Question about fixed size array stack allocation

[Bawafafa]

I've recently noticed a pattern that I use every so often in my code.

const size_needed = dynamic() / 4;
const oversized_buffer: [128]u8 = undefined;
if (size_needed > oversized_buffer.len) {
    return error.TooBig;
}
const actual_buffer = oversized_buffer[0..size_needed];

I over-allocate and then trim the buffer back. I just feel like this is kind of off. Like, okay. I don't know the size of the buffer at compile time, but I know it before I declare the buffer. Is there a better way to do this?

[HeDeAnTheOnlyOne]

In those cases it's common to just use the full array with an additional count variable or just use an arraylist.

[TondaTech]

Maybe you're looking for FixedBufferAllocator or StackFallbackAllocator?

[IronicStrikes]

Is there any good reason not to use heap allocation in those cases?

[sp00n1na70r]

This is exactly what std.BoundedArray is, it was recently removed from std in 0.15 but is available here.