Issues with Fw::Buffers in Unit Tests

[EbenezerA99]

Hello,

I am working on writing a unit test for a component(fprime v3.1.1) and I'm seeing some weird issues when serializing data into a Fw::Buffer.

A snipped of my code is shown below:

    Fw::Buffer data(nullptr, 32);
    Fw::SerializeStatus status = data.getSerializeRepr().serialize(apid);
    data.setSize(sizeof(apid));
    FW_ASSERT(status == Fw::FW_SERIALIZE_OK, status);

The code asserts with status 2 which corresponds to FW_SERIALIZE_NO_ROOM_LEFT, //!< No room left in the buffer to serialize data even when apid is a U16(2 bytes)...

This error happens regardless of whether I am serializing data into a buffer in my Tester.cpp file or my component's cpp file.

Does anyone have any idea why this might be happening?

[EbenezerA99]

Have I made a mistake in how I am serializing data into a buffer?

[timcanham]

Without running the test code, I see one issue:

Fw::Buffer data(nullptr, 32);

Fw::Buffer requires real memory to back it, not a null pointer. Without a non-null pointer, the underlying serialization buffer initializes to size 0.

[EbenezerA99]

Yes this makes sense ofc! I changed the first line to this and it now works!

U8 *const dataArr = new U8[100];
memset(dataArr, 0, 100);
Fw::Buffer data(dataArr, 100);

[timcanham]

Good! Now just make sure you delete the memory when the Fw::Buffer is out of scope. 😀 A typical F Prime pattern is to use Svc/BufferManager to allocate and manage memory buffers. You ask it for an Fw::Buffer with the right amount of memory, and then return it when you are done. It avoids dynamic memory allocation while cycling software.

https://nasa.github.io/fprime/UsersGuide/best/dynamic-memory.html

[EbenezerA99]

Yup, sounds good! We use this pattern for our actual component cpp, but I just needed to create a buffer in my unit test Tester.cpp file! I appreciate the quick responses!