RingBuffer.Resample throws IndexOutOfRangeException and loses the buffer's contents for ~46k+ elements (int overflow)

[matt-edmondson]

What's wrong

RingBuffer<T>.Resample (Containers/RingBuffer.cs, in the resample loop) computes the source index like this:

double oldIndex = i * (oldCount - 1) / (double)Math.Max(length - 1, 1);
int index = (int)Math.Round(oldIndex);
index = Math.Min(index, oldCount - 1);

i * (oldCount - 1) is evaluated in int before the double division. Once (length - 1) * (oldCount - 1) passes int.MaxValue, the product wraps negative, so index comes out negative. Math.Min only clamps the upper end, and oldData[negative] throws.

By then AllocateBuffer(length) has already reset the buffer, so the exception also leaves it half-refilled. The original contents are lost.

Why it matters

The doc comment presents Resample as a tool for time-series and sample-rate changes. One second of 48 kHz audio is 48,000 samples, which is well past the threshold.

Repro:

foreach (int n in new[] { 46340, 46342, 48000 })
{
    var rb = new RingBuffer<int>(Enumerable.Range(0, n), n);
    try { rb.Resample(n); Console.WriteLine($"n={n}: ok"); }
    catch (Exception e) { Console.WriteLine($"n={n}: {e.GetType().Name}; Count={rb.Count} (was {n})"); }
}
// also: new RingBuffer<int>(Enumerable.Range(0, 1000), 1000).Resample(3_000_000) -> IndexOutOfRangeException

Output:

n=46340: ok
n=46342: IndexOutOfRangeException; Count=46341 (was 46342)
n=48000: IndexOutOfRangeException; Count=44741 (was 48000)

Expected: every size succeeds, ending with Count == length and the last element equal to the old last element. The only documented exception is ArgumentOutOfRangeException for length < 1.

Suggested fix

double oldIndex = (double)i * (oldCount - 1) / Math.Max(length - 1, 1);
int index = Math.Clamp((int)Math.Round(oldIndex), 0, oldCount - 1);

Acceptance criteria

• Resampling a 50,000-element buffer to the same length succeeds, and rb[^1] == 49999.
• Upsampling 1,000 elements to 3,000,000 succeeds.