feat(crypto-js): Encode the WASM as base64 for portability

bindings/matrix-sdk-crypto-js/package.json

@@ -37,12 +37,9 @@
         "node": ">= 10"
     },
     "scripts": {
-        "build": "cross-env RUSTFLAGS='-C opt-level=z' WASM_BINDGEN_WEAKREF=1 wasm-pack build --release --target nodejs --scope matrix-org --out-dir ./pkg",
+        "build": "./scripts/build.sh",
         "test": "jest --verbose",
         "doc": "typedoc --tsconfig .",
-        "prepack": "npm run build && npm run test",
-        "pack": "wasm-pack pack",
-        "prepublish": "npm run pack",
-        "publish": "wasm-pack publish"
+        "prepack": "npm run build && npm run test"
     }
 }

bindings/matrix-sdk-crypto-js/scripts/build.sh

@@ -0,0 +1,37 @@
+#!/bin/bash
+#
+# Build the JavaScript modules
+#
+# This script is really a workaround for https://github.com/rustwasm/wasm-pack/issues/1074.
+#
+# Currently, the only reliable way to load WebAssembly in all the JS
+# environments we want to target (web-via-webpack, web-via-browserify, jest)
+# seems to be to pack the WASM into base64, and then unpack it and instantiate
+# it at runtime.
+#
+# Hopefully one day, https://github.com/rustwasm/wasm-pack/issues/1074 will be
+# fixed and this will be unnecessary.
+
+set -e
+
+cd $(dirname "$0")/..
+
+RUSTFLAGS='-C opt-level=z' WASM_BINDGEN_WEAKREF=1 wasm-pack build --release --target nodejs --scope matrix-org --out-dir pkg
+
+# Convert the Wasm into a JS file that exports the base64'ed Wasm.
+echo "module.exports = \`$(base64 pkg/matrix_sdk_crypto_js_bg.wasm)\`;" > pkg/matrix_sdk_crypto_js_bg.wasm.js
+
+# Copy in the unbase64 module
+cp scripts/unbase64.js pkg/
+
+# In the JavaScript:
+#  1. Replace the lines that load the Wasm,
+#  2. Remove the imports of `TextDecoder` and `TextEncoder`. We rely on the global defaults.
+loadwasm='const bytes = require("./unbase64.js")(require("./matrix_sdk_crypto_js_bg.wasm.js"));'
+
+# sed on OSX uses different syntax for sed -i, so let's just avoid it.
+sed -e "/^const path = /d" \
+    -e "s@^const bytes =.*@${loadwasm}@" \
+    -e '/Text..coder.*= require(.util.)/d' \
+    pkg/matrix_sdk_crypto_js.js >pkg/matrix_sdk_crypto_js.js.new
+mv pkg/matrix_sdk_crypto_js.js.new pkg/matrix_sdk_crypto_js.js

bindings/matrix-sdk-crypto-js/scripts/unbase64.js

@@ -0,0 +1,32 @@
+// JavaScript module which exports a function which will un-base64 a string.
+//
+// Based on the code at https://developer.mozilla.org/en-US/docs/Glossary/Base64#solution_2_%E2%80%93_rewriting_atob_and_btoa_using_typedarrays_and_utf-8
+
+const lookup = new Uint8Array([0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 62, 0, 62, 0, 63, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 0, 0, 0, 0, 0, 0, 0, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 0, 0, 0, 0, 63, 0, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51]);
+
+module.exports = (sBase64) => {
+  const sB64Enc = sBase64.replace(/[^A-Za-z0-9+/]/g, "");
+  const nInLen = sB64Enc.length;
+  const nOutLen = (nInLen * 3 + 1) >> 2;
+  const taBytes = new Uint8Array(nOutLen);
+
+  let nMod3;
+  let nMod4;
+  let nUint24 = 0;
+  let nOutIdx = 0;
+  for (let nInIdx = 0; nInIdx < nInLen; nInIdx++) {
+    nMod4 = nInIdx & 3;
+    nUint24 |= lookup[sB64Enc.charCodeAt(nInIdx)] << (6 * (3 - nMod4));
+    if (nMod4 === 3 || nInLen - nInIdx === 1) {
+      nMod3 = 0;
+      while (nMod3 < 3 && nOutIdx < nOutLen) {
+        taBytes[nOutIdx] = (nUint24 >>> ((16 >>> nMod3) & 24)) & 255;
+        nMod3++;
+        nOutIdx++;
+      }
+      nUint24 = 0;
+    }
+  }
+
+  return taBytes;
+};