49 lines
1.3 KiB
Go
49 lines
1.3 KiB
Go
|
// Copyright 2022 Dolthub, Inc.
|
||
|
|
//
|
||
|
|
// Licensed under the Apache License, Version 2.0 (the "License");
|
||
|
|
// you may not use this file except in compliance with the License.
|
||
|
|
// You may obtain a copy of the License at
|
||
|
|
//
|
||
|
|
// http://www.apache.org/licenses/LICENSE-2.0
|
||
|
|
//
|
||
|
|
// Unless required by applicable law or agreed to in writing, software
|
||
|
|
// distributed under the License is distributed on an "AS IS" BASIS,
|
||
|
|
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
|
||
|
|
// See the License for the specific language governing permissions and
|
||
|
|
// limitations under the License.
|
||
|
|
|
||
|
|
package maphash
|
||
|
|
|
||
|
|
import "unsafe"
|
||
|
|
|
||
|
|
// Hasher hashes values of type K.
|
||
|
|
// Uses runtime AES-based hashing.
|
||
|
|
type Hasher[K comparable] struct {
|
||
|
|
hash hashfn
|
||
|
|
seed uintptr
|
||
|
|
}
|
||
|
|
|
||
|
|
// NewHasher creates a new Hasher[K] with a random seed.
|
||
|
|
func NewHasher[K comparable]() Hasher[K] {
|
||
|
|
return Hasher[K]{
|
||
|
|
hash: getRuntimeHasher[K](),
|
||
|
|
seed: newHashSeed(),
|
||
|
|
}
|
||
|
|
}
|
||
|
|
|
||
|
|
// NewSeed returns a copy of |h| with a new hash seed.
|
||
|
|
func NewSeed[K comparable](h Hasher[K]) Hasher[K] {
|
||
|
|
return Hasher[K]{
|
||
|
|
hash: h.hash,
|
||
|
|
seed: newHashSeed(),
|
||
|
|
}
|
||
|
|
}
|
||
|
|
|
||
|
|
// Hash hashes |key|.
|
||
|
|
func (h Hasher[K]) Hash(key K) uint64 {
|
||
|
|
// promise to the compiler that pointer
|
||
|
|
// |p| does not escape the stack.
|
||
|
|
p := noescape(unsafe.Pointer(&key))
|
||
|
|
return uint64(h.hash(p, h.seed))
|
||
|
|
}
|