Crate itoap[][src]

This crate provides even faster functions for printing integers with decimal format than itoa crate.

If you want to write integers in decimal format to String, Vec or any other contiguous buffer, then this crate is the best choice.

If you want to write integers to a std::io::Write or std::fmt::Write, itoa crate and itoap crate shows almost same performance.

The implementation is based on the sse2 algorithm from itoa-benchmark repository. While itoa crate writes integers from last digits, this algorithm writes from first digits. It allows integers to be written directly to the buffer. That's why itoap is faster than itoa.

Feature Flags

  • alloc: use alloc crate (enabled by default)
  • std: use std crate (enabled by default)
  • simd: use SIMD intrinsics if available


let value = 17u64;

let mut buf = String::new();
buf.push_str("value: ");
itoap::write_to_string(&mut buf, value);

assert_eq!(buf, "value: 17");
use core::mem::{MaybeUninit, transmute};
use itoap::Integer;

unsafe {
    let mut buf = [MaybeUninit::<u8>::uninit(); i32::MAX_LEN];
    let len = itoap::write_to_ptr(buf.as_mut_ptr() as *mut u8, -2953);
    let result: &[u8] = transmute(&buf[..len]);
    assert_eq!(result, b"-2953");



An integer that can be written to pointer.



Write integer to an fmt::Write


Write integer to an io::Write


Write integer to the buffer pointer directly.


Write integer to String.


Write integer to Vec<u8>.