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unix: reduce the size of DirEntry #94750

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merged 1 commit into from
Mar 9, 2022
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unix: reduce the size of DirEntry #94750

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57 changes: 47 additions & 10 deletions library/std/src/sys/unix/fs.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -228,23 +228,54 @@ struct Dir(*mut libc::DIR);
unsafe impl Send for Dir {}
unsafe impl Sync for Dir {}

#[cfg(any(
target_os = "android",
target_os = "linux",
target_os = "solaris",
target_os = "illumos",
target_os = "fuchsia",
target_os = "redox"
))]
pub struct DirEntry {
entry: dirent64,
dir: Arc<InnerReadDir>,
entry: dirent64_min,
// We need to store an owned copy of the entry name on platforms that use
// readdir() (not readdir_r()), because a) struct dirent may use a flexible
// array to store the name, b) it lives only until the next readdir() call.
#[cfg(any(
target_os = "android",
target_os = "linux",
target_os = "solaris",
target_os = "illumos",
target_os = "fuchsia",
target_os = "redox"
))]
name: CString,
}

// Define a minimal subset of fields we need from `dirent64`, especially since
// we're not using the immediate `d_name` on these targets. Keeping this as an
// `entry` field in `DirEntry` helps reduce the `cfg` boilerplate elsewhere.
#[cfg(any(
target_os = "android",
target_os = "linux",
target_os = "solaris",
target_os = "illumos",
target_os = "fuchsia",
target_os = "redox"
))]
struct dirent64_min {
d_ino: u64,
#[cfg(not(any(target_os = "solaris", target_os = "illumos")))]
d_type: u8,
}

#[cfg(not(any(
target_os = "android",
target_os = "linux",
target_os = "solaris",
target_os = "illumos",
target_os = "fuchsia",
target_os = "redox"
)))]
pub struct DirEntry {
dir: Arc<InnerReadDir>,
// The full entry includes a fixed-length `d_name`.
entry: dirent64,
}

#[derive(Clone, Debug)]
pub struct OpenOptions {
// generic
Expand Down Expand Up @@ -501,8 +532,14 @@ impl Iterator for ReadDir {
let entry_name = entry_bytes.add(name_offset);
ptr::copy_nonoverlapping(entry_bytes, copy_bytes, name_offset);

let entry = dirent64_min {
d_ino: copy.d_ino as u64,
#[cfg(not(any(target_os = "solaris", target_os = "illumos")))]
d_type: copy.d_type as u8,
};

let ret = DirEntry {
entry: copy,
entry,
// d_name is guaranteed to be null-terminated.
name: CStr::from_ptr(entry_name as *const _).to_owned(),
dir: Arc::clone(&self.inner),
Expand Down