Introduced a specialization trait ReadDirFromPath for ReadDir struct on most platforms to construct a ReadDir with zero cost conversion if given a PathBuf or something that could be converted into a PathBuf

Author: asder8215

library/std/src/sys/fs/hermit.rs

@@ -1,3 +1,5 @@
+use alloc_crate::borrow::Cow;
+
 use crate::ffi::{CStr, OsStr, OsString, c_char};
 use crate::fs::TryLockError;
 use crate::io::{self, BorrowedCursor, Error, ErrorKind, IoSlice, IoSliceMut, SeekFrom};
@@ -53,6 +55,37 @@ impl ReadDir {
     }
 }
 
+/// Specialization trait used to construct a `ReadDir`
+trait ReadDirFromPath<P> {
+    fn from_path(dir: Vec<u8>, path: P) -> Self;
+}
+
+impl<P: AsRef<Path>> ReadDirFromPath<P> for ReadDir {
+    default fn from_path(dir: Vec<u8>, path: P) -> Self {
+        let inner = InnerReadDir { root: path.as_ref().to_path_buf(), dir };
+        ReadDir::new(inner)
+    }
+}
+
+/// This constructs a `ReadDir` for all types that can be converted
+/// into `PathBuf` without allocating
+macro_rules! impl_read_dir_from_path {
+    ($t:ty) => {
+        impl ReadDirFromPath<$t> for ReadDir {
+            fn from_path(dir: Vec<u8>, path: $t) -> Self {
+                let inner = InnerReadDir::new(path.into(), dir);
+                ReadDir::new(inner)
+            }
+        }
+    };
+}
+
+impl_read_dir_from_path!(PathBuf);
+impl_read_dir_from_path!(Box<Path>);
+impl_read_dir_from_path!(Cow<'_, Path>);
+impl_read_dir_from_path!(OsString);
+impl_read_dir_from_path!(String);
+
 pub struct DirEntry {
     /// path to the entry
     root: PathBuf,
@@ -512,12 +545,11 @@ impl FromRawFd for File {
     }
 }
 
-pub fn readdir(path: &Path) -> io::Result<ReadDir> {
-    let fd_raw = run_path_with_cstr(path, &|path| {
+pub fn readdir<P: AsRef<Path>>(path: P) -> io::Result<ReadDir> {
+    let fd_raw = run_path_with_cstr(path.as_ref(), &|path| {
         cvt(unsafe { hermit_abi::open(path.as_ptr(), O_RDONLY | O_DIRECTORY, 0) })
     })?;
     let fd = unsafe { FileDesc::from_raw_fd(fd_raw as i32) };
-    let root = path.to_path_buf();
 
     // read all director entries
     let mut vec: Vec<u8> = Vec::new();
@@ -551,7 +583,7 @@ pub fn readdir(path: &Path) -> io::Result<ReadDir> {
         }
     }
 
-    Ok(ReadDir::new(InnerReadDir::new(root, vec)))
+    Ok(<ReadDir as ReadDirFromPath<P>>::from_path(vec, path))
 }
 
 pub fn unlink(path: &Path) -> io::Result<()> {

library/std/src/sys/fs/mod.rs

@@ -63,7 +63,7 @@ pub use imp::{
     ReadDir,
 };
 
-pub fn read_dir(path: &Path) -> io::Result<ReadDir> {
+pub fn read_dir<P: AsRef<Path>>(path: P) -> io::Result<ReadDir> {
     // FIXME: use with_native_path on all platforms
     imp::readdir(path)
 }

library/std/src/sys/fs/motor.rs

@@ -1,3 +1,5 @@
+use alloc_crate::borrow::Cow;
+
 use crate::ffi::OsString;
 use crate::hash::Hash;
 use crate::io::{self, BorrowedCursor, IoSlice, IoSliceMut, SeekFrom};
@@ -377,12 +379,49 @@ impl Drop for ReadDir {
     }
 }
 
-pub fn readdir(path: &Path) -> io::Result<ReadDir> {
-    let path = path.to_str().ok_or(io::Error::from(io::ErrorKind::InvalidFilename))?;
-    Ok(ReadDir {
-        rt_fd: moto_rt::fs::opendir(path).map_err(map_motor_error)?,
-        path: path.to_owned(),
-    })
+/// Specialization trait used to construct a `ReadDir`
+trait ReadDirFromPath<P> {
+    fn from_path(path: P) -> io::Result<ReadDir>;
+}
+
+impl<P: AsRef<Path>> ReadDirFromPath<P> for ReadDir {
+    default fn from_path(path: P) -> io::Result<ReadDir> {
+        let path = path.as_ref().to_str().ok_or(io::Error::from(io::ErrorKind::InvalidFilename))?;
+        Ok(ReadDir {
+            rt_fd: moto_rt::fs::opendir(path).map_err(map_motor_error)?,
+            path: path.to_owned(),
+        })
+    }
+}
+
+/// This constructs a `ReadDir` for all types that can be converted
+/// into `String` without allocating
+macro_rules! impl_read_dir_from_path {
+    ($t:ty) => {
+        impl ReadDirFromPath<$t> for ReadDir {
+            fn from_path(path: $t) -> io::Result<ReadDir> {
+                let path_buf: PathBuf = path.into();
+                let path = path_buf.into_os_string().into_string();
+                match path {
+                    Err(_) => return Err(io::Error::from(io::ErrorKind::InvalidFilename)),
+                    Ok(path) => Ok(ReadDir {
+                        rt_fd: moto_rt::fs::opendir(path).map_err(map_motor_error)?,
+                        path,
+                    }),
+                }
+            }
+        }
+    };
+}
+
+impl_read_dir_from_path!(PathBuf);
+impl_read_dir_from_path!(Box<Path>);
+impl_read_dir_from_path!(Cow<'_, Path>);
+impl_read_dir_from_path!(OsString);
+impl_read_dir_from_path!(String);
+
+pub fn readdir<P: AsRef<Path>>(path: P) -> io::Result<ReadDir> {
+    <ReadDir as ReadDirFromPath<P>>::from_path(path)
 }
 
 impl Iterator for ReadDir {

library/std/src/sys/fs/solid.rs

@@ -1,5 +1,7 @@
 #![allow(dead_code)]
 
+use alloc_crate::borrow::Cow;
+
 use crate::ffi::{CStr, CString, OsStr, OsString};
 use crate::fmt;
 use crate::fs::TryLockError;
@@ -146,19 +148,49 @@ impl FileType {
     }
 }
 
-pub fn readdir(p: &Path) -> io::Result<ReadDir> {
+pub fn readdir<P: AsRef<Path>>(p: P) -> io::Result<ReadDir> {
     unsafe {
         let mut dir = MaybeUninit::uninit();
         error::SolidError::err_if_negative(abi::SOLID_FS_OpenDir(
-            cstr(p)?.as_ptr(),
+            cstr(p.as_ref())?.as_ptr(),
             dir.as_mut_ptr(),
         ))
         .map_err(|e| e.as_io_error())?;
-        let inner = Arc::new(InnerReadDir { dirp: dir.assume_init(), root: p.to_owned() });
-        Ok(ReadDir { inner })
+        Ok(<ReadDir as ReadDirFromPath<P>>::from_path(dir.assume_init(), p))
+    }
+}
+
+/// Specialization trait used to construct a `ReadDir`
+trait ReadDirFromPath<P> {
+    fn from_path(dirp: abi::S_DIR, path: P) -> Self;
+}
+
+impl<P: AsRef<Path>> ReadDirFromPath<P> for ReadDir {
+    default fn from_path(dirp: abi::S_DIR, path: P) -> Self {
+        let inner = InnerReadDir { dirp, root: path.as_ref().to_path_buf() };
+        ReadDir { inner: Arc::new(inner) }
     }
 }
 
+/// This constructs a `ReadDir` for all types that can be converted
+/// into `PathBuf` without allocating
+macro_rules! impl_read_dir_from_path {
+    ($t:ty) => {
+        impl ReadDirFromPath<$t> for ReadDir {
+            fn from_path(dirp: abi::S_DIR, path: $t) -> Self {
+                let inner = InnerReadDir { dirp, root: path.into() };
+                ReadDir { inner: Arc::new(inner) }
+            }
+        }
+    };
+}
+
+impl_read_dir_from_path!(PathBuf);
+impl_read_dir_from_path!(Box<Path>);
+impl_read_dir_from_path!(Cow<'_, Path>);
+impl_read_dir_from_path!(OsString);
+impl_read_dir_from_path!(String);
+
 impl fmt::Debug for ReadDir {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         // This will only be called from std::fs::ReadDir, which will add a "ReadDir()" frame.

library/std/src/sys/fs/uefi.rs

@@ -415,9 +415,8 @@ impl fmt::Debug for File {
     }
 }
 
-pub fn readdir(p: &Path) -> io::Result<ReadDir> {
-    let path = crate::path::absolute(p)?;
-    let f = uefi_fs::File::from_path(&path, file::MODE_READ, 0)?;
+pub fn readdir<P: AsRef<Path>>(p: P) -> io::Result<ReadDir> {
+    let f = uefi_fs::File::from_path(p.as_ref(), file::MODE_READ, 0)?;
     let file_info = f.file_info()?;
     let file_attr = FileAttr::from_uefi(file_info);
 

library/std/src/sys/fs/unix.rs

@@ -6,6 +6,7 @@
 #[cfg(test)]
 mod tests;
 
+use alloc_crate::borrow::Cow;
 #[cfg(all(target_os = "linux", target_env = "gnu"))]
 use libc::c_char;
 #[cfg(any(
@@ -272,6 +273,37 @@ impl ReadDir {
     }
 }
 
+/// Specialization trait used to construct a `ReadDir`
+trait ReadDirFromPath<P> {
+    fn from_path(dirp: DirStream, path: P) -> Self;
+}
+
+impl<P: AsRef<Path>> ReadDirFromPath<P> for ReadDir {
+    default fn from_path(dirp: DirStream, path: P) -> Self {
+        let inner = InnerReadDir { dirp, root: path.as_ref().to_path_buf() };
+        ReadDir::new(inner)
+    }
+}
+
+/// This constructs a `ReadDir` for all types that can be converted
+/// into `PathBuf` without allocating
+macro_rules! impl_read_dir_from_path {
+    ($t:ty) => {
+        impl ReadDirFromPath<$t> for ReadDir {
+            fn from_path(dirp: DirStream, path: $t) -> Self {
+                let inner = InnerReadDir { dirp, root: path.into() };
+                ReadDir::new(inner)
+            }
+        }
+    };
+}
+
+impl_read_dir_from_path!(PathBuf);
+impl_read_dir_from_path!(Box<Path>);
+impl_read_dir_from_path!(Cow<'_, Path>);
+impl_read_dir_from_path!(OsString);
+impl_read_dir_from_path!(String);
+
 struct DirStream(*mut libc::DIR);
 
 // dir::Dir requires openat support
@@ -2077,14 +2109,12 @@ impl fmt::Debug for Mode {
     }
 }
 
-pub fn readdir(path: &Path) -> io::Result<ReadDir> {
-    let ptr = run_path_with_cstr(path, &|p| unsafe { Ok(libc::opendir(p.as_ptr())) })?;
+pub fn readdir<P: AsRef<Path>>(path: P) -> io::Result<ReadDir> {
+    let ptr = run_path_with_cstr(path.as_ref(), &|p| unsafe { Ok(libc::opendir(p.as_ptr())) })?;
     if ptr.is_null() {
         Err(Error::last_os_error())
     } else {
-        let root = path.to_path_buf();
-        let inner = InnerReadDir { dirp: DirStream(ptr), root };
-        Ok(ReadDir::new(inner))
+        Ok(<ReadDir as ReadDirFromPath<P>>::from_path(DirStream(ptr), path))
     }
 }
 

library/std/src/sys/fs/unsupported.rs

@@ -297,7 +297,7 @@ impl fmt::Debug for File {
     }
 }
 
-pub fn readdir(_p: &Path) -> io::Result<ReadDir> {
+pub fn readdir<P: AsRef<Path>>(_p: P) -> io::Result<ReadDir> {
     unsupported()
 }
 

library/std/src/sys/fs/vexos.rs

@@ -477,7 +477,7 @@ impl Drop for File {
     }
 }
 
-pub fn readdir(_p: &Path) -> io::Result<ReadDir> {
+pub fn readdir<P: AsRef<Path>>(_p: P) -> io::Result<ReadDir> {
     // While there *is* a userspace function for reading file directories,
     // the necessary implementation cannot currently be done cleanly, as
     // VEXos does not expose directory length to user programs.

library/std/src/sys/fs/windows.rs

@@ -53,6 +53,47 @@ pub struct ReadDir {
     first: Option<c::WIN32_FIND_DATAW>,
 }
 
+/// Specialization trait used to construct a `ReadDir`
+trait ReadDirFromPath<P> {
+    fn from_path(
+        handle: Option<FindNextFileHandle>,
+        path: P,
+        first: Option<c::WIN32_FIND_DATAW>,
+    ) -> Self;
+}
+
+impl<P: AsRef<Path>> ReadDirFromPath<P> for ReadDir {
+    default fn from_path(
+        handle: Option<FindNextFileHandle>,
+        path: P,
+        first: Option<c::WIN32_FIND_DATAW>,
+    ) -> Self {
+        ReadDir { handle, root: Arc::new(path.as_ref().to_path_buf()), first }
+    }
+}
+
+/// This constructs a `ReadDir` for all types that can be converted
+/// into `PathBuf` without allocating
+macro_rules! impl_read_dir_from_path {
+    ($t:ty) => {
+        impl ReadDirFromPath<$t> for ReadDir {
+            fn from_path(
+                handle: Option<FindNextFileHandle>,
+                path: $t,
+                first: Option<c::WIN32_FIND_DATAW>,
+            ) -> Self {
+                ReadDir { handle, root: Arc::new(path.into()), first }
+            }
+        }
+    };
+}
+
+impl_read_dir_from_path!(PathBuf);
+impl_read_dir_from_path!(Box<Path>);
+impl_read_dir_from_path!(Cow<'_, Path>);
+impl_read_dir_from_path!(OsString);
+impl_read_dir_from_path!(String);
+
 struct FindNextFileHandle(c::HANDLE);
 
 unsafe impl Send for FindNextFileHandle {}
@@ -1222,17 +1263,16 @@ impl DirBuilder {
     }
 }
 
-pub fn readdir(p: &Path) -> io::Result<ReadDir> {
+pub fn readdir<P: AsRef<Path>>(p: P) -> io::Result<ReadDir> {
     // We push a `*` to the end of the path which cause the empty path to be
     // treated as the current directory. So, for consistency with other platforms,
     // we explicitly error on the empty path.
-    if p.as_os_str().is_empty() {
+    if p.as_ref().as_os_str().is_empty() {
         // Return an error code consistent with other ways of opening files.
         // E.g. fs::metadata or File::open.
         return Err(io::Error::from_raw_os_error(c::ERROR_PATH_NOT_FOUND as i32));
     }
-    let root = p.to_path_buf();
-    let star = p.join("*");
+    let star = p.as_ref().join("*");
     let path = maybe_verbatim(&star)?;
 
     unsafe {
@@ -1254,11 +1294,11 @@ pub fn readdir(p: &Path) -> io::Result<ReadDir> {
         );
 
         if find_handle != c::INVALID_HANDLE_VALUE {
-            Ok(ReadDir {
-                handle: Some(FindNextFileHandle(find_handle)),
-                root: Arc::new(root),
-                first: Some(wfd),
-            })
+            Ok(<ReadDir as ReadDirFromPath<P>>::from_path(
+                Some(FindNextFileHandle(find_handle)),
+                p,
+                Some(wfd),
+            ))
         } else {
             // The status `ERROR_FILE_NOT_FOUND` is returned by the `FindFirstFileExW` function
             // if no matching files can be found, but not necessarily that the path to find the
@@ -1273,7 +1313,7 @@ pub fn readdir(p: &Path) -> io::Result<ReadDir> {
             // See issue #120040: https://github.com/rust-lang/rust/issues/120040.
             let last_error = api::get_last_error();
             if last_error == WinError::FILE_NOT_FOUND {
-                return Ok(ReadDir { handle: None, root: Arc::new(root), first: None });
+                return Ok(<ReadDir as ReadDirFromPath<P>>::from_path(None, p, None));
             }
 
             // Just return the error constructed from the raw OS error if the above is not the case.