Introduce directory traversal

native/src/base/files.rs

@@ -1,53 +1,25 @@
 use mem::MaybeUninit;
 use std::cmp::min;
 use std::ffi::CStr;
+use std::fs::File;
 use std::io::{BufRead, Read, Seek, SeekFrom, Write};
+use std::marker::PhantomData;
+use std::ops::Deref;
+use std::os::fd::{AsFd, BorrowedFd, IntoRawFd};
 use std::os::unix::io::{AsRawFd, FromRawFd, OwnedFd, RawFd};
-use std::{io, mem};
+use std::{io, mem, slice};
 
-use libc::{c_char, c_uint, mode_t, EEXIST, ENOENT, O_CLOEXEC, O_PATH};
+use libc::{c_char, c_uint, dirent, mode_t, EEXIST, ENOENT, O_CLOEXEC, O_PATH, O_RDONLY};
 
-use crate::{bfmt_cstr, errno, error, xopen};
+use crate::{bfmt_cstr, copy_cstr, cstr, errno, error};
 
-pub mod unsafe_impl {
-    use std::ffi::CStr;
-
-    use libc::c_char;
-
-    use crate::slice_from_ptr_mut;
-
-    pub unsafe fn readlink(path: *const c_char, buf: *mut u8, bufsz: usize) -> isize {
-        let r = libc::readlink(path, buf.cast(), bufsz - 1);
-        if r >= 0 {
-            *buf.offset(r) = b'\0';
-        }
-        r
-    }
-
-    #[no_mangle]
-    unsafe extern "C" fn canonical_path(path: *const c_char, buf: *mut u8, bufsz: usize) -> isize {
-        super::realpath(CStr::from_ptr(path), slice_from_ptr_mut(buf, bufsz))
-    }
-}
-
-pub fn __open_fd_impl(path: &CStr, flags: i32, mode: mode_t) -> Option<OwnedFd> {
+pub fn __open_fd_impl(path: &CStr, flags: i32, mode: mode_t) -> io::Result<OwnedFd> {
     unsafe {
         let fd = libc::open(path.as_ptr(), flags, mode as c_uint);
         if fd >= 0 {
-            Some(OwnedFd::from_raw_fd(fd))
+            Ok(OwnedFd::from_raw_fd(fd))
         } else {
-            None
-        }
-    }
-}
-
-pub fn __xopen_fd_impl(path: &CStr, flags: i32, mode: mode_t) -> Option<OwnedFd> {
-    unsafe {
-        let fd = xopen(path.as_ptr(), flags, mode);
-        if fd >= 0 {
-            Some(OwnedFd::from_raw_fd(fd))
-        } else {
-            None
+            Err(io::Error::last_os_error())
         }
     }
 }
@@ -62,78 +34,74 @@ macro_rules! open_fd {
     };
 }
 
-#[macro_export]
-macro_rules! xopen_fd {
-    ($path:expr, $flags:expr) => {
-        $crate::__xopen_fd_impl($path, $flags, 0)
-    };
-    ($path:expr, $flags:expr, $mode:expr) => {
-        $crate::__xopen_fd_impl($path, $flags, $mode)
-    };
+pub unsafe fn readlink_unsafe(path: *const c_char, buf: *mut u8, bufsz: usize) -> isize {
+    let r = libc::readlink(path, buf.cast(), bufsz - 1);
+    if r >= 0 {
+        *buf.offset(r) = b'\0';
+    }
+    r
 }
 
-pub fn readlink(path: &CStr, data: &mut [u8]) -> isize {
-    unsafe { unsafe_impl::readlink(path.as_ptr(), data.as_mut_ptr(), data.len()) }
+pub fn readlink(path: &CStr, data: &mut [u8]) -> io::Result<usize> {
+    let r = unsafe { readlink_unsafe(path.as_ptr(), data.as_mut_ptr(), data.len()) };
+    if r < 0 {
+        return Err(io::Error::last_os_error());
+    }
+    Ok(r as usize)
 }
 
-pub fn fd_path(fd: RawFd, buf: &mut [u8]) -> isize {
-    let mut fd_buf: [u8; 40] = [0; 40];
+pub fn fd_path(fd: RawFd, buf: &mut [u8]) -> io::Result<usize> {
+    let mut fd_buf = [0_u8; 40];
     let fd_path = bfmt_cstr!(&mut fd_buf, "/proc/self/fd/{}", fd);
     readlink(fd_path, buf)
 }
 
 // Inspired by https://android.googlesource.com/platform/bionic/+/master/libc/bionic/realpath.cpp
-pub fn realpath(path: &CStr, buf: &mut [u8]) -> isize {
-    if let Some(fd) = open_fd!(path, O_PATH | O_CLOEXEC) {
-        let mut st1: libc::stat;
-        let mut st2: libc::stat;
-        let mut skip_check = false;
-        unsafe {
-            st1 = mem::zeroed();
-            if libc::fstat(fd.as_raw_fd(), &mut st1) < 0 {
-                // This shall only fail on Linux < 3.6
-                skip_check = true;
-            }
+pub fn realpath(path: &CStr, buf: &mut [u8]) -> io::Result<usize> {
+    let fd = open_fd!(path, O_PATH | O_CLOEXEC)?;
+    let mut st1: libc::stat;
+    let mut st2: libc::stat;
+    let mut skip_check = false;
+    unsafe {
+        st1 = mem::zeroed();
+        if libc::fstat(fd.as_raw_fd(), &mut st1) < 0 {
+            // This shall only fail on Linux < 3.6
+            skip_check = true;
         }
-        let len = fd_path(fd.as_raw_fd(), buf);
-        unsafe {
-            st2 = mem::zeroed();
-            if libc::stat(buf.as_ptr().cast(), &mut st2) < 0
-                || (!skip_check && (st2.st_dev != st1.st_dev || st2.st_ino != st1.st_ino))
-            {
-                *errno() = ENOENT;
-                return -1;
-            }
-        }
-        len
-    } else {
-        *errno() = ENOENT;
-        -1
     }
+    let len = fd_path(fd.as_raw_fd(), buf)?;
+    unsafe {
+        st2 = mem::zeroed();
+        if libc::stat(buf.as_ptr().cast(), &mut st2) < 0
+            || (!skip_check && (st2.st_dev != st1.st_dev || st2.st_ino != st1.st_ino))
+        {
+            *errno() = ENOENT;
+            return Err(io::Error::last_os_error());
+        }
+    }
+    Ok(len)
 }
 
-extern "C" {
-    fn strscpy(dst: *mut c_char, src: *const c_char, size: usize) -> usize;
-}
-
-#[no_mangle]
-pub unsafe extern "C" fn mkdirs(path: *const c_char, mode: mode_t) -> i32 {
+pub fn mkdirs(path: &CStr, mode: mode_t) -> io::Result<()> {
     let mut buf = [0_u8; 4096];
-    let ptr: *mut c_char = buf.as_mut_ptr().cast();
-    let len = strscpy(ptr, path, buf.len());
-    let mut curr = &mut buf[1..len];
-    while let Some(p) = curr.iter().position(|c| *c == b'/') {
-        curr[p] = b'\0';
-        if libc::mkdir(ptr, mode) < 0 && *errno() != EEXIST {
-            return -1;
+    let len = copy_cstr(&mut buf, path);
+    let buf = &mut buf[..len];
+    let mut off = 1;
+    unsafe {
+        while let Some(p) = buf[off..].iter().position(|c| *c == b'/') {
+            buf[off + p] = b'\0';
+            if libc::mkdir(buf.as_ptr().cast(), mode) < 0 && *errno() != EEXIST {
+                return Err(io::Error::last_os_error());
+            }
+            buf[off + p] = b'/';
+            off += p + 1;
+        }
+        if libc::mkdir(buf.as_ptr().cast(), mode) < 0 && *errno() != EEXIST {
+            return Err(io::Error::last_os_error());
         }
-        curr[p] = b'/';
-        curr = &mut curr[(p + 1)..];
     }
-    if libc::mkdir(ptr, mode) < 0 && *errno() != EEXIST {
-        return -1;
-    }
-    0
+    *errno() = 0;
+    Ok(())
 }
 
 pub trait ReadExt {
@@ -221,3 +189,276 @@ impl<T: Write> WriteExt for T {
         Ok(())
     }
 }
+
+pub struct DirEntry<'a> {
+    dir: &'a Directory<'a>,
+    entry: &'a dirent,
+    name_len: usize,
+}
+
+impl DirEntry<'_> {
+    pub fn d_name(&self) -> &CStr {
+        unsafe {
+            CStr::from_bytes_with_nul_unchecked(slice::from_raw_parts(
+                self.d_name.as_ptr().cast(),
+                self.name_len,
+            ))
+        }
+    }
+
+    pub fn path(&self, buf: &mut [u8]) -> io::Result<usize> {
+        let mut len = self.dir.path(buf)?;
+        buf[len] = b'/';
+        len += 1;
+        len += copy_cstr(&mut buf[len..], self.d_name());
+        Ok(len)
+    }
+
+    pub fn is_dir(&self) -> bool {
+        self.d_type == libc::DT_DIR
+    }
+
+    pub fn is_file(&self) -> bool {
+        self.d_type == libc::DT_REG
+    }
+
+    pub fn is_lnk(&self) -> bool {
+        self.d_type == libc::DT_LNK
+    }
+
+    pub fn unlink(&self) -> io::Result<()> {
+        let flag = if self.is_dir() { libc::AT_REMOVEDIR } else { 0 };
+        unsafe {
+            if libc::unlinkat(self.dir.as_raw_fd(), self.d_name.as_ptr(), flag) < 0 {
+                return Err(io::Error::last_os_error());
+            }
+        }
+        Ok(())
+    }
+
+    pub fn open_as_dir(&self) -> io::Result<Directory> {
+        if !self.is_dir() {
+            return Err(io::Error::from(io::ErrorKind::NotADirectory));
+        }
+        unsafe {
+            let fd = libc::openat(
+                self.dir.as_raw_fd(),
+                self.d_name.as_ptr(),
+                O_RDONLY | O_CLOEXEC,
+            );
+            if fd < 0 {
+                return Err(io::Error::last_os_error());
+            }
+            Directory::try_from(OwnedFd::from_raw_fd(fd))
+        }
+    }
+
+    pub fn open_as_file(&self, flags: i32) -> io::Result<File> {
+        if self.is_dir() {
+            return Err(io::Error::from(io::ErrorKind::IsADirectory));
+        }
+        unsafe {
+            let fd = libc::openat(
+                self.dir.as_raw_fd(),
+                self.d_name.as_ptr(),
+                flags | O_CLOEXEC,
+            );
+            if fd < 0 {
+                return Err(io::Error::last_os_error());
+            }
+            Ok(File::from_raw_fd(fd))
+        }
+    }
+}
+
+impl Deref for DirEntry<'_> {
+    type Target = dirent;
+
+    fn deref(&self) -> &dirent {
+        self.entry
+    }
+}
+
+pub struct Directory<'a> {
+    dirp: *mut libc::DIR,
+    _phantom: PhantomData<&'a libc::DIR>,
+}
+
+pub enum WalkResult {
+    Continue,
+    Abort,
+    Skip,
+}
+
+impl<'a> Directory<'a> {
+    pub fn open(path: &CStr) -> io::Result<Directory> {
+        let dirp = unsafe { libc::opendir(path.as_ptr()) };
+        if dirp.is_null() {
+            return Err(io::Error::last_os_error());
+        }
+        Ok(Directory {
+            dirp,
+            _phantom: PhantomData,
+        })
+    }
+
+    pub fn read(&mut self) -> io::Result<Option<DirEntry<'_>>> {
+        *errno() = 0;
+        let e = unsafe { libc::readdir(self.dirp) };
+        if e.is_null() {
+            return if *errno() != 0 {
+                Err(io::Error::last_os_error())
+            } else {
+                Ok(None)
+            };
+        }
+        // Skip both "." and ".."
+        unsafe {
+            let entry = &*e;
+            let d_name = CStr::from_ptr(entry.d_name.as_ptr());
+            return if d_name == cstr!(".") || d_name == cstr!("..") {
+                self.read()
+            } else {
+                let e = DirEntry {
+                    dir: self,
+                    entry,
+                    name_len: d_name.to_bytes().len(),
+                };
+                Ok(Some(e))
+            };
+        }
+    }
+
+    pub fn rewind(&mut self) {
+        unsafe { libc::rewinddir(self.dirp) }
+    }
+
+    pub fn path(&self, buf: &mut [u8]) -> io::Result<usize> {
+        fd_path(self.as_raw_fd(), buf)
+    }
+
+    pub fn post_order_walk<F: FnMut(&DirEntry) -> io::Result<WalkResult>>(
+        &mut self,
+        mut f: F,
+    ) -> io::Result<WalkResult> {
+        self.post_order_walk_impl(&mut f)
+    }
+
+    pub fn pre_order_walk<F: FnMut(&DirEntry) -> io::Result<WalkResult>>(
+        &mut self,
+        mut f: F,
+    ) -> io::Result<WalkResult> {
+        self.pre_order_walk_impl(&mut f)
+    }
+
+    pub fn remove_all(&mut self) -> io::Result<()> {
+        self.post_order_walk(|e| {
+            e.unlink()?;
+            Ok(WalkResult::Continue)
+        })?;
+        Ok(())
+    }
+}
+
+impl Directory<'_> {
+    fn post_order_walk_impl<F: FnMut(&DirEntry) -> io::Result<WalkResult>>(
+        &mut self,
+        f: &mut F,
+    ) -> io::Result<WalkResult> {
+        use WalkResult::*;
+        loop {
+            match self.read()? {
+                None => return Ok(Continue),
+                Some(ref e) => {
+                    if e.is_dir() {
+                        let mut dir = e.open_as_dir()?;
+                        if let Abort = dir.post_order_walk_impl(f)? {
+                            return Ok(Abort);
+                        }
+                    }
+                    match f(e)? {
+                        Abort => return Ok(Abort),
+                        Skip => return Ok(Continue),
+                        Continue => {}
+                    }
+                }
+            }
+        }
+    }
+
+    fn pre_order_walk_impl<F: FnMut(&DirEntry) -> io::Result<WalkResult>>(
+        &mut self,
+        f: &mut F,
+    ) -> io::Result<WalkResult> {
+        use WalkResult::*;
+        loop {
+            match self.read()? {
+                None => return Ok(Continue),
+                Some(ref e) => match f(e)? {
+                    Abort => return Ok(Abort),
+                    Skip => return Ok(Continue),
+                    Continue => {
+                        if e.is_dir() {
+                            let mut dir = e.open_as_dir()?;
+                            if let Abort = dir.pre_order_walk_impl(f)? {
+                                return Ok(Abort);
+                            }
+                        }
+                    }
+                },
+            }
+        }
+    }
+}
+
+impl TryFrom<OwnedFd> for Directory<'_> {
+    type Error = io::Error;
+
+    fn try_from(fd: OwnedFd) -> io::Result<Self> {
+        let dirp = unsafe { libc::fdopendir(fd.into_raw_fd()) };
+        if dirp.is_null() {
+            return Err(io::Error::last_os_error());
+        }
+        Ok(Directory {
+            dirp,
+            _phantom: PhantomData,
+        })
+    }
+}
+
+impl AsRawFd for Directory<'_> {
+    fn as_raw_fd(&self) -> RawFd {
+        unsafe { libc::dirfd(self.dirp) }
+    }
+}
+
+impl<'a> AsFd for Directory<'a> {
+    fn as_fd(&self) -> BorrowedFd<'a> {
+        unsafe { BorrowedFd::borrow_raw(self.as_raw_fd()) }
+    }
+}
+
+impl Drop for Directory<'_> {
+    fn drop(&mut self) {
+        unsafe {
+            libc::closedir(self.dirp);
+        }
+    }
+}
+
+pub fn rm_rf(path: &CStr) -> io::Result<()> {
+    unsafe {
+        let mut stat: libc::stat = mem::zeroed();
+        if libc::lstat(path.as_ptr(), &mut stat) < 0 {
+            return Err(io::Error::last_os_error());
+        }
+        if (stat.st_mode & libc::S_IFMT as u32) == libc::S_IFDIR as u32 {
+            let mut dir = Directory::open(path)?;
+            dir.remove_all()?;
+        }
+        if libc::remove(path.as_ptr()) < 0 {
+            return Err(io::Error::last_os_error());
+        }
+    }
+    Ok(())
+}