mirror of
https://github.com/VictoriaMetrics/VictoriaMetrics.git
synced 2024-12-22 16:36:27 +01:00
96 lines
2.6 KiB
Go
96 lines
2.6 KiB
Go
package jump
|
|
|
|
import (
|
|
"hash"
|
|
"hash/crc32"
|
|
"hash/crc64"
|
|
"hash/fnv"
|
|
"io"
|
|
)
|
|
|
|
// Hash takes a 64 bit key and the number of buckets. It outputs a bucket
|
|
// number in the range [0, buckets).
|
|
// If the number of buckets is less than or equal to 0 then one 1 is used.
|
|
func Hash(key uint64, buckets int32) int32 {
|
|
var b, j int64
|
|
|
|
if buckets <= 0 {
|
|
buckets = 1
|
|
}
|
|
|
|
for j < int64(buckets) {
|
|
b = j
|
|
key = key*2862933555777941757 + 1
|
|
j = int64(float64(b+1) * (float64(int64(1)<<31) / float64((key>>33)+1)))
|
|
}
|
|
|
|
return int32(b)
|
|
}
|
|
|
|
// HashString takes string as key instead of an int and uses a KeyHasher to
|
|
// generate a key compatible with Hash().
|
|
func HashString(key string, buckets int32, h KeyHasher) int32 {
|
|
h.Reset()
|
|
_, err := io.WriteString(h, key)
|
|
if err != nil {
|
|
panic(err)
|
|
}
|
|
return Hash(h.Sum64(), buckets)
|
|
}
|
|
|
|
// KeyHasher is a subset of hash.Hash64 in the standard library.
|
|
type KeyHasher interface {
|
|
// Write (via the embedded io.Writer interface) adds more data to the
|
|
// running hash.
|
|
// It never returns an error.
|
|
io.Writer
|
|
|
|
// Reset resets the KeyHasher to its initial state.
|
|
Reset()
|
|
|
|
// Return the result of the added bytes (via io.Writer).
|
|
Sum64() uint64
|
|
}
|
|
|
|
// Hasher represents a jump consistent hasher using a string as key.
|
|
type Hasher struct {
|
|
n int32
|
|
h KeyHasher
|
|
}
|
|
|
|
// New returns a new instance of of Hasher.
|
|
func New(n int, h KeyHasher) *Hasher {
|
|
return &Hasher{int32(n), h}
|
|
}
|
|
|
|
// N returns the number of buckets the hasher can assign to.
|
|
func (h *Hasher) N() int {
|
|
return int(h.n)
|
|
}
|
|
|
|
// Hash returns the integer hash for the given key.
|
|
func (h *Hasher) Hash(key string) int {
|
|
return int(HashString(key, h.n, h.h))
|
|
}
|
|
|
|
// KeyHashers available in the standard library for use with HashString() and Hasher.
|
|
var (
|
|
// CRC32 uses the 32-bit Cyclic Redundancy Check (CRC-32) with the IEEE
|
|
// polynomial.
|
|
NewCRC32 func() hash.Hash64 = func() hash.Hash64 { return &crc32Hasher{crc32.NewIEEE()} }
|
|
// CRC64 uses the 64-bit Cyclic Redundancy Check (CRC-64) with the ECMA
|
|
// polynomial.
|
|
NewCRC64 func() hash.Hash64 = func() hash.Hash64 { return crc64.New(crc64.MakeTable(crc64.ECMA)) }
|
|
// FNV1 uses the non-cryptographic hash function FNV-1.
|
|
NewFNV1 func() hash.Hash64 = func() hash.Hash64 { return fnv.New64() }
|
|
// FNV1a uses the non-cryptographic hash function FNV-1a.
|
|
NewFNV1a func() hash.Hash64 = func() hash.Hash64 { return fnv.New64a() }
|
|
|
|
// These are deprecated because they're not safe for concurrent use. Please
|
|
// use the New* functions instead.
|
|
CRC32 hash.Hash64 = &crc32Hasher{crc32.NewIEEE()}
|
|
CRC64 hash.Hash64 = crc64.New(crc64.MakeTable(crc64.ECMA))
|
|
FNV1 hash.Hash64 = fnv.New64()
|
|
FNV1a hash.Hash64 = fnv.New64a()
|
|
)
|