Add caching utils

src/caching-utils.ts

@@ -0,0 +1,18 @@
+import { Logger } from "./logging";
+import { tryGetFolderBytes } from "./util";
+
+/**
+ * Returns the total size of all the specified paths.
+ * @param paths The paths for which to calculate the total size.
+ * @param logger A logger to record some informational messages to.
+ * @returns The total size of all specified paths.
+ */
+export async function getTotalCacheSize(
+  paths: string[],
+  logger: Logger,
+): Promise<number> {
+  const sizes = await Promise.all(
+    paths.map((cacheDir) => tryGetFolderBytes(cacheDir, logger)),
+  );
+  return sizes.map((a) => a || 0).reduce((a, b) => a + b, 0);
+}