Rewrite magisk logging implementation

native/src/base/files.rs

@@ -1,27 +1,27 @@
-use mem::MaybeUninit;
-use std::cmp::min;
-use std::ffi::CStr;
-use std::fs::File;
-use std::io::{BufRead, BufReader, Read, Seek, SeekFrom, Write};
-use std::ops::Deref;
-use std::os::fd::{AsFd, BorrowedFd, IntoRawFd};
-use std::os::unix::ffi::OsStrExt;
-use std::os::unix::io::{AsRawFd, FromRawFd, OwnedFd, RawFd};
-use std::path::Path;
-use std::{io, mem, ptr, slice};
-
-use bytemuck::{bytes_of_mut, Pod};
-use libc::{
-    c_uint, dirent, makedev, mode_t, EEXIST, ENOENT, F_OK, O_CLOEXEC, O_CREAT, O_PATH, O_RDONLY,
-    O_RDWR, O_TRUNC, O_WRONLY,
-};
-use num_traits::AsPrimitive;
-
 use crate::cxx_extern::readlinkat_for_cxx;
 use crate::{
     cstr, errno, error, FsPath, FsPathBuf, LibcReturn, Utf8CStr, Utf8CStrBuf, Utf8CStrBufArr,
     Utf8CStrWrite,
 };
+use bytemuck::{bytes_of_mut, Pod};
+use libc::{
+    c_uint, dirent, makedev, mode_t, EEXIST, ENOENT, F_OK, O_CLOEXEC, O_CREAT, O_PATH, O_RDONLY,
+    O_RDWR, O_TRUNC, O_WRONLY,
+};
+use mem::MaybeUninit;
+use num_traits::AsPrimitive;
+use std::cmp::min;
+use std::ffi::CStr;
+use std::fs::File;
+use std::io::{BufRead, BufReader, Read, Seek, SeekFrom, Write};
+use std::mem::ManuallyDrop;
+use std::ops::Deref;
+use std::os::fd::{AsFd, BorrowedFd, IntoRawFd};
+use std::os::unix::ffi::OsStrExt;
+use std::os::unix::io::{AsRawFd, FromRawFd, OwnedFd, RawFd};
+use std::path::Path;
+use std::sync::Arc;
+use std::{io, mem, ptr, slice};
 
 pub fn __open_fd_impl(path: &Utf8CStr, flags: i32, mode: mode_t) -> io::Result<OwnedFd> {
     unsafe {
@@ -1030,3 +1030,37 @@ pub fn parse_mount_info(pid: &str) -> Vec<MountInfo> {
     }
     res
 }
+
+#[derive(Clone)]
+pub enum SharedFd {
+    None,
+    Shared(Arc<OwnedFd>),
+}
+
+impl From<OwnedFd> for SharedFd {
+    fn from(fd: OwnedFd) -> Self {
+        SharedFd::Shared(Arc::new(fd))
+    }
+}
+
+impl SharedFd {
+    pub const fn new() -> Self {
+        SharedFd::None
+    }
+
+    // This is unsafe because we cannot create multiple mutable references to the same fd.
+    // This can only be safely used if and only if the underlying fd points to a pipe,
+    // and the read/write operations performed on the file involves bytes less than PIPE_BUF.
+    pub unsafe fn as_file(&self) -> Option<ManuallyDrop<File>> {
+        match self {
+            SharedFd::None => None,
+            SharedFd::Shared(arc) => Some(ManuallyDrop::new(File::from_raw_fd(arc.as_raw_fd()))),
+        }
+    }
+}
+
+impl Default for SharedFd {
+    fn default() -> Self {
+        SharedFd::None
+    }
+}