DELAEMON BLOG

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WebAssembly with Rust

環境

OS X: 10.3
Xcode: 9.2
Python: 3.6.1

必要物のバージョン確認

$ python --version; node -v; git --version; java -version; gcc --version; g++; cmake
Python 3.6.1
v8.9.1
git version 2.10.1
Picked up JAVA_TOOL_OPTIONS: -Dfile.encoding=UTF-8
java version "1.8.0_65"
Java(TM) SE Runtime Environment (build 1.8.0_65-b17)
Java HotSpot(TM) 64-Bit Server VM (build 25.65-b01, mixed mode)
Configured with: --prefix=/Library/Developer/CommandLineTools/usr --with-gxx-include-dir=/usr/include/c++/4.2.1
Apple LLVM version 9.0.0 (clang-900.0.38)
Target: x86_64-apple-darwin17.3.0
Thread model: posix
InstalledDir: /Library/Developer/CommandLineTools/usr/bin
clang: error: no input files
Usage

  cmake [options] <path-to-source>
  cmake [options] <path-to-existing-build>

Specify a source directory to (re-)generate a build system for it in the
current working directory.  Specify an existing build directory to
re-generate its build system.

Run 'cmake --help' for more information.

ecmascriptenインストール

$ git clone https://github.com/juj/emsdk.git
$ cd emsdk
$ source ~/emsdk/emsdk_env.sh
$ ./emsdk install sdk-incoming-64bit binaryen-master-64bit
$ ./emsdk activate sdk-incoming-64bit binaryen-master-64bit

emsdkコマンドはどうでもいいところがうまく動かなくてテキトウにいじった。ただのpython

とりあえずRustなしでWebAssemblyをお試し

Hello World

$ cat hello.c 
#include <stdio.h>

int main() {
  printf("Hello world!");
  return 0;
}

コンパイル / Webサーバーを起動して確認

$ emcc -o hello.html -s WASM=1 hello.c -s NO_EXIT_RUNTIME=0

$ ls 
hello.c hello.html hello.js hello.wasm

$ emrun hello.html

-s NO_EXIT_RUNTIME=0 ないとコンパイルエラー
emrunだと勝手にSafariが立ち上がるけど、Chromeでみるとかなら php -S php -S localhost:8080 等でも良い

cppでフィボナッチ

$ cat fib.cpp
#include <iostream>
#include <iomanip>
using namespace std;

int fib(int n) {
    if (n < 2) return n;
    return fib(n - 1) + fib(n - 2);
}

int main(int argc, const char* argv[]) {
    int n = 10000;
    int i = fib(n);
    std::cout << "n: " << n << " i: " << i << endl;
    return 0;
}

$ emcc -o fib.html -s WASM=1 fib.cpp -s NO_EXIT_RUNTIME=0
$ emrun fib.html

n を10000000とか大きくするとコンパイル通るけど、ブラウザで Maximum call stack size exceeded

RustでWebAssembly

古いRustを消す

$ /usr/local/lib/rustlib/uninstall.sh

Rustインストール

$ curl https://sh.rustup.rs -sSf | sh

Rust で Hello World

$ cargo new --bin hello
$ cd hello
$ cat src/main.rs
fn main() {
    println!("Hello, world!");
}

$ cargo run
Hello, world!

Rust でフィボナッチ

$ cargo new --bin fib
$ cat src/main.rs
pub fn fibonacci_reccursive(n: i32) -> u64 {
    if n < 0 {
        panic!("{} is negative!", n);
    }
    match n {
        0     => panic!("zero is not a right argument to fibonacci_reccursive()!"),
        1 | 2 => 1,
        3     => 2,
        /*
         * 50 => 12586269025,
         */
        _     => fibonacci_reccursive(n - 1) + fibonacci_reccursive(n - 2)
    }
}

fn main() {
    let found = fibonacci_reccursive(10);
    println!("{}", found);
}

$ cargo run
55

Rustでasmjsコンパイル

$ rustup target add asmjs-unknown-emscripten
$ cargo build --target asmjs-unknown-emscripten
$ ls fib/target/asmjs-unknown-emscripten/debug/ 
build       deps        examples    fib.d       fib.js      incremental native

ブラウザから確認

$ cat fib_rust.html
<!DOCTYPE html>
<html>
    <head>
        <meta charset="utf-8"/>
        <title>Rust to asm.js example</title>
    </head>
    <body>
        <script src="fib/target/asmjs-unknown-emscripten/debug/fib.js"></script>
    </body>
</html>

$ php -S localhost:8080