pezkuwi-api/packages/papi-utils/upstream-src/hex.ts

// https://jsben.ch/uWZw3
const HEX_STR = "0123456789abcdef"
export function toHex(bytes: Uint8Array): string {
  const result = new Array<string>(bytes.length + 1)

  result[0] = "0x"

  for (let i = 0; i < bytes.length; ) {
    const b = bytes[i++]
    result[i] = HEX_STR[b >> 4] + HEX_STR[b & 15]
  }

  return result.join("")
}

// https://jsben.ch/URe1X
const HEX_MAP: Record<string, number> = {
  0: 0,
  1: 1,
  2: 2,
  3: 3,
  4: 4,
  5: 5,
  6: 6,
  7: 7,
  8: 8,
  9: 9,
  a: 10,
  b: 11,
  c: 12,
  d: 13,
  e: 14,
  f: 15,
  A: 10,
  B: 11,
  C: 12,
  D: 13,
  E: 14,
  F: 15,
}
export function fromHex(hexString: string): Uint8Array {
  const isOdd = hexString.length % 2
  const base = (hexString[1] === "x" ? 2 : 0) + isOdd
  const nBytes = (hexString.length - base) / 2 + isOdd
  const bytes = new Uint8Array(nBytes)

  if (isOdd) bytes[0] = 0 | HEX_MAP[hexString[2]]

  for (let i = 0; i < nBytes; ) {
    const idx = base + i * 2
    const a = HEX_MAP[hexString[idx]]
    const b = HEX_MAP[hexString[idx + 1]]
    bytes[isOdd + i++] = (a << 4) | b
  }

  return bytes
}