2 files changed, 26 insertions, 4 deletions
diff --git a/src/library.js b/src/library.js
index 6662e9b7..1bb58833 100644
--- a/src/library.js
+++ b/src/library.js
@@ -304,12 +304,14 @@ LibraryManager.library = {
     // You can also call this with a typed array instead of a url. It will then
     // do preloading for the Image/Audio part, as if the typed array were the
     // result of an XHR that you did manually.
-    createPreloadedFile: function(parent, name, url, canRead, canWrite, onload, onerror) {
+    createPreloadedFile: function(parent, name, url, canRead, canWrite, onload, onerror, dontCreateFile) {
       Browser.ensureObjects();
       var fullname = FS.joinPath([parent, name], true);
       function processData(byteArray) {
         function finish(byteArray) {
-          FS.createDataFile(parent, name, byteArray, canRead, canWrite);
+          if (!dontCreateFile) {
+            FS.createDataFile(parent, name, byteArray, canRead, canWrite);
+          }
           if (onload) onload();
           removeRunDependency('cp ' + fullname);
         }
diff --git a/src/library_browser.js b/src/library_browser.js
index 27bf4a0c..6985e04a 100644
--- a/src/library_browser.js
+++ b/src/library_browser.js
@@ -364,14 +364,34 @@ mergeInto(LibraryManager.library, {
       _file.substr(index +1),
       _url, true, true,
       function() {
-        FUNCTION_TABLE[onload](file);
+        if (onload) FUNCTION_TABLE[onload](file);
       },
       function() {
-        FUNCTION_TABLE[onerror](file);
+        if (onerror) FUNCTION_TABLE[onerror](file);
       }
     );
   },
 
+  emscripten_async_prepare: function(file, onload, onerror) {
+    var _file = Pointer_stringify(file);
+    var data = FS.analyzePath(_file);
+    if (!data.exists) return -1;
+    var index = _file.lastIndexOf('/');
+    FS.createPreloadedFile(
+      _file.substr(0, index),
+      _file.substr(index +1),
+      new Uint8Array(data.object.contents), true, true,
+      function() {
+        if (onload) FUNCTION_TABLE[onload](file);
+      },
+      function() {
+        if (onerror) FUNCTION_TABLE[onerror](file);
+      },
+      true // don'tCreateFile - it's already there
+    );
+    return 0;
+  },
+
   emscripten_async_run_script__deps: ['emscripten_run_script'],
   emscripten_async_run_script: function(script, millis) {
     Module['noExitRuntime'] = true;