@li0ard/tsemrtd
Version:
simple library for eMRTD. supports browsers, node, bun and more!
55 lines (54 loc) • 1.87 kB
JavaScript
// Code from @noble/hashes/utils.ts
const hexes = Array.from({ length: 256 }, (_, i) => i.toString(16).padStart(2, '0'));
const asciis = { _0: 48, _9: 57, A: 65, F: 70, a: 97, f: 102 };
const asciiToBase16 = (ch) => {
if (ch >= asciis._0 && ch <= asciis._9)
return ch - asciis._0; // '2' => 50-48
if (ch >= asciis.A && ch <= asciis.F)
return ch - (asciis.A - 10); // 'B' => 66-(65-10)
if (ch >= asciis.a && ch <= asciis.f)
return ch - (asciis.a - 10); // 'b' => 98-(97-10)
return;
};
/**
* Convert byte array to hex string.
* @example bytesToHex(Uint8Array.from([0xca, 0xfe, 0x01, 0x23])) // 'cafe0123'
*/
export const bytesToHex = (bytes) => {
let hex = '';
for (let i = 0; i < bytes.length; i++) {
hex += hexes[bytes[i]];
}
return hex;
};
/**
* Convert hex string to byte array.
* @example hexToBytes('cafe0123') // Uint8Array.from([0xca, 0xfe, 0x01, 0x23])
*/
export const hexToBytes = (hex) => {
const hl = hex.length;
const al = hl / 2;
if (hl % 2)
throw new Error('hex string expected, got unpadded hex of length ' + hl);
const array = new Uint8Array(al);
for (let ai = 0, hi = 0; ai < al; ai++, hi += 2) {
const n1 = asciiToBase16(hex.charCodeAt(hi));
const n2 = asciiToBase16(hex.charCodeAt(hi + 1));
if (n1 === undefined || n2 === undefined) {
const char = hex[hi] + hex[hi + 1];
throw new Error('hex string expected, got non-hex character "' + char + '" at index ' + hi);
}
array[ai] = n1 * 16 + n2; // multiply first octet, e.g. 'a3' => 10*16+3 => 160 + 3 => 163
}
return array;
};
/**
* Convert byte array to ASCII string.
*/
export const bytesToAscii = (bytes) => {
let string = '';
for (let i of bytes) {
string += String.fromCharCode(i);
}
return string;
};