly state otherwise, any contribution intentionally submitted
for inclusion in this crate by you, as defined in the Apache-2.0 license, shall
be dual licensed as above, without any additional terms or conditions.