Hash every validated server copy and register it as verified content

server/hash.js

@@ -0,0 +1,26 @@
+/* hash.js — streaming SHA-256 of files on disk (never loads a whole video).
+ * The hex digest of a validated file is its P2P content id (cid). */
+import { createHash } from 'node:crypto';
+import { createReadStream } from 'node:fs';
+
+export function sha256File(path) {
+  return new Promise((resolve, reject) => {
+    const h = createHash('sha256');
+    createReadStream(path, { highWaterMark: 1024 * 1024 })
+      .on('data', (d) => h.update(d))
+      .on('error', reject)
+      .on('end', () => resolve(h.digest('hex')));
+  });
+}
+
+// Hash of bytes [offset, offset+length) — used for holder range challenges.
+export function sha256Range(path, offset, length) {
+  return new Promise((resolve, reject) => {
+    if (!(length > 0)) { resolve(createHash('sha256').digest('hex')); return; }
+    const h = createHash('sha256');
+    createReadStream(path, { start: offset, end: offset + length - 1 })
+      .on('data', (d) => h.update(d))
+      .on('error', reject)
+      .on('end', () => resolve(h.digest('hex')));
+  });
+}