asterinas/kernel/src/device/zero.rs

// SPDX-License-Identifier: MPL-2.0

#![allow(unused_variables)]

use super::*;
use crate::{
    events::IoEvents,
    fs::inode_handle::FileIo,
    prelude::*,
    process::signal::{Pollable, Poller},
};

pub struct Zero;

impl Device for Zero {
    fn type_(&self) -> DeviceType {
        DeviceType::CharDevice
    }

    fn id(&self) -> DeviceId {
        // Same value with Linux
        DeviceId::new(1, 5)
    }

    fn open(&self) -> Result<Option<Arc<dyn FileIo>>> {
        Ok(Some(Arc::new(Zero)))
    }
}

impl Pollable for Zero {
    fn poll(&self, mask: IoEvents, poller: Option<&mut Poller>) -> IoEvents {
        let events = IoEvents::IN | IoEvents::OUT;
        events & mask
    }
}

impl FileIo for Zero {
    fn read(&self, writer: &mut VmWriter) -> Result<usize> {
        let read_len = writer.fill_zeros(writer.avail())?;
        Ok(read_len)
    }

    fn write(&self, reader: &mut VmReader) -> Result<usize> {
        Ok(reader.remain())
    }
}