byteweise.cpp

class VersionExchangeParser {
	VersionExchangeState state;

	uint16_t num_versions = 0;
	uint16_t current_version = 0;
	vector<Version> versions;

	LengthDecoder aes_key_length_decoder;
	length_t aes_key_length;

	LengthDecoder hash_length_decoder;
	length_t hash_length;

	void update(uint8_t const& byte) {
		switch(state) {
			case FIRST_NUM_VERSIONS:
				num_versions = byte;
				state = SECOND_NUM_VERSIONS:
				break;
			case SECOND_NUM_VERSIONS:
				num_versions |= byte << 8;
				state = MAJ_VERSION:
				break;
			case MAJ_VERSION:
				versions.push_back(Version());
				versions[current_version].major = byte;
				state = MIN_VERSION:
				break;
			case MIN_VERSION:
				versions[current_version].minor = byte;
				++current_version;
				if(current_version == num_versions) {
					state = KEYLEN:
				} else {
					state = MAJ_VERSION;
				}
				break;
			case KEYLEN:
				aes_key_length_decoder.update(byte);
				if(aes_key_length_decoder.is_finished()) {
					aes_key_length = aes_key_length_decoder.getValue();
					state = HASHLEN_VERSION;
				}
				break;
			case HASHLEN_VERSION:
				hash_length_decoder.update(byte);
				if(hash_length_decoder.is_finished()) {
					hash_length = hash_length_decoder.getValue();
					state = FINISHED;
				}
				break;
		}
	}
};

mit_buffer.cpp

class VersionExchange {
	uint16_t num_versions = 0;
	vector<Version> versions;
	length_t aes_key_length;
	length_t hash_length;

	void parse(Buffer& buf) {
		num_versions = buf.read();
		num_versions |= buf.read() << 8;

		for(uint16_t i = 0; i < num_versions; ++i) {
			versions.push_back(Version());
			versions[i].major = buf.read();
			versions[i].minor = buf.read();
		}

		aes_key_length = parse_length_t(buf);
		hash_length    = parse_length_t(buf);
	}
}