An XArray struct implemented by Rust.

LoGin de93b57c34 feat: Make XNode field `slots` slab-friendly and cacheline-aligned (#1) 2 months ago
src de93b57c34 feat: Make XNode field `slots` slab-friendly and cacheline-aligned (#1) 2 months ago
.gitignore fc0b17d274 A minimal runnable version of XArray. 11 months ago
Cargo.lock 8212d351a9 Adjust the semantics of details and enhance the abstraction of internal locks. 10 months ago
Cargo.toml de93b57c34 feat: Make XNode field `slots` slab-friendly and cacheline-aligned (#1) 2 months ago
README.md 74fe3f75a7 Refactor the documentation 8 months ago

README.md

XArray

XArray is an abstract data type functioning like an expansive array of items where each item must be an 8-byte object, such as Arc<T> or Box<T>. User-stored pointers must have a minimum alignment of 4 bytes. XArray facilitates efficient sequential access to adjacent entries, supporting multiple concurrent reads and exclusively allowing one write operation at a time.

Features

  • Cursors: Provide cursors for precise and efficient iteration over the array. Cursors have both immutable and mutable versions. One can hold multiple immutable cursors or hold a mutable cursor exclusively at a time.
  • Marking: Provide ability to mark entries and the XArray itself for easy state tracking.
  • Generics: Generic implementation that can work with any entry type that fits the use case.
  • Copy-on-Write (COW): Efficient cloning of XArrays with shared structure until mutation.

Installation

Add this to your Cargo.toml:

[dependencies]
xarray = "0.1.0"

Usage

This crate is developed in no_std environment, but std users can still use this crate with --feature="std":

The following section covers how to interact with XArray including creating an XArray, using cursors, marking, cloning, and more.


Creating an XArray:

// In std environment
extern crate alloc;

use alloc::sync::Arc;
use xarray::XArray;

// Create a new XArray instance
let mut xarray: XArray<Arc<i32>> = XArray::new();
  • Users should declare the type of items (Arc) stored in the XArray, and the item type should implement ItemEntry trait.
  • We implement ItemEntry for alloc::sync::Arc and alloc::sync::Box by default, hence std users can use them directly.
  • Using Cursor

    extern crate alloc;
    
    use alloc::sync::Arc;
    use xarray::XArray;
    
    let mut xarray_arc: XArray<Arc<i32>> = XArray::new();
    
    let mut cursor = xarray_arc.cursor_mut(0);
    // Store the Arc at the index range 0~10000.
    for i in 0..10000 {
        let value = Arc::new(i * 2);
        cursor.store(value);
        cursor.next();
    }
    
    cursor.reset_to(0);
    for i in 0..10000 {
        let value = cursor.load().unwrap();
        assert!(*value.as_ref() == i * 2);
        cursor.next();
    }
    

    Using Marks

    Here is an example of using marks for the stored pages in the XArray, where PageMark represents the states of each individual Page:

    extern crate alloc;
    
    use alloc::sync::Arc;
    use xarray::{XArray, XMark, StdMutex};
    
    #[derive(Clone, Copy)]
    
    enum PageMark {
        DirtyPage 
        ...
    }
    
    impl From<PageState> for XMark {
        fn from(mark: PageState) -> Self {
            match mark {
                PageState::DirtyPage => Self::Mark0,
                ...
            }
        }
    }
    
    let mut pages: XArray<Page, StdMutex, PageState> = XArray::new();
    
    let mut cursor = pages.cursor_mut(1000);
    cursor.store(Page::alloc_zero());
    // Mark the Page as DirtyPage.
    cursor.set_mark(PageState::DirtyPage).unwrap();
    assert!(cursor.is_marked(PageState::DirtyPage));
    
    • Items and the XArray can have up to three distinct marks by default, with each mark independently maintained.
    • Users need to use a struct to represent the marks that need to be used. For the situation where multiple marks are required, these marks are typically encapsulated within an enumeration class.
    • If users want to use a struct M for marks, they should implement From<M> trait for XMark and declare M in the generics list of XArray.

    Copy-On-Write (COW) Clone

    use std::sync::Arc;
    use xarray::{XArray};
    
    let mut xarray: XArray<Arc<i32>> = XArray::new();
    
    // Store values
    let value = Arc::new(10);
    xarray.store(1, value.clone());
    assert_eq!(*xarray.load(1).unwrap().as_ref(), 10);
    
    // Clone the XArray
    let mut xarray_clone = xarray.clone();
    assert_eq!(*xarray_clone.load(1).unwrap().as_ref(), 10);
    
    // Store a new value in the clone
    let new_value = Arc::new(100);
    xarray_clone.store(1, new_value);
    
    // The original XArray is unaffected by changes in the clone
    assert_eq!(*xarray.load(1).unwrap().as_ref(), 10);
    assert_eq!(*xarray_clone.load(1).unwrap().as_ref(), 100);
    

    Iteration

    use std::sync::Arc;
    use xarray::XArray;
    
    let mut xarray: XArray<Arc<i32>> = XArray::new();
    
    // Store item to even index in the range 100~200.
    for i in 100..200 {
        if i % 2 == 0 {
            let value = Arc::new(i * 2);
            cursor.store(value);
        }
        cursor.next();
    }
    
    // Iterate at the range 100~200.
    let mut count = 0;
    for item in xarray.range(100..200) {
        count += 1;
    }
    assert_eq!(count == 50);
    

    License