random

fn random(userdata: ?*anyopaque, buffer: []u8) void {
    const ev: *Evented = @ptrCast(@alignCast(userdata));
    var thread: *Thread = .current();
    if (!thread.csprng.isInitialized()) {
        @branchHint(.unlikely);
        var seed: [Csprng.seed_len]u8 = undefined;
        {
            const ev_io = ev.io();
            ev.csprng_mutex.lockUncancelable(ev_io);
            defer ev.csprng_mutex.unlock(ev_io);
            if (!ev.csprng.isInitialized()) {
                @branchHint(.unlikely);
                var cancel_region: CancelRegion = .initBlocked();
                defer cancel_region.deinit();
                ev.urandomReadAll(&cancel_region, &seed) catch |err| switch (err) {
                    error.Canceled => unreachable, // blocked
                    else => fallbackSeed(ev, &seed),
                };
                ev.csprng.rng = .init(seed);
                thread = .current();
            }
            ev.csprng.rng.fill(&seed);
        }
        if (!thread.csprng.isInitialized()) {
            @branchHint(.likely);
            thread.csprng.rng = .init(seed);
        } else thread.csprng.rng.addEntropy(&seed);
    }
    thread.csprng.rng.fill(buffer);
}