frontend: use single wasm instance

Author: TerrorJack

.github/workflows/build.yml

@@ -68,7 +68,7 @@ jobs:
 
       - name: test
         run: |
-          $CROSS_EMULATOR dist/pandoc.wasm pandoc/README.md -o pandoc/README.rst
+          wasmtime run --dir $PWD::/ -- dist/pandoc.wasm pandoc/README.md -o pandoc/README.rst
           head --lines=20 pandoc/README.rst
 
       - name: upload-pages-artifact

frontend/index.html

@@ -67,16 +67,13 @@
       <input type="text" id="arguments" value="-f markdown -t rst" />
     </div>
     <script type="module">
-      import { run_pandoc } from "./index.js";
+      import { pandoc } from "./index.js";
 
       async function updateOutput() {
         const inputText = document.getElementById("input").value;
-        const argumentsText = document
-          .getElementById("arguments")
-          .value.trim()
-          .split(" ");
+        const argumentsText = document.getElementById("arguments").value;
         try {
-          const output = await run_pandoc(argumentsText, inputText);
+          const output = pandoc(argumentsText, inputText);
           document.getElementById("output").value = output;
         } catch (err) {
           document.getElementById("output").value = `Error: ${err.message}`;

frontend/index.js

@@ -3,60 +3,63 @@ import {
   OpenFile,
   File,
   ConsoleStdout,
+  PreopenDirectory,
 } from "https://cdn.jsdelivr.net/npm/@bjorn3/[email protected]/dist/index.js";
 
-const mod = await WebAssembly.compileStreaming(fetch("./pandoc.wasm"));
-
-const instance_promise_pool_size = 8;
+const args = ["pandoc.wasm", "+RTS", "-H64m", "-RTS"];
+const env = [];
+const in_file = new File(new Uint8Array(), { readonly: true });
+const out_file = new File(new Uint8Array(), { readonly: false });
+const fds = [
+  new OpenFile(new File(new Uint8Array(), { readonly: true })),
+  ConsoleStdout.lineBuffered((msg) => console.log(`[WASI stdout] ${msg}`)),
+  ConsoleStdout.lineBuffered((msg) => console.warn(`[WASI stderr] ${msg}`)),
+  new PreopenDirectory("/", [
+    ["in", in_file],
+    ["out", out_file],
+  ]),
+];
+const options = { debug: false };
+const wasi = new WASI(args, env, fds, options);
+const { instance } = await WebAssembly.instantiateStreaming(
+  fetch("./pandoc.wasm"),
+  {
+    wasi_snapshot_preview1: wasi.wasiImport,
+  }
+);
 
-const instance_promise_pool = [];
+wasi.initialize(instance);
+instance.exports.__wasm_call_ctors();
 
-function instance_promise_pool_fill() {
-  if (instance_promise_pool.length < instance_promise_pool_size) {
-    for (
-      let i = instance_promise_pool.length;
-      i < instance_promise_pool_size;
-      ++i
-    ) {
-      const args = [];
-      const env = [];
-      const stdin_file = new File(new Uint8Array(), { readonly: true });
-      const stdout_file = new File(new Uint8Array(), { readonly: false });
-      const fds = [
-        new OpenFile(stdin_file),
-        new OpenFile(stdout_file),
-        ConsoleStdout.lineBuffered((msg) =>
-          console.warn(`[WASI stderr] ${msg}`)
-        ),
-      ];
-      const options = { debug: false };
-      const wasi = new WASI(args, env, fds, options);
-      instance_promise_pool.push(
-        WebAssembly.instantiate(mod, {
-          wasi_snapshot_preview1: wasi.wasiImport,
-        }).then((instance) => ({ instance, wasi, stdin_file, stdout_file }))
-      );
-    }
-  }
+function memory_data_view() {
+  return new DataView(instance.exports.memory.buffer);
 }
 
-instance_promise_pool_fill();
+const argc_ptr = instance.exports.malloc(4);
+memory_data_view().setUint32(argc_ptr, args.length, true);
+const argv = instance.exports.malloc(4 * (args.length + 1));
+for (let i = 0; i < args.length; ++i) {
+  const arg = instance.exports.malloc(args[i].length + 1);
+  new TextEncoder().encodeInto(
+    args[i],
+    new Uint8Array(instance.exports.memory.buffer, arg, args[i].length)
+  );
+  memory_data_view().setUint8(arg + args[i].length, 0);
+  memory_data_view().setUint32(argv + 4 * i, arg, true);
+}
+memory_data_view().setUint32(argv + 4 * args.length, 0, true);
+const argv_ptr = instance.exports.malloc(4);
+memory_data_view().setUint32(argv_ptr, argv, true);
 
-const instances = (async function* () {
-  while (true) {
-    yield await instance_promise_pool.shift();
-    instance_promise_pool_fill();
-  }
-})();
+instance.exports.hs_init_with_rtsopts(argc_ptr, argv_ptr);
 
-export async function run_pandoc(args, stdin_str) {
-  const { instance, wasi, stdin_file, stdout_file } = (await instances.next())
-    .value;
-  wasi.args = ["pandoc.wasm", ...args];
-  stdin_file.data = new TextEncoder().encode(stdin_str);
-  const ec = wasi.start(instance);
-  if (ec !== 0) {
-    throw new Error(`Non-zero exit code ${ec}`);
-  }
-  return new TextDecoder("utf-8", { fatal: true }).decode(stdout_file.data);
+export function pandoc(args_str, in_str) {
+  const args_ptr = instance.exports.malloc(args_str.length);
+  new TextEncoder().encodeInto(
+    args_str,
+    new Uint8Array(instance.exports.memory.buffer, args_ptr, args_str.length)
+  );
+  in_file.data = new TextEncoder().encode(in_str);
+  instance.exports.wasm_main(args_ptr, args_str.length);
+  return new TextDecoder("utf-8", { fatal: true }).decode(out_file.data);
 }