使用Rust制作康威生命游戏的实现代码

目录

前言

之前学了几遍，后来忘记了，通过制作该游戏再复习复习。

安装准备

wasm-pack>cargo-generate:

cargo install cargo-generate

初始项目

初始rust项目

使用wasm的项目模板：

cargo generate --git https://github.com/rustwasm/wasm-pack-template

提示输入project名wasm-game-of-life在lib.rs中可以看见如下内容：

mod utils;
use wasm_bindgen::prelude::*;
// When the `wee_alloc` feature is enabled, use `wee_alloc` as the global
// allocator.
#[cfg(feature = "wee_alloc")]
#[global_allocator]
static ALLOC: wee_alloc::WeeAlloc = wee_alloc::WeeAlloc::INIT;

#[wasm_bindgen]
extern {
    fn alert(s: &str);
}

#[wasm_bindgen]
pub fn greet() {
    alert("Hello, wasm-game-of-life!");
}

它导入 window.alertJavaScript 函数，并导出greet的Rust 函数。

Cargo.toml

Cargo.toml预置了[lib]和[dependencies]。解释一下crate-type中f=“https://users.rust-lang.org/t/what-is-the-difference-between-dylib-and-cdylib/28847”>cdylib和rlib的作用：cdylib：顾名思义，是C的动态链接库的意思，可以被C和C++程序链接使用rlib：Rust静态链接库，用于静态连接其他crates依赖中使用的：wasm-bindgen可以将Rust编写的函数和结构体暴露到JS中或者把JS的方法引入到Rust中使用console_error_panic_hook提供了Wasm输出Rust>wee_alloc是一个轻量的Wasm内存分配器，但是会比默认分配器慢一些。

初始web项目

npm init wasm-app www

看到生成的pkg.json:

{
  "name": "create-wasm-app",
  "version": "0.1.0",
  "description": "create an app to consume rust-generated wasm packages",
  "main": "index.js",
  "bin": {
    "create-wasm-app": ".bin/create-wasm-app.js"
  },
  "scripts": {
    "build": "webpack --config webpack.config.js",
    "start": "webpack-dev-server"
  },

html里导入boostrap.js，boostrap.js里导入index.js。 index.js里面导入了其已经制作好的一个包：

import * as wasm from "hello-wasm-pack";
wasm.greet();

我们修改pkg.json，导入自己的包（该包需要使用wasm-pack build生成）

  "wasm-game-of-life": "file:../pkg"

将index.js更换下：

import * as wasm from "wasm-game-of-life";
wasm.greet();

使用npm i 安装依赖。使用npm run start 启动页面，打开http://localhost:8080/即可看见alert。

游戏规则

Conway’s>百度百科https://baike.baidu.com/item/%E5%BA%B7%E5%A8%81%E7%94%9F%E5%91%BD%E6%B8%B8%E6%88%8F/22668799?fr=aladdin主要规则如下：1、任何少于两个活邻居的活细胞都会死亡，就像是由于人口不足造成的。2、任何有两三个活邻居的活细胞都可以活到下一代。3、任何有超过三个活邻居的活细胞都会死亡，就像人口过剩一样。4、任何只有三个活邻居的死细胞都会变成活细胞，就像通过繁殖一样。

游戏设计

为啥说这个呢，因为2种语言去做这个东西会考虑哪个东西在哪个里面去实现。rust推荐大型、长寿命的数据结构被实现为>这个游戏中，会将universe的显示效果暴露给js渲染，其余计算在rust去实现。由于宇宙是n*n的，所以我们可以用一维数组去表示它，比如4x4的宇宙就是这样：



将数组每个row换下来就是需要的4x4的显示了。因为这种表现形式，所以我们需要对数组索引和行列进行转换，公式为：

index(row, column, universe) = row * width(universe) + column

就比如我要知道4行4列是索引几，根据公式就是3*4 + 3。每个单元格有一个字节，其中0表示死亡，1表示存活。

Rust实现

首先我们需要定义每个单元格：

#[wasm_bindgen]
#[repr(u8)]
#[derive(Clone, Copy, Debug, PartialEq, Eq)]
pub enum Cell {
    Dead = 0,
    Alive = 1,
}

枚举类型，0是死亡，1是存活，#[repr(u8)]表示一个单元格1字节。复习下：

长度	有符号	无符号
8-bit	i8	u8
16-bit	i16	u16
32-bit	i32	u32
64-bit	i64	u64
128-bit	i128	u128
arch	isize	usize

接下来定义宇宙：

#[wasm_bindgen]
pub struct Universe {
    width: u32,
    height: u32,
    cells: Vec<Cell>,
}

宇宙是长宽和一个动态数组。我们对universe实现一些方法便于操作：

#[wasm_bindgen]
impl Universe {
    fn get_index(&self, row: u32, column: u32) -> usize {
        (row * self.width + column) as usize
    }
}

get_index就是上面公式做索引。从前面游戏规则上可知，我们需要对每个单元格求出周围格子的存活数量，于是加上这个函数：

  fn live_neighbor_count(&self, row: u32, column: u32) -> u8 {
        let mut count = 0;
        for delta_row in [self.height - 1, 0, 1].iter().cloned() {
            for delta_col in [self.width - 1, 0, 1].iter().cloned() {
                if delta_row == 0 && delta_col == 0 {
                    continue;
                }
                let neighbor_row = (row + delta_row) % self.height;
                let neighbor_col = (column + delta_col) % self.width;
                println!("{},{}-s-", neighbor_row, neighbor_col);
                let idx = self.get_index(neighbor_row, neighbor_col);
                count += self.cells[idx] as u8;
            }
        }
        count
    }

解释下这个函数，其中迭代height-1 , 0 , 1 以及 width-1,0,1就是求传入row与col的周围的格子里存活数量。当迭代到0，0时，这个格子代表其自身，所以直接忽略。比如64x64的宇宙，查询2，2周围的格子就是：

1,1
1,2
1,3
2,1
2,3
3,1
3,2
3,3

边界处理靠取余，这样也能避免无符号向下溢出，所以0，0的周围格子就是：

63,63
63,0-
63,1
0,63
0,1
1,63
1,0
1,1

再从当前宇宙中获取格子的状态，如果是0，那么加上也不会增加，这样最终返回的就是周围格子的存活数量了。下面根据规则迭代每个细胞状态，暴露出来：

 pub fn tick(&mut self) {
        let mut next = self.cells.clone();
        for row in 0..self.height {
            for col in 0..self.width {
                let idx = self.get_index(row, col);
                let cell = self.cells[idx];
                let live_neighbors = self.live_neighbor_count(row, col);
                let next_cell = match (cell, live_neighbors) {
                    // Rule 1: Any live cell with fewer than two live neighbours
                    // dies, as if caused by underpopulation.
                    (Cell::Alive, x) if x < 2 => Cell::Dead,
                    // Rule 2: Any live cell with two or three live neighbours
                    // lives on to the next generation.
                    (Cell::Alive, 2) | (Cell::Alive, 3) => Cell::Alive,
                    // Rule 3: Any live cell with more than three live
                    // neighbours dies, as if by overpopulation.
                    (Cell::Alive, x) if x > 3 => Cell::Dead,
                    // Rule 4: Any dead cell with exactly three live neighbours
                    // becomes a live cell, as if by reproduction.
                    (Cell::Dead, 3) => Cell::Alive,
                    // All other cells remain in the same state.
                    (otherwise, _) => otherwise,
                };
                next[idx] = next_cell;
            }
        }
        self.cells = next;
    }

最后需要对universe实现输出功能，先将其输出成文本，实现display方法：

impl fmt::Display for Universe {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        for line in self.cells.as_slice().chunks(self.width as usize) {
            for &cell in line {
                let symbol = if cell == Cell::Dead { '◻' } else { '◼' };
                write!(f, "{}", symbol)?;
            }
            write!(f, "\n")?;
        }
        Ok(())
    }
}

最后进行暴露初始化和渲染方法：

pub fn new() -> Universe {
        let width = 64;
        let height = 64;

        let cells = (0..width * height)
            .map(|i| {
                if i % 2 == 0 || i % 7 == 0 {
                    Cell::Alive
                } else {
                    Cell::Dead
                }
            })
            .collect();

        Universe {
            width,
            height,
            cells,
        }
    }

    pub fn render(&self) -> String {
        self.to_string()
    }

使用wasm-pack build打包使用js渲染，修改html加入标签：

 <pre id="game-of-life-canvas"></pre>

index.js加入下面代码：

import { Universe } from "wasm-game-of-life";
const pre = document.getElementById("game-of-life-canvas");
const universe = Universe.new();
const renderLoop = () => {
	pre.textContent = universe.render();
	universe.tick();
	requestAnimationFrame(renderLoop);
};
renderLoop();

即可看见效果。下面使用canvas进行渲染，将universe中暴露其属性：

    pub fn width(&self) -> u32 {
        self.width
    }

    pub fn height(&self) -> u32 {
        self.height
    }

    pub fn cells(&self) -> *const Cell {
        self.cells.as_ptr()
    }

html中替换为canvas:

<canvas id="game-of-life-canvas"></canvas>

修改js：

import { Universe, Cell } from "wasm-game-of-life";
import { memory } from "wasm-game-of-life/wasm_game_of_life_bg";
const CELL_SIZE = 5; // px
const GRID_COLOR = "#CCCCCC";
const DEAD_COLOR = "#FFFFFF";
const ALIVE_COLOR = "#000000";
const universe = Universe.new();
const width = universe.width();
const height = universe.height();

// Give the canvas room for all of our cells and a 1px border
// around each of them.
const canvas = document.getElementById("game-of-life-canvas");
canvas.height = (CELL_SIZE + 1) * height + 1;
canvas.width = (CELL_SIZE + 1) * width + 1;

const ctx = canvas.getContext("2d");
const drawGrid = () => {
	ctx.beginPath();
	ctx.strokeStyle = GRID_COLOR;
	// Vertical lines.
	for (let i = 0; i <= width; i++) {
		ctx.moveTo(i * (CELL_SIZE + 1) + 1, 0);
		ctx.lineTo(i * (CELL_SIZE + 1) + 1, (CELL_SIZE + 1) * height + 1);
	}
	// Horizontal lines.
	for (let j = 0; j <= height; j++) {
		ctx.moveTo(0, j * (CELL_SIZE + 1) + 1);
		ctx.lineTo((CELL_SIZE + 1) * width + 1, j * (CELL_SIZE + 1) + 1);
	}
	ctx.stroke();
};
const getIndex = (row, column) => {
	return row * width + column;
};

const drawCells = () => {
	const cellsPtr = universe.cells();
	const cells = new Uint8Array(memory.buffer, cellsPtr, width * height);
	ctx.beginPath();
	for (let row = 0; row < height; row++) {
		for (let col = 0; col < width; col++) {
			const idx = getIndex(row, col);
			ctx.fillStyle = cells[idx] === Cell.Dead ? DEAD_COLOR : ALIVE_COLOR;
			ctx.fillRect(
				col * (CELL_SIZE + 1) + 1,
				row * (CELL_SIZE + 1) + 1,
				CELL_SIZE,
				CELL_SIZE
			);
		}
	}
	ctx.stroke();
};
const renderLoop = () => {
	universe.tick();
	drawGrid();
	drawCells();
	requestAnimationFrame(renderLoop);
};
renderLoop();

即可看见效果：



测试

一般代码需要写单元测试，看一下rust的测试怎么写。首先，对Universe增加2个实现，可以将元组转换为universe的cell：

impl Universe {
    /// Get the dead and alive values of the entire universe.
    pub fn get_cells(&self) -> &[Cell] {
        &self.cells
    }

    /// Set cells to be alive in a universe by passing the row and column
    /// of each cell as an array.
    pub fn set_cells(&mut self, cells: &[(u32, u32)]) {
        for (row, col) in cells.iter().cloned() {
            let idx = self.get_index(row, col);
            self.cells[idx] = Cell::Alive;
        }
    }
}

新增重置的方法：

  /// Set the width of the universe.
    ///
    /// Resets all cells to the dead state.
    pub fn set_width(&mut self, width: u32) {
        self.width = width;
        self.cells = (0..width * self.height).map(|_i| Cell::Dead).collect();
    }

    /// Set the height of the universe.
    ///
    /// Resets all cells to the dead state.
    pub fn set_height(&mut self, height: u32) {
        self.height = height;
        self.cells = (0..self.width * height).map(|_i| Cell::Dead).collect();
    }

下面编写测试，测试在tests文件夹下的web.rs中。增加以下代码：

#![cfg(target_arch = "wasm32")]

extern crate wasm_bindgen_test;
use std::assert_eq;

use wasm_bindgen_test::*;
extern crate wasm_game_of_life;
use wasm_game_of_life::Universe;
wasm_bindgen_test_configure!(run_in_browser);

#[cfg(test)]
pub fn input_spaceship() -> Universe {
    let mut universe = Universe::new();
    universe.set_width(6);
    universe.set_height(6);
    universe.set_cells(&[(1, 2), (2, 3), (3, 1), (3, 2), (3, 3)]);
    universe
}

#[cfg(test)]
pub fn expected_spaceship() -> Universe {
    let mut universe = Universe::new();
    universe.set_width(6);
    universe.set_height(6);
    universe.set_cells(&[(2, 1), (2, 3), (3, 2), (3, 3), (4, 2)]);
    universe
}
#[wasm_bindgen_test]
pub fn test_tick() {
    // Let's create a smaller Universe with a small spaceship to test!
    let mut input_universe = input_spaceship();

    // This is what our spaceship should look like
    // after one tick in our universe.
    let expected_universe = expected_spaceship();

    // Call `tick` and then see if the cells in the `Universe`s are the same.
    input_universe.tick();
    assert_eq!(&input_universe.get_cells(), &expected_universe.get_cells());
}

然后使用wasm-pack test --firefox --headless即可运行测试结果。如果安装浏览器失败，可以使用谷歌，或者去掉无头属性，直接网页上看测试结果。

调试

我们知道，web上使用console.log去输出调试内容，rust的代码如何在web中调试呢？这里需要安装下web-sys

[dependencies.web-sys]
version = "0.3"
features = [
  "console",
]

导入外部websys，制作自定义宏：

extern crate web_sys;
// A macro to provide `println!(..)`-style syntax for `console.log` logging.
macro_rules! log {
    ( $( $t:tt )* ) => {
        web_sys::console::log_1(&format!( $( $t )* ).into());
    }
}

format宏与其他几个输出区别在于其使用write，不输出到标准输出中：

format!: write formatted text to String
print!: same as format! but the text is printed to the console (io::stdout).
println!: same as print! but a newline is appended.
eprint!: same as format! but the text is printed to the standard error (io::stderr).
eprintln!: same as eprint!but a newline is appended.

然后就可以在需要的地方console了，比如neighbours那：

 let live_neighbors = self.live_neighbor_count(row, col);
                log!(
                    "cell[{}, {}] is initially {:?} and has {} live neighbors",
                    row,
                    col,
                    cell,
                    live_neighbors
                );
                let next_cell = match (cell, live_neighbors) {
                    // Rule 1: Any live cell with fewer than two live neighbours
                    // dies, as if caused by underpopulation.
                    (Cell::Alive, x) if x < 2 => Cell::Dead,
                    // Rule 2: Any live cell with two or three live neighbours
                    // lives on to the next generation.
                    (Cell::Alive, 2) | (Cell::Alive, 3) => Cell::Alive,
                    // Rule 3: Any live cell with more than three live
                    // neighbours dies, as if by overpopulation.
                    (Cell::Alive, x) if x > 3 => Cell::Dead,
                    // Rule 4: Any dead cell with exactly three live neighbours
                    // becomes a live cell, as if by reproduction.
                    (Cell::Dead, 3) => Cell::Alive,
                    // All other cells remain in the same state.
                    (otherwise, _) => otherwise,
                };
                log!("    it becomes {:?}", next_cell);
                next[idx] = next_cell;

打开web，即可看见console的内容。

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