drain

fn drain(w: *Writer, data: []const []const u8, splat: usize) Writer.Error!usize {
    const c: *Client = @alignCast(@fieldParentPtr("writer", w));
    const output = c.output;
    const ciphertext_buf = try output.writableSliceGreedy(min_buffer_len);
    var ciphertext_end: usize = 0;
    var total_clear: usize = 0;
    done: {
        {
            const buf = w.buffered();
            const prepared = prepareCiphertextRecord(c, ciphertext_buf[ciphertext_end..], buf, .application_data);
            total_clear += prepared.cleartext_len;
            ciphertext_end += prepared.ciphertext_end;
            if (prepared.cleartext_len < buf.len) break :done;
        }
        for (data[0 .. data.len - 1]) |buf| {
            const prepared = prepareCiphertextRecord(c, ciphertext_buf[ciphertext_end..], buf, .application_data);
            total_clear += prepared.cleartext_len;
            ciphertext_end += prepared.ciphertext_end;
            if (prepared.cleartext_len < buf.len) break :done;
        }
        const buf = data[data.len - 1];
        for (0..splat) |_| {
            const prepared = prepareCiphertextRecord(c, ciphertext_buf[ciphertext_end..], buf, .application_data);
            total_clear += prepared.cleartext_len;
            ciphertext_end += prepared.ciphertext_end;
            if (prepared.cleartext_len < buf.len) break :done;
        }
    }
    output.advance(ciphertext_end);
    return w.consume(total_clear);
}