Convert string to key code

rc keymaps list keycodes as strings. These need to be converted to
numeric keycodes before the keymap can be loaded. So, add a function
to convert a string to keycode.

Signed-off-by: Sean Young <sean@mess.org>

src/attribute_set.rs

@@ -182,6 +182,20 @@ macro_rules! evdev_enum {
         impl $t {
             $($(#[$attr])* pub const $c: Self = Self($val);)*
         }
+        impl std::str::FromStr for $t {
+            type Err = crate::EnumParseError;
+
+            fn from_str(s: &str) ->  Result<Self, Self::Err> {
+                let map: &[(&'static str, $t)] = &[
+                    $((stringify!($c), Self::$c),)*
+                ];
+
+                match map.iter().find(|e| e.0 == s) {
+                    Some(e) => Ok(e.1),
+                    None => Err(crate::EnumParseError(())),
+                }
+            }
+        }
         impl std::fmt::Debug for $t {
             fn fmt(&self, f: &mut std::fmt::Formatter) -> std::fmt::Result {
                 match *self {

src/lib.rs

@@ -290,3 +290,6 @@ pub(crate) fn nix_err(err: nix::Error) -> io::Error {
 pub(crate) unsafe fn cast_to_bytes<T: ?Sized>(mem: &T) -> &[u8] {
     std::slice::from_raw_parts(mem as *const T as *const u8, std::mem::size_of_val(mem))
 }
+
+#[derive(Debug, Clone, PartialEq, Eq)]
+pub struct EnumParseError(());

src/scancodes.rs

@@ -555,3 +555,11 @@ evdev_enum!(
     BTN_TRIGGER_HAPPY39 = 0x2e6,
     BTN_TRIGGER_HAPPY40 = 0x2e7,
 );
+
+#[test]
+fn from_str() {
+    use std::str::FromStr;
+
+    assert_eq!(Key::from_str("KEY_A"), Ok(Key::KEY_A));
+    assert!(Key::from_str("KEY_FOOBAR").is_err());
+}