NumToA

#![no_std] Compatible with Zero Heap Allocations

The standard library provides a convenient method of converting numbers into strings, but these strings are heap-allocated. If you have an application which needs to convert large volumes of numbers into strings, but don't want to pay the price of heap allocation, this crate provides an efficient no_std-compatible method of heaplessly converting numbers into their string representations, storing the representation within a reusable byte array.

Supports Multiple Bases

In addition to supporting the standard base 10 conversion, this implementation allows you to select the base of your choice. Therefore, if you want a binary representation, set the base to 2. If you want hexadecimal, set the base to 16.

No Unsafe

Both the standard library and itoa crate rely on unsafe functions, but this implementation has been able to avoid the use of unsafe entirely.

Fast

Performance is roughly identical to that of the itoa crate when performing base 10 conversions. Below is a benchmark of printing 0 through 5,000,000 to /dev/null

std:   1150615048 ns
itoa:   838556714 ns
numtoa: 825544518 ns

Base 10 Example

use numtoa::NumToA;
use std::io::{self, Write};

let stdout = io::stdout();
let mut stdout = stdout.lock();
let mut buffer = [0u8; 20];

let number: u32 = 162392;
let mut start_index = number.numtoa(10, &mut buffer);
let _ = stdout.write(&buffer[start_index..]);
let _ = stdout.write(b"\n");
assert_eq!(&buffer[start_index..], b"162392");

let other_number: i32 = -6235;
start_index = other_number.numtoa(10, &mut buffer);
let _ = stdout.write(&buffer[start_index..]);
let _ = stdout.write(b"\n");
assert_eq!(&buffer[start_index..], b"-6235");

let large_num: u64 = 35320842;
start_index = large_num.numtoa(10, &mut buffer);
let _ = stdout.write(&buffer[start_index..]);
let _ = stdout.write(b"\n");
assert_eq!(&buffer[start_index..], b"35320842");

let max_u64: u64 = 18446744073709551615;
start_index = max_u64.numtoa(10, &mut buffer);
let _ = stdout.write(&buffer[start_index..]);
let _ = stdout.write(b"\n");
assert_eq!(&buffer[start_index..], b"18446744073709551615");