partial key for searching wildcard keys

btrfs/src/tree.rs

@@ -13,6 +13,81 @@ use alloc::{
 use scroll::Pread;
 use zerocopy::FromBytes;
 
+pub struct PartialKey {
+    id: Option<KnownObjectId>,
+    ty: Option<ObjectType>,
+    offset: Option<u64>,
+}
+
+impl PartialKey {
+    pub fn new(id: Option<KnownObjectId>, ty: Option<ObjectType>, offset: Option<u64>) -> Self {
+        Self { id, ty, offset }
+    }
+}
+
+impl PartialEq<Key> for PartialKey {
+    fn eq(&self, other: &Key) -> bool {
+        self.id.map(|id| id == other.id()).unwrap_or(true)
+            && self.ty.map(|ty| ty == other.ty()).unwrap_or(true)
+            && self
+                .offset
+                .map(|offset| offset == other.offset.get())
+                .unwrap_or(true)
+    }
+}
+
+/// compares Self to a key, by comparing each item with the element in key if present, and skipping to the next item if missing.
+impl PartialOrd<Key> for PartialKey {
+    fn partial_cmp(&self, other: &Key) -> Option<core::cmp::Ordering> {
+        let id = self.id.and_then(|id| id.partial_cmp(&other.id()));
+        let ty = self.ty.and_then(|ty| ty.partial_cmp(&other.ty()));
+        let offset = self
+            .offset
+            .and_then(|offset| offset.partial_cmp(&other.offset.get()));
+
+        match id {
+            Some(core::cmp::Ordering::Equal) | None => match ty {
+                Some(core::cmp::Ordering::Equal) | None => offset,
+                ord => ord,
+            },
+            ord => ord,
+        }
+    }
+}
+
+#[cfg(test)]
+mod partial_key_tests {
+    use test_log::test;
+
+    use super::*;
+
+    #[test]
+    fn test_partial_key_ord() {
+        let key = Key::new(
+            KnownObjectId::ChunkTree,
+            ObjectType::DirItem,
+            0x8dbfc2d2, // crc of "default"
+        );
+
+        let pkey = PartialKey::new(
+            Some(KnownObjectId::ChunkTree),
+            Some(ObjectType::DirItem),
+            None,
+        );
+        assert_eq!(pkey.partial_cmp(&key), None);
+
+        let pkey = PartialKey::new(
+            Some(KnownObjectId::ChunkTree),
+            Some(ObjectType::DirItem),
+            Some(0xdeadbeef),
+        );
+        assert_ne!(pkey.partial_cmp(&key), Some(core::cmp::Ordering::Equal));
+
+        let pkey = PartialKey::new(None, Some(ObjectType::DirItem), Some(0xdeadbeef));
+        assert_ne!(pkey.partial_cmp(&key), None);
+    }
+}
+
 #[derive(Debug, Clone)]
 pub struct BTreeLeafNode {
     pub header: Header,