How to use the sodium-native.crypto_box_SEALBYTES function in sodium-native

function unseal(cipher, publicKey, secretKey) {
  if (cipher.length < sodium.crypto_box_SEALBYTES) return null
  var msg = new Buffer(cipher.length - sodium.crypto_box_SEALBYTES)
  if (!sodium.crypto_box_seal_open(msg, cipher, publicKey, secretKey)) return null
  return msg
}

function unseal(cipher, publicKey, secretKey) {
  if (cipher.length < sodium.crypto_box_SEALBYTES) return null
  var msg = Buffer.alloc(cipher.length - sodium.crypto_box_SEALBYTES)
  if (!sodium.crypto_box_seal_open(msg, cipher, publicKey, secretKey)) return null
  return msg
}

function unseal(cipher, publicKey, secretKey) {
  if (cipher.length < sodium.crypto_box_SEALBYTES) return null
  var msg = new Buffer(cipher.length - sodium.crypto_box_SEALBYTES)
  if (!sodium.crypto_box_seal_open(msg, cipher, publicKey, secretKey)) return null
  return msg
}

export function openSealedBox(
  keyPair: EncodedEncryptionKeyPair,
  sealedBox: EncodedSealedBox
): Buffer {
  const keyPairBuffer = decodePair(keyPair)
  const sealedBoxBuffer = decode(sealedBox)
  const message = Buffer.alloc(sealedBoxBuffer.length - sodium.crypto_box_SEALBYTES)
  const success = sodium.crypto_box_seal_open(
    message,
    sealedBoxBuffer,
    keyPairBuffer.publicKey,
    keyPairBuffer.secretKey
  )
  if (!success) throw new Error('Unable to open sealed box')
  return message
}

function seal(msg, publicKey) {
  var cipher = new Buffer(msg.length + sodium.crypto_box_SEALBYTES)
  sodium.crypto_box_seal(cipher, msg, publicKey)
  return cipher
}

function seal(msg, publicKey) {
  var cipher = Buffer.alloc(msg.length + sodium.crypto_box_SEALBYTES)
  sodium.crypto_box_seal(cipher, msg, publicKey)
  return cipher
}