map: allow partial unmarshaling

Signed-off-by: Florian Lehner <[email protected]>

Author: florianl

internal/sysenc/buffer.go

@@ -68,10 +68,17 @@ func (b Buffer) Pointer() sys.Pointer {
 
 // Unmarshal the buffer into the provided value.
 func (b Buffer) Unmarshal(data any) error {
+	return b.UnmarshalWithLimit(data, b.size)
+}
+
+// UnmarshalWithLimit unmarshals the buffer up to limit into the provided value.
+func (b Buffer) UnmarshalWithLimit(data any, limit int) error {
 	if b.size == syscallPointerOnly {
 		return nil
 	}
-
+	if b.size != limit {
+		return Unmarshal(data, b.unsafeBytes()[:limit])
+	}
 	return Unmarshal(data, b.unsafeBytes())
 }
 

map.go

@@ -1155,7 +1155,7 @@ func (m *Map) batchLookupCmd(cmd sys.Cmd, cursor *MapBatchCursor, count int, key
 		return int(attr.Count), sysErr
 	}
 
-	if err := keyBuf.Unmarshal(keysOut); err != nil {
+	if err := keyBuf.UnmarshalWithLimit(keysOut, int(attr.Count)*int(m.keySize)); err != nil {
 		return 0, err
 	}