Preserve unchanged-file reflection after revision history pruning

src/features/ReviewHarness/reviewHarnessFileContentHashBenchmarkRuntime.ts

@@ -0,0 +1,20 @@
+import { computeFileContentHash } from "@vrtmrz/livesync-commonlib/hashing";
+import { xxhashNew } from "octagonal-wheels/hash/xxhash.js";
+import {
+    createFixedFileContentHashInput,
+    type FileContentHashBenchmarkOperations,
+} from "./reviewHarnessFileContentHashBenchmark";
+
+export async function createFileContentHashBenchmarkOperations(
+    clock: Pick<Performance, "now"> = performance
+): Promise<FileContentHashBenchmarkOperations> {
+    const started = clock.now();
+    const xxHash = await xxhashNew();
+    const xxHashInitialisationMs = clock.now() - started;
+    return {
+        xxHashInitialisationMs,
+        createInput: createFixedFileContentHashInput,
+        sha256: (content) => computeFileContentHash(content),
+        xxHash64: async (content) => xxHash.h64Raw(new Uint8Array(await content.arrayBuffer())),
+    };
+}