kernel: Add a higher level find api

This is just a bit nicer for callers as especially by using `AsRef<[u8]>`
they can pass a string and not a byte array as a lookup key.

Signed-off-by: Colin Walters <[email protected]>

Author: cgwalters

crates/lib/src/install.rs

@@ -1663,7 +1663,7 @@ struct RootMountInfo {
 /// Discover how to mount the root filesystem, using existing kernel arguments and information
 /// about the root mount.
 fn find_root_args_to_inherit(cmdline: &Cmdline, root_info: &Filesystem) -> Result<RootMountInfo> {
-    let root = cmdline.iter().find(|p| p.key == b"root");
+    let root = cmdline.find("root");
     // If we have a root= karg, then use that
     let (mount_spec, kargs) = if let Some(root) = root {
         let rootflags = cmdline

crates/lib/src/kernel.rs

@@ -32,6 +32,12 @@ impl<'a> Cmdline<'a> {
             })
             .map(Parameter::from)
     }
+
+    /// Locate a kernel argument with the given key name.
+    pub fn find(&'a self, key: impl AsRef<[u8]>) -> Option<Parameter<'a>> {
+        let key = key.as_ref();
+        self.iter().find(|p| p.key == key)
+    }
 }
 
 #[derive(Debug, Eq)]
@@ -237,6 +243,10 @@ mod tests {
         );
 
         assert_eq!(iter.next(), None);
+
+        // Test the find API
+        assert_eq!(kargs.find("foo").unwrap().value.unwrap(), b"bar");
+        assert!(kargs.find("nothing").is_none());
     }
 
     #[test]