rust存取一个含有borrowed域的结构体
直接存取不可以：
use std::io;
use serde::{Serialize, Deserialize};
extern crate bincode;
#[derive(Debug, Serialize, Deserialize)]
struct A<'a> {
a: &'a [u8]
}
fn main() {
let a: &[u8] = &[2, 3, 5, 7, 11, 13];
let b = A{a};
let mut v = Vec::new();
bincode::serialize_into(&mut v, &b).unwrap();
let mut reader = io::Cursor::new(&v);
let c = bincode::deserialize_from::<_, A>(&mut reader).unwrap();
println!("{:?}", c);
}
会报错：
error: implementation of `Deserialize` is not general enough
--> src/main.rs:19:13
|
19 | let c = bincode::deserialize_from::<_, A>(&mut reader).unwrap();
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ implementation of `Deserialize` is not general enough
|
= note: `A<'_>` must implement `Deserialize<'0>`, for any lifetime `'0`...
= note: ...but `A<'_>` actually implements `Deserialize<'1>`, for some specific lifetime `'1`
error: could not compile `serde-borrowed` due to previous error
这是因为BufWriter里的缓存的所有权不是调用者的，可能会被释放，这样构造含有borrowed域的结构体时就不能安全地借用读出来的数据了。
可以用std::borrow::Cow实现在serialize的时候borrow，但是在deserialize的时候create，从而解决这个问题:
use std::{io, borrow::Cow};
use serde::{Serialize, Deserialize};
extern crate bincode;
#[derive(Debug, Serialize, Deserialize)]
struct A<'a> {
a: Cow<'a, [u8]>,
}
fn main() {
let a: &[u8] = &[2, 3, 5, 7, 11, 13];
let b = A{a: Cow::Borrowed(a)};
let mut v = Vec::new();
bincode::serialize_into(&mut v, &b).unwrap();
let mut reader = io::Cursor::new(&v);
let c = bincode::deserialize_from::<_, A>(&mut reader).unwrap();
if let Cow::Borrowed(_) = c.a {
panic!();
}
println!("{:?}", c);
}
此外，bincode有forward_read_*系列函数，好像也可以通过转移所有权解决这个问题：
https://docs.rs/bincode/1.3.1/bincode/de/read/trait.BincodeRead.html
但是我不会。
