WebAssembly support!

Quite a lot going on in this PR:
 * Updates to support recent emscripten, switching to WASM which is now the default
 * Use emscripten's MODULARIZE option rather than wrapping it ourself, since doing
   so in pre-post js doesn't work anymore.
 * Most changes are moving the emscripten runtime functions to top-level
   calls rather than in the Module object.
 * Get rid of duplicated NULL_BYTE_PADDING_LENGTH
 * Fix ciphertext_length used without being declared
 * Fix things that caused the closure compiler to error, eg. using
   OLM_OPTIONS without a declaration.
 * Wait until module is inited to do OLM_ERROR = olm_error()

The main BREAKING CHANGE here is that the module now needs to initialise
asyncronously (because it has to load the wasm file). require()ing olm
now gives a function which needs to be called to create an instance.
The resulting object has a promise-like then() method that can be used
to detect when the module is ready. (We could use MODULARIZE_INSTANCE
to return the module directly as before, rather than the function,
but then we don't get the .then() method).

1 files changed, 22 insertions, 13 deletions

diff --git a/javascript/olm_pre.js b/javascript/olm_pre.js
index ae7aba5..5e8ed12 100644
--- a/javascript/olm_pre.js
+++ b/javascript/olm_pre.js
@@ -1,10 +1,8 @@
 var olm_exports = {};
 var get_random_values;
-var process; // Shadow the process object so that emscripten won't get
-             // confused by browserify
 
 if (typeof(window) !== 'undefined') {
-    // We've in a browser (directly, via browserify, or via webpack).
+    // We're in a browser (directly, via browserify, or via webpack).
     get_random_values = function(buf) {
         window.crypto.getRandomValues(buf);
     };
@@ -12,7 +10,9 @@ if (typeof(window) !== 'undefined') {
     // We're running in node.
     var nodeCrypto = require("crypto");
     get_random_values = function(buf) {
-        var bytes = nodeCrypto.randomBytes(buf.length);
+        // [''] syntax needed here rather than '.' to prevent
+        // closure compiler from mangling the import(!)
+        var bytes = nodeCrypto['randomBytes'](buf.length);
         buf.set(bytes);
     };
     process = global["process"];
@@ -20,14 +20,23 @@ if (typeof(window) !== 'undefined') {
     throw new Error("Cannot find global to attach library to");
 }
 
-(function() {
-    /* applications should define OLM_OPTIONS in the environment to override
-     * emscripten module settings */
-    var Module = {};
-    if (typeof(OLM_OPTIONS) !== 'undefined') {
-        for (var key in OLM_OPTIONS) {
-            if (OLM_OPTIONS.hasOwnProperty(key)) {
-                Module[key] = OLM_OPTIONS[key];
-            }
+/* applications should define OLM_OPTIONS in the environment to override
+ * emscripten module settings (we still need to (re) declare the variable
+ * otherwise the closure compiler becomes sad).
+ */
+var OLM_OPTIONS;
+if (typeof(OLM_OPTIONS) !== 'undefined') {
+    for (var olm_option_key in OLM_OPTIONS) {
+        if (OLM_OPTIONS.hasOwnProperty(olm_option_key)) {
+            Module[olm_option_key] = OLM_OPTIONS[olm_option_key];
         }
     }
+}
+
+/* The 'length' argument to Pointer_stringify doesn't work if the input
+ * includes characters >= 128, which makes Pointer_stringify unreliable. We
+ * could use it on strings which are known to be ascii, but that seems
+ * dangerous. Instead we add a NULL character to all of our strings and just
+ * use UTF8ToString.
+ */
+var NULL_BYTE_PADDING_LENGTH = 1;