Add instructions for WASM

src/wasm/README.md

@@ -0,0 +1,71 @@
+# WASM
+
+Steps to compile to WASM to run from Node.js This is likely faster than the js
+version.
+
+Install emscripten.org
+https://emscripten.org/docs/getting_started/downloads.html
+
+Download C++ source from https://qqwing.com/download.html
+
+Run `./configure`
+
+edit `main.cpp` add to top
+
+```
+#include <stdio.h>
+#include <emscripten.h>
+```
+
+Add `EMSCRIPTEN_KEEPALIVE` above int main so it looks like
+
+```
+EMSCRIPTEN_KEEPALIVE
+int main(int argc, char *argv[]){
+```
+
+Run
+`emcc main.cpp qqwing.cpp -o main.js -sMODULARIZE -sEXPORTED_RUNTIME_METHODS=ccall,callMain -sINVOKE_RUN=0`
+
+This outputs main.js and main.wasm
+
+Create an index.js file like the following
+
+```
+var factory = require('./main.js');
+
+factory({
+  print: (x) => {
+    // Change to capture output
+    console.info(x);
+  }
+}).then((instance) => {
+  instance.callMain(['--version']);
+  instance.callMain(['--generate']);
+  instance.callMain(['--generate', '--difficulty', 'expert', '--solution', '--csv']);
+});
+```
+
+Run `node index.js`
+
+This outputs
+
+```
+qqwing 1.3.4
+ . . . | . 7 2 | 1 . .
+ . . . | 8 . . | . . 9
+ . . . | . 3 . | 8 2 .
+-------|-------|-------
+ . 9 . | 2 . . | . . .
+ 8 2 . | . 1 . | . . .
+ . . . | . . . | 3 . .
+-------|-------|-------
+ 3 6 . | . 8 . | . . .
+ . . . | . 2 1 | 5 . .
+ . . 9 | 5 . . | . . 6
+
+Puzzle,Solution,
+....721.....8....9....3.82..9.2.....82..1..........3..36..8........215....95....6,486972135132854679957136824593267418824315967671498352365789241748621593219543786,
+```
+
+We can change the print method to capture it to a variable instead of console.