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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 Version 1, by Geoff Pike and Jyrki Alakuijala

 //

 // This file provides CityHash64() and related functions.

 //

 // It's probably possible to create even faster hash functions by

 // writing a program that systematically explores some of the space of

 // possible hash functions, by using SIMD instructions, or by

 // compromising on hash quality.

 #include "city.h"

 #include <algorithm>

 using namespace std;

 #define UNALIGNED_LOAD64(p) (*(const uint64*)(p))

 #define UNALIGNED_LOAD32(p) (*(const uint32*)(p))

 #if !defined(LIKELY)

 #if defined(__GNUC__)

 #define LIKELY(x) (__builtin_expect(!!(x), 1))

 #else

 #define LIKELY(x) (x)

 #endif

 #endif

 // Some primes between 2^63 and 2^64 for various uses.

 static const uint64 k0 = 0xc3a5c85c97cb3127;

 static const uint64 k1 = 0xb492b66fbe98f273;

 static const uint64 k2 = 0x9ae16a3b2f90404f;

 static const uint64 k3 = 0xc949d7c7509e6557;

 // Bitwise right rotate.  Normally this will compile to a single

 // instruction, especially if the shift is a manifest constant.

 static uint64 Rotate(uint64 val, int shift) {

   // Avoid shifting by 64: doing so yields an undefined result.

   return shift == 0 ? val : ((val >> shift) | (val << (64 - shift)));

 }

 // Equivalent to Rotate(), but requires the second arg to be non-zero.

 // On x86-64, and probably others, it's possible for this to compile

 // to a single instruction if both args are already in registers.

 static uint64 RotateByAtLeast1(uint64 val, int shift) {

   return (val >> shift) | (val << (64 - shift));

 }

 static uint64 ShiftMix(uint64 val) {

   return val ^ (val >> 47);

 }

 static uint64 HashLen16(uint64 u, uint64 v) {

   return Hash128to64(uint128(u, v));

 }

 static uint64 HashLen0to16(const char *s, size_t len) {

   if (len > 8) {

     uint64 a = UNALIGNED_LOAD64(s);

     uint64 b = UNALIGNED_LOAD64(s + len - 8);

     return HashLen16(a, RotateByAtLeast1(b + len, len)) ^ b;

   }

   if (len >= 4) {

     uint64 a = UNALIGNED_LOAD32(s);

     return HashLen16(len + (a << 3), UNALIGNED_LOAD32(s + len - 4));

   }

   if (len > 0) {

     uint8 a = s[0];

     uint8 b = s[len >> 1];

     uint8 c = s[len - 1];

     uint32 y = static_cast<uint32>(a) + (static_cast<uint32>(b) << 8);

     uint32 z = len + (static_cast<uint32>(c) << 2);

     return ShiftMix(y * k2 ^ z * k3) * k2;

   }

   return k2;

 }

 // This probably works well for 16-byte strings as well, but it may be overkill

 // in that case.

 static uint64 HashLen17to32(const char *s, size_t len) {

   uint64 a = UNALIGNED_LOAD64(s) * k1;

   uint64 b = UNALIGNED_LOAD64(s + 8);

   uint64 c = UNALIGNED_LOAD64(s + len - 8) * k2;

   uint64 d = UNALIGNED_LOAD64(s + len - 16) * k0;

   return HashLen16(Rotate(a - b, 43) + Rotate(c, 30) + d,

                    a + Rotate(b ^ k3, 20) - c + len);

 }

 // Return a 16-byte hash for 48 bytes.  Quick and dirty.

 // Callers do best to use "random-looking" values for a and b.

 static pair<uint64, uint64> WeakHashLen32WithSeeds(

     uint64 w, uint64 x, uint64 y, uint64 z, uint64 a, uint64 b) {

   a += w;

   b = Rotate(b + a + z, 21);

   uint64 c = a;

   a += x;

   a += y;

   b += Rotate(a, 44);

   return make_pair(a + z, b + c);

 }

 // Return a 16-byte hash for s[0] ... s[31], a, and b.  Quick and dirty.

 static pair<uint64, uint64> WeakHashLen32WithSeeds(

     const char* s, uint64 a, uint64 b) {

   return WeakHashLen32WithSeeds(UNALIGNED_LOAD64(s),

                                 UNALIGNED_LOAD64(s + 8),

                                 UNALIGNED_LOAD64(s + 16),

                                 UNALIGNED_LOAD64(s + 24),

                                 a,

                                 b);

 }

 // Return an 8-byte hash for 33 to 64 bytes.

 static uint64 HashLen33to64(const char *s, size_t len) {

   uint64 z = UNALIGNED_LOAD64(s + 24);

   uint64 a = UNALIGNED_LOAD64(s) + (len + UNALIGNED_LOAD64(s + len - 16)) * k0;

   uint64 b = Rotate(a + z, 52);

   uint64 c = Rotate(a, 37);

   a += UNALIGNED_LOAD64(s + 8);

   c += Rotate(a, 7);

   a += UNALIGNED_LOAD64(s + 16);

   uint64 vf = a + z;

   uint64 vs = b + Rotate(a, 31) + c;

   a = UNALIGNED_LOAD64(s + 16) + UNALIGNED_LOAD64(s + len - 32);

   z = UNALIGNED_LOAD64(s + len - 8);

   b = Rotate(a + z, 52);

   c = Rotate(a, 37);

   a += UNALIGNED_LOAD64(s + len - 24);

   c += Rotate(a, 7);

   a += UNALIGNED_LOAD64(s + len - 16);

   uint64 wf = a + z;

   uint64 ws = b + Rotate(a, 31) + c;

   uint64 r = ShiftMix((vf + ws) * k2 + (wf + vs) * k0);

   return ShiftMix(r * k0 + vs) * k2;

 }

 uint64 CityHash64(const char *s, size_t len) {

   if (len <= 32) {

     if (len <= 16) {

       return HashLen0to16(s, len);

     } else {

       return HashLen17to32(s, len);

     }

   } else if (len <= 64) {

     return HashLen33to64(s, len);

   }

   // For strings over 64 bytes we hash the end first, and then as we

   // loop we keep 56 bytes of state: v, w, x, y, and z.

   uint64 x = UNALIGNED_LOAD64(s);

   uint64 y = UNALIGNED_LOAD64(s + len - 16) ^ k1;

   uint64 z = UNALIGNED_LOAD64(s + len - 56) ^ k0;

   pair<uint64, uint64> v = WeakHashLen32WithSeeds(s + len - 64, len, y);

   pair<uint64, uint64> w = WeakHashLen32WithSeeds(s + len - 32, len * k1, k0);

   z += ShiftMix(v.second) * k1;

   x = Rotate(z + x, 39) * k1;

   y = Rotate(y, 33) * k1;

   // Decrease len to the nearest multiple of 64, and operate on 64-byte chunks.

   len = (len - 1) & ~static_cast<size_t>(63);

   do {

     x = Rotate(x + y + v.first + UNALIGNED_LOAD64(s + 16), 37) * k1;

     y = Rotate(y + v.second + UNALIGNED_LOAD64(s + 48), 42) * k1;

     x ^= w.second;

     y ^= v.first;

     z = Rotate(z ^ w.first, 33);

     v = WeakHashLen32WithSeeds(s, v.second * k1, x + w.first);

     w = WeakHashLen32WithSeeds(s + 32, z + w.second, y);

     std::swap(z, x);

     s += 64;

     len -= 64;

   } while (len != 0);

   return HashLen16(HashLen16(v.first, w.first) + ShiftMix(y) * k1 + z,

                    HashLen16(v.second, w.second) + x);

 }

 uint64 CityHash64WithSeed(const char *s, size_t len, uint64 seed) {

   return CityHash64WithSeeds(s, len, k2, seed);

 }

 uint64 CityHash64WithSeeds(const char *s, size_t len,

                            uint64 seed0, uint64 seed1) {

   return HashLen16(CityHash64(s, len) - seed0, seed1);

 }

 // A subroutine for CityHash128().  Returns a decent 128-bit hash for strings

 // of any length representable in ssize_t.  Based on City and Murmur.

 static uint128 CityMurmur(const char *s, size_t len, uint128 seed) {

   uint64 a = Uint128Low64(seed);

   uint64 b = Uint128High64(seed);

   uint64 c = 0;

   uint64 d = 0;

   ssize_t l = len - 16;

   if (l <= 0) {  // len <= 16

     c = b * k1 + HashLen0to16(s, len);

     d = Rotate(a + (len >= 8 ? UNALIGNED_LOAD64(s) : c), 32);

   } else {  // len > 16

     c = HashLen16(UNALIGNED_LOAD64(s + len - 8) + k1, a);

     d = HashLen16(b + len, c + UNALIGNED_LOAD64(s + len - 16));

     a += d;

     do {

       a ^= ShiftMix(UNALIGNED_LOAD64(s) * k1) * k1;

       a *= k1;

       b ^= a;

       c ^= ShiftMix(UNALIGNED_LOAD64(s + 8) * k1) * k1;

       c *= k1;

       d ^= c;

       s += 16;

       l -= 16;

     } while (l > 0);

   }

   a = HashLen16(a, c);

   b = HashLen16(d, b);

   return uint128(a ^ b, HashLen16(b, a));

 }

 uint128 CityHash128WithSeed(const char *s, size_t len, uint128 seed) {

   if (len < 128) {

     return CityMurmur(s, len, seed);

   }

   // We expect len >= 128 to be the common case.  Keep 56 bytes of state:

   // v, w, x, y, and z.

   pair<uint64, uint64> v, w;

   uint64 x = Uint128Low64(seed);

   uint64 y = Uint128High64(seed);

   uint64 z = len * k1;

   v.first = Rotate(y ^ k1, 49) * k1 + UNALIGNED_LOAD64(s);

   v.second = Rotate(v.first, 42) * k1 + UNALIGNED_LOAD64(s + 8);

   w.first = Rotate(y + z, 35) * k1 + x;

   w.second = Rotate(x + UNALIGNED_LOAD64(s + 88), 53) * k1;

   // This is the same inner loop as CityHash64(), manually unrolled.

   do {

     x = Rotate(x + y + v.first + UNALIGNED_LOAD64(s + 16), 37) * k1;

     y = Rotate(y + v.second + UNALIGNED_LOAD64(s + 48), 42) * k1;

     x ^= w.second;

     y ^= v.first;

     z = Rotate(z ^ w.first, 33);

     v = WeakHashLen32WithSeeds(s, v.second * k1, x + w.first);

     w = WeakHashLen32WithSeeds(s + 32, z + w.second, y);

     std::swap(z, x);

     s += 64;

     x = Rotate(x + y + v.first + UNALIGNED_LOAD64(s + 16), 37) * k1;

     y = Rotate(y + v.second + UNALIGNED_LOAD64(s + 48), 42) * k1;

     x ^= w.second;

     y ^= v.first;

     z = Rotate(z ^ w.first, 33);

     v = WeakHashLen32WithSeeds(s, v.second * k1, x + w.first);

     w = WeakHashLen32WithSeeds(s + 32, z + w.second, y);

     std::swap(z, x);

     s += 64;

     len -= 128;

   } while (LIKELY(len >= 128));

   y += Rotate(w.first, 37) * k0 + z;

   x += Rotate(v.first + z, 49) * k0;

   // If 0 < len < 128, hash up to 4 chunks of 32 bytes each from the end of s.

   for (size_t tail_done = 0; tail_done < len; ) {

     tail_done += 32;

     y = Rotate(y - x, 42) * k0 + v.second;

     w.first += UNALIGNED_LOAD64(s + len - tail_done + 16);

     x = Rotate(x, 49) * k0 + w.first;

     w.first += v.first;

     v = WeakHashLen32WithSeeds(s + len - tail_done, v.first, v.second);

   }

   // At this point our 48 bytes of state should contain more than

   // enough information for a strong 128-bit hash.  We use two

   // different 48-byte-to-8-byte hashes to get a 16-byte final result.

   x = HashLen16(x, v.first);

   y = HashLen16(y, w.first);

   return uint128(HashLen16(x + v.second, w.second) + y,

                  HashLen16(x + w.second, y + v.second));

 }

 uint128 CityHash128(const char *s, size_t len) {

   if (len >= 16) {

     return CityHash128WithSeed(s + 16,

                                len - 16,

                                uint128(UNALIGNED_LOAD64(s) ^ k3,

                                        UNALIGNED_LOAD64(s + 8)));

   } else if (len >= 8) {

     return CityHash128WithSeed(NULL,

                                0,

                                uint128(UNALIGNED_LOAD64(s) ^ (len * k0),

                                        UNALIGNED_LOAD64(s + len - 8) ^ k1));

   } else {

     return CityHash128WithSeed(s, len, uint128(k0, k1));

   }

 }