1  // Copyright (c) 2019-2025 Alpha-Delta Network Inc.
 2  // This file is part of the alphavm library.
 3  
 4  // Licensed under the Apache License, Version 2.0 (the "License");
 5  // you may not use this file except in compliance with the License.
 6  // You may obtain a copy of the License at:
 7  
 8  // http://www.apache.org/licenses/LICENSE-2.0
 9  
10  // Unless required by applicable law or agreed to in writing, software
11  // distributed under the License is distributed on an "AS IS" BASIS,
12  // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13  // See the License for the specific language governing permissions and
14  // limitations under the License.
15  
16  /// A `Defer` holds a closure that is executed when the instance is dropped.
17  pub struct Defer<F: FnOnce()> {
18      f: Option<F>,
19  }
20  
21  impl<F: FnOnce()> Defer<F> {
22      pub fn new(f: F) -> Self {
23          Defer { f: Some(f) }
24      }
25  }
26  
27  impl<F: FnOnce()> Drop for Defer<F> {
28      fn drop(&mut self) {
29          if let Some(f) = self.f.take() {
30              f();
31          }
32      }
33  }
34  
35  #[macro_export]
36  macro_rules! defer {
37      ($($body:tt)*) => {
38          let _defer_guard = $crate::Defer::new(|| { $($body)* });
39      };
40  }