fix JS event loop blocking
This commit is contained in:
Adam Powers
@@ -34,12 +34,10 @@ Where is the header file for the API you ask? There isn't one. It's three functi
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## API: nethack.js
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The WebAssembly API has a similar signature to `libnethack.a` with minor syntactic differences:
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* `main(int argc, char argv[])` - The main function for NetHack
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* `shim_graphics_set_callback(shim_callback_t cb)` - The same as above, but the signature of the callback is slightly different because WASM can't handle variadic callbacks. The callback is: `void shim_callback_t(const char *name, void *ret_ptr, const char *fmt, void *args[])`
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* `name` - same as above
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* `ret_ptr` - same as above
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* `fmt` - same as above
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* `args` - an array of pointers to the arguments, where each pointer can be de-referenced to a value as specified in the `fmt` string.
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* `shim_graphics_set_callback(char *cbName)` - A `String` representing a name of a callback function. The callback function be registered as `globalThis[cbName] = function yourCallback(name, ... args) { /* your stuff */ }`. Note that [globalThis](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/globalThis) points to `window` in browsers and `global` in node.js.
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* `name` is the name of the [window function](https://github.com/NetHack/NetHack/blob/NetHack-3.7/doc/window.doc) that needs to be handled
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* `... args` is a variable number and type of arguments depending on the `window function` that is being called. The arguments associated with each `name` are described in the [NetHack window.doc](https://github.com/NetHack/NetHack/blob/NetHack-3.7/doc/window.doc)
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* The function must return the value expected for the specified `name`
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## API Stability
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@@ -54,7 +52,7 @@ typedef void(*shim_callback_t)(const char *name, void *ret_ptr, const char *fmt,
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void shim_graphics_set_callback(shim_callback_t cb);
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void window_cb(const char *name, void *ret_ptr, const char *fmt, ...) {
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/* TODO -- see windowCallback below for hints */
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/* TODO */
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}
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int main(int argc, char *argv[]) {
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@@ -65,117 +63,33 @@ int main(int argc, char *argv[]) {
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## nethack.js example
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``` js
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// Module is defined by emscripten
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// https://emscripten.org/docs/api_reference/module.html
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let Module = {
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// if this is true, main() won't be called automatically
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// noInitialRun: true,
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const path = require("path");
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// after loading the library, set the callback function
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onRuntimeInitialized: function (... args) {
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setGraphicsCallback();
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}
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};
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// starts nethack
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function nethackStart(cb, inputModule = {}) {
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// set callback
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let cbName = cb.name;
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if (cbName === "") cbName = "__anonymousNetHackCallback";
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let userCallback = globalThis[cbName] = cb;
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var factory = require("./src/nethack.js");
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// Emscripten Module config
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let Module = inputModule;
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savedOnRuntimeInitialized = Module.onRuntimeInitialized;
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Module.onRuntimeInitialized = function (... args) {
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// after the WASM is loaded, add the shim graphics callback function
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Module.ccall(
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"shim_graphics_set_callback", // C function name
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null, // return type
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["string"], // arg types
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[cbName], // arg values
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{async: true} // options
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);
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};
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// run NetHack!
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factory(Module);
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// register the callback with the WASM library
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function setGraphicsCallback() {
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console.log("creating WASM callback function");
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let cb = Module.addFunction(windowCallback, "viiii");
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console.log("setting callback function with library");
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Module.ccall(
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"shim_graphics_set_callback", // C function name
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null, // return type
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["number"], // arg types
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[cb], // arg values
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{async: true} // options
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);
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/* TODO: removeFunction */
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// load and run the module
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var factory = require(path.join(__dirname, "../build/nethack.js"));
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factory(Module);
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}
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// this is the "shim graphics" callback function
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// it gets called every time something needs to be displayed
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// or input needs to be gathered from the user
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function windowCallback(name, retPtr, fmt, args) {
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name = Module.UTF8ToString(name);
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fmt = Module.UTF8ToString(fmt);
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let argTypes = fmt.split("");
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let retType = argTypes.shift();
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// convert arguments to JavaScript types
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let jsArgs = [];
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for (let i = 0; i < argTypes.length; i++) {
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let ptr = args + (4*i);
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let val = typeLookup(argTypes[i], ptr);
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jsArgs.push(val);
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}
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console.log(`graphics callback: ${name} [${jsArgs}]`);
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/**********
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* YOU HAVE TO IMPLEMENT THIS FUNCTION to render things
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**********/
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let ret = yourFunctionToRenderGraphics(name, jsArgs);
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setReturn(retPtr, retType, ret);
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}
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// takes a character `type` and a WASM pointer and returns a JavaScript value
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function typeLookup(type, ptr) {
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switch(type) {
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case "s": // string
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return Module.UTF8ToString(Module.getValue(ptr, "*"));
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case "p": // pointer
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return Module.getValue(Module.getValue(ptr, "*"), "*");
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case "c": // char
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return String.fromCharCode(Module.getValue(Module.getValue(ptr, "*"), "i8"));
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case "0": /* 2^0 = 1 byte */
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return Module.getValue(Module.getValue(ptr, "*"), "i8");
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case "1": /* 2^1 = 2 bytes */
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return Module.getValue(Module.getValue(ptr, "*"), "i16");
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case "2": /* 2^2 = 4 bytes */
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case "i": // integer
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case "n": // number
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return Module.getValue(Module.getValue(ptr, "*"), "i32");
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case "f": // float
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return Module.getValue(Module.getValue(ptr, "*"), "float");
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case "d": // double
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return Module.getValue(Module.getValue(ptr, "*"), "double");
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default:
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throw new TypeError ("unknown type:" + type);
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}
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}
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// takes a a WASM pointer, a charater `type` and a value and sets the value at pointer
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function setReturn(ptr, type, value = 0) {
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switch (type) {
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case "p":
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throw new Error("not implemented");
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case "s":
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value=value?value:"(no value)";
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var strPtr = Module.getValue(ptr, "i32");
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Module.stringToUTF8(value, strPtr, 1024);
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break;
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case "i":
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Module.setValue(ptr, value, "i32");
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break;
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case "c":
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Module.setValue(ptr, value, "i8");
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break;
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case "f":
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// XXX: I'm not sure why 'double' works and 'float' doesn't
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Module.setValue(ptr, value, "double");
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break;
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case "d":
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Module.setValue(ptr, value, "double");
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break;
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case "v":
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break;
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default:
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throw new Error("unknown type");
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}
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}
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nethackStart(yourCallbackFunction);
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```
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