github.com/cockroachdb/cockroachdb-parser@v0.23.3-0.20240213214944-911057d40c9a/pkg/util/hash.go (about)

     1  // Copyright 2017 The Cockroach Authors.
     2  //
     3  // Use of this software is governed by the Business Source License
     4  // included in the file licenses/BSL.txt.
     5  //
     6  // As of the Change Date specified in that file, in accordance with
     7  // the Business Source License, use of this software will be governed
     8  // by the Apache License, Version 2.0, included in the file
     9  // licenses/APL.txt.
    10  
    11  package util
    12  
    13  import (
    14  	"hash/crc32"
    15  
    16  	"github.com/cockroachdb/errors"
    17  )
    18  
    19  // CRC32 computes the Castagnoli CRC32 of the given data.
    20  func CRC32(data []byte) uint32 {
    21  	hash := crc32.New(crc32.MakeTable(crc32.Castagnoli))
    22  	if _, err := hash.Write(data); err != nil {
    23  		panic(errors.Wrap(err, `"It never returns an error." -- https://golang.org/pkg/hash`))
    24  	}
    25  	return hash.Sum32()
    26  }
    27  
    28  // Magic FNV Base constant as suitable for a FNV-64 hash.
    29  const fnvBase = uint64(14695981039346656037)
    30  const fnvPrime = 1099511628211
    31  
    32  // FNV64 encapsulates the hash state.
    33  type FNV64 struct {
    34  	sum uint64
    35  }
    36  
    37  // MakeFNV64 initializes a new FNV64 hash state.
    38  func MakeFNV64() FNV64 {
    39  	return FNV64{sum: fnvBase}
    40  }
    41  
    42  // Init initializes FNV64 to starting value.
    43  func (f *FNV64) Init() {
    44  	f.sum = fnvBase
    45  }
    46  
    47  // IsInitialized returns true if the hash struct was initialized, which happens
    48  // automatically when created through MakeFNV64 above.
    49  func (f *FNV64) IsInitialized() bool {
    50  	return f.sum != 0
    51  }
    52  
    53  // Add modifies the underlying FNV64 state by accumulating the given integer
    54  // hash to the existing state.
    55  func (f *FNV64) Add(c uint64) {
    56  	f.sum *= fnvPrime
    57  	f.sum ^= c
    58  }
    59  
    60  // Sum returns the hash value accumulated till now.
    61  func (f *FNV64) Sum() uint64 {
    62  	return f.sum
    63  }