Merge pull request rust-osdev#1014 from nicholasbishop/bishop-simplif…

…y-to-string

Simplify DevicePath to_string return type

uefi-test-runner/src/proto/device_path.rs

@@ -77,7 +77,7 @@ pub fn test(image: Handle, bt: &BootServices) {
         let path_components = device_path
             .node_iter()
             .map(|node| node.to_string(bt, DisplayOnly(false), AllowShortcuts(false)))
-            .map(|str| str.unwrap().unwrap().to_string())
+            .map(|str| str.unwrap().to_string())
             .collect::<Vec<_>>();
 
         let expected_device_path_str_components = &[
@@ -104,7 +104,6 @@ pub fn test(image: Handle, bt: &BootServices) {
         let path = device_path
             .to_string(bt, DisplayOnly(false), AllowShortcuts(false))
             .unwrap()
-            .unwrap()
             .to_string();
 
         assert_eq!(path, expected_device_path_str);

uefi/CHANGELOG.md

@@ -4,6 +4,10 @@
 - Implemented `PartialEq<char>` for `Char8` and `Char16`.
 - Added `CStr16::from_char16_with_nul` and `Char16::from_char16_with_nul_unchecked`.
 
+## Changed
+- `DevicePath::to_string` and `DevicePathNode::to_string` now return
+  out-of-memory errors as part of the error type rather than with an `Option`.
+
 # uefi - 0.26.0 (2023-11-12)
 
 ## Added

uefi/src/proto/device_path/mod.rs

@@ -217,27 +217,24 @@ impl DevicePathNode {
 
     /// Transforms the device path node to its string representation using the
     /// [`DevicePathToText`] protocol.
-    ///
-    /// The resulting string is only None, if there was not enough memory.
     #[cfg(feature = "alloc")]
     pub fn to_string(
         &self,
         bs: &BootServices,
         display_only: DisplayOnly,
         allow_shortcuts: AllowShortcuts,
-    ) -> Result<Option<CString16>, DevicePathToTextError> {
+    ) -> Result<CString16, DevicePathToTextError> {
         let to_text_protocol = open_text_protocol(bs)?;
 
-        let cstring16 = to_text_protocol
+        to_text_protocol
             .convert_device_node_to_text(bs, self, display_only, allow_shortcuts)
-            .ok()
             .map(|pool_string| {
                 let cstr16 = &*pool_string;
                 // Another allocation; pool string is dropped. This overhead
                 // is negligible. CString16 is more convenient to use.
                 CString16::from(cstr16)
-            });
-        Ok(cstring16)
+            })
+            .map_err(|_| DevicePathToTextError::OutOfMemory)
     }
 }
 
@@ -430,27 +427,24 @@ impl DevicePath {
 
     /// Transforms the device path to its string representation using the
     /// [`DevicePathToText`] protocol.
-    ///
-    /// The resulting string is only None, if there was not enough memory.
     #[cfg(feature = "alloc")]
     pub fn to_string(
         &self,
         bs: &BootServices,
         display_only: DisplayOnly,
         allow_shortcuts: AllowShortcuts,
-    ) -> Result<Option<CString16>, DevicePathToTextError> {
+    ) -> Result<CString16, DevicePathToTextError> {
         let to_text_protocol = open_text_protocol(bs)?;
 
-        let cstring16 = to_text_protocol
+        to_text_protocol
             .convert_device_path_to_text(bs, self, display_only, allow_shortcuts)
-            .ok()
             .map(|pool_string| {
                 let cstr16 = &*pool_string;
                 // Another allocation; pool string is dropped. This overhead
                 // is negligible. CString16 is more convenient to use.
                 CString16::from(cstr16)
-            });
-        Ok(cstring16)
+            })
+            .map_err(|_| DevicePathToTextError::OutOfMemory)
     }
 }
 
@@ -789,6 +783,8 @@ pub enum DevicePathToTextError {
     /// The handle supporting the [`DevicePathToText`] protocol exists but it
     /// could not be opened.
     CantOpenProtocol(crate::Error),
+    /// Failed to allocate pool memory.
+    OutOfMemory,
 }
 
 impl Display for DevicePathToTextError {