merge with upstream

1 files changed, 90 insertions, 0 deletions

diff --git a/utils/city.h b/utils/city.h
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+// Copyright (c) 2011 Google, Inc.
+//
+// Permission is hereby granted, free of charge, to any person obtaining a copy
+// of this software and associated documentation files (the "Software"), to deal
+// in the Software without restriction, including without limitation the rights
+// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+// copies of the Software, and to permit persons to whom the Software is
+// furnished to do so, subject to the following conditions:
+//
+// The above copyright notice and this permission notice shall be included in
+// all copies or substantial portions of the Software.
+//
+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+// THE SOFTWARE.
+//
+// CityHash, by Geoff Pike and Jyrki Alakuijala
+//
+// This file provides a few functions for hashing strings. On x86-64
+// hardware in 2011, CityHash64() is faster than other high-quality
+// hash functions, such as Murmur.  This is largely due to higher
+// instruction-level parallelism.  CityHash64() and CityHash128() also perform
+// well on hash-quality tests.
+//
+// CityHash128() is optimized for relatively long strings and returns
+// a 128-bit hash.  For strings more than about 2000 bytes it can be
+// faster than CityHash64().
+//
+// Functions in the CityHash family are not suitable for cryptography.
+//
+// WARNING: This code has not been tested on big-endian platforms!
+// It is known to work well on little-endian platforms that have a small penalty
+// for unaligned reads, such as current Intel and AMD moderate-to-high-end CPUs.
+//
+// By the way, for some hash functions, given strings a and b, the hash
+// of a+b is easily derived from the hashes of a and b.  This property
+// doesn't hold for any hash functions in this file.
+
+#ifndef CITY_HASH_H_
+#define CITY_HASH_H_
+
+#include <stdlib.h>  // for size_t.
+#include <stdint.h>
+#include <utility>
+
+typedef uint8_t uint8;
+typedef uint32_t uint32;
+typedef uint64_t uint64;
+typedef std::pair<uint64, uint64> uint128;
+
+inline uint64 Uint128Low64(const uint128& x) { return x.first; }
+inline uint64 Uint128High64(const uint128& x) { return x.second; }
+
+// Hash function for a byte array.
+uint64 CityHash64(const char *buf, size_t len);
+
+// Hash function for a byte array.  For convenience, a 64-bit seed is also
+// hashed into the result.
+uint64 CityHash64WithSeed(const char *buf, size_t len, uint64 seed);
+
+// Hash function for a byte array.  For convenience, two seeds are also
+// hashed into the result.
+uint64 CityHash64WithSeeds(const char *buf, size_t len,
+                           uint64 seed0, uint64 seed1);
+
+// Hash function for a byte array.
+uint128 CityHash128(const char *s, size_t len);
+
+// Hash function for a byte array.  For convenience, a 128-bit seed is also
+// hashed into the result.
+uint128 CityHash128WithSeed(const char *s, size_t len, uint128 seed);
+
+// Hash 128 input bits down to 64 bits of output.
+// This is intended to be a reasonably good hash function.
+inline uint64 Hash128to64(const uint128& x) {
+  // Murmur-inspired hashing.
+  const uint64 kMul = 0x9ddfea08eb382d69ULL;
+  uint64 a = (Uint128Low64(x) ^ Uint128High64(x)) * kMul;
+  a ^= (a >> 47);
+  uint64 b = (Uint128High64(x) ^ a) * kMul;
+  b ^= (b >> 47);
+  b *= kMul;
+  return b;
+}
+
+#endif  // CITY_HASH_H_