Create quick-checksum.ts

src/quick-checksum.ts

@@ -0,0 +1,35 @@
+import { statSync, openSync, readSync, closeSync } from "node:fs";
+import { createHash } from "node:crypto";
+
+const BINARY_PARTIAL_SIZE = 1024 * 256; // KiB
+
+export function quickFingerprint(filePath: string): string {
+  const { size, mtimeMs, ino } = statSync(filePath);
+
+  const headBuf = Buffer.alloc(BINARY_PARTIAL_SIZE);
+  const tailBuf = Buffer.alloc(BINARY_PARTIAL_SIZE);
+
+  const fd = openSync(filePath, "r");
+  let headRead: number;
+  let tailRead: number;
+  try {
+    headRead = readSync(fd, headBuf, 0, BINARY_PARTIAL_SIZE, 0);
+    const tailOffset = Math.max(0, size - BINARY_PARTIAL_SIZE);
+    tailRead = readSync(fd, tailBuf, 0, BINARY_PARTIAL_SIZE, tailOffset);
+  } finally {
+    closeSync(fd);
+  }
+
+  const headHash = createHash("sha512")
+    .update(headBuf.subarray(0, headRead))
+    .digest("hex");
+  const tailHash = createHash("sha512")
+    .update(tailBuf.subarray(0, tailRead))
+    .digest("hex");
+
+  const combined =
+    `size:${size}|mtimeMs:${mtimeMs}|ino:${ino}` +
+    `|head:${headHash}|tail:${tailHash}`;
+
+  return "sha512:" + createHash("sha512").update(combined).digest("hex");
+}