Drv::ByteStreamDriverModel Byte Stream Driver Model

Drv::ByteStreamDriverModel Byte Stream Driver Model

The byte stream driver is a generic model for drivers implementing a "stream of bytes" interface. Typically these drivers operate with an outgoing stream and an incoming stream. The outgoing stream is represented by the "send" port and the incoming stream is either polled using the "poll" port or return asynchronously via the "readCallback" port.

Design

The manager component (typically the ground interface) initiates the transfer of send data by calling the "send" port. The caller will provide a Fw::Buffer containing the data to send and the port call will return a status of that send. These responses are an enumeration whose values are described in the following table:

Value	Description	Buffer Ownership
Drv::SEND_OK	Send functioned normally.	Ownership of the Fw::Buffer passes to the byte stream driver.
Drv::SEND_RETRY	Send should be retried, but a subsequent send should return SEND_OK.	The caller retains ownership of the Fw::Buffer.
Drv::SEND_ERROR	Send produced an error, future sends likely to fail.	Ownership of the Fw::Buffer passes to the byte stream driver.

Note: in either formation described below, send will operate as described here.

Callback Formation

In the callback formation, the byte stream driver component initiates the transfer of received data by calling the "readCallback" output port. This port transfers any read data in a Fw::Buffer along with a status for the receive. This status is an enumeration whose values are described in the following table:

Value	Description
Drv::RECV_OK	Receive functioned normally buffer contains valid data.
Drv::RECV_ERROR	Receive produced an error and buffer contains no valid data.

The following components implement the byte stream model using a callback formation:

• DrvTcpClient: a F´ component wrapper of the tcp client
• DrvTcpServer: a F´ component wrapper of the tcp server
• DrvUdp: a F´ component wrapper of the udp

Polling Formation

In the polling formation, the manager component (typically the ground interface) initiates the transfer of received data by calling the "poll" input port. This port fills in the provided Fw::Buffer along with a status for the poll. This status is an enumeration whose values are described in the following table:

Value	Description
Drv::POLL_OK	Poll functioned normally buffer contains valid data.
Drv::POLL_RETRY	Poll should be retried and a subsequent send should return POLL_OK.
Drv::POLL_ERROR	Poll produced an error and buffer contains no valid data.

Note: there are no known implementers of the polling formation, although this formation is best suited for implementations running on baremetal machines.

Class Diagram

Requirements

Name	Description	Validation
BYTEDRV-001	The ByteStreamDriverModel shall provide the capability to send bytes	inspection
BYTEDRV-002	The ByteStreamDriverModel shall provide the capability to poll for bytes	inspection
BYTEDRV-003	The ByteStreamDriverModel shall provide the capability to produce bytes	inspection