C# track, Hyper-optimized Telemetry exercise - unclear instructions

[vlabensky-sana]

Hello,

In the Hyper-optimized Telemetry exercise of the C# track the last paragraph seems to give vague sentence which contradicts the task.

Here's the exercise

The last paragraph goes like this:

2. Decode a received buffer

Please implement the static method TelemetryBuffer.FromBuffer() to decode the buffer received and return the value in the form of a long.

TelemetryBuffer.FromBuffer(new byte[] {0xfc, 0xff, 0xff, 0xff, 0x7f, 0x0, 0x0, 0x0, 0x0 })
// => 2147483647

If the prefix byte is not one of -8, -4, -2, 2 or 4 then 0 should be returned.

In the last sentence it says that if the prefix byte is not one of -8, -4, -2, 2 or 4 then 0 should be returned. But at the same time in the example above it has the prefix byte 0xFC, which is 252, which is none of the numbers listed in the last sentence, and the returned type is expected to be 2147483647 which contradicts the 0 from the last sentence.

So this last sentence - what is it supposed to mean? Perhaps it needs to re-phrased to make it more clear for the reader.

Thanks!

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[ErikSchierboom]

So this last sentence - what is it supposed to mean? Perhaps it needs to re-phrased to make it more clear for the reader.

Do you perhaps have a better suggestion for how to handle this?

[vlabensky-sana]

As I understood the task, the only valid values of the prefix byte are these:

• for signed short: 254
• for unsigned short: 2
• for signed int: 252
• for unsigned int: 4
• for signed long: 248
• for unsigned long: 8.

If that's correct it means that if any of 2, 4, 8, 248, 252 or 254 is passed as a prefix byte to TelemetryBuffer.FromBuffer method then the method will return correct numeric value. If the prefix byte is none of these six values, then the method will return 0. If what I just said is correct then shouldn't the last sentence say this:

If the prefix byte is not one of 2, 4, 8, 248, 252 or 254 then 0 should be returned.

instead of this If the prefix byte is not one of -8, -4, -2, 2 or 4 then 0 should be returned.?

Or perhaps it can be removed completely. Or it may be less specific, like If the prefix byte is of unexpected value then 0 should be returned.

[ErikSchierboom]

If the prefix byte is of unexpected value then 0 should be returned.

I like that! Would you be willing to submit a PR?

[vlabensky-sana]

Took me a while to get back to it, sorry. Here's the PR #2163.

[michalporeba]

@ErikSchierboom The PR has been merged, I think this issue can be closed.