web/workers: use opfs instead of blobs for better memory management

spent almost an entire day figuring this out but it's so worth it

web/src/lib/storage.ts

@@ -0,0 +1,53 @@
+export class OPFSStorage {
+    #root;
+    #handle;
+    #io;
+
+    constructor(root: FileSystemDirectoryHandle, handle: FileSystemFileHandle, reader: FileSystemSyncAccessHandle) {
+        this.#root = root;
+        this.#handle = handle;
+        this.#io = reader;
+    }
+
+    static async init() {
+        const root = await navigator.storage.getDirectory();
+        const cobaltDir = await root.getDirectoryHandle('cobalt-processing-data', { create: true });
+        const handle = await cobaltDir.getFileHandle(crypto.randomUUID(), { create: true });
+        const reader = await handle.createSyncAccessHandle();
+
+        return new this(cobaltDir, handle, reader);
+    }
+
+    async res() {
+        // await for compat with ios 15
+        await this.#io.flush();
+        await this.#io.close();
+        return await this.#handle.getFile();
+    }
+
+    read(size: number, offset: number) {
+        const out = new Uint8Array(size);
+        const bytesRead = this.#io.read(out, { at: offset });
+
+        return out.subarray(0, bytesRead);
+    }
+
+    async write(data: Uint8Array | Int8Array, offset: number) {
+        const writ = this.#io.write(data, { at: offset });
+
+        if (data.length !== writ) {
+            console.log(data.length, writ);
+        }
+
+        return writ;
+    }
+
+    async destroy() {
+        await this.#root.removeEntry(this.#handle.name);
+    }
+
+    static isAvailable() {
+        return !!navigator.storage?.getDirectory;
+    }
+}
+