bf interpreter because lulz

assets/bf.js

@@ -0,0 +1,66 @@
+// exec_args: bf.js input_file optional_memsize
+let memsize = exec_args[2]|0;
+if (memsize <= 0) memsize = (system.maxmem() < 30000) ? system.maxmem()-256 : 30000;
+let nativePtr = undefined;
+try {
+    nativePtr = sys.malloc(memsize);
+}
+catch (e) {
+    printerrln("Could not allocate memory with size "+memsize);
+    return 10;
+}
+let stubHead = "let mx="+memsize+";"+
+"let fmod=function(a,b){return Number((a-(Math.floor(a/b)*b)).toPrecision(8));};"+
+"let ip=function(){p=fmod(p+1,mx)};"+
+"let dp=function(){p=fmod(p-1,mx)};"+
+"let iv=function(){sys.poke(p,fmod(sys.peek(p)+1,256))};"+
+"let dv=function(){sys.poke(p,fmod(sys.peek(p)-1,256))};"+
+"let p="+nativePtr+";"
+let translation = {
+    62: "ip();",
+    60: "dp();",
+    43: "iv();",
+    45: "dv();",
+    46: "sys.print(String.fromCharCode(sys.peek(p)));",
+    44: "sys.poke(p,sys.readKey());",
+    91: "while(sys.peek(p)!=0){",
+    93: "}"
+};
+if (exec_args[1] === undefined) {
+    printerrln("Usage: bf <path-to-BF-program>");
+    return 1;
+}
+let bfprg = "";
+try {
+    filesystem.open(_G.shell.getCurrentDrive(), exec_args[1], "R");
+    bfprg = filesystem.readAll(_G.shell.getCurrentDrive());
+}
+catch(e) {
+    printerrln(e);
+    sys.free(nativePtr);
+    return 1;
+}
+try {
+    // translate
+    let tprg = stubHead;
+    for (let k = 0; k < bfprg.length; k++) {
+        tprg += (translation[bfprg.charCodeAt(k)] || "");
+    }
+
+    // clear memory
+    for (let k = 0; k < memsize; k++) {
+        sys.poke(nativePtr+k, 0);
+    }
+
+    // run
+    execApp(tprg);
+}
+catch (e) {
+    printerrln(e);
+    return 1;
+}
+finally {
+    sys.free(nativePtr);
+}
+
+return 0;