github.com/mhmtszr/concurrent-swiss-map@v1.0.8/maphash/hasher.go (about)

     1  // Copyright 2022 Dolthub, Inc.
     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 maphash
    16  
    17  import "unsafe"
    18  
    19  // Hasher hashes values of type K.
    20  // Uses runtime AES-based hashing.
    21  type Hasher[K comparable] struct {
    22  	hash hashfn
    23  	seed uintptr
    24  }
    25  
    26  // NewHasher creates a new Hasher[K] with a random seed.
    27  func NewHasher[K comparable]() Hasher[K] {
    28  	return Hasher[K]{
    29  		hash: getRuntimeHasher[K](),
    30  		seed: newHashSeed(),
    31  	}
    32  }
    33  
    34  // NewSeed returns a copy of |h| with a new hash seed.
    35  func NewSeed[K comparable](h Hasher[K]) Hasher[K] {
    36  	return Hasher[K]{
    37  		hash: h.hash,
    38  		seed: newHashSeed(),
    39  	}
    40  }
    41  
    42  // Hash hashes |key|.
    43  func (h Hasher[K]) Hash(key K) uint64 {
    44  	// promise to the compiler that pointer
    45  	// |p| does not escape the stack.
    46  	p := noescape(unsafe.Pointer(&key))
    47  	return uint64(h.hash(p, h.seed))
    48  }