This patch adds DirentDesc and DirCollection in Rust. It will later be used as helper to read_dir and lookup operations. Signed-off-by: Yiyang Wu <toolmanp@xxxxxxx> --- fs/erofs/rust/erofs_sys.rs | 1 + fs/erofs/rust/erofs_sys/dir.rs | 98 ++++++++++++++++++++++++++++++++++ 2 files changed, 99 insertions(+) create mode 100644 fs/erofs/rust/erofs_sys/dir.rs diff --git a/fs/erofs/rust/erofs_sys.rs b/fs/erofs/rust/erofs_sys.rs index 15ed65866097..65dc563986c3 100644 --- a/fs/erofs/rust/erofs_sys.rs +++ b/fs/erofs/rust/erofs_sys.rs @@ -26,6 +26,7 @@ pub(crate) mod alloc_helper; pub(crate) mod data; pub(crate) mod devices; +pub(crate) mod dir; pub(crate) mod errnos; pub(crate) mod inode; pub(crate) mod map; diff --git a/fs/erofs/rust/erofs_sys/dir.rs b/fs/erofs/rust/erofs_sys/dir.rs new file mode 100644 index 000000000000..d4255582b7c0 --- /dev/null +++ b/fs/erofs/rust/erofs_sys/dir.rs @@ -0,0 +1,98 @@ +// Copyright 2024 Yiyang Wu +// SPDX-License-Identifier: MIT or GPL-2.0-or-later + +/// On-disk Directory Descriptor Format for EROFS +/// Documented on [EROFS Directory](https://erofs.docs.kernel.org/en/latest/core_ondisk.html#directories) +use core::mem::size_of; + +#[repr(C, packed)] +#[derive(Debug, Clone, Copy)] +pub(crate) struct DirentDesc { + pub(crate) nid: u64, + pub(crate) nameoff: u16, + pub(crate) file_type: u8, + pub(crate) reserved: u8, +} + +/// In memory representation of a real directory entry. +#[derive(Debug, Clone, Copy)] +pub(crate) struct Dirent<'a> { + pub(crate) desc: DirentDesc, + pub(crate) name: &'a [u8], +} + +impl From<[u8; size_of::<DirentDesc>()]> for DirentDesc { + fn from(data: [u8; size_of::<DirentDesc>()]) -> Self { + Self { + nid: u64::from_le_bytes([ + data[0], data[1], data[2], data[3], data[4], data[5], data[6], data[7], + ]), + nameoff: u16::from_le_bytes([data[8], data[9]]), + file_type: data[10], + reserved: data[11], + } + } +} + +/// Create a collection of directory entries from a buffer. +/// This is a helper struct to iterate over directory entries. +pub(crate) struct DirCollection<'a> { + data: &'a [u8], + offset: usize, + total: usize, +} + +impl<'a> DirCollection<'a> { + pub(crate) fn new(buffer: &'a [u8]) -> Self { + let desc: &DirentDesc = unsafe { &*(buffer.as_ptr() as *const DirentDesc) }; + Self { + data: buffer, + offset: 0, + total: desc.nameoff as usize / core::mem::size_of::<DirentDesc>(), + } + } + pub(crate) fn dirent(&self, index: usize) -> Option<Dirent<'a>> { + let descs: &'a [[u8; size_of::<DirentDesc>()]] = + unsafe { core::slice::from_raw_parts(self.data.as_ptr().cast(), self.total) }; + if index >= self.total { + None + } else if index == self.total - 1 { + let desc = DirentDesc::from(descs[index]); + let len = self.data.len() - desc.nameoff as usize; + Some(Dirent { + desc, + name: &self.data[desc.nameoff as usize..(desc.nameoff as usize) + len], + }) + } else { + let desc = DirentDesc::from(descs[index]); + let next_desc = DirentDesc::from(descs[index + 1]); + let len = (next_desc.nameoff - desc.nameoff) as usize; + Some(Dirent { + desc, + name: &self.data[desc.nameoff as usize..(desc.nameoff as usize) + len], + }) + } + } + pub(crate) fn skip_dir(&mut self, offset: usize) { + self.offset += offset; + } + pub(crate) fn total(&self) -> usize { + self.total + } +} + +impl<'a> Iterator for DirCollection<'a> { + type Item = Dirent<'a>; + fn next(&mut self) -> Option<Self::Item> { + self.dirent(self.offset).map(|x| { + self.offset += 1; + x + }) + } +} + +impl<'a> Dirent<'a> { + pub(crate) fn dirname(&self) -> &'a [u8] { + self.name + } +} -- 2.46.0
