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Svc::BufferRepeater: Buffer Repeater (Passive Component)

1. Introduction

The BufferRepeater component is designed to take in an Fw::buffer port call and repeat it to multiple output ports. New memory is allocated from a Svc::BufferManager and the data is copied to ensure that each downstream component has full ownership of its data. The original buffer is deallocated. Users call configure to set the response of the component when allocation requests fail.

2. Requirements

Name Description Validation
BUFFER_REPEATER_01 The buffer repeater shall accept incoming Fw::Buffer port calls Unit Test
BUFFER_REPEATER_02 The buffer repeater shall copy the incoming data before each repeated send Unit Test
BUFFER_REPEATER_03 The buffer repeater shall only send a copy to connected components Unit Test
BUFFER_REPEATER_04 The buffer repeater shall have a configurable response to allocation failures Unit Test

3. Design

The buffer repeater has a single portIn port of type Fw.BufferSend and an array of portOut ports of the same type. Each port call received on portIn is repeated to each connected portOut port. These repetitions emit a copy of the Fw::Buffer data.

3.1 Ports

Svc::BufferRepeater has the following ports:

Kind Name Port Type Usage
sync input portIn Fw.BufferSend Port for receiving initial Fw::Buffer
output portOut [BufferRepeaterOutputPorts] Fw.BufferSend Port array for repeating Fw::Buffers
output deallocate Fw.BufferSend Deallocate the original buffer
output allocate Fw.BufferGet Port for allocating new memory
event Log Fw.Log Port for emitting events
text event LogText Fw.LogText Port for emitting text events
time get Time Fw.Time Port for getting the time

3.1.1 portIn handler

The portIn port handler receives an Fw::Buffer data type and a port number. For each connected portOut port it allocates new memory large enough to hold a copy of the Fw::Buffer data via the allocate port, copies the data to the new invocation, and sends it to the active portOut port. This continues until each portOut port has been tried and at the end it returns the original buffer via deallocate.

Should an allocation fail, portOut is not called and an event may be emitted (see below).

3.2 Events

Name Description
AllocationSoftFailure WARNING_HI indicating allocation failure when configured to WARNING_ON_OUT_OF_MEMORY
AllocationHardFailure FATAL indicating allocation failure when configured to FATAL_ON_OUT_OF_MEMORY

4. Configuration

Buffer repeater maximum output ports are configured using AcConstants.fpp as shown below:

constant BufferRepeaterOutputPorts = 10

The component's response to allocation failures is configured with a call to the configure method during system initialization. Possible values include:

Setting Description
NO_RESPONSE_ON_OUT_OF_MEMORY The component drops the portOut call and otherwise takes no response action
WARNING_ON_OUT_OF_MEMORY The component drops the portOut call and emits a WARNING_HI event
FATAL_ON_OUT_OF_MEMORY The component drops the portOut call and emits a FATAL event 
bufferRepeater.configure(Svc::BufferRepeater::FATAL_ON_OUT_OF_MEMORY);