github.com/songzhibin97/gkit@v1.2.13/structure/skipmap/util.go (about) 1 // Copyright 2021 ByteDance 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 skipmap 16 17 import ( 18 "github.com/songzhibin97/gkit/internal/wyhash" 19 "github.com/songzhibin97/gkit/sys/fastrand" 20 _ "unsafe" // for linkname 21 ) 22 23 const ( 24 maxLevel = 16 25 p = 0.25 26 defaultHighestLevel = 3 27 ) 28 29 func hash(s string) uint64 { 30 return wyhash.Sum64String(s) 31 } 32 33 //go:linkname cmpstring runtime.cmpstring 34 func cmpstring(a, b string) int 35 36 func randomLevel() int { 37 level := 1 38 for fastrand.Uint32n(1/p) == 0 { 39 level++ 40 } 41 if level > maxLevel { 42 return maxLevel 43 } 44 return level 45 }