Function mut_from_prefix_suffix 

pub(crate) fn mut_from_prefix_suffix<T: FromBytes + IntoBytes + KnownLayout + ?Sized>(
    source: &mut [u8],
    meta: Option<T::PointerMetadata>,
    cast_type: CastType,
) -> Result<(&mut T, &mut [u8]), CastError<&mut [u8], T>>

Interprets the given affix of the given bytes as a &mut Self without copying.

This method computes the largest possible size of Self that can fit in the prefix or suffix bytes of source, then attempts to return both a reference to those bytes interpreted as a Self, and a reference to the excess bytes. If there are insufficient bytes, or if that affix of source is not appropriately aligned, this returns Err.