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/* Copyright (c) [2023] [Syswonder Community]
 *   [Rukos] is licensed under Mulan PSL v2.
 *   You can use this software according to the terms and conditions of the Mulan PSL v2.
 *   You may obtain a copy of Mulan PSL v2 at:
 *               http://license.coscl.org.cn/MulanPSL2
 *   THIS SOFTWARE IS PROVIDED ON AN "AS IS" BASIS, WITHOUT WARRANTIES OF ANY KIND, EITHER EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO NON-INFRINGEMENT, MERCHANTABILITY OR FIT FOR A PARTICULAR PURPOSE.
 *   See the Mulan PSL v2 for more details.
 */

use axfs_vfs::{VfsNodeAttr, VfsNodeOps, VfsNodePerm, VfsNodeType, VfsResult};

/// A zero device behaves like `/dev/zero`.
///
/// It always returns a chunk of `\0` bytes when read, and all writes are discarded.
pub struct ZeroDev;

impl VfsNodeOps for ZeroDev {
    fn get_attr(&self) -> VfsResult<VfsNodeAttr> {
        Ok(VfsNodeAttr::new(
            VfsNodePerm::default_file(),
            VfsNodeType::CharDevice,
            0,
            0,
        ))
    }

    fn read_at(&self, _offset: u64, buf: &mut [u8]) -> VfsResult<usize> {
        buf.fill(0);
        Ok(buf.len())
    }

    fn write_at(&self, _offset: u64, buf: &[u8]) -> VfsResult<usize> {
        Ok(buf.len())
    }

    fn truncate(&self, _size: u64) -> VfsResult {
        Ok(())
    }

    axfs_vfs::impl_vfs_non_dir_default! {}
}