Sample Counter: Signed or Unsigned 32-Bit Integer?

RapidCode API
1

[RMP 8.3.1], [RMP 10.3.1]

Is the value returned from MotionController::SampleCounterGet() really a signed integer?

Here’s the method signature

virtual int32 SampleCounterGet() = 0;

Suppose RMP ran until the sample counter was 0x7FFFFFFF. After the next time slice, would the function return 0x8000000 (a negative number with a large magnitude) or would it return 0 (since a negative sample count is kind of nonsense)?

(I thought asking the question would be quicker than waiting 24.85 days to see what would happen.)

2

Yep. It is a signed 32 bit integer. The only operation done on the number is a simple ++ every sample. You can always interpret the value however you like.

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3

So, when I ++ an int32_t,

	int32_t t = 0x7FFFFFF0;
	std::cout << std::hex << t << "\n";
	for (int32_t i=0; i<32; i++) {
		t++;
		std::cout << std::hex << t << "\n";
	}

I get something like

...
7ffffffd
7ffffffe
7fffffff
80000000
80000001
80000002
80000003
...

…which also means that I could interpret the value as an unsigned integer and get the full 32 bits of sample counter space.

Is this what you’d expect from RMP?

4

For example, what will RapidSetup display for the sample counter? Will it display a negative number?

5

Yes. That is what we would expect. If you’d like to experiment, use RapidSetup->Tools->Vm3. Hit F4. Sample Counter is the 11th item in the list. Type 8000000 and hit enter.

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