Function std::io::copy::generic_copy

pub(crate) fn generic_copy<R, W>(reader: &mut R, writer: &mut W) -> Result<u64>where
    R: Read + ?Sized,
    W: Write + ?Sized,

The userspace read-write-loop implementation of io::copy that is used when OS-specific specializations for copy offloading are not available or not applicable.