From 124a9de309e41a40098b98eb25566a01f59dbb7d Mon Sep 17 00:00:00 2001
From: Marcus Holland-Moritz <github@mhxnet.de>
Date: Wed, 6 Aug 2025 14:15:12 +0200
Subject: [PATCH] fix(checksum): always store xxh3 digests as little-endian for
 compat

---
 src/checksum.cpp | 11 +++++++++--
 1 file changed, 9 insertions(+), 2 deletions(-)

diff --git a/src/checksum.cpp b/src/checksum.cpp
index 55ff8772..5ad5c14c 100644
--- a/src/checksum.cpp
+++ b/src/checksum.cpp
@@ -151,16 +151,20 @@ class checksum_evp : public checksum::impl {
 
 struct xxh3_64_policy {
   using result_type = XXH64_hash_t;
+  using canonical_type = XXH64_canonical_t;
   static constexpr auto reset = XXH3_64bits_reset;
   static constexpr auto update = XXH3_64bits_update;
   static constexpr auto digest = XXH3_64bits_digest;
+  static constexpr auto canonical = XXH64_canonicalFromHash;
 };
 
 struct xxh3_128_policy {
   using result_type = XXH128_hash_t;
+  using canonical_type = XXH128_canonical_t;
   static constexpr auto reset = XXH3_128bits_reset;
   static constexpr auto update = XXH3_128bits_update;
   static constexpr auto digest = XXH3_128bits_digest;
+  static constexpr auto canonical = XXH128_canonicalFromHash;
 };
 
 template <typename Policy>
@@ -182,9 +186,12 @@ class checksum_xxh3 : public checksum::impl {
     if (!state_) {
       return false;
     }
-    auto hash = Policy::digest(state_.get());
+    typename Policy::canonical_type canonical;
+    Policy::canonical(&canonical, Policy::digest(state_.get()));
     state_.reset();
-    ::memcpy(digest, &hash, sizeof(hash));
+    // compat: we always store the digest in little-endian order :/
+    std::ranges::reverse(canonical.digest);
+    ::memcpy(digest, &canonical, sizeof(canonical));
     return true;
   }