pow

    pub fn pow(rma: *Managed, a: *const Managed, b: u32) !void {
        const needed_limbs = calcPowLimbsBufferLen(a.bitCountAbs(), b);
        const capacity_alias = limbsAliasDistinct(rma, a);
        const same_buffer = rma.limbs.ptr == a.limbs.ptr;

        try rma.ensureAliasAwareCapacity(needed_limbs, capacity_alias);
        const limbs_buffer = try rma.allocator.alloc(Limb, needed_limbs);
        defer rma.allocator.free(limbs_buffer);

        if (same_buffer) {
            const a_len = a.len();
            const tmp = try rma.allocator.alloc(Limb, a_len);
            defer rma.allocator.free(tmp);
            @memcpy(tmp[0..a_len], a.limbs[0..a_len]);
            const a_const: Const = .{ .limbs = tmp[0..a_len], .positive = a.isPositive() };
            var rma_mut = rma.toMutable();
            rma_mut.pow(a_const, b, limbs_buffer);
            rma.setMetadata(rma_mut.positive, rma_mut.len);
        } else {
            var rma_mut = rma.toMutable();
            rma_mut.pow(a.toConst(), b, limbs_buffer);
            rma.setMetadata(rma_mut.positive, rma_mut.len);
        }
    }