Merge pull request #898 from nicholasbishop/bishop-try-exists

uefi: Change try_exists to return FileSystemResult<bool>

Author: phip1611

CHANGELOG.md

@@ -11,6 +11,7 @@
 - `uefi::proto::shim` is now available on 32-bit x86 targets.
 - `Parity` and `StopBits` are now a newtype-enums instead of Rust enums. Their
   members now have upper-case names.
+- `FileSystem::try_exists` now returns `FileSystemResult<bool>`.
 
 ## uefi-macros - [Unreleased]
 

uefi-test-runner/src/fs/mod.rs

@@ -62,8 +62,7 @@ pub fn test(sfs: ScopedProtocol<SimpleFileSystem>) -> Result<(), fs::Error> {
     // test remove dir all
     fs.remove_dir_all(cstr16!("foo_dir\\1"))?;
     // file should not be available after remove all
-    let err = fs.try_exists(cstr16!("foo_dir\\1"));
-    assert!(err.is_err());
+    assert!(!fs.try_exists(cstr16!("foo_dir\\1"))?);
 
     Ok(())
 }

uefi/src/fs/file_system/fs.rs

@@ -27,10 +27,22 @@ impl<'a> FileSystem<'a> {
         Self(proto)
     }
 
-    /// Tests if the underlying file exists. If this returns `Ok`, the file
-    /// exists.
-    pub fn try_exists(&mut self, path: impl AsRef<Path>) -> FileSystemResult<()> {
-        self.metadata(path).map(|_| ())
+    /// Returns `Ok(true)` if the path points at an existing file.
+    ///
+    /// If the file does not exist, `Ok(false)` is returned. If it cannot be
+    /// determined whether the file exists or not, an error is returned.
+    pub fn try_exists(&mut self, path: impl AsRef<Path>) -> FileSystemResult<bool> {
+        match self.open(path.as_ref(), UefiFileMode::Read, false) {
+            Ok(_) => Ok(true),
+            Err(Error::Io(err)) => {
+                if err.uefi_error.status() == Status::NOT_FOUND {
+                    Ok(false)
+                } else {
+                    Err(Error::Io(err))
+                }
+            }
+            Err(err) => Err(err),
+        }
     }
 
     /// Copies the contents of one file to another. Creates the destination file
@@ -69,7 +81,7 @@ impl<'a> FileSystem<'a> {
         dirs_to_create.reverse();
 
         for parent in dirs_to_create {
-            if self.try_exists(&parent).is_err() {
+            if !self.try_exists(&parent)? {
                 self.create_dir(parent)?;
             }
         }
@@ -260,7 +272,7 @@ impl<'a> FileSystem<'a> {
 
         // since there is no .truncate() in UEFI, we delete the file first it it
         // exists.
-        if self.try_exists(path).is_ok() {
+        if self.try_exists(path)? {
             self.remove_file(path)?;
         }