1 files changed, 76 insertions, 0 deletions
diff --git a/packages/excalidraw/subset/woff2/woff2-loader.ts b/packages/excalidraw/subset/woff2/woff2-loader.ts
new file mode 100644
index 0000000..446dc9f
--- /dev/null
+++ b/packages/excalidraw/subset/woff2/woff2-loader.ts
@@ -0,0 +1,76 @@
+/**
+ * DON'T depend on anything from the outside like `promiseTry`, as this module is part of a separate lazy-loaded chunk.
+ *
+ * Including anything from the main chunk would include the whole chunk by default.
+ * Even it it would be tree-shaken during build, it won't be tree-shaken in dev.
+ *
+ * In the future consider separating common utils into a separate shared chunk.
+ */
+
+import binary from "./woff2-wasm";
+import bindings from "./woff2-bindings";
+
+/**
+ * Lazy loads wasm and respective bindings for woff2 compression and decompression.
+ */
+type Vector = any;
+
+let loadedWasm: ReturnType<typeof load> | null = null;
+
+// re-map from internal vector into byte array
+function convertFromVecToUint8Array(vector: Vector): Uint8Array {
+  const arr = [];
+  for (let i = 0, l = vector.size(); i < l; i++) {
+    arr.push(vector.get(i));
+  }
+
+  return new Uint8Array(arr);
+}
+
+// TODO: consider adding support for fetching the wasm from an URL (external CDN, data URL, etc.)
+const load = (): Promise<{
+  compress: (buffer: ArrayBuffer) => Uint8Array;
+  decompress: (buffer: ArrayBuffer) => Uint8Array;
+}> => {
+  return new Promise((resolve, reject) => {
+    try {
+      // initializing the module manually, so that we could pass in the wasm binary
+      // note that the `bindings.then` is not not promise/A+ compliant, hence the need for another explicit try/catch
+      bindings({ wasmBinary: binary }).then(
+        (module: {
+          woff2Enc: (buffer: ArrayBuffer, byteLength: number) => Vector;
+          woff2Dec: (buffer: ArrayBuffer, byteLength: number) => Vector;
+        }) => {
+          try {
+            // re-exporting only compress and decompress functions (also avoids infinite loop inside emscripten bindings)
+            const woff2 = {
+              compress: (buffer: ArrayBuffer) =>
+                convertFromVecToUint8Array(
+                  module.woff2Enc(buffer, buffer.byteLength),
+                ),
+              decompress: (buffer: ArrayBuffer) =>
+                convertFromVecToUint8Array(
+                  module.woff2Dec(buffer, buffer.byteLength),
+                ),
+            };
+
+            resolve(woff2);
+          } catch (e) {
+            reject(e);
+          }
+        },
+      );
+    } catch (e) {
+      reject(e);
+    }
+  });
+};
+
+// lazy loaded default export
+export default (): ReturnType<typeof load> => {
+  if (!loadedWasm) {
+    loadedWasm = load();
+  }
+
+  return loadedWasm;
+};