How to use the safe-buffer.Buffer.byteLength function in safe-buffer

// Check message ID
  if (typeof id !== 'number') {
    stream.emit('error', new Error('Invalid messageId'))
    return false
  } else {
    length += 2
  }
  // Check unsubs
  if (typeof unsubs === 'object' && unsubs.length) {
    for (var i = 0; i < unsubs.length; i += 1) {
      if (typeof unsubs[i] !== 'string') {
        stream.emit('error', new Error('Invalid unsubscriptions'))
        return false
      }
      length += Buffer.byteLength(unsubs[i]) + 2
    }
  } else {
    stream.emit('error', new Error('Invalid unsubscriptions'))
    return false
  }
  // properies mqtt 5
  var propertiesData = null
  if (version === 5) {
    propertiesData = getProperties(stream, properties)
    length += propertiesData.length
  }

  // Header
  stream.write(protocol.UNSUBSCRIBE_HEADER[1][dup ? 1 : 0][0])

  // Length

} else {
          length += will.payload.length + 2
        }
      } else {
        stream.emit('error', new Error('Invalid will payload'))
        return false
      }
    } else {
      length += 2
    }
  }

  // Username
  if (username) {
    if (username.length) {
      length += Buffer.byteLength(username) + 2
    } else {
      stream.emit('error', new Error('Invalid username'))
      return false
    }
  }

  // Password
  if (password) {
    if (password.length) {
      length += byteLength(password) + 2
    } else {
      stream.emit('error', new Error('Invalid password'))
      return false
    }
  }

PacketWriter.prototype.writeString = function(value) {
  // Typecast undefined into '' and numbers into strings
  value = value || '';
  value = value + '';

  var bytes = Buffer.byteLength(value, 'utf-8');
  this._allocate(bytes);

  this._buffer.write(value, this._offset, 'utf-8');

  this._offset += bytes;
};

throw new TypeError('The `body` option must be a plain Object or Array when the `form` or `json` option is used');
		}

		if (isFormData(body)) {
			// Special case for https://github.com/form-data/form-data
			headers['content-type'] = headers['content-type'] || `multipart/form-data; boundary=${body.getBoundary()}`;
		} else if (opts.form && canBodyBeStringified) {
			headers['content-type'] = headers['content-type'] || 'application/x-www-form-urlencoded';
			opts.body = querystring.stringify(body);
		} else if (opts.json && canBodyBeStringified) {
			headers['content-type'] = headers['content-type'] || 'application/json';
			opts.body = JSON.stringify(body);
		}

		if (is.undefined(headers['content-length']) && is.undefined(headers['transfer-encoding']) && !is.nodeStream(body)) {
			const length = is.string(opts.body) ? Buffer.byteLength(opts.body) : opts.body.length;
			headers['content-length'] = length;
		}

		// Convert buffer to stream to receive upload progress events
		// see https://github.com/sindresorhus/got/pull/322
		if (is.buffer(body)) {
			opts.body = intoStream(body);
			opts.body._buffer = body;
		}

		opts.method = (opts.method || 'POST').toUpperCase();
	}

	if (opts.hostname === 'unix') {
		const matches = /(.+?):(.+)/.exec(opts.path);

it('should return 24 bytes of entropy hex encoded', () => {
        let entropy = BITBOX.Crypto.randomBytes(24);
        assert.equal(Buffer.byteLength(entropy), 24);
      });

t.test('decoding a string of length ' + str.length, function (t) {
      var buf = Buffer.allocUnsafe(3 + Buffer.byteLength(str))
      buf[0] = 0xda
      buf.writeUInt16BE(Buffer.byteLength(str), 1)
      buf.write(str, 3)
      t.equal(encoder.decode(buf), str, 'must decode correctly')
      t.end()
    })

rtxt.encodingLength = function (data) {
  if (!data) return 2
  return (Buffer.isBuffer(data) ? data.length : Buffer.byteLength(data)) + 2
}

function writeString (stream, string) {
  var strlen = Buffer.byteLength(string)
  writeNumber(stream, strlen)

  return stream.write(string, 'utf8')
}

var body = util.removeProtocol(rule.value, true);
    var isRawFile = isRawFileProtocol(protocol);
    var reader = isRawFile ? getRawResByValue(body) : {
      statusCode: 200,
      body: body,
      headers: {
        'content-type': (rule.key ? mime.lookup(rule.key, defaultType) : defaultType) + '; charset=utf-8'
      }
    };

    if (isTplProtocol(protocol)){
      reader.realUrl = rule.matcher;
      render(reader);
    } else {
      if (!isRawFile) {
        var size = Buffer.byteLength(body);
        var range = util.parseRange(req, size);
        if (range) {
          body = Buffer.from(body);
          reader.body = body.slice(range.start, range.end + 1);
          addRangeHeaders(reader, range, size);
        }
      }
      reader = util.wrapResponse(reader);
      reader.realUrl = rule.matcher;
      res.response(reader);
    }
    return;
  }

  readFiles(util.getRuleFiles(rule), function(err, path, size) {
    if (err) {