[RFC PATCH 10/24] erofs: add device_infos implementation in Rust

[Jianan Huang]

Yiyang Wu via Linux-erofs <linux-erofs at lists.ozlabs.org> 于2024年9月16日周一 21:57写道：
>
> Add device_infos implementation in rust. It will later be used
> to be put inside the SuperblockInfo. This mask and spec can later
> be used to chunk-based image file block mapping.
>
> Signed-off-by: Yiyang Wu <toolmanp at tlmp.cc>
> ---
>  fs/erofs/rust/erofs_sys/devices.rs | 47 ++++++++++++++++++++++++++++++
>  1 file changed, 47 insertions(+)
>
> diff --git a/fs/erofs/rust/erofs_sys/devices.rs b/fs/erofs/rust/erofs_sys/devices.rs
> index 097676ee8720..7495164c7bd0 100644
> --- a/fs/erofs/rust/erofs_sys/devices.rs
> +++ b/fs/erofs/rust/erofs_sys/devices.rs
> @@ -1,6 +1,10 @@
>  // Copyright 2024 Yiyang Wu
>  // SPDX-License-Identifier: MIT or GPL-2.0-or-later
>
> +use super::alloc_helper::*;
> +use super::data::raw_iters::*;
> +use super::data::*;
> +use super::*;
>  use alloc::vec::Vec;
>
>  /// Device specification.
> @@ -21,8 +25,51 @@ pub(crate) struct DeviceSlot {
>      reserved: [u8; 56],
>  }
>
> +impl From<[u8; 128]> for DeviceSlot {
> +    fn from(data: [u8; 128]) -> Self {
> +        Self {
> +            tags: data[0..64].try_into().unwrap(),
> +            blocks: u32::from_le_bytes([data[64], data[65], data[66], data[67]]),
> +            mapped_blocks: u32::from_le_bytes([data[68], data[69], data[70], data[71]]),
> +            reserved: data[72..128].try_into().unwrap(),
> +        }
> +    }
> +}
> +
>  /// Device information.
>  pub(crate) struct DeviceInfo {
>      pub(crate) mask: u16,
>      pub(crate) specs: Vec<DeviceSpec>,
>  }
> +
> +pub(crate) fn get_device_infos<'a>(
> +    iter: &mut (dyn ContinuousBufferIter<'a> + 'a),
> +) -> PosixResult<DeviceInfo> {
> +    let mut specs = Vec::new();
> +    for data in iter {
> +        let buffer = data?;
> +        let mut cur: usize = 0;
> +        let len = buffer.content().len();
> +        while cur + 128 <= len {


It is better to use macros instead of hardcode, like:
const EROFS_DEVT_SLOT_SIZE: usize = size_of::<DeviceSlot>();
Also works to the other similar usages in this patch set.

Thanks,
Jianan

>
> +            let slot_data: [u8; 128] = buffer.content()[cur..cur + 128].try_into().unwrap();
> +            let slot = DeviceSlot::from(slot_data);
> +            cur += 128;
> +            push_vec(
> +                &mut specs,
> +                DeviceSpec {
> +                    tags: slot.tags,
> +                    blocks: slot.blocks,
> +                    mapped_blocks: slot.mapped_blocks,
> +                },
> +            )?;
> +        }
> +    }
> +
> +    let mask = if specs.is_empty() {
> +        0
> +    } else {
> +        (1 << (specs.len().ilog2() + 1)) - 1
> +    };
> +
> +    Ok(DeviceInfo { mask, specs })
> +}
> --
> 2.46.0
>