Add LinearBufferTemplate: template class for fixed-size linear buffers

[devin-ai-integration]

Related Issue(s)	nasa#5018
Has Unit Tests (y/n)	n
Documentation Included (y/n)	y (Doxygen comments)
Generative AI was used in this contribution (y/n)	AI

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Change Description

Adds Fw::LinearBufferTemplate<int TypeId, FwSizeType MaxSize>, a header-only class template in Fw/Types/LinearBufferTemplate.hpp that provides a fixed-size LinearBufferBase subclass parameterized by serialized type ID and buffer capacity.

This is the first step toward replacing hand-coded buffer classes that all share identical structure:

// Before: ~90 lines across .hpp + .cpp per buffer type
class CmdArgBuffer final : public LinearBufferBase { /* ... */ };

// After: one line
using CmdArgBuffer = LinearBufferTemplate<FW_TYPEID_CMD_BUFF, FW_CMD_ARG_BUFFER_MAX_SIZE>;

Follows the same pattern as the existing Fw::StringTemplate<size>. Uses modern C++14 idioms: override, = default, final.

Rationale

Six concrete LinearBufferBase subclasses (CmdArgBuffer, LogBuffer, TlmBuffer, ComBuffer, ParamBuffer, SmSignalBuffer) each duplicate the same ~90 lines of boilerplate. A single template eliminates this duplication, improving readability and maintainability, and reducing the surface area for copy-paste errors (per nasa#5018).

Testing/Review Recommendations

• This PR only introduces the template header; it does not yet replace any existing buffer class. That migration can be done incrementally in follow-up PRs.
• Verify the template provides the same interface as the existing concrete classes: constructors, operator=, getCapacity(), getBuffAddr(), getBuffCapacity() (deprecated), SERIALIZED_TYPE_ID, SERIALIZED_SIZE.
• The deprecated getBuffCapacity() is included for backward compatibility when using aliases eventually replace the hand-coded classes.

Future Work

• Replace each hand-coded buffer class with a using alias of LinearBufferTemplate (one PR per class, or batched).
• Consider similar unification for the concrete string classes using StringTemplate.

AI Usage (see policy)

AI (Devin) was used to analyze the existing buffer class hierarchy, identify the common pattern, and generate the template class following established codebase conventions (StringTemplate pattern, modern C++ idioms). IAMAI

Link to Devin session: https://nasa-jpl-demo.devinenterprise.com/sessions/469e7bbc20f145f48eef872b618ecee2

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[devin-ai-integration]

Original prompt from michael.d.starch

Can you please start this issue by identifying or making the template class? nasa#5018. Make sure it conforms to all the modern C++ guidelines.

[devin-ai-integration]

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[devin-ai-integration]

Devin Review found 1 potential issue.

View 1 additional finding in Devin Review.

[devin-ai-integration]

🚩 Template not yet used anywhere in the codebase

The LinearBufferTemplate is introduced but not yet used to replace any existing concrete buffer class (TlmBuffer, LogBuffer, CmdArgBuffer, etc.). The comment in the usage example (Fw/Types/LinearBufferTemplate.hpp:25) shows the intended replacement pattern, but a follow-up PR would be needed to actually substitute the existing hand-coded classes. This means the template is effectively dead code until adopted. This is presumably intentional (incremental rollout), but worth confirming.

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[devin-ai-integration]

Correct — this is intentional. This PR only introduces the template (step 1 of nasa#5018). Follow-up PRs will migrate the existing concrete buffer classes to using aliases.

[github-actions]

Coverage report — base devel

No baseline branch coverage/devel found. This run becomes the seed once it lands on devel.

Overall (line): 81.22% (no baseline)
Regression threshold: 0.50% (line).

Regressions

(none over threshold)

Modules changed

(no measurable change)

New modules

Module	Line	Function	Branch
CFDP/Checksum	71.15	57.14	53.85
Drv/AsyncByteStreamBufferAdapter	100.00	100.00	100.00
Drv/ByteStreamBufferAdapter	100.00	100.00	100.00
Drv/Ip	44.32	57.38	25.36
Drv/TcpClient	75.00	100.00	47.37
Drv/TcpServer	84.72	100.00	60.00
Drv/Udp	68.09	90.91	42.86
Fw/Buffer	81.25	89.47	58.62
Fw/DataStructures	98.30	97.14	83.03
Fw/Dp	94.83	96.67	95.95
Fw/FilePacket	75.24	89.06	54.30
Fw/Log	71.43	72.41	60.00
Fw/Logger	100.00	100.00	100.00
Fw/SerializableFile	90.00	100.00	79.41
Fw/Time	88.62	85.48	86.84
Fw/Tlm	53.76	60.00	37.50
Fw/Types	54.75	57.62	34.96
Os	18.07	19.52	14.52
Os/Generic	89.10	96.30	67.18
Os/Generic/Types	92.45	91.67	82.14
Os/Posix	62.00	84.21	43.87
Svc/ActiveRateGroup	100.00	100.00	92.31
Svc/ActiveTextLogger	79.05	90.00	71.23
Svc/AssertFatalAdapter	94.74	100.00	86.67
Svc/BufferAccumulator	88.00	94.12	74.49
Svc/BufferLogger	92.62	86.96	80.46
Svc/BufferManager	99.05	100.00	83.64
Svc/BufferRepeater	91.67	100.00	75.00
Svc/ChronoTime	100.00	100.00	100.00
Svc/CmdDispatcher	96.97	91.67	91.75
Svc/CmdSequencer	93.89	97.12	84.63
Svc/CmdSplitter	100.00	100.00	100.00
Svc/ComLogger	97.37	91.67	83.91
Svc/ComSplitter	100.00	100.00	100.00
Svc/ComStub	98.51	100.00	85.19
Svc/DpCatalog	78.00	100.00	66.27
Svc/DpManager	97.44	100.00	100.00
Svc/DpWriter	97.58	90.00	97.22
Svc/FileDownlink	84.15	90.91	71.90
Svc/FileManager	88.41	93.33	82.44
Svc/FileUplink	92.35	96.55	80.95
Svc/FileWorker	90.29	100.00	84.87
Svc/FprimeDeframer	100.00	100.00	97.92
Svc/FprimeFramer	100.00	100.00	95.45
Svc/FprimeRouter	88.89	100.00	78.26
Svc/FpySequencer	86.76	99.04	76.89
Svc/GenericHub	100.00	100.00	85.64
Svc/Health	100.00	100.00	88.66
Svc/LinuxTimer	97.06	100.00	82.35
Svc/OsTime	70.00	83.33	60.98
Svc/PassiveRateGroup	100.00	100.00	89.47
Svc/PolyDb	100.00	100.00	53.57
Svc/PosixTime	100.00	100.00	75.00
Svc/PrmDb	92.75	89.47	88.24
Svc/RateGroupDriver	100.00	100.00	68.75
Svc/SeqDispatcher	73.08	80.00	71.05
Svc/StaticMemory	100.00	100.00	100.00
Svc/SystemResources	98.63	100.00	76.19
Svc/TlmChan	77.59	85.71	63.03
Svc/TlmPacketizer	92.49	100.00	77.45
Svc/Version	96.10	100.00	86.96
Utils	20.04	26.44	24.07
Utils/Types	92.11	95.83	77.08

Modules without UTs

CFDP/Checksum/GTest, Drv/ByteStreamDriverModel, Drv/Interfaces, Drv/LinuxGpioDriver, Drv/LinuxI2cDriver, Drv/LinuxSpiDriver, Drv/LinuxUartDriver, Drv/Ports, Drv/Ports/DataTypes, FppTestProject/FppTest/interfaces, FppTestProject/FppTest/topology/async, FppTestProject/FppTest/topology/components/Comp, FppTestProject/FppTest/topology/components/Framework, FppTestProject/FppTest/topology/components/Receiver, FppTestProject/FppTest/topology/components/Sender, FppTestProject/FppTest/topology/guarded, FppTestProject/FppTest/topology/ports, FppTestProject/FppTest/topology/sync, FppTestProject/FppTest/topology/top_ports, FppTestProject/FppTest/topology/types, Fw/Cmd, Fw/Com, Fw/Comp, Fw/FilePacket/GTest, Fw/Fpy, Fw/Interfaces, Fw/Obj, Fw/Port, Fw/Ports/CompletionStatus, Fw/Ports/Ready, Fw/Ports/Signal, Fw/Ports/SuccessCondition, Fw/Prm, Fw/SerializableFile/test/TestSerializable, Fw/Sm, Fw/Test, Fw/Types/GTest, Os/Models, Svc/Cycle, Svc/DpPorts, Svc/Fatal, Svc/FatalHandler, Svc/FileDownlinkPorts, Svc/FprimeProtocol, Svc/Interfaces, Svc/PassiveConsoleTextLogger, Svc/Ping, Svc/PolyIf, Svc/Ports/CommsPorts, Svc/Ports/FilePorts, Svc/Ports/OsTimeEpoch, Svc/Ports/TlmPacketizerPorts, Svc/Ports/VersionPorts, Svc/Sched, Svc/Seq, Svc/Subtopologies/CdhCore, Svc/Subtopologies/ComCcsds, Svc/Subtopologies/ComFprime, Svc/Subtopologies/ComLoggerTee, Svc/Subtopologies/DataProducts, Svc/Subtopologies/FileHandling, Svc/Types/TlmPacketizerTypes, Svc/WatchDog, TestDeploymentsProject/Ref/PingReceiver, TestDeploymentsProject/Ref/RecvBuffApp, TestDeploymentsProject/Ref/SendBuffApp, TestDeploymentsProject/Ref/Top, TestDeploymentsProject/Ref/TypeDemo, cmake/test/data/TestDeployment/TestBuildAutocoder, cmake/test/data/TestDeployment/TestChainedAutocoder, cmake/test/data/TestDeployment/TestHeaderAutocoder, cmake/test/data/TestDeployment/TestTargetAutocoder, cmake/test/data/test-fprime-library/TestLibrary/TestComponent, cmake/test/data/test-fprime-library2/TestLibrary2/TestComponent

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