intermediate changes

ref:7e8696b4742c75a3ab825709512075b3710a0a6f

3 files changed, 19 insertions, 0 deletions

diff --git a/library/cpp/digest/crc32c/crc32c.cpp b/library/cpp/digest/crc32c/crc32c.cpp
index 369b46a213..bc9de52134 100644
--- a/library/cpp/digest/crc32c/crc32c.cpp
+++ b/library/cpp/digest/crc32c/crc32c.cpp
@@ -24,6 +24,12 @@ namespace {
             Pimpl->Compute(data, n, &sum);
             return (ui32)sum;
         }
+
+        inline ui32 Combine(ui32 blockACrc, ui32 blockBCrc, size_t blockBSize) const noexcept {
+            crcutil_interface::UINT64 sum = blockACrc;
+            Pimpl->Concatenate(blockBCrc, 0, blockBSize, &sum);
+            return (ui32)sum;
+        }
     };
 }
 
@@ -35,6 +41,10 @@ ui32 Crc32cExtend(ui32 init, const void* data, size_t n) noexcept {
     return Singleton<TCrcUtilSse4>()->Extend(init, data, n);
 }
 
+ui32 Crc32cCombine(ui32 blockACrc, ui32 blockBCrc, size_t blockBSize) noexcept {
+    return Singleton<TCrcUtilSse4>()->Combine(blockACrc, blockBCrc, blockBSize);
+}
+
 bool HaveFastCrc32c() noexcept {
     return TCrc::IsSSE42Available();
 }
diff --git a/library/cpp/digest/crc32c/crc32c.h b/library/cpp/digest/crc32c/crc32c.h
index 17b554c8e1..e6b767c607 100644
--- a/library/cpp/digest/crc32c/crc32c.h
+++ b/library/cpp/digest/crc32c/crc32c.h
@@ -5,5 +5,6 @@
 // Threadsafe
 ui32 Crc32c(const void* p, size_t size) noexcept;
 ui32 Crc32cExtend(ui32 init, const void* data, size_t n) noexcept;
+ui32 Crc32cCombine(ui32 blockACrc, ui32 blockBCrc, size_t blockBSize) noexcept;
 
 bool HaveFastCrc32c() noexcept;
diff --git a/library/cpp/digest/crc32c/crc32c_ut.cpp b/library/cpp/digest/crc32c/crc32c_ut.cpp
index aa31b83422..dcafaf278d 100644
--- a/library/cpp/digest/crc32c/crc32c_ut.cpp
+++ b/library/cpp/digest/crc32c/crc32c_ut.cpp
@@ -20,4 +20,12 @@ Y_UNIT_TEST_SUITE(TestCrc32c) {
     Y_UNIT_TEST(TestExtend) {
         UNIT_ASSERT_VALUES_EQUAL(Crc32cExtend(1, "abc", 3), ui32(2466950601));
     }
+
+    Y_UNIT_TEST(TestCombine) {
+        ui32 aSum = Crc32c("abc", 3);
+        ui32 bSum = Crc32c("de", 2);
+        ui32 abSum = Crc32c("abcde", 5);
+
+        UNIT_ASSERT_VALUES_EQUAL(Crc32cCombine(aSum, bSum, 2), abSum);
+    }
 }