From 713b18709dfbe37c0b62f83fa7ca834aa0527fd6 Mon Sep 17 00:00:00 2001
From: Marcus Holland-Moritz <github@mhxnet.de>
Date: Mon, 5 Apr 2021 00:55:51 +0200
Subject: [PATCH] Use XXH3-128 for duplicate detection

---
 include/dwarfs/checksum.h |  3 +++
 include/dwarfs/entry.h    |  2 +-
 src/dwarfs/checksum.cpp   | 40 +++++++++++++++++++++++++++++++++++++++
 src/dwarfs/entry.cpp      |  2 +-
 4 files changed, 45 insertions(+), 2 deletions(-)

diff --git a/include/dwarfs/checksum.h b/include/dwarfs/checksum.h
index 453f95adc..cc646c41f 100644
--- a/include/dwarfs/checksum.h
+++ b/include/dwarfs/checksum.h
@@ -35,6 +35,7 @@ class checksum {
     SHA1,
     SHA2_512_256,
     XXH3_64,
+    XXH3_128,
   };
 
   static constexpr size_t digest_size(algorithm alg) {
@@ -45,6 +46,8 @@ class checksum {
       return 32;
     case algorithm::XXH3_64:
       return 8;
+    case algorithm::XXH3_128:
+      return 16;
     }
     DWARFS_CHECK(false, "unknown algorithm");
   }
diff --git a/include/dwarfs/entry.h b/include/dwarfs/entry.h
index 8a38de929..a31faa661 100644
--- a/include/dwarfs/entry.h
+++ b/include/dwarfs/entry.h
@@ -137,7 +137,7 @@ class file : public entry {
 
  private:
   struct data {
-    using hash_type = std::array<char, 20>;
+    using hash_type = std::array<char, 16>;
     hash_type hash{0};
     uint32_t refcount{1};
     std::optional<uint32_t> inode_num;
diff --git a/src/dwarfs/checksum.cpp b/src/dwarfs/checksum.cpp
index 822572abd..39e4deda3 100644
--- a/src/dwarfs/checksum.cpp
+++ b/src/dwarfs/checksum.cpp
@@ -49,6 +49,14 @@ bool compute_xxh3_64(void const* data, size_t size, void* digest) {
   return true;
 }
 
+bool compute_xxh3_128(void const* data, size_t size, void* digest) {
+  auto hash = XXH3_128bits(data, size);
+  static_assert(checksum::digest_size(checksum::algorithm::XXH3_128) ==
+                sizeof(hash));
+  ::memcpy(digest, &hash, sizeof(hash));
+  return true;
+}
+
 class checksum_evp : public checksum::impl {
  public:
   checksum_evp(EVP_MD const* evp, checksum::algorithm alg)
@@ -109,6 +117,32 @@ class checksum_xxh3_64 : public checksum::impl {
   XXH3_state_t* state_;
 };
 
+class checksum_xxh3_128 : public checksum::impl {
+ public:
+  checksum_xxh3_128()
+      : state_(XXH3_createState()) {
+    DWARFS_CHECK(XXH3_128bits_reset(state_) == XXH_OK,
+                 "XXH3_128bits_reset() failed");
+  }
+
+  ~checksum_xxh3_128() override { XXH3_freeState(state_); }
+
+  void update(void const* data, size_t size) override {
+    auto err = XXH3_128bits_update(state_, data, size);
+    DWARFS_CHECK(err == XXH_OK, fmt::format("XXH3_128bits_update() failed: {}",
+                                            static_cast<int>(err)));
+  }
+
+  bool finalize(void* digest) override {
+    auto hash = XXH3_128bits_digest(state_);
+    ::memcpy(digest, &hash, sizeof(hash));
+    return true;
+  }
+
+ private:
+  XXH3_state_t* state_;
+};
+
 } // namespace
 
 bool checksum::compute(algorithm alg, void const* data, size_t size,
@@ -126,6 +160,9 @@ bool checksum::compute(algorithm alg, void const* data, size_t size,
   case algorithm::XXH3_64:
     rv = compute_xxh3_64(data, size, digest);
     break;
+  case algorithm::XXH3_128:
+    rv = compute_xxh3_128(data, size, digest);
+    break;
   }
 
   if (rv && dig_size > 0) {
@@ -157,6 +194,9 @@ checksum::checksum(algorithm alg)
   case algorithm::XXH3_64:
     impl_ = std::make_unique<checksum_xxh3_64>();
     break;
+  case algorithm::XXH3_128:
+    impl_ = std::make_unique<checksum_xxh3_128>();
+    break;
   default:
     DWARFS_CHECK(false, "unknown algorithm");
     break;
diff --git a/src/dwarfs/entry.cpp b/src/dwarfs/entry.cpp
index 6988f519c..2f42411e4 100644
--- a/src/dwarfs/entry.cpp
+++ b/src/dwarfs/entry.cpp
@@ -168,7 +168,7 @@ void file::scan(os_access& os, progress& prog) {
 }
 
 void file::scan(std::shared_ptr<mmif> const& mm, progress& prog) {
-  constexpr auto alg = checksum::algorithm::SHA1;
+  constexpr auto alg = checksum::algorithm::XXH3_128;
   static_assert(checksum::digest_size(alg) == sizeof(data::hash_type));
 
   if (size_t s = size(); s > 0) {