From 2c8e314f8fff8633fe2cf026badfbf6180845ae0 Mon Sep 17 00:00:00 2001
From: arcadia-devtools <arcadia-devtools@yandex-team.ru>
Date: Thu, 17 Feb 2022 12:04:09 +0300
Subject: intermediate changes ref:d5f945ecdc1f5af1ad57e12787c6b8ed1a9f0f12
---
library/cpp/digest/murmur/murmur.h | 100 +++++++++++++++++++++++++++++++++++++
1 file changed, 100 insertions(+)
create mode 100644 library/cpp/digest/murmur/murmur.h
(limited to 'library/cpp/digest/murmur/murmur.h')
diff --git a/library/cpp/digest/murmur/murmur.h b/library/cpp/digest/murmur/murmur.h
new file mode 100644
index 0000000000..cbf2886412
--- /dev/null
+++ b/library/cpp/digest/murmur/murmur.h
@@ -0,0 +1,100 @@
+#pragma once
+
+#include <util/system/defaults.h>
+#include <util/system/unaligned_mem.h>
+
+/*
+ * https://sites.google.com/site/murmurhash/
+ */
+
+namespace NMurmurPrivate {
+ template <size_t>
+ struct TMurmurHash2ATraits;
+
+ template <>
+ struct TMurmurHash2ATraits<32> {
+ using TValue = ui32;
+ static const TValue Multiplier = 0x5bd1e995;
+ enum { R1 = 24,
+ R2 = 13,
+ R3 = 15 };
+ };
+
+ template <>
+ struct TMurmurHash2ATraits<64> {
+ using TValue = ui64;
+ static const TValue Multiplier = ULL(0xc6a4a7935bd1e995);
+ enum { R1 = 47,
+ R2 = 47,
+ R3 = 47 };
+ };
+}
+
+template <class T>
+class TMurmurHash2A {
+private:
+ using TTraits = typename NMurmurPrivate::TMurmurHash2ATraits<8 * sizeof(T)>;
+ using TValue = typename TTraits::TValue;
+
+public:
+ inline TMurmurHash2A(TValue seed = 0)
+ : Hash(seed)
+ {
+ }
+
+ inline TMurmurHash2A& Update(const void* buf, size_t len) noexcept {
+ Size += len;
+
+ MixTail(buf, len);
+
+ while (len >= sizeof(TValue)) {
+ Hash = Mix(Hash, ReadUnaligned<TValue>(buf));
+ buf = static_cast<const char*>(buf) + sizeof(TValue);
+ len -= sizeof(TValue);
+ }
+
+ MixTail(buf, len);
+
+ return *this;
+ }
+
+ inline TValue Value() const noexcept {
+ TValue hash = Mix(Mix(Hash, Tail), (TValue)Size);
+
+ hash ^= hash >> TTraits::R2;
+ hash *= TTraits::Multiplier;
+ hash ^= hash >> TTraits::R3;
+
+ return hash;
+ }
+
+private:
+ static inline TValue Mix(TValue h, TValue k) noexcept {
+ k *= TTraits::Multiplier;
+ k ^= k >> TTraits::R1;
+ k *= TTraits::Multiplier;
+ h *= TTraits::Multiplier;
+ h ^= k;
+ return h;
+ }
+
+ inline void MixTail(const void*& buf, size_t& len) noexcept {
+ while (len && (len < sizeof(TValue) || Count)) {
+ Tail |= (TValue) * ((const unsigned char*&)buf)++ << (Count++ * 8);
+
+ --len;
+
+ if (Count == sizeof(TValue)) {
+ Hash = Mix(Hash, Tail);
+ Tail = 0;
+ Count = 0;
+ }
+ }
+ }
+
+private:
+ TValue Hash = 0;
+ TValue Tail = 0;
+ size_t Count = 0;
+ size_t Size = 0;
+};
--
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