Set up example w/ wasm-bindgen, clang 8 wasm target

Author: maxbrunsfeld

.gitignore

@@ -1,2 +1,5 @@
 /target
 **/*.rs.bk
+node_modules
+pkg
+package-lock.json

Cargo.lock

@@ -6,8 +6,10 @@ edition = "2018"
 
 [lib]
 name = "wasm_lib_with_c"
-path = "src/lib.rs"
-crate-type = ["staticlib"]
+crate-type = ["cdylib"]
+
+[dependencies]
+wasm-bindgen = "0.2.51"
 
 [build-dependencies]
 cc = "1.0"

Cargo.toml

@@ -0,0 +1,10 @@
+### Setup
+
+1. Run `npm install` to install the `TextEncoder` polyfill.
+2. Install Rust and the `wasm32-unknown-unknown` target with `rustup`.
+3. Install LLVM >= 8.0. ([downloads](http://releases.llvm.org/download.html))
+4. Make sure the `PATH` variable in `test.sh` points to LLVM >= 8.0
+
+### Testing
+
+The `test.sh` script will compile this project to Wasm/JS and test it with Node.

README.md

@@ -1,8 +1,7 @@
 extern crate cc;
 
 fn main() {
-    let mut config = cc::Build::new();
-    config
+    cc::Build::new()
         .file("src/lib.c")
-        .compile("wasm-lib-with-c");
+        .compile("wasm-c-component");
 }

build.rs

@@ -0,0 +1,5 @@
+{
+  "dependencies": {
+    "text-encoding": "0.7"
+  }
+}

package.json

@@ -1,5 +1,14 @@
 #include <stdint.h>
 
-uint32_t increment_in_c(uint32_t i) {
-  return i + 1;
+typedef struct {
+  uint32_t line;
+  uint32_t column;
+} Point;
+
+Point add_points_in_c(Point a, Point b) {
+  if (b.line > 0) {
+    return (Point) {a.line + b.line, b.column};
+  } else {
+    return (Point) {a.line, a.column + b.column};
+  }
 }

src/lib.c

@@ -1,9 +1,22 @@
+use wasm_bindgen::prelude::*;
+
+#[wasm_bindgen]
+#[repr(C)]
+pub struct Point {
+    pub line: u32,
+    pub column: u32,
+}
+
 extern "C" {
-    #[no_mangle]
-    fn increment_in_c(i: u32) -> u32;
+    fn add_points_in_c(a: Point, b: Point) -> Point;
+}
+
+#[wasm_bindgen]
+pub fn add_points_in_rust(a: Point, b: Point) -> Point {
+    unsafe { add_points_in_c(a, b) }
 }
 
-#[no_mangle]
-extern "C" fn increment_in_rust(i: u32) -> u32 {
-    unsafe { increment_in_c(i) }
+#[wasm_bindgen]
+pub fn new_point(line: u32, column: u32) -> Point {
+    Point { line, column }
 }

src/lib.rs

@@ -0,0 +1,13 @@
+import init, {add_points_in_rust, new_point} from "./pkg/wasm_lib_with_c.mjs"
+
+run();
+
+async function run() {
+  await init('./pkg/wasm_lib_with_c_bg.wasm');
+
+  let p = add_points_in_rust(new_point(4, 5), new_point(1, 10));
+  console.log(p.line, p.column);
+
+  p = add_points_in_rust(new_point(4, 5), new_point(0, 10));
+  console.log(p.line, p.column);
+}

test.mjs

@@ -0,0 +1,31 @@
+#!/bin/bash
+
+# Must be LLVM version >= 8
+export PATH=/opt/local/llvm/bin:${PATH}
+
+# Compile the Rust/C into JS/Wasm
+AR=llvm-ar cargo build --target=wasm32-unknown-unknown
+wasm-bindgen \
+  target/wasm32-unknown-unknown/debug/wasm_lib_with_c.wasm \
+  --target web \
+  --out-dir pkg
+
+# Convert the generated `.js` file into a node-compatible `.mjs` file.
+cat > pkg/wasm_lib_with_c.mjs <<JS
+import encoding from 'text-encoding';
+import fs from 'fs';
+
+const {TextDecoder} = encoding;
+
+async function fetch(path) {
+  return {
+    async arrayBuffer() {
+      return fs.readFileSync(path);
+    }
+  }
+}
+JS
+cat pkg/wasm_lib_with_c.js >> pkg/wasm_lib_with_c.mjs
+
+# Run the script with Node.
+node --experimental-modules test.mjs