Derive Macro BitString 

#[derive(BitString)]
{
    // Attributes available to this derive:
    #[asn1]
}

Derive the BitString on a struct with bool fields.

use der::BitString;

#[derive(BitString)]
pub struct MyFlags {
    pub flag_0: bool,
    pub flag_1: bool,
    pub flag_2: bool,
}