Issue 4125 - [emscripten] Convert filter classes to C++

lib/compiledTools.js

Index: lib/compiledTools.js
===================================================================
new file mode 100644
--- /dev/null
+++ b/lib/compiledTools.js
@@ -0,0 +1,73 @@
+"use strict";
+
+let {
+  Runtime, AsciiToString, HEAP16, HEAP32, _free, _getException
+} = require("./compiled");
+
+function wrapCall(call)
+{
+  return function()
+  {
+    let sp = Runtime.stackSave();
+    try
+    {
+      return call.apply(this, arguments);
+    }
+    catch (e)
+    {
+      throw typeof e == "number" ? new Error(AsciiToString(_getException(e))) : e;
+    }
+    finally
+    {
+      Runtime.stackRestore(sp);
+    }
+  };
+}
+exports.wrapCall = wrapCall;
+
+function convertString(str)
+{
+  let length = str.length;
+  let buffer = Runtime.stackAlloc(length * 2);
+  for (let i = 0, pointer = (buffer >> 1); i < length; i++, pointer++)
+    HEAP16[pointer] = str.charCodeAt(i);
+  return buffer;
+}
+
+function stringArg(argNumber, call)
+{
+  return function()
+  {
+    let params = Array.slice(arguments);
+    let str = params[argNumber];
+    if (str != null)
+      params.splice(argNumber, 1, convertString(str), str.length);
+    else
+      params.splice(argNumber, 1, 0, 0);
+    return call.apply(this, params);
+  };
+}
+exports.stringArg = stringArg;
+
+function stringResult(call)
+{
+  return function()
+  {
+    let params = Array.slice(arguments);
+    let resultLen = Runtime.stackAlloc(4);
+    params.push(resultLen);
+
+    let buffer = call.apply(this, params);
+    if (buffer)
+    {
+      let length = HEAP32[resultLen >> 2];
+      let pointer = buffer >> 1;
+      let str = String.fromCharCode.apply(String, HEAP16.slice(pointer, pointer + length));
+      _free(buffer);
+      return str;
+    }
+    else
+      return null;
+  };
+}
+exports.stringResult = stringResult;