index_vec

此crate帮助定义围绕usize（或其他整数）和Vec<T>的“newtype”风格的包装，以在零成本下获得额外的类型安全性。

示例/概述

use index_vec::{IndexVec, IndexSlice, index_vec};

index_vec::define_index_type! {
    // Define StrIdx to use only 32 bits internally (you can use usize, u16,
    // and even u8).
    pub struct StrIdx = u32;

    // The defaults are very reasonable, but this macro can let
    // you customize things quite a bit:

    // By default, creating a StrIdx would check an incoming `usize against
    // `u32::max_value()`, as u32 is the wrapped index type. Lets imagine that
    // StrIdx has to interface with an external system that uses signed ints.
    // We can change the checking behavior to complain on i32::max_value()
    // instead:
    MAX_INDEX = i32::max_value() as usize;

    // We can also disable checking all-together if we are more concerned with perf
    // than any overflow problems, or even do so, but only for debug builds: Quite
    // pointless here, but an okay example
    DISABLE_MAX_INDEX_CHECK = cfg!(not(debug_assertions));

    // And more too, see this macro's docs for more info.
}

// Create a vector which can be accessed using `StrIdx`s.
let mut strs: IndexVec<StrIdx, &'static str> = index_vec!["strs", "bar", "baz"];

// l is a `StrIdx`
let l = strs.last_idx();
assert_eq!(strs[l], "baz");

let new_i = strs.push("quux");
assert_eq!(strs[new_i], "quux");

// The slice APIs are wrapped as well.
let s: &IndexSlice<StrIdx, [&'static str]> = &strs[StrIdx::new(1)..];
assert_eq!(s[0], "bar");

// Indices are mostly interoperable with `usize`, and support
// a lot of what you might want to do to an index.

// Comparison
assert_eq!(StrIdx::new(0), 0usize);

// Addition
assert_eq!(StrIdx::new(0) + 1, StrIdx::new(1));

// Subtraction
assert_eq!(StrIdx::new(1) - 1, StrIdx::new(0));

// Wrapping
assert_eq!(StrIdx::new(5) % strs.len(), StrIdx::new(1));
// ...

背景

目标是帮助使用type FooIdx = usize来访问具有某种东西的Vec<Foo>，从而可以静态地防止在Vec<Bar>中使用FooIdx。如果你有一堆指向不同类型向量的索引，它最有用。

该代码最初基于rustc的IndexVec代码，但除了简单的情况（例如Vec包装器）外，几乎全部重写。

其他crate

indexed_vec crate早于此crate，并且是rustc代码的更接近的副本。遗憾的是，这意味着它无法在稳定版上编译。

如果你在找一个比vec更接近map的东西，你可能会发现handy、slotmap或slab更符合你的需求。