Trait VmIoFill

pub trait VmIoFill {
    // Required method
    fn fill_zeros(
        &self,
        offset: usize,
        len: usize,
    ) -> Result<(), (Error, usize)>;
}

A trait that enables filling bytes (e.g., filling zeros) to a VM object.

Required Methods

fn fill_zeros(&self, offset: usize, len: usize) -> Result<(), (Error, usize)>

Writes len zeros at a specified offset.

Unlike the methods in VmIo, this method allows for short writes because len can be effectively unbounded. However, if not all bytes can be written successfully, an Err(_) will be returned with the error and the number of zeros that have been written thus far.

A slow, general implementation

Suppose that VmIo has already been implemented for the type, this method can be implemented in the following general way.

fn fill_zeros(&self, offset: usize, len: usize) -> core::result::Result<(), (Error, usize)> {
    for i in 0..len {
        match self.write_slice(offset + i, &[0u8]) {
            Ok(()) => continue,
            Err(err) => return Err((err, i)),
        }
    }
    Ok(())
}

But we choose not to provide a general, default implementation because doing so would make it too easy for a concrete type of VmIoFill to settle with a slower implementation for such a performance-sensitive operation.

Implementors

impl<S: HasVmReaderWriter> VmIoFill for S