decodeVarint static method

(int, int) decodeVarint(List<int> byteint)

Decodes a variable-length byte array into an integer value according to Bitcoin's variable-length integer encoding scheme.

Implementation

static (int, int) decodeVarint(List<int> byteint) {
  final int ni = byteint[0];
  int size = 0;

  if (ni < 253) {
    return (ni, 1);
  }

  if (ni == 253) {
    size = 2;
  } else if (ni == 254) {
    size = 4;
  } else {
    size = 8;
  }

  final BigInt value = BigintUtils.fromBytes(
    byteint.sublist(1, 1 + size),
    byteOrder: Endian.little,
  );
  if (!value.isValidInt) {
    throw ArgumentException.invalidOperationArguments(
      "decodeVarint",
      name: "byteint",
      reason: "Unable to read variable-length in this environment.",
    );
  }
  return (value.toInt(), size + 1);
}