Reject non-positive lengths in RingBuffer<T>

[matt-edmondson]

Fixes #50

Problem

RingBuffer<T> passed length straight to AllocateBuffer with no guard, unlike DelayLine(int maxDelaySamples) and SpscRingBuffer<T>(int capacity) in the same directory, which both call ArgumentOutOfRangeException.ThrowIfNegativeOrZero up front.

• new RingBuffer<int>(0) succeeded silently (Capacity 0, backing array T[0]), then the first PushBack threw an unhandled IndexOutOfRangeException instead of a clear ArgumentOutOfRangeException at construction time.
• new RingBuffer<int>(-1) was likewise accepted — both NextPower2(0) and NextPower2(-1) evaluate to 0 — and crashed the same way, leaving Length at -1 internally.
• RingBuffer(T value, int length) was worse: with a negative length the prefill loop never ran, so the object was constructed with a negative internal Length and no error at all.

Change

The guard goes in AllocateBuffer, so all three constructors reject length <= 0 immediately. That also closes the same hole in Resize(int) and Resample(int), which share the allocation path and accepted non-positive lengths with identical consequences. Every affected parameter is named length, so the thrown ParamName is correct at each public entry point.

XML docs on the three constructors, Resize and Resample now carry the matching <exception> element.

Tests

Six tests added to RingBufferTests.cs:

Test	Covers
Constructor_NonPositiveLength_Throws	RingBuffer<int>(0), RingBuffer<int>(-1)
Constructor_PrefillValue_NonPositiveLength_Throws	RingBuffer<int>(42, 0 / -1)
Constructor_PrefillItems_NonPositiveLength_Throws	RingBuffer<int>(items, 0 / -1)
Resize_NonPositiveLength_Throws	Resize(0), Resize(-1)
Resample_NonPositiveLength_Throws	Resample(0), Resample(-1)
Constructor_MinimumLength_IsUsable	boundary guard that length == 1 still works

The five validation tests were confirmed to fail without the fix — reverting the guard and re-running gives failed: 5, succeeded: 358. With the guard restored: 363/363 pass, and no existing test or assertion was altered.

The library also builds clean in Release across all five target frameworks (net10.0, net9.0, net8.0, netstandard2.1, netstandard2.0) with 0 warnings — ThrowIfNegativeOrZero resolves via the same polyfill the sibling buffers already depend on.

🤖 Generated with Claude Code

https://claude.ai/code/session_019Z6jU64bBLVThqNZiXkL3c

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Generated by Claude Code

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
100.0% Coverage on New Code
0.0% Duplication on New Code

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