fix JS event loop blocking

sys/lib/npm-package/src/nethackShim.js

@@ -3,27 +3,38 @@ const path = require("path");
 let Module;
 let userCallback;
 let savedOnRuntimeInitialized;
+
+// starts nethack
 function nethackStart(cb, inputModule = {}) {
-    if(typeof cb !== "function") throw new TypeError("expected first argument to be callback function");
+    if(typeof cb !== "string" && typeof cb !== "function") throw new TypeError("expected first argument to be 'Function' or 'String' representing global callback function name");
     if(typeof inputModule !== "object") throw new TypeError("expected second argument to be object");
 
+    let cbName;
+    if(typeof cb === "function") {
+        cbName = cb.name;
+        if (cbName === "") cbName = "__anonymousNetHackCallback";
+        if (globalThis[cbName] === undefined) globalThis[cbName] = cb;
+        else if (globalThis[cbName] !== cb) throw new Error (`'globalThis["${cbName}"]' is not the same as specified callback`);
+    }
+
+    /* global globalThis */
+    userCallback = globalThis[cbName];
+    if(typeof userCallback !==  "function") throw new TypeError(`expected 'globalThis["${cbName}"]' to be a function`);
+    // if(userCallback.constructor.name !== "AsyncFunction") throw new TypeError(`expected 'globalThis["${cbName}"]' to be an async function`);
+
     // Emscripten Module config
     Module = inputModule;
-    userCallback = cb;
     savedOnRuntimeInitialized = Module.onRuntimeInitialized;
     Module.onRuntimeInitialized = function (... args) {
         // after the WASM is loaded, add the shim graphics callback function
-        let cb = Module.addFunction(windowCallback, "viiii");
         Module.ccall(
             "shim_graphics_set_callback", // C function name
             null, // return type
-            ["number"], // arg types
-            [cb], // arg values
+            ["string"], // arg types
+            [cbName], // arg values
             {async: true} // options
         );
 
-        /* TODO: Module.removeFunction() */
-
         // if the user had their own onRuntimeInitialized(), call it now
         if (savedOnRuntimeInitialized) savedOnRuntimeInitialized(... args);
     };
@@ -33,94 +44,6 @@ function nethackStart(cb, inputModule = {}) {
     factory(Module);
 }
 
-function windowCallback(name, retPtr, fmt, args) {
-    name = Module.UTF8ToString(name);
-    fmt = Module.UTF8ToString(fmt);
-    let argTypes = fmt.split("");
-    let retType = argTypes.shift();
-
-    // build array of JavaScript args from WASM parameters
-    let jsArgs = [];
-    for (let i = 0; i < argTypes.length; i++) {
-        let ptr = args + (4*i);
-        let val = typeLookup(argTypes[i], ptr);
-        jsArgs.push(val);
-    }
-    let retVal = userCallback(name, ... jsArgs);
-    setReturn(name, retPtr, retType, retVal);
-}
-
-function typeLookup(type, ptr) {
-    switch(type) {
-    case "s": // string
-        return Module.UTF8ToString(Module.getValue(ptr, "*"));
-    case "p": // pointer
-        ptr = Module.getValue(ptr, "*");
-        if(!ptr) return 0; // null pointer
-        return Module.getValue(ptr, "*");
-    case "c": // char
-        return String.fromCharCode(Module.getValue(Module.getValue(ptr, "*"), "i8"));
-    case "0": /* 2^0 = 1 byte */
-        return Module.getValue(Module.getValue(ptr, "*"), "i8");
-    case "1": /* 2^1 = 2 bytes */
-        return Module.getValue(Module.getValue(ptr, "*"), "i16");
-    case "2": /* 2^2 = 4 bytes */
-    case "i": // integer
-    case "n": // number
-        return Module.getValue(Module.getValue(ptr, "*"), "i32");
-    case "f": // float
-        return Module.getValue(Module.getValue(ptr, "*"), "float");
-    case "d": // double
-        return Module.getValue(Module.getValue(ptr, "*"), "double");
-    default:
-        throw new TypeError ("unknown type:" + type);
-    }
-}
-
-function setReturn(name, ptr, type, value = 0) {
-
-    switch (type) {
-    case "p":
-        throw new Error("not implemented");
-    case "s":
-        if(typeof value !== "string")
-            throw new TypeError(`expected ${name} return type to be string`);
-        value=value?value:"(no value)";
-        var strPtr = Module.getValue(ptr, "i32");
-        Module.stringToUTF8(value, strPtr, 1024);
-        break;
-    case "i":
-        if(typeof value !== "number" || !Number.isInteger(value))
-            throw new TypeError(`expected ${name} return type to be integer`);
-        Module.setValue(ptr, value, "i32");
-        break;
-    case "c":
-        if(typeof value !== "number" || value < 0 || value > 128)
-            throw new TypeError(`expected ${name} return type to be integer representing an ASCII character`);
-        Module.setValue(ptr, value, "i8");
-        break;
-    case "f":
-        if(typeof value !== "number" || isFloat(value))
-            throw new TypeError(`expected ${name} return type to be float`);
-        // XXX: I'm not sure why 'double' works and 'float' doesn't
-        Module.setValue(ptr, value, "double");
-        break;
-    case "d":
-        if(typeof value !== "number" || isFloat(value))
-            throw new TypeError(`expected ${name} return type to be float`);
-        Module.setValue(ptr, value, "double");
-        break;
-    case "v":
-        break;
-    default:
-        throw new Error("unknown type");
-    }
-
-    function isFloat(n){
-        return n === +n && n !== (n|0) && !Number.isInteger(n);
-    }
-}
-
 // TODO: ES6 'import' style module
 module.exports = nethackStart;