Converting a hexadecimal string to a decimal integer

44
votes

I'm writing a Rust program that reads off of an I2C bus and saves the data. When I read the I2C bus, I get hex values like 0x11, 0x22, etc.

Right now, I can only handle this as a string and save it as is. Is there a way I can parse this into an integer? Is there any built in function for it?

1
parsinghexrust

1 Answers

63
votes

In most cases, you want to parse more than one hex byte at once. In those cases, use the hex crate.

parse this into an integer

You want to use from_str_radix. It's implemented on the integer types. 

use std::i64;

fn main() {
    let z = i64::from_str_radix("1f", 16);
    println!("{:?}", z);
}

If your strings actually have the 0x prefix, then you will need to skip over them. The best way to do that is via trim_start_matches:

use std::i64;

fn main() {
    let raw = "0x1f";
    let without_prefix = raw.trim_start_matches("0x");
    let z = i64::from_str_radix(without_prefix, 16);
    println!("{:?}", z);
}