如何在字节(Vec<u8>或&[u8])上使用Rust正则表达式？

Question

我有一个&[u8]，我需要验证它是否符合某种模式。在&[u8]上使用regexes的例子有文档中和模块文档中。我从例句部分获取代码并将其放入main()中，并添加了一些声明：

extern crate regex;
use regex::Regex;

fn main() {
    let re = Regex::new(r"'([^']+)'\s+\((\d{4})\)").unwrap();
    let text = b"Not my favorite movie: 'Citizen Kane' (1941).";
    let caps = re.captures(text).unwrap();
    assert_eq!(&caps[1], &b"Citizen Kane"[..]);
    assert_eq!(&caps[2], &b"1941"[..]);
    assert_eq!(&caps[0], &b"'Citizen Kane' (1941)"[..]);
    // You can also access the groups by index using the Index notation.
    // Note that this will panic on an invalid index.
    assert_eq!(&caps[1], b"Citizen Kane");
    assert_eq!(&caps[2], b"1941");
    assert_eq!(&caps[0], b"'Citizen Kane' (1941)");
}

我不明白这个示例代码与常规字符串匹配有什么不同，而且编译器确实抱怨期待一个&str。通常，代码并不暗示它与通常的字符串匹配有何不同，我对此没有任何问题。

我想我做了一些基本错误，比如缺少或更精确的进口。我在这里玩猜谜游戏，因为文档没有提供工作示例(就像它们经常做的那样)，而这一次编译器也没能推动我朝正确的方向前进。

下面是编译器消息：

error[E0308]: mismatched types
 --> src/main.rs:7:28
  |
7 |     let caps = re.captures(text).unwrap();
  |                            ^^^^ expected str, found array of 45 elements
  |
  = note: expected type `&str`
             found type `&[u8; 45]`

error[E0277]: the trait bound `str: std::cmp::PartialEq<[u8]>` is not satisfied
 --> src/main.rs:8:5
  |
8 |     assert_eq!(&caps[1], &b"Citizen Kane"[..]);
  |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ can't compare `str` with `[u8]`
  |
  = help: the trait `std::cmp::PartialEq<[u8]>` is not implemented for `str`
  = note: required because of the requirements on the impl of `std::cmp::PartialEq<&[u8]>` for `&str`
  = note: this error originates in a macro outside of the current crate

error[E0277]: the trait bound `str: std::cmp::PartialEq<[u8]>` is not satisfied
 --> src/main.rs:9:5
  |
9 |     assert_eq!(&caps[2], &b"1941"[..]);
  |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ can't compare `str` with `[u8]`
  |
  = help: the trait `std::cmp::PartialEq<[u8]>` is not implemented for `str`
  = note: required because of the requirements on the impl of `std::cmp::PartialEq<&[u8]>` for `&str`
  = note: this error originates in a macro outside of the current crate

error[E0277]: the trait bound `str: std::cmp::PartialEq<[u8]>` is not satisfied
  --> src/main.rs:10:5
   |
10 |     assert_eq!(&caps[0], &b"'Citizen Kane' (1941)"[..]);
   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ can't compare `str` with `[u8]`
   |
   = help: the trait `std::cmp::PartialEq<[u8]>` is not implemented for `str`
   = note: required because of the requirements on the impl of `std::cmp::PartialEq<&[u8]>` for `&str`
   = note: this error originates in a macro outside of the current crate

error[E0277]: the trait bound `str: std::cmp::PartialEq<[u8; 12]>` is not satisfied
  --> src/main.rs:13:5
   |
13 |     assert_eq!(&caps[1], b"Citizen Kane");
   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ can't compare `str` with `[u8; 12]`
   |
   = help: the trait `std::cmp::PartialEq<[u8; 12]>` is not implemented for `str`
   = note: required because of the requirements on the impl of `std::cmp::PartialEq<&[u8; 12]>` for `&str`
   = note: this error originates in a macro outside of the current crate

error[E0277]: the trait bound `str: std::cmp::PartialEq<[u8; 4]>` is not satisfied
  --> src/main.rs:14:5
   |
14 |     assert_eq!(&caps[2], b"1941");
   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ can't compare `str` with `[u8; 4]`
   |
   = help: the trait `std::cmp::PartialEq<[u8; 4]>` is not implemented for `str`
   = note: required because of the requirements on the impl of `std::cmp::PartialEq<&[u8; 4]>` for `&str`
   = note: this error originates in a macro outside of the current crate

error[E0277]: the trait bound `str: std::cmp::PartialEq<[u8; 21]>` is not satisfied
  --> src/main.rs:15:5
   |
15 |     assert_eq!(&caps[0], b"'Citizen Kane' (1941)");
   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ can't compare `str` with `[u8; 21]`
   |
   = help: the trait `std::cmp::PartialEq<[u8; 21]>` is not implemented for `str`
   = note: required because of the requirements on the impl of `std::cmp::PartialEq<&[u8; 21]>` for `&str`
   = note: this error originates in a macro outside of the current crate

Answer 1

并添加了一些声明

不幸的是，你加错了。请注意，您链接到的文档是如何用于结构regex::bytes::Regex，而不是regex::Regex的--它们是两种不同的类型！

extern crate regex;
use regex::bytes::Regex;
//         ^^^^^

fn main() {
    let re = Regex::new(r"'([^']+)'\s+\((\d{4})\)").unwrap();
    let text = b"Not my favorite movie: 'Citizen Kane' (1941).";
    let caps = re.captures(text).unwrap();

    assert_eq!(&caps[1], &b"Citizen Kane"[..]);
    assert_eq!(&caps[2], &b"1941"[..]);
    assert_eq!(&caps[0], &b"'Citizen Kane' (1941)"[..]);

    assert_eq!(&caps[1], b"Citizen Kane");
    assert_eq!(&caps[2], b"1941");
    assert_eq!(&caps[0], b"'Citizen Kane' (1941)");
}

因为文档没有提供工作示例(就像他们经常做的那样)

请注意，文档中的代码块是默认编译和执行的，因此我的经验是，这些示例不起作用是非常罕见的。