8.8.1 完整示例

Tue, 11 Aug 2026 11:30:00 +0800

译文 · 基于 Comprehensive Rust

原文链接: https://google.github.io/comprehensive-rust/unsafe-deep-dive/pinning/drop-and-not-unpin-worked-example.html

8.8.1 完整示例

 1
 2
 3
 4
 5
 6
 7
 8
 9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53


// Copyright 2026 Google LLC
// SPDX-License-Identifier: Apache-2.0
use std::cell::RefCell;
use std::marker::PhantomPinned;
use std::mem;
use std::pin::Pin;

thread_local! {
 static BATCH_FOR_PROCESSING: RefCell<Vec<String>> = RefCell::new(Vec::new());
}

#[derive(Debug)]
struct CustomString(String);

#[derive(Debug)]
struct SelfRef {
 data: CustomString,
 ptr: *const CustomString,
 _pin: PhantomPinned,
}

impl SelfRef {
 fn new(data: &str) -> Pin<Box<SelfRef>> {
 let mut boxed = Box::pin(SelfRef {
 data: CustomString(data.to_owned()),
 ptr: std::ptr::null(),
 _pin: PhantomPinned,
 });

 let ptr: *const CustomString = &boxed.data;
 unsafe {
 Pin::get_unchecked_mut(Pin::as_mut(&mut boxed)).ptr = ptr;
 }
 boxed
 }
}

impl Drop for SelfRef {
 fn drop(&mut self) {
 // SAFETY: 安全，因为我们从 String 中读取字节
 let payload = unsafe { std::ptr::read(&self.data) };
 BATCH_FOR_PROCESSING.with(|log| log.borrow_mut().push(payload.0));
 }
}

fn main() {
 let pinned = SelfRef::new("Rust 🦀");
 drop(pinned);

 BATCH_FOR_PROCESSING.with(|batch| {
 println!("Batch: {:?}", batch.borrow());
 });
}

本示例使用 Drop trait 添加数据以供后续处理，例如遥测或日志。

8.8 `Pin` 与 `Drop` on 编程那些事儿

8.8.1 完整示例

8.8.1 完整示例