Rename ErrorKind::Unknown to Uncategorized.

[rust.git] / library / std / src / sys / windows / fs.rs

diff --git a/library/std/src/sys/windows/fs.rs b/library/std/src/sys/windows/fs.rs
index 8e6bd76f85f0614fc5a6b210fc1db19921708599..c677adae6888e0c30e24e182539584bef1873784 100644 (file)
--- a/library/std/src/sys/windows/fs.rs
+++ b/library/std/src/sys/windows/fs.rs
@@ -514,7 +514,7 @@ fn readlink(&self) -> io::Result<PathBuf> {
                 }
                 _ => {
                     return Err(io::Error::new_const(
-                        io::ErrorKind::Other,
+                        io::ErrorKind::Uncategorized,
                         &"Unsupported reparse point type",
                     ));
                 }
@@ -944,3 +944,31 @@ fn symlink_junction_inner(original: &Path, junction: &Path) -> io::Result<()> {
         .map(drop)
     }
 }
+
+// Try to see if a file exists but, unlike `exists`, report I/O errors.
+pub fn try_exists(path: &Path) -> io::Result<bool> {
+    // Open the file to ensure any symlinks are followed to their target.
+    let mut opts = OpenOptions::new();
+    // No read, write, etc access rights are needed.
+    opts.access_mode(0);
+    // Backup semantics enables opening directories as well as files.
+    opts.custom_flags(c::FILE_FLAG_BACKUP_SEMANTICS);
+    match File::open(path, &opts) {
+        Err(e) => match e.kind() {
+            // The file definitely does not exist
+            io::ErrorKind::NotFound => Ok(false),
+
+            // `ERROR_SHARING_VIOLATION` means that the file has been locked by
+            // another process. This is often temporary so we simply report it
+            // as the file existing.
+            _ if e.raw_os_error() == Some(c::ERROR_SHARING_VIOLATION as i32) => Ok(true),
+
+            // Other errors such as `ERROR_ACCESS_DENIED` may indicate that the
+            // file exists. However, these types of errors are usually more
+            // permanent so we report them here.
+            _ => Err(e),
+        },
+        // The file was opened successfully therefore it must exist,
+        Ok(_) => Ok(true),
+    }
+}