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).

10 files changed, 84 insertions, 76 deletions

diff --git a/Makefile b/Makefile
index 154954c..f6c2ab4 100644
--- a/Makefile
+++ b/Makefile
@@ -20,6 +20,7 @@ DEBUG_TARGET := $(BUILD_DIR)/libolm_debug.so.$(VERSION)
 JS_TARGET := javascript/olm.js
 
 JS_EXPORTED_FUNCTIONS := javascript/exported_functions.json
+JS_EXTRA_EXPORTED_RUNTIME_METHODS := ALLOC_STACK
 
 PUBLIC_HEADERS := include/olm/olm.h include/olm/outbound_group_session.h include/olm/inbound_group_session.h include/olm/pk.h
 
@@ -60,7 +61,7 @@ CFLAGS += -Wall -Werror -std=c99 -fPIC
 CXXFLAGS += -Wall -Werror -std=c++11 -fPIC
 LDFLAGS += -Wall -Werror
 
-EMCCFLAGS = --closure 1 --memory-init-file 0 -s NO_FILESYSTEM=1 -s INVOKE_RUN=0
+EMCCFLAGS = --closure 1 --memory-init-file 0 -s NO_FILESYSTEM=1 -s INVOKE_RUN=0 -s MODULARIZE=1
 # NO_BROWSER is kept for compatibility with emscripten 1.35.24, but is no
 # longer needed.
 EMCCFLAGS += -s NO_BROWSER=1
@@ -150,6 +151,7 @@ $(JS_TARGET): $(JS_OBJECTS) $(JS_PRE) $(JS_POST) $(JS_EXPORTED_FUNCTIONS)
                $(foreach f,$(JS_PRE),--pre-js $(f)) \
                $(foreach f,$(JS_POST),--post-js $(f)) \
                -s "EXPORTED_FUNCTIONS=@$(JS_EXPORTED_FUNCTIONS)" \
+               -s "EXTRA_EXPORTED_RUNTIME_METHODS=$(JS_EXTRA_EXPORTED_RUNTIME_METHODS)" \
                $(JS_OBJECTS) -o $@
 
 build_tests: $(TEST_BINARIES)
diff --git a/javascript/.gitignore b/javascript/.gitignore
index ec22345..3437f73 100644
--- a/javascript/.gitignore
+++ b/javascript/.gitignore
@@ -2,4 +2,5 @@
 /node_modules
 /npm-debug.log
 /olm.js
+/olm.wasm
 /reports
diff --git a/javascript/olm_inbound_group_session.js b/javascript/olm_inbound_group_session.js
index 6bc745d..7d9e401 100644
--- a/javascript/olm_inbound_group_session.js
+++ b/javascript/olm_inbound_group_session.js
@@ -1,9 +1,3 @@
-/* The 'length' argument to Pointer_stringify doesn't work if the input includes
- * characters >= 128; we therefore need to add a NULL character to all of our
- * strings. This acts as a symbolic constant to help show what we're doing.
- */
-var NULL_BYTE_PADDING_LENGTH = 1;
-
 function InboundGroupSession() {
     var size = Module['_olm_inbound_group_session_size']();
     this.buf = malloc(size);
@@ -77,14 +71,14 @@ InboundGroupSession.prototype['decrypt'] = restore_stack(function(
 
     try {
         message_buffer = malloc(message.length);
-        Module['writeAsciiToMemory'](message, message_buffer, true);
+        writeAsciiToMemory(message, message_buffer, true);
 
         var max_plaintext_length = inbound_group_session_method(
             Module['_olm_group_decrypt_max_plaintext_length']
         )(this.ptr, message_buffer, message.length);
 
         // caculating the length destroys the input buffer, so we need to re-copy it.
-        Module['writeAsciiToMemory'](message, message_buffer, true);
+        writeAsciiToMemory(message, message_buffer, true);
 
         plaintext_buffer = malloc(max_plaintext_length + NULL_BYTE_PADDING_LENGTH);
         var message_index = stack(4);
@@ -100,14 +94,14 @@ InboundGroupSession.prototype['decrypt'] = restore_stack(function(
 
         // UTF8ToString requires a null-terminated argument, so add the
         // null terminator.
-        Module['setValue'](
+        setValue(
             plaintext_buffer+plaintext_length,
             0, "i8"
         );
 
         return {
             "plaintext": UTF8ToString(plaintext_buffer),
-            "message_index": Module['getValue'](message_index, "i32")
+            "message_index": getValue(message_index, "i32")
         }
     } finally {
         if (message_buffer !== undefined) {
diff --git a/javascript/olm_outbound_group_session.js b/javascript/olm_outbound_group_session.js
index 24ea644..e232883 100644
--- a/javascript/olm_outbound_group_session.js
+++ b/javascript/olm_outbound_group_session.js
@@ -1,10 +1,3 @@
-/* The 'length' argument to Pointer_stringify doesn't work if the input includes
- * characters >= 128; we therefore need to add a NULL character to all of our
- * strings. This acts as a symbolic constant to help show what we're doing.
- */
-var NULL_BYTE_PADDING_LENGTH = 1;
-
-
 function OutboundGroupSession() {
     var size = Module['_olm_outbound_group_session_size']();
     this.buf = malloc(size);
@@ -66,7 +59,7 @@ OutboundGroupSession.prototype['create'] = restore_stack(function() {
 OutboundGroupSession.prototype['encrypt'] = function(plaintext) {
     var plaintext_buffer, message_buffer, plaintext_length;
     try {
-        plaintext_length = Module['lengthBytesUTF8'](plaintext);
+        plaintext_length = lengthBytesUTF8(plaintext);
 
         var message_length = outbound_group_session_method(
             Module['_olm_group_encrypt_message_length']
@@ -75,7 +68,7 @@ OutboundGroupSession.prototype['encrypt'] = function(plaintext) {
         // need to allow space for the terminator (which stringToUTF8 always
         // writes), hence + 1.
         plaintext_buffer = malloc(plaintext_length + 1);
-        Module['stringToUTF8'](plaintext, plaintext_buffer, plaintext_length + 1);
+        stringToUTF8(plaintext, plaintext_buffer, plaintext_length + 1);
 
         message_buffer = malloc(message_length + NULL_BYTE_PADDING_LENGTH);
         outbound_group_session_method(Module['_olm_group_encrypt'])(
@@ -86,12 +79,12 @@ OutboundGroupSession.prototype['encrypt'] = function(plaintext) {
 
         // UTF8ToString requires a null-terminated argument, so add the
         // null terminator.
-        Module['setValue'](
+        setValue(
             message_buffer+message_length,
             0, "i8"
         );
 
-        return Module['UTF8ToString'](message_buffer);
+        return UTF8ToString(message_buffer);
     } finally {
         if (plaintext_buffer !== undefined) {
             // don't leave a copy of the plaintext in the heap.
diff --git a/javascript/olm_pk.js b/javascript/olm_pk.js
index 2542707..25e0fee 100644
--- a/javascript/olm_pk.js
+++ b/javascript/olm_pk.js
@@ -35,9 +35,9 @@ PkEncryption.prototype['encrypt'] = restore_stack(function(
 ) {
     var plaintext_buffer, ciphertext_buffer, plaintext_length;
     try {
-        plaintext_length = Module['lengthBytesUTF8'](plaintext)
+        plaintext_length = lengthBytesUTF8(plaintext)
         plaintext_buffer = malloc(plaintext_length + 1);
-        Module['stringToUTF8'](plaintext, plaintext_buffer, plaintext_length + 1);
+        stringToUTF8(plaintext, plaintext_buffer, plaintext_length + 1);
         var random_length = pk_encryption_method(
             Module['_olm_pk_encrypt_random_length']
         )();
@@ -50,7 +50,7 @@ PkEncryption.prototype['encrypt'] = restore_stack(function(
             Module['_olm_pk_mac_length']
         )(this.ptr);
         var mac_buffer = stack(mac_length + NULL_BYTE_PADDING_LENGTH);
-        Module['setValue'](
+        setValue(
             mac_buffer+mac_length,
             0, "i8"
         );
@@ -58,7 +58,7 @@ PkEncryption.prototype['encrypt'] = restore_stack(function(
             Module['_olm_pk_key_length']
         )();
         var ephemeral_buffer = stack(ephemeral_length + NULL_BYTE_PADDING_LENGTH);
-        Module['setValue'](
+        setValue(
             ephemeral_buffer+ephemeral_length,
             0, "i8"
         );
@@ -72,12 +72,12 @@ PkEncryption.prototype['encrypt'] = restore_stack(function(
         );
         // UTF8ToString requires a null-terminated argument, so add the
         // null terminator.
-        Module['setValue'](
+        setValue(
             ciphertext_buffer+ciphertext_length,
             0, "i8"
         );
         return {
-            "ciphertext": Module['UTF8ToString'](ciphertext_buffer),
+            "ciphertext": UTF8ToString(ciphertext_buffer),
             "mac": Pointer_stringify(mac_buffer),
             "ephemeral": Pointer_stringify(ephemeral_buffer)
         };
@@ -169,9 +169,9 @@ PkDecryption.prototype['decrypt'] = restore_stack(function (
 ) {
     var plaintext_buffer, ciphertext_buffer, plaintext_max_length;
     try {
-        ciphertext_length = Module['lengthBytesUTF8'](ciphertext)
+        var ciphertext_length = lengthBytesUTF8(ciphertext)
         ciphertext_buffer = malloc(ciphertext_length + 1);
-        Module['stringToUTF8'](ciphertext, ciphertext_buffer, ciphertext_length + 1);
+        stringToUTF8(ciphertext, ciphertext_buffer, ciphertext_length + 1);
         var ephemeralkey_array = array_from_string(ephemeral_key);
         var ephemeralkey_buffer = stack(ephemeralkey_array);
         var mac_array = array_from_string(mac);
@@ -190,11 +190,11 @@ PkDecryption.prototype['decrypt'] = restore_stack(function (
         );
         // UTF8ToString requires a null-terminated argument, so add the
         // null terminator.
-        Module['setValue'](
+        setValue(
             plaintext_buffer+plaintext_length,
             0, "i8"
         );
-        return Module['UTF8ToString'](plaintext_buffer);
+        return UTF8ToString(plaintext_buffer);
     } finally {
         if (plaintext_buffer !== undefined) {
             // don't leave a copy of the plaintext in the heap.
diff --git a/javascript/olm_post.js b/javascript/olm_post.js
index 7a1d284..071021c 100644
--- a/javascript/olm_post.js
+++ b/javascript/olm_post.js
@@ -1,27 +1,17 @@
-var runtime = Module['Runtime'];
 var malloc = Module['_malloc'];
 var free = Module['_free'];
-var Pointer_stringify = Module['Pointer_stringify'];
-var OLM_ERROR = Module['_olm_error']();
-
-/* 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;
+var OLM_ERROR;
 
 /* allocate a number of bytes of storage on the stack.
  *
  * If size_or_array is a Number, allocates that number of zero-initialised bytes.
  */
 function stack(size_or_array) {
-    return Module['allocate'](size_or_array, 'i8', Module['ALLOC_STACK']);
+    return allocate(size_or_array, 'i8', Module['ALLOC_STACK']);
 }
 
 function array_from_string(string) {
-    return Module['intArrayFromString'](string, true);
+    return intArrayFromString(string, true);
 }
 
 function random_stack(size) {
@@ -33,11 +23,11 @@ function random_stack(size) {
 
 function restore_stack(wrapped) {
     return function() {
-        var sp = runtime.stackSave();
+        var sp = stackSave();
         try {
             return wrapped.apply(this, arguments);
         } finally {
-            runtime.stackRestore(sp);
+            stackRestore(sp);
         }
     }
 }
@@ -315,7 +305,7 @@ Session.prototype['encrypt'] = restore_stack(function(
             Module['_olm_encrypt_message_type']
         )(this.ptr);
 
-        plaintext_length = Module['lengthBytesUTF8'](plaintext);
+        plaintext_length = lengthBytesUTF8(plaintext);
         var message_length = session_method(
             Module['_olm_encrypt_message_length']
         )(this.ptr, plaintext_length);
@@ -325,7 +315,7 @@ Session.prototype['encrypt'] = restore_stack(function(
         // need to allow space for the terminator (which stringToUTF8 always
         // writes), hence + 1.
         plaintext_buffer = malloc(plaintext_length + 1);
-        Module['stringToUTF8'](plaintext, plaintext_buffer, plaintext_length + 1);
+        stringToUTF8(plaintext, plaintext_buffer, plaintext_length + 1);
 
         message_buffer = malloc(message_length + NULL_BYTE_PADDING_LENGTH);
 
@@ -338,14 +328,14 @@ Session.prototype['encrypt'] = restore_stack(function(
 
         // UTF8ToString requires a null-terminated argument, so add the
         // null terminator.
-        Module['setValue'](
+        setValue(
             message_buffer+message_length,
             0, "i8"
         );
 
         return {
             "type": message_type,
-            "body": Module['UTF8ToString'](message_buffer),
+            "body": UTF8ToString(message_buffer),
         };
     } finally {
         if (plaintext_buffer !== undefined) {
@@ -366,14 +356,14 @@ Session.prototype['decrypt'] = restore_stack(function(
 
     try {
         message_buffer = malloc(message.length);
-        Module['writeAsciiToMemory'](message, message_buffer, true);
+        writeAsciiToMemory(message, message_buffer, true);
 
         max_plaintext_length = session_method(
             Module['_olm_decrypt_max_plaintext_length']
         )(this.ptr, message_type, message_buffer, message.length);
 
         // caculating the length destroys the input buffer, so we need to re-copy it.
-        Module['writeAsciiToMemory'](message, message_buffer, true);
+        writeAsciiToMemory(message, message_buffer, true);
 
         plaintext_buffer = malloc(max_plaintext_length + NULL_BYTE_PADDING_LENGTH);
 
@@ -385,7 +375,7 @@ Session.prototype['decrypt'] = restore_stack(function(
 
         // UTF8ToString requires a null-terminated argument, so add the
         // null terminator.
-        Module['setValue'](
+        setValue(
             plaintext_buffer+plaintext_length,
             0, "i8"
         );
@@ -474,8 +464,6 @@ olm_exports["get_library_version"] = restore_stack(function() {
     ];
 });
 
-})();
-
 // export the olm functions into the environment.
 //
 // make sure that we do this *after* populating olm_exports, so that we don't
@@ -483,7 +471,11 @@ olm_exports["get_library_version"] = restore_stack(function() {
 
 if (typeof module !== 'undefined' && module.exports) {
     // node / browserify
-    module.exports = olm_exports;
+    for (var olm_export in olm_exports) {
+        if (olm_exports.hasOwnProperty(olm_export)) {
+            Module[olm_export] = olm_exports[olm_export];
+        }
+    }
 }
 
 if (typeof(window) !== 'undefined') {
@@ -492,3 +484,7 @@ if (typeof(window) !== 'undefined') {
     // Olm in the global scope for browserified and webpacked apps.)
     window["Olm"] = olm_exports;
 }
+
+Module.then(function() {
+    OLM_ERROR = Module['_olm_error']();
+});
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;
diff --git a/javascript/test/megolm.spec.js b/javascript/test/megolm.spec.js
index 8f9d24a..9d5eb72 100644
--- a/javascript/test/megolm.spec.js
+++ b/javascript/test/megolm.spec.js
@@ -16,12 +16,15 @@ limitations under the License.
 
 "use strict";
 
-var Olm = require('../olm');
+var Olm = require('../olm')();
 
 describe("megolm", function() {
     var aliceSession, bobSession;
 
-    beforeEach(function() {
+    beforeEach(function(done) {
+        Olm.then(function() {
+            done();
+        });
         aliceSession = new Olm.OutboundGroupSession();
         bobSession = new Olm.InboundGroupSession();
     });
diff --git a/javascript/test/olm.spec.js b/javascript/test/olm.spec.js
index b7cc3ae..94fa87b 100644
--- a/javascript/test/olm.spec.js
+++ b/javascript/test/olm.spec.js
@@ -16,7 +16,7 @@ limitations under the License.
 
 "use strict";
 
-var Olm = require('../olm');
+var Olm = require('../olm')();
 
 if (!Object.keys) {
     Object.keys = function(o) {
@@ -30,7 +30,13 @@ describe("olm", function() {
     var aliceAccount, bobAccount;
     var aliceSession, bobSession;
 
-    beforeEach(function() {
+    beforeEach(function(done) {
+        // This should really be in a beforeAll, but jasmine-node
+        // doesn't support that
+        Olm.then(function() {
+            done();
+        });
+
         aliceAccount = new Olm.Account();
         bobAccount = new Olm.Account();
         aliceSession = new Olm.Session();
diff --git a/javascript/test/pk.spec.js b/javascript/test/pk.spec.js
index aec90ac..9f7dbfd 100644
--- a/javascript/test/pk.spec.js
+++ b/javascript/test/pk.spec.js
@@ -16,7 +16,7 @@ limitations under the License.
 
 "use strict";
 
-var Olm = require('../olm');
+var Olm = require('../olm')();
 
 if (!Object.keys) {
     Object.keys = function(o) {
@@ -29,7 +29,11 @@ if (!Object.keys) {
 describe("pk", function() {
     var encryption, decryption;
 
-    beforeEach(function() {
+    beforeEach(function(done) {
+        Olm.then(function() {
+            done();
+        });
+
         encryption = new Olm.PkEncryption();
         decryption = new Olm.PkDecryption();
     });