getConstantDecoder function

FixedSizeDecoder<void> getConstantDecoder(Uint8List constant)

Returns a decoder that verifies a predefined constant byte sequence.

This decoder reads the next bytes and checks that they match the provided constant. If the bytes differ, it throws an error.

Implementation

FixedSizeDecoder<void> getConstantDecoder(Uint8List constant) {
  return FixedSizeDecoder<void>(
    fixedSize: constant.length,
    read: (bytes, offset) {
      if (!containsBytes(bytes, constant, offset)) {
        // Build hex strings inline to avoid dependency on codecs_strings.
        final hexConstant = _toHex(constant);
        final hexData = _toHex(bytes);
        throw SolanaError(SolanaErrorCode.codecsInvalidConstant, {
          'hexConstant': hexConstant,
          'hexData': hexData,
          'offset': offset,
        });
      }
      return (null, offset + constant.length);
    },
  );
}