# Module `iota::hex` HEX (Base16) encoding utility. - [Constants](#@Constants_0) - [Function `encode`](#iota_hex_encode) - [Function `decode`](#iota_hex_decode) - [Function `decode_byte`](#iota_hex_decode_byte)

use std::vector;

## Constants

const EInvalidHexLength: u64 = 0;

const ENotValidHexCharacter: u64 = 1;

Vector of Base16 values from 00 to FF

const HEX: vector<vector<u8>> = vector[vector[48, 48], vector[48, 49], vector[48, 50], vector[48, 51], vector[48, 52], vector[48, 53], vector[48, 54], vector[48, 55], vector[48, 56], vector[48, 57], vector[48, 97], vector[48, 98], vector[48, 99], vector[48, 100], vector[48, 101], vector[48, 102], vector[49, 48], vector[49, 49], vector[49, 50], vector[49, 51], vector[49, 52], vector[49, 53], vector[49, 54], vector[49, 55], vector[49, 56], vector[49, 57], vector[49, 97], vector[49, 98], vector[49, 99], vector[49, 100], vector[49, 101], vector[49, 102], vector[50, 48], vector[50, 49], vector[50, 50], vector[50, 51], vector[50, 52], vector[50, 53], vector[50, 54], vector[50, 55], vector[50, 56], vector[50, 57], vector[50, 97], vector[50, 98], vector[50, 99], vector[50, 100], vector[50, 101], vector[50, 102], vector[51, 48], vector[51, 49], vector[51, 50], vector[51, 51], vector[51, 52], vector[51, 53], vector[51, 54], vector[51, 55], vector[51, 56], vector[51, 57], vector[51, 97], vector[51, 98], vector[51, 99], vector[51, 100], vector[51, 101], vector[51, 102], vector[52, 48], vector[52, 49], vector[52, 50], vector[52, 51], vector[52, 52], vector[52, 53], vector[52, 54], vector[52, 55], vector[52, 56], vector[52, 57], vector[52, 97], vector[52, 98], vector[52, 99], vector[52, 100], vector[52, 101], vector[52, 102], vector[53, 48], vector[53, 49], vector[53, 50], vector[53, 51], vector[53, 52], vector[53, 53], vector[53, 54], vector[53, 55], vector[53, 56], vector[53, 57], vector[53, 97], vector[53, 98], vector[53, 99], vector[53, 100], vector[53, 101], vector[53, 102], vector[54, 48], vector[54, 49], vector[54, 50], vector[54, 51], vector[54, 52], vector[54, 53], vector[54, 54], vector[54, 55], vector[54, 56], vector[54, 57], vector[54, 97], vector[54, 98], vector[54, 99], vector[54, 100], vector[54, 101], vector[54, 102], vector[55, 48], vector[55, 49], vector[55, 50], vector[55, 51], vector[55, 52], vector[55, 53], vector[55, 54], vector[55, 55], vector[55, 56], vector[55, 57], vector[55, 97], vector[55, 98], vector[55, 99], vector[55, 100], vector[55, 101], vector[55, 102], vector[56, 48], vector[56, 49], vector[56, 50], vector[56, 51], vector[56, 52], vector[56, 53], vector[56, 54], vector[56, 55], vector[56, 56], vector[56, 57], vector[56, 97], vector[56, 98], vector[56, 99], vector[56, 100], vector[56, 101], vector[56, 102], vector[57, 48], vector[57, 49], vector[57, 50], vector[57, 51], vector[57, 52], vector[57, 53], vector[57, 54], vector[57, 55], vector[57, 56], vector[57, 57], vector[57, 97], vector[57, 98], vector[57, 99], vector[57, 100], vector[57, 101], vector[57, 102], vector[97, 48], vector[97, 49], vector[97, 50], vector[97, 51], vector[97, 52], vector[97, 53], vector[97, 54], vector[97, 55], vector[97, 56], vector[97, 57], vector[97, 97], vector[97, 98], vector[97, 99], vector[97, 100], vector[97, 101], vector[97, 102], vector[98, 48], vector[98, 49], vector[98, 50], vector[98, 51], vector[98, 52], vector[98, 53], vector[98, 54], vector[98, 55], vector[98, 56], vector[98, 57], vector[98, 97], vector[98, 98], vector[98, 99], vector[98, 100], vector[98, 101], vector[98, 102], vector[99, 48], vector[99, 49], vector[99, 50], vector[99, 51], vector[99, 52], vector[99, 53], vector[99, 54], vector[99, 55], vector[99, 56], vector[99, 57], vector[99, 97], vector[99, 98], vector[99, 99], vector[99, 100], vector[99, 101], vector[99, 102], vector[100, 48], vector[100, 49], vector[100, 50], vector[100, 51], vector[100, 52], vector[100, 53], vector[100, 54], vector[100, 55], vector[100, 56], vector[100, 57], vector[100, 97], vector[100, 98], vector[100, 99], vector[100, 100], vector[100, 101], vector[100, 102], vector[101, 48], vector[101, 49], vector[101, 50], vector[101, 51], vector[101, 52], vector[101, 53], vector[101, 54], vector[101, 55], vector[101, 56], vector[101, 57], vector[101, 97], vector[101, 98], vector[101, 99], vector[101, 100], vector[101, 101], vector[101, 102], vector[102, 48], vector[102, 49], vector[102, 50], vector[102, 51], vector[102, 52], vector[102, 53], vector[102, 54], vector[102, 55], vector[102, 56], vector[102, 57], vector[102, 97], vector[102, 98], vector[102, 99], vector[102, 100], vector[102, 101], vector[102, 102]];

## Function `encode` Encode bytes in lowercase hex

public fun encode(bytes: vector<u8>): vector<u8>

Implementation

public fun encode(bytes: vector<u8>): vector<u8> {
    let (mut i, mut r, l) = (0, vector[], bytes.length());
    let hex_vector = HEX;
    while (i < l) {
        r.append(hex_vector[bytes[i] as u64]);
        i = i + 1;
    };
    r
}

## Function `decode` Decode hex into bytes Takes a hex string (no 0x prefix) (e.g. b"0f3a") Returns vector of bytes that represents the hex string (e.g. x"0f3a") Hex string can be case insensitive (e.g. b"0F3A" and b"0f3a" both return x"0f3a") Aborts if the hex string does not have an even number of characters (as each hex character is 2 characters long) Aborts if the hex string contains non-valid hex characters (valid characters are 0 - 9, a - f, A - F)

public fun decode(hex: vector<u8>): vector<u8>

Implementation

public fun decode(hex: vector<u8>): vector<u8> {
    let (mut i, mut r, l) = (0, vector[], hex.length());
    assert!(l % 2 == 0, EInvalidHexLength);
    while (i < l) {
        let decimal = decode_byte(hex[i]) * 16 + decode_byte(hex[i + 1]);
        r.push_back(decimal);
        i = i + 2;
    };
    r
}

## Function `decode_byte`

fun decode_byte(hex: u8): u8

Implementation

fun decode_byte(hex: u8): u8 {
    if (/* 0 .. 9 */ 48 <= hex && hex < 58) {
        hex - 48
    } else if (/* A .. F */ 65 <= hex && hex < 71) {
        10 + hex - 65
    } else if (/* a .. f */ 97 <= hex && hex < 103) {
        10 + hex - 97
    } else {
        abort ENotValidHexCharacter
    }
}