637 lines
21 KiB
Rust
637 lines
21 KiB
Rust
//! # A [`Vec<T: ?Sized>`]
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//!
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//! A dynamic length collection of unsized elements, akin to [`std::vec::Vec`].
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//!
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//! This crate depends on a number of unstable features, namely:
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//! - `#![feature(ptr_metadata)]`, to allow manipulating the metadata of pointers.
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//! - `#![feature(layout_for_ptr)]`, to allow getting the size/alignment of a value with only a pointer to it.
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//! - `#![feature(coerce_unsized)]`, to add trait bounds for types which can be unsized to another type.
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//!
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//! # Examples
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//!
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//! You can create a vector with [`Vec::new`]:
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//!
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//! ```
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//! # use std::fmt::Debug;
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//! # use dyn_vec::prelude::*;
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//! let vec: Vec<dyn Debug> = Vec::new();
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//! # assert_eq!(format!("{:?}", vec), "[]");
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//! ```
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//!
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//! or with the [`vec!`] macro:
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//!
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//! ```
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//! # use dyn_vec::prelude::{*, vec};
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//! # use std::fmt::Debug;
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//! let vec: Vec<i32> = vec![1, 2, 3];
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//! // check the docs for `vec!` for more info on this syntax
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//! let vec_boxed: Vec<dyn Debug> = vec![box:
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//! Box::new(1) as _,
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//! Box::new("foo") as _,
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//! Box::new(true) as _
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//! ];
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//! let vec_unsized: Vec<dyn Debug> = vec![unsized: 1, "foo", true];
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//! let vec_from_elem: Vec<i32> = vec![3; 5];
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//! # assert_eq!(vec, [1, 2, 3]);
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//! # assert_eq!(format!("{:?}", vec_boxed), r#"[1, "foo", true]"#);
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//! # assert_eq!(format!("{:?}", vec_unsized), r#"[1, "foo", true]"#);
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//! # assert_eq!(vec_from_elem, [3; 5]);
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//! ```
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//!
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//! A vector can be pushed to with [`Vec::push`]:
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//!
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//! ```
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//! # use dyn_vec::prelude::{*, vec};
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//! let mut vec: Vec<i32> = vec![];
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//! vec.push(1);
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//! vec.push(2);
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//! vec.push(3);
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//! # assert_eq!(format!("{:?}", vec), "[1, 2, 3]");
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//! ```
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//!
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//! ...and with [`push_box`] and [`push_unsize`]:
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//!
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//! ```
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//! # use dyn_vec::prelude::{*, vec};
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//! # use std::fmt::Debug;
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//! let mut vec: Vec<dyn Debug> = vec![];
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//! vec.push_box(Box::new(1));
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//! vec.push_box(Box::new("foo"));
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//! vec.push_box(Box::new(true));
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//!
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//! vec.push_unsize(2);
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//! vec.push_unsize("bar");
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//! vec.push_unsize(false);
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//! # assert_eq!(format!("{:?}", vec), r#"[1, "foo", true, 2, "bar", false]"#);
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//! ```
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//!
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//! Finally, a vector can be `unsize`d to another vector:
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//!
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//! ```
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//! # use dyn_vec::prelude::{*, vec};
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//! # use std::fmt::Debug;
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//! let vec: Vec<i32> = vec![1, 2, 3];
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//! // vec.push_unsize("foo"); // not yet...
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//! let mut vec: Vec<dyn Debug> = vec.unsize();
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//! vec.push_unsize("foo"); // now we can!
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//! # assert_eq!(format!("{:?}", vec), r#"[1, 2, 3, "foo"]"#);
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//! ```
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//!
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//! # Data Layout
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//!
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//! ```text
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//! Vec<T>
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//! ┌────┬────┬────┬────┐
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//! │ptr │len │cap │end │
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//! └─┬──┴────┴─┬──┴─┬──┘
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//! │ │ │
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//! │ └────┼───────────────────────────────────────────────┐
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//! ┌─┘ └───────────────────┐ │
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//! │ │ │
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//! ▼ ▼ ▼
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//! ┌────┬────┬─────┬──────────┬───┬─────┬───────────────┬───┬───┬───┐
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//! │pad │elem│pad │elem │pad│elem │ │ptr│ptr│ptr│
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//! └────┴────┴─────┴──────────┴───┴─────┴───────────────┴─┬─┴─┬─┴─┬─┘
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//! ▲ ▲ ▲ ▲ │ │ │ ▲
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//! │ │ │ └───────────────────────┘ │ │ │
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//! │ │ └──────────────────────────────────────────┘ │ │
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//! │ └─────────────────────────────────────────────────────────┘ │
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//! │ │
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//! └─ aligned to 8 also aligned to 8 ─┘
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//! ```
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//!
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//! [`Vec<T: ?Sized>`]: Vec
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//! [`push_box`]: Vec::push_box
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//! [`push_unsize`]: Vec::push_unsize
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#![feature(ptr_metadata)]
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#![feature(layout_for_ptr)]
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#![feature(coerce_unsized)]
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#![warn(missing_docs)]
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#![warn(clippy::pedantic)]
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#![allow(clippy::must_use_candidate)]
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#[cfg(test)]
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mod test;
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// TODO: maybe remove this?
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// Too small to put in its own file
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/// Prelude, suitable for glob imports.
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///
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/// Using `prelude::*` will cause a conflict for the `vec!` macro. `prelude::{*, vec}` is recommended.
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pub mod prelude {
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pub use super::{Vec, vec};
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}
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use core::panic;
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use std::{
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ptr::{NonNull, self, drop_in_place, metadata},
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marker::PhantomData,
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alloc::{alloc, Layout, dealloc},
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mem::{size_of, size_of_val, align_of_val, self, size_of_val_raw},
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slice,
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ops::{CoerceUnsized, Index, IndexMut},
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any::Any
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};
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/// Copy `size` bytes of memory from `src` to `dst`.
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///
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/// # Safety
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///
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/// `src` must be valid for reads, `dst` must be valid for writes, etc, you get the idea.
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// TODO: inline me! i didnt realize it was avaliable as `copy_to` until the code was mostly complete.
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unsafe fn memcpy(src: *const u8, dst: *mut u8, size: usize) {
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src.copy_to(dst, size);
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}
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fn align_up<T: ?Sized>(ptr: *const T, align: usize) -> *const T {
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let (mut data, meta) = ptr.to_raw_parts();
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data = ((data as usize + align - 1) & !(align - 1)) as _;
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ptr::from_raw_parts(data, meta)
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}
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fn align_up_mut<T: ?Sized>(ptr: *mut T, align: usize) -> *mut T {
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align_up(ptr as _, align) as _
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}
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/// A heap allocated, dynamic length collection of `?Sized` elements.
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///
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/// See [`std::vec::Vec`] (the standard library `Vec` type) for more information.
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pub struct Vec<T: ?Sized> {
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ptr: NonNull<u8>,
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len: usize,
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capacity: usize,
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end_ptr: NonNull<u8>,
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_phantom: PhantomData<T>
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}
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// keeps this file cleaner
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mod impls;
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mod iter;
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pub use iter::*;
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/// The extra data stored at the end of the allocation.
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type Extra<T> = *const T;
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impl<T: ?Sized> Vec<T> {
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/// Creates a new, empty vector.
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pub fn new() -> Self {
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let ptr = NonNull::dangling();
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Self {
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ptr,
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len: 0,
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capacity: 0,
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end_ptr: ptr,
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_phantom: PhantomData
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}
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}
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/// Creates a new vector that holds `len` copies of `v`.
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///
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/// Only avaliable when `T: Sized`.
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pub fn from_elem(v: T, len: usize) -> Self where T: Sized + Clone {
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let mut vec = Self::with_capacity(len);
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for _ in 0..len {
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vec.push(v.clone());
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}
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vec
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}
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/// Creates a new vector that can hold the given amount of `T`s.
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///
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/// Only avaliable when `T: Sized`.
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pub fn with_capacity(cap: usize) -> Self where T: Sized {
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Self::with_capacity_for::<T>(cap)
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}
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/// Creates a new vector with the given capacity, measured in bytes.\
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pub fn with_capacity_bytes(cap: usize) -> Self {
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let mut vec = Self::new();
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unsafe { vec.realloc(cap); }
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vec
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}
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/// Creates a new vector with enough capacity to hold the given amount of `U`s.
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pub fn with_capacity_for<U>(cap: usize) -> Self {
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Self::with_capacity_bytes(cap * (size_of::<U>() + size_of::<Extra<U>>()))
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}
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/// Appends an element to the end of the vector.
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///
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/// Only avaliable if `T: Sized`.
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pub fn push(&mut self, v: T) where T: Sized {
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unsafe { self.push_raw(&v) }
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mem::forget(v);
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}
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/// Appends an (possibly unsized) boxed element to the end of the vector.
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pub fn push_box(&mut self, v: Box<T>) {
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let ptr = Box::into_raw(v);
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unsafe {
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self.push_raw(ptr);
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dealloc(ptr.cast(), Layout::for_value_raw(ptr));
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}
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}
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/// Appends a sized element of type `U` to the end of the vector, given that it can be `CoerceUnsized` to a `T`.
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pub fn push_unsize<U>(&mut self, v: U) where for<'a> &'a U: CoerceUnsized<&'a T> {
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let v_unsized: &T = &v;
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unsafe { self.push_raw(v_unsized) };
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mem::forget(v);
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}
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unsafe fn push_raw(&mut self, v: *const T) {
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let size = size_of_val(&*v);
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if !self.will_fit(&*v) {
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// oh no! allocation too small!
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// make sure we have enough space for a new element, but also space for future elements
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// this bit is tricky, we must make sure we have enough space for padding too, so its probably UB somehow
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// FIXME: ^^^
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let new_alloc_size = self.capacity * 2 + size * 2 + size_of::<Extra<T>>();
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self.realloc(new_alloc_size);
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}
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self.push_raw_unchecked(v);
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}
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/// Given an element, returns a pointer to where it would be written if it was pushed, assuming no reallocation is needed.
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///
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/// The pointer will be aligned, but writing to it may overwrite data belonging to the Vec.
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/// To check for this, call `will_fit`.
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/// In addition, the extra data for the element must be set using `set_extra_from_ptr`.
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fn get_next_elem_ptr(&self, v: &T) -> *mut u8 {
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align_up_mut(self.end_ptr.as_ptr(), align_of_val(v))
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}
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/// Checks if a given element will fit in the vector without reallocations.
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pub fn will_fit(&self, v: &T) -> bool {
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let remaining_space = self.get_ptr_to_extra(self.len) as usize - self.end_ptr.as_ptr() as usize;
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let needed_space = size_of_val(v) + size_of::<Extra<T>>();
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remaining_space >= needed_space
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}
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unsafe fn push_raw_unchecked(&mut self, v: *const T) {
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let size = size_of_val(&*v);
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let dest = self.get_next_elem_ptr(&*v); // this is mentioned by the `// SAFETY:` in `as_slice_flatten`
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memcpy(v.cast(), dest, size);
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let new_ptr = ptr::from_raw_parts::<T>(dest.cast(), metadata(v));
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self.set_extra_from_ptr(self.len, new_ptr);
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self.end_ptr = NonNull::new_unchecked(dest.wrapping_add(size));
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self.len += 1;
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}
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/// Pops an element off the end of the vector, putting it in a [`Box`].
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pub fn pop(&mut self) -> Option<Box<T>> {
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unsafe {
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self.len = self.len.checked_sub(1)?;
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let el = self.get_ptr(self.len);
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let alloc = alloc(Layout::for_value_raw(el));
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memcpy(el.cast(), alloc, size_of_val_raw(el));
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Some(Box::from_raw(ptr::from_raw_parts_mut(alloc.cast(), metadata(el))))
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}
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}
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unsafe fn realloc(&mut self, size: usize) {
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let layout = Layout::from_size_align_unchecked(size, 8).pad_to_align();
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if self.capacity == 0 {
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// will panic if OOM
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self.ptr = NonNull::new(alloc(layout)).unwrap();
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self.end_ptr = self.ptr;
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} else {
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// cannot use realloc here
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let new_alloc = NonNull::new(alloc(layout)).unwrap();
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// data
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let mut ptr = new_alloc.as_ptr();
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for i in 0..self.len {
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let v = self.get_unchecked(i);
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let size = size_of_val(v);
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ptr = align_up_mut(ptr, align_of_val(v));
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memcpy((v as *const T).cast(), ptr, size);
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let meta = self.get_ptr(i).to_raw_parts().1;
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self.set_extra_from_ptr(i, ptr::from_raw_parts(ptr.cast(), meta));
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ptr = ptr.wrapping_add(size);
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}
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self.end_ptr = NonNull::new_unchecked(ptr);
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// metadata
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let meta_src = self.get_ptr_to_extra(self.len);
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let meta_dst = {
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let current_alloc_end = self.ptr.as_ptr().wrapping_add(self.capacity);
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let new_alloc_end = new_alloc.as_ptr().wrapping_add(layout.size());
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let meta_len = current_alloc_end as usize - meta_src as usize;
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new_alloc_end.wrapping_sub(meta_len)
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};
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let meta_size = self.len * size_of::<Extra<T>>();
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memcpy(meta_src.cast(), meta_dst, meta_size);
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dealloc(self.ptr.as_ptr(), Layout::from_size_align_unchecked(self.capacity, 8));
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self.ptr = new_alloc;
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}
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self.capacity = layout.size();
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}
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/// for internal use
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///
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/// NOTE: 1-indexed, to allow getting a pointer to the end of the alloc easily
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fn get_ptr_to_extra(&self, index: usize) -> *mut Extra<T> {
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self.ptr.as_ptr()
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.wrapping_add(self.capacity)
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.cast::<Extra<T>>()
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.wrapping_sub(index)
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}
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unsafe fn set_extra_from_ptr(&self, index: usize, ptr: *const T) {
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self.get_ptr_to_extra(index + 1).write(ptr);
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}
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unsafe fn get_ptr(&self, index: usize) -> *const T {
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*self.get_ptr_to_extra(index + 1)
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}
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/// Gets a reference to the element at the specified index.
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///
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/// Returns `None` if the index is out-of-bounds.
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pub fn get(&self, index: usize) -> Option<&T> {
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if index < self.len {
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Some(unsafe { self.get_unchecked(index) })
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} else {
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None
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}
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}
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/// Gets a reference to the element at the specified index.
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///
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/// # Safety
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///
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/// Immediate UB if the index is out-of-bounds.
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pub unsafe fn get_unchecked(&self, index: usize) -> &T {
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&*self.get_ptr(index)
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}
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/// Gets a mutable reference to the element at the specified index.
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///
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/// Returns `None` if the index is out-of-bounds.
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pub fn get_mut(&mut self, index: usize) -> Option<&mut T> {
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if index < self.len {
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Some(unsafe { self.get_unchecked_mut(index) })
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} else {
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None
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}
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}
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/// Gets a mutable reference to the element at the specified index.
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///
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/// # Safety
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///
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/// Immediate UB if the index is out-of-bounds.
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pub unsafe fn get_unchecked_mut(&mut self, index: usize) -> &mut T {
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&mut *(self.get_ptr(index) as *mut _)
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}
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/// Returns the length of the vector, which is how many items it contains.
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pub fn len(&self) -> usize {
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self.len
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}
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/// Returns `true` if the vector holds no elements.
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pub fn is_empty(&self) -> bool {
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self.len == 0
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}
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/// Returns the capacity, which is the size of the allocation in bytes.
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pub fn capacity(&self) -> usize {
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self.capacity
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}
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/// Returns a pointer to the allocation of the vector.
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pub fn as_ptr(&self) -> *const u8 {
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self.ptr.as_ptr()
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}
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/// Returns a mutable pointer to the allocation of the vector.
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pub fn as_mut_ptr(&mut self) -> *mut u8 {
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self.ptr.as_ptr()
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}
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/// Iterates over the vector by-ref.
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pub fn iter(&self) -> Iter<T> {
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Iter::new(self)
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}
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/// Iterates over the vector by-mut.
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pub fn iter_mut(&mut self) -> IterMut<T> {
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IterMut::new(self)
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}
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/// Converts a `Vec<T: Sized>` into a `Vec<U: ?Sized>`, given that `T` can be `CoerceUnsized` into `U`.
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pub fn unsize<U: ?Sized>(mut self) -> Vec<U> where for<'a> &'a T: CoerceUnsized<&'a U> {
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if size_of::<Extra<U>>() > size_of::<Extra<T>>() {
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let elem_size = self.end_ptr.as_ptr() as usize - self.ptr.as_ptr() as usize;
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let extra_size = self.len * size_of::<Extra<U>>();
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let needed_size = elem_size + extra_size;
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if needed_size > self.capacity {
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unsafe { self.realloc(needed_size); }
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}
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}
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let new_vec = Vec::<U> {
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ptr: self.ptr,
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len: self.len,
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capacity: self.capacity,
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end_ptr: self.end_ptr,
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_phantom: PhantomData,
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};
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if size_of::<Extra<U>>() > size_of::<Extra<T>>() {
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// new extra larger than old extra, must go from back to front
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for i in (0..self.len).rev() {
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let current = unsafe { &*self.get_ptr(i) };
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unsafe { new_vec.set_extra_from_ptr(i, current as &U) }
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}
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} else {
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// new extra smaller or same size as old extra, must go from front to back
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for i in 0..self.len {
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let current = unsafe { &*self.get_ptr(i) };
|
|
unsafe { new_vec.set_extra_from_ptr(i, current as &U) }
|
|
}
|
|
}
|
|
|
|
mem::forget(self);
|
|
new_vec
|
|
}
|
|
|
|
unsafe fn dealloc(&self) {
|
|
if self.capacity != 0 {
|
|
dealloc(self.ptr.as_ptr(), Layout::from_size_align_unchecked(self.capacity, 8));
|
|
}
|
|
}
|
|
|
|
/// Extends this vector with an iterator.
|
|
///
|
|
/// Similar to [`Extend::extend`], but seperate to prevent conflicting implementations.
|
|
pub fn extend_unsize<U, I: IntoIterator<Item = U>>(&mut self, iter: I) where for<'a> &'a U: CoerceUnsized<&'a T> {
|
|
for item in iter {
|
|
self.push_unsize(item);
|
|
}
|
|
}
|
|
}
|
|
|
|
impl<T> Vec<[T]> {
|
|
/// Returns a slice over all the elements in the vector.
|
|
///
|
|
/// Only avaliable for `Vec<[T]>`.
|
|
pub fn as_slice_flatten(&self) -> &[T] {
|
|
if self.len == 0 {
|
|
return unsafe { slice::from_raw_parts(NonNull::dangling().as_ptr(), 0) }
|
|
}
|
|
|
|
// SAFETY: the slices should be contiguous by the logic of `push_raw_unchecked`
|
|
unsafe {
|
|
slice::from_raw_parts(self.get_ptr(0).to_raw_parts().0.cast(), {
|
|
let start = self.get_ptr(0).to_raw_parts().0 as usize;
|
|
let end = self.end_ptr.as_ptr() as usize;
|
|
debug_assert_eq!((end - start) % size_of::<T>(), 0);
|
|
(end - start) / size_of::<T>() // integer division!
|
|
})
|
|
}
|
|
}
|
|
|
|
/// Returns a mutable slice over all the elements in the vector.
|
|
///
|
|
/// Only avaliable for `Vec<[T]>`.
|
|
pub fn as_mut_slice_flatten(&mut self) -> &mut [T] {
|
|
if self.len == 0 {
|
|
return unsafe { slice::from_raw_parts_mut(NonNull::dangling().as_ptr(), 0) }
|
|
}
|
|
|
|
// SAFETY: the slices should be contiguous by the logic of `push_raw_unchecked`
|
|
unsafe {
|
|
slice::from_raw_parts_mut(self.get_ptr(0).to_raw_parts().0 as _, {
|
|
let start = self.get_ptr(0).to_raw_parts().0 as usize;
|
|
let end = self.end_ptr.as_ptr() as usize;
|
|
debug_assert_eq!((end - start) % size_of::<T>(), 0);
|
|
(end - start) / size_of::<T>() // integer division!
|
|
})
|
|
}
|
|
}
|
|
}
|
|
|
|
impl Vec<dyn Any> {
|
|
/// Gets a reference to the element at then specified index, downcasting it to the specified type.
|
|
///
|
|
/// Same as `.get().map(|v| v.downcast()).flatten()`.
|
|
pub fn downcast_get<T: Any>(&self, index: usize) -> Option<&T> {
|
|
self.get(index)?.downcast_ref()
|
|
}
|
|
|
|
/// Gets a mutable reference to the element at then specified index, downcasting it to the specified type.
|
|
///
|
|
/// Same as `.get_mut().map(|v| v.downcast_mut()).flatten()`.
|
|
pub fn downcast_get_mut<T: Any>(&mut self, index: usize) -> Option<&mut T> {
|
|
self.get_mut(index)?.downcast_mut()
|
|
}
|
|
|
|
/// Pops an element off the end of the vector, downcasting it to the specified type.
|
|
///
|
|
/// If the element is not of type `T`, the element will not be popped.
|
|
///
|
|
/// Similiar to `.pop().map(|v| v.downcast()).flatten()`, but without an intermediate allocation.
|
|
pub fn downcast_pop<T: Any>(&mut self) -> Option<T> {
|
|
unsafe {
|
|
let el = self.get_ptr(self.len.checked_sub(1)?) as *mut dyn Any;
|
|
let v = Some(((&mut *el).downcast_mut()? as *mut T).read());
|
|
self.len -= 1;
|
|
v
|
|
}
|
|
}
|
|
}
|
|
|
|
impl<T: ?Sized> Drop for Vec<T> {
|
|
fn drop(&mut self) {
|
|
unsafe {
|
|
for i in 0..self.len {
|
|
drop_in_place(self.get_unchecked_mut(i));
|
|
}
|
|
self.dealloc();
|
|
}
|
|
}
|
|
}
|
|
|
|
impl<T: ?Sized> Index<usize> for Vec<T> {
|
|
type Output = T;
|
|
|
|
#[track_caller]
|
|
fn index(&self, index: usize) -> &Self::Output {
|
|
match self.get(index) {
|
|
Some(v) => v,
|
|
None => panic!("index out of bounds: the len is {} but the index is {}", self.len, index),
|
|
}
|
|
}
|
|
}
|
|
|
|
impl<T: ?Sized> IndexMut<usize> for Vec<T> {
|
|
#[track_caller]
|
|
fn index_mut(&mut self, index: usize) -> &mut Self::Output {
|
|
let len = self.len;
|
|
match self.get_mut(index) {
|
|
Some(v) => v,
|
|
None => panic!("index out of bounds: the len is {} but the index is {}", len, index),
|
|
}
|
|
}
|
|
}
|
|
|
|
/// Creates a [`Vec`].
|
|
///
|
|
/// # Examples
|
|
///
|
|
/// ```
|
|
/// # use dyn_vec::prelude::{vec, Vec};
|
|
/// # use std::fmt::Debug;
|
|
/// let vec1: Vec<i32> = vec![1, 2, 3];
|
|
/// let vec2: Vec<dyn Debug> = vec![box:
|
|
/// Box::new(1) as _,
|
|
/// Box::new(String::from("foo")) as _,
|
|
/// Box::new(true) as _
|
|
/// ];
|
|
/// let vec3: Vec<dyn Debug> = vec![unsized: 1, String::from("foo"), true];
|
|
/// ```
|
|
#[macro_export]
|
|
macro_rules! vec {
|
|
() => {
|
|
$crate::Vec::new();
|
|
};
|
|
(box: $($elem:expr),+ $(,)?) => {{
|
|
let mut vec = $crate::Vec::new();
|
|
$(vec.push_box($elem);)+
|
|
vec
|
|
}};
|
|
(unsized: $($elem:expr),+ $(,)?) => {{
|
|
let mut vec = $crate::Vec::new();
|
|
$(vec.push_unsize($elem);)+
|
|
vec
|
|
}};
|
|
($elem:expr; $n:expr) => {
|
|
$crate::Vec::from_elem($elem, $n)
|
|
};
|
|
($($elem:expr),+ $(,)?) => {{
|
|
let mut vec = $crate::Vec::new();
|
|
$(vec.push($elem);)+
|
|
vec
|
|
}};
|
|
} |