From 2825a534157000d6546feb59a1dc2a3486b51d38 Mon Sep 17 00:00:00 2001
From: yoshikazu <yoshikazu@yfox.jp>
Date: Mon, 27 Jul 2026 15:38:06 +0000
Subject: [PATCH] Add ContentHasher

---
 Sources/Photochk/Core/ContentHasher.swift | 18 ++++++++++++++++++
 1 file changed, 18 insertions(+)
 create mode 100644 Sources/Photochk/Core/ContentHasher.swift

diff --git a/Sources/Photochk/Core/ContentHasher.swift b/Sources/Photochk/Core/ContentHasher.swift
new file mode 100644
index 0000000..78c1ebc
--- /dev/null
+++ b/Sources/Photochk/Core/ContentHasher.swift
@@ -0,0 +1,18 @@
+import CryptoKit
+import Foundation
+
+enum ContentHasher {
+    private static let chunkSize = 1 << 20  // 1 MB
+
+    /// ファイル全体を読み込まずに SHA-256 を求める。
+    static func sha256(of url: URL) throws -> String {
+        let handle = try FileHandle(forReadingFrom: url)
+        defer { try? handle.close() }
+
+        var hasher = SHA256()
+        while let chunk = try handle.read(upToCount: chunkSize), !chunk.isEmpty {
+            hasher.update(data: chunk)
+        }
+        return hasher.finalize().map { String(format: "%02x", $0) }.joined()
+    }
+}