Big number to HEX in golang

Question

I'm trying to convert big numbers (big.Int or even better big.Rat) to hex values.

I'm always having issue converting number when they are negative 0xff..xx or Fixed numbers.

Is there a way to do that?

`big.Int` has a `Text()` function that converts the number to a string in a given base. To create a hex string, use `value.Text(16)`. Will that do what you want? — Andy Schweig, Dec 25 '16 at 22:07

Yandry Pozo · Accepted Answer · 2021-09-16T17:32:51.360

14

Not sure what kind of issues are you having, but big.Int, big.Float and big.Rat implement the fmt.Formatter interface, you can use the printf family with the %x %X to convert to hexadecimal string representation, example:

package main

import (
    "fmt"
    "math/big"
)

func toHexInt(n *big.Int) string {
    return fmt.Sprintf("%x", n) // or %x or upper case
}

func toHexRat(n *big.Rat) string {
    return fmt.Sprintf("%x", n) // or %x or upper case
}

func main() {
    a := big.NewInt(-59)
    b := big.NewInt(59)

    fmt.Printf("negative int lower case: %x\n", a)
    fmt.Printf("negative int upper case: %X\n", a) // %X for upper case

    fmt.Println("using Int function:", toHexInt(b))

    f := big.NewRat(3, 4) // fraction: 3/4

    fmt.Printf("rational lower case: %x\n", f)
    fmt.Printf("rational lower case: %X\n", f)

    fmt.Println("using Rat function:", toHexRat(f))
}

https://play.golang.org/p/BVh7wAYfbF

edited Sep 16 '21 at 17:32

answered Dec 25 '16 at 22:14

Yandry Pozo

4,505
3
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27

well for example shouldn't -54 be FFFFFFFFFFFFFFCA or FFCA instead of -34 ? maybe something i didn't get – Cam.phiefr Dec 26 '16 at 00:01
not sure where did you get that representation, at least what I know for all the languages in the **C** family is they sacrifice the first bit to represent the sign, that's why we have unsigned ints vs. ints, but if you want to know the internals you may check [here](http://stackoverflow.com/questions/37582550/golang-twos-complement-and-fmt-printf) Also in this case we're referring to big numbers and internally they're stored in a slice or list 'cause they don't fit in a regular register, so not sure how useful may be having the internal representation of that array – Yandry Pozo Dec 26 '16 at 04:12
-54 (base 10) would be -36 (base 16) . FFCA would be the twos complement representation. Many objects like big.Int like to keep the details of how they store data a secret. Not because they don't want to share but they want to be able to change the implementation without breaking their users code. – brian beuning Dec 28 '16 at 00:00
That method will strip leading whitespace. So `0x0ABC` will get you the hex string `abc`. That may not be what you want. – Jeffrey Goldberg May 16 '22 at 14:50

Ramtin Heidarrezaei · Answer 2 · 2022-05-24T09:45:43.310

-1

package main

import (
    "github.com/sirupsen/logrus"
)



hex := "0x00000000000000000000000000000000000000000000392cbab546b0ccc00000"
n := new(big.Int)
n.SetString(hex, 0)
logrus.Info(n.String())

edited May 24 '22 at 09:45

answered May 24 '22 at 09:41

Ramtin Heidarrezaei

1
2

1

Welcome to Stack Overflow! While this code may solve the question, including an explanation of how and why this solves the problem would really help to improve the quality of your post, and probably result in more up-votes. Remember that you are answering the question for readers in the future, not just the person asking now. Please edit your answer to add explanations and give an indication of what limitations and assumptions apply. – Matt Andruff May 25 '22 at 13:38

Big number to HEX in golang

2 Answers2