From 354bb40e75d94466e91fe6960523612c9d17ccfb Mon Sep 17 00:00:00 2001
From: Karen Arutyunov <karen@codesynthesis.com>
Date: Thu, 2 Nov 2017 23:11:29 +0300
Subject: Add implementation

---
 mysql/mysys_ssl/my_murmur3.cpp | 134 +++++++++++++++++++++++++++++++++++++++++
 1 file changed, 134 insertions(+)
 create mode 100644 mysql/mysys_ssl/my_murmur3.cpp

(limited to 'mysql/mysys_ssl/my_murmur3.cpp')

diff --git a/mysql/mysys_ssl/my_murmur3.cpp b/mysql/mysys_ssl/my_murmur3.cpp
new file mode 100644
index 0000000..82dccb6
--- /dev/null
+++ b/mysql/mysys_ssl/my_murmur3.cpp
@@ -0,0 +1,134 @@
+/* Copyright (c) 2013, Oracle and/or its affiliates. All rights reserved.
+
+   This program is free software; you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation; version 2 of the License.
+
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program; if not, write to the Free Software
+   Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA */
+
+/*
+  Implementation of 32-bit version of MurmurHash3 - fast non-cryptographic
+  hash function with good statistical properties, which is based on public
+  domain code by Austin Appleby.
+*/
+
+#include <my_murmur3.h>
+
+
+/*
+  Platform-specific implementations of ROTL32 helper.
+*/
+
+#if defined(_MSC_VER)
+
+/* Microsoft Visual Studio supports intrinsic for rotate left. */
+
+#include <stdlib.h>
+
+#define ROTL32(x, y)	_rotl(x, y)
+
+/*
+  Force inlining of intrinsic even though /Oi option is turned off
+  in release builds.
+*/
+#pragma intrinsic(_rotl)
+
+#else // !defined(_MSC_VER)
+
+/*
+  Many other compilers should be able to optimize the below
+  function to single instruction.
+*/
+
+inline uint32 rotl32 (uint32 x, char r)
+{
+  return (x << r) | (x >> (32 - r));
+}
+
+#define	ROTL32(x,y)	rotl32(x,y)
+
+#endif // !defined(_MSC_VER)
+
+
+/**
+  Compute 32-bit version of MurmurHash3 hash for the key.
+
+  @param key   Key for which hash value to be computed.
+  @param len   Key length.
+  @param seed  Seed for hash computation.
+
+  @note WARNING! Since MurmurHash3 is known to be susceptible to "hash DoS"
+        attack it should not be used in any situation where attacker has
+        control over key being hashed and thus can cause performance problems
+        due to degradation of hash lookup to linear list search.
+
+  @returns Hash value for the key.
+*/
+
+uint32 murmur3_32(const uchar *key, size_t len, uint32 seed)
+{
+  const uchar *tail= key + (len  - len % 4);
+
+  uint32 h1= seed;
+
+  /* Constants for magic numbers that are used more than once. */
+  const uint32 c1= 0xcc9e2d51;
+  const uint32 c2= 0x1b873593;
+
+  /* Body: process all 32-bit blocks in the key. */
+
+  for (const uchar *data= key; data != tail; data+= 4)
+  {
+    uint32 k1= uint4korr(data);
+
+    k1*= c1;
+    k1= ROTL32(k1, 15);
+    k1*= c2;
+
+    h1^= k1;
+    h1= ROTL32(h1, 13);
+    h1= h1 * 5 + 0xe6546b64;
+  }
+
+  /* Tail: handle remaining len % 4 bytes. */
+
+  uint32 k1= 0;
+
+  switch(len % 4)
+  {
+  case 3:
+    k1^= static_cast<uint32>(tail[2]) << 16;
+    /* Fall through. */
+  case 2:
+    k1^= static_cast<uint32>(tail[1]) << 8;
+    /* Fall through. */
+  case 1:
+    k1^= tail[0];
+    k1*= c1;
+    k1= ROTL32(k1, 15);
+    k1*= c2;
+    h1^= k1;
+  };
+
+  /*
+    Finalization mix:
+    Add length and force all bits of a hash block to avalanche.
+  */
+
+  h1^= len;
+
+  h1^= h1 >> 16;
+  h1*= 0x85ebca6b;
+  h1^= h1 >> 13;
+  h1*= 0xc2b2ae35;
+  h1^= h1 >> 16;
+
+  return h1;
+}
-- 
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