device path: add iter method and test (#264)

Author: nicholasbishop

src/proto/device_path.rs

@@ -55,6 +55,51 @@ impl DevicePath {
     pub fn length(&self) -> u16 {
         self.header.length
     }
+
+    /// True if this node ends the entire path.
+    pub fn is_end_entire(&self) -> bool {
+        self.device_type() == DeviceType::END && self.sub_type() == DeviceSubType::END_ENTIRE
+    }
+
+    /// Get an iterator over the [`DevicePath`] nodes starting at
+    /// `self`. Iteration ends when a path is reached where
+    /// [`is_end_entire`][DevicePath::is_end_entire] is true. That ending path
+    /// is not returned by the iterator.
+    pub fn iter(&self) -> DevicePathIterator {
+        DevicePathIterator { path: self }
+    }
+}
+
+/// Iterator over [`DevicePath`] nodes.
+///
+/// Iteration ends when a path is reached where [`DevicePath::is_end_entire`]
+/// is true. That ending path is not returned by the iterator.
+///
+/// This struct is returned by [`DevicePath::iter`].
+pub struct DevicePathIterator<'a> {
+    path: &'a DevicePath,
+}
+
+impl<'a> Iterator for DevicePathIterator<'a> {
+    type Item = &'a DevicePath;
+
+    fn next(&mut self) -> Option<Self::Item> {
+        let cur = self.path;
+
+        if cur.is_end_entire() {
+            return None;
+        }
+
+        // Advance self.path to the next entry.
+        let len = cur.header.length;
+        let byte_ptr = cur as *const DevicePath as *const u8;
+        unsafe {
+            let next_path_ptr = byte_ptr.add(len as usize) as *const DevicePath;
+            self.path = &*next_path_ptr;
+        }
+
+        Some(cur)
+    }
 }
 
 newtype_enum! {

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

@@ -0,0 +1,27 @@
+use uefi::prelude::*;
+use uefi::proto::device_path::DevicePath;
+use uefi::proto::loaded_image::LoadedImage;
+use uefi::table::boot::BootServices;
+
+pub fn test(image: Handle, bt: &BootServices) {
+    info!("Running device path protocol test");
+
+    let loaded_image = bt
+        .handle_protocol::<LoadedImage>(image)
+        .expect_success("Failed to open LoadedImage protocol");
+    let loaded_image = unsafe { &*loaded_image.get() };
+
+    let device_path = bt
+        .handle_protocol::<DevicePath>(loaded_image.device())
+        .expect_success("Failed to open DevicePath protocol");
+    let device_path = unsafe { &*device_path.get() };
+
+    for path in device_path.iter() {
+        info!(
+            "path: type={:?}, subtype={:?}, length={}",
+            path.device_type(),
+            path.sub_type(),
+            path.length(),
+        );
+    }
+}

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

@@ -13,6 +13,7 @@ pub fn test(image: Handle, st: &mut SystemTable<Boot>) {
     test_protocols_per_handle(image, bt);
 
     debug::test(bt);
+    device_path::test(image, bt);
     media::test(bt);
     pi::test(bt);
 
@@ -54,6 +55,7 @@ fn test_protocols_per_handle(image: Handle, bt: &BootServices) {
 
 mod console;
 mod debug;
+mod device_path;
 mod media;
 mod pi;
 #[cfg(any(