impossible borrows in `l3_restore_reservoir` about rinimp3 HOT 1 OPEN

So we have:

#[derive(Copy, Clone, Debug, Default)]
#[repr(C)]
pub struct Bs<'a> {
    pub buf: &'a [u8],
    pub pos: i32,
    pub limit: i32,
}


#[derive(Copy, Clone)]
#[repr(C)]
pub struct Mp3DecScratch<'a> {
    pub bs: Bs<'a>,
    pub maindata: [u8; 2815],
    pub gr_info: [L3GrInfo; 4],
    pub grbuf: [[f32; 576]; 2],
    pub scf: [f32; 40],
    pub syn: [[f32; 64]; 33],
    pub ist_pos: [[u8; 39]; 2],
}

And per the report, the slice in the Bs is initialized to point to maindata, which results in a self-borrowing struct, which is verboten.

I can think of a few potential solutions. For one, maindata is not actually used in very many places; perhaps we could just stuff it into the Bs struct and have an index instead of a slice.

It also looks like Bs is used almost exclusively to pass to get_bits(), there are very few places where buf is accessed directly outside that. So rearranging things might not be such a global change after all.

We're not gonna bother with nightly; I'd use heap allocation first.

from rinimp3.