itoa 0.3.4

Fast functions for printing integer primitives to an io::Write


Build Status Latest Version

This crate provides fast functions for printing integer primitives to an io::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.

Performance (lower is better)



extern crate itoa;

// 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 = [b'\0'; 20];
let n = itoa::write(&mut bytes[..], 128u64)?;
println!("{:?}", &bytes[..n]);

The function signature is:

fn write<W: io::Write, V: itoa::Integer>(writer: W, value: V) -> io::Result<usize>

where itoa::Integer is implemented for i8, u8, i16, u16, i32, u32, i64, u64, i128, u128, isize and usize. 128-bit integer support is only available with the nightly compiler when the i128 feature is enabled for this crate. The return value gives the number of bytes written.


Itoa is available on Use the following in Cargo.toml:

itoa = "0.3"


Licensed under either of

at your option.


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