github.com/XiaoMi/Gaea@v1.2.5/util/murmur.go (about)

     1  // Copyright 2019 The Gaea Authors. All Rights Reserved.
     2  //
     3  // Licensed under the Apache License, Version 2.0 (the "License");
     4  // you may not use this file except in compliance with the License.
     5  // You may obtain a copy of the License at
     6  //
     7  //     http://www.apache.org/licenses/LICENSE-2.0
     8  //
     9  // Unless required by applicable law or agreed to in writing, software
    10  // distributed under the License is distributed on an "AS IS" BASIS,
    11  // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    12  // See the License for the specific language governing permissions and
    13  // limitations under the License.
    14  
    15  package util
    16  
    17  const (
    18  	c1 = 0xcc9e2d51
    19  	c2 = 0x1b873593
    20  )
    21  
    22  // MurmurHash copy from guava Murmur3_32HashFunction
    23  type MurmurHash struct {
    24  	seed int
    25  }
    26  
    27  // NewMurmurHash constructor of MurmurHash
    28  func NewMurmurHash(seed int) *MurmurHash {
    29  	return &MurmurHash{
    30  		seed: seed,
    31  	}
    32  }
    33  
    34  // HashUnencodedChars check if has unencoded chars
    35  func (m *MurmurHash) HashUnencodedChars(inputStr string) int {
    36  	input := []rune(inputStr)
    37  	h1 := int32(m.seed)
    38  
    39  	for i := 1; i < len(input); i += 2 {
    40  		k1 := int32(input[i-1] | (input[i] << 16))
    41  		k1 = mixK1(k1)
    42  		h1 = mixH1(h1, k1)
    43  	}
    44  
    45  	if len(input)&1 == 1 {
    46  		k1 := int32(input[len(input)-1])
    47  		k1 = mixK1(k1)
    48  		h1 ^= k1
    49  	}
    50  
    51  	return int(fmix(h1, int32(2*len(input))))
    52  }
    53  
    54  func mixK1(k1 int32) int32 {
    55  	k1_64 := int64(k1)
    56  	k1_64 *= c1
    57  	k1 = int32(k1_64)
    58  	k1 = rotateLeft(k1, 15)
    59  	k1_64 = int64(k1)
    60  	k1_64 *= c2
    61  	return int32(k1_64)
    62  }
    63  
    64  func mixH1(h1, k1 int32) int32 {
    65  	h1 ^= k1
    66  	h1 = rotateLeft(h1, 13)
    67  	h1_64 := int64(h1)
    68  	h1_64 = h1_64*5 + 0xe6546b64
    69  	return int32(h1_64)
    70  }
    71  
    72  func fmix(h1, length int32) int32 {
    73  	uh1 := uint32(h1)
    74  	ulength := uint32(length)
    75  	uh1 ^= ulength
    76  	uh1 ^= uh1 >> 16
    77  	uh1 *= 0x85ebca6b
    78  	uh1 ^= uh1 >> 13
    79  	uh1 *= 0xc2b2ae35
    80  	uh1 ^= uh1 >> 16
    81  	return int32(uh1)
    82  }
    83  
    84  func rotateLeft(i, distance int32) int32 {
    85  	ui := uint32(i)
    86  	udistance := uint32(distance)
    87  	a1 := ui << udistance
    88  	b1 := ui >> (32 - udistance)
    89  	return int32(a1 | b1)
    90  }