meditime/vendor/github.com/AndreasBriese/bbloom/bbloom.go

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// The MIT License (MIT)
// Copyright (c) 2014 Andreas Briese, eduToolbox@Bri-C GmbH, Sarstedt
// Permission is hereby granted, free of charge, to any person obtaining a copy of
// this software and associated documentation files (the "Software"), to deal in
// the Software without restriction, including without limitation the rights to
// use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of
// the Software, and to permit persons to whom the Software is furnished to do so,
// subject to the following conditions:
// The above copyright notice and this permission notice shall be included in all
// copies or substantial portions of the Software.
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
// FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
// COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER
// IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
// CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
// 2019/08/25 code revision to reduce unsafe use
// Parts are adopted from the fork at ipfs/bbloom after performance rev by
// Steve Allen (https://github.com/Stebalien)
// (see https://github.com/ipfs/bbloom/blob/master/bbloom.go)
// -> func Has
// -> func set
// -> func add
package bbloom
import (
"bytes"
"encoding/json"
"log"
"math"
"sync"
"unsafe"
)
// helper
// not needed anymore by Set
// var mask = []uint8{1, 2, 4, 8, 16, 32, 64, 128}
func getSize(ui64 uint64) (size uint64, exponent uint64) {
if ui64 < uint64(512) {
ui64 = uint64(512)
}
size = uint64(1)
for size < ui64 {
size <<= 1
exponent++
}
return size, exponent
}
func calcSizeByWrongPositives(numEntries, wrongs float64) (uint64, uint64) {
size := -1 * numEntries * math.Log(wrongs) / math.Pow(float64(0.69314718056), 2)
locs := math.Ceil(float64(0.69314718056) * size / numEntries)
return uint64(size), uint64(locs)
}
// New
// returns a new bloomfilter
func New(params ...float64) (bloomfilter Bloom) {
var entries, locs uint64
if len(params) == 2 {
if params[1] < 1 {
entries, locs = calcSizeByWrongPositives(params[0], params[1])
} else {
entries, locs = uint64(params[0]), uint64(params[1])
}
} else {
log.Fatal("usage: New(float64(number_of_entries), float64(number_of_hashlocations)) i.e. New(float64(1000), float64(3)) or New(float64(number_of_entries), float64(number_of_hashlocations)) i.e. New(float64(1000), float64(0.03))")
}
size, exponent := getSize(uint64(entries))
bloomfilter = Bloom{
Mtx: &sync.Mutex{},
sizeExp: exponent,
size: size - 1,
setLocs: locs,
shift: 64 - exponent,
}
bloomfilter.Size(size)
return bloomfilter
}
// NewWithBoolset
// takes a []byte slice and number of locs per entry
// returns the bloomfilter with a bitset populated according to the input []byte
func NewWithBoolset(bs *[]byte, locs uint64) (bloomfilter Bloom) {
bloomfilter = New(float64(len(*bs)<<3), float64(locs))
for i, b := range *bs {
*(*uint8)(unsafe.Pointer(uintptr(unsafe.Pointer(&bloomfilter.bitset[0])) + uintptr(i))) = b
}
return bloomfilter
}
// bloomJSONImExport
// Im/Export structure used by JSONMarshal / JSONUnmarshal
type bloomJSONImExport struct {
FilterSet []byte
SetLocs uint64
}
// JSONUnmarshal
// takes JSON-Object (type bloomJSONImExport) as []bytes
// returns Bloom object
func JSONUnmarshal(dbData []byte) Bloom {
bloomImEx := bloomJSONImExport{}
json.Unmarshal(dbData, &bloomImEx)
buf := bytes.NewBuffer(bloomImEx.FilterSet)
bs := buf.Bytes()
bf := NewWithBoolset(&bs, bloomImEx.SetLocs)
return bf
}
//
// Bloom filter
type Bloom struct {
Mtx *sync.Mutex
ElemNum uint64
bitset []uint64
sizeExp uint64
size uint64
setLocs uint64
shift uint64
}
// <--- http://www.cse.yorku.ca/~oz/hash.html
// modified Berkeley DB Hash (32bit)
// hash is casted to l, h = 16bit fragments
// func (bl Bloom) absdbm(b *[]byte) (l, h uint64) {
// hash := uint64(len(*b))
// for _, c := range *b {
// hash = uint64(c) + (hash << 6) + (hash << bl.sizeExp) - hash
// }
// h = hash >> bl.shift
// l = hash << bl.shift >> bl.shift
// return l, h
// }
// Update: found sipHash of Jean-Philippe Aumasson & Daniel J. Bernstein to be even faster than absdbm()
// https://131002.net/siphash/
// siphash was implemented for Go by Dmitry Chestnykh https://github.com/dchest/siphash
// Add
// set the bit(s) for entry; Adds an entry to the Bloom filter
func (bl *Bloom) Add(entry []byte) {
l, h := bl.sipHash(entry)
for i := uint64(0); i < bl.setLocs; i++ {
bl.set((h + i*l) & bl.size)
bl.ElemNum++
}
}
// AddTS
// Thread safe: Mutex.Lock the bloomfilter for the time of processing the entry
func (bl *Bloom) AddTS(entry []byte) {
bl.Mtx.Lock()
defer bl.Mtx.Unlock()
bl.Add(entry)
}
// Has
// check if bit(s) for entry is/are set
// returns true if the entry was added to the Bloom Filter
func (bl Bloom) Has(entry []byte) bool {
l, h := bl.sipHash(entry)
res := true
for i := uint64(0); i < bl.setLocs; i++ {
res = res && bl.isSet((h+i*l)&bl.size)
// https://github.com/ipfs/bbloom/commit/84e8303a9bfb37b2658b85982921d15bbb0fecff
// // Branching here (early escape) is not worth it
// // This is my conclusion from benchmarks
// // (prevents loop unrolling)
// switch bl.IsSet((h + i*l) & bl.size) {
// case false:
// return false
// }
}
return res
}
// HasTS
// Thread safe: Mutex.Lock the bloomfilter for the time of processing the entry
func (bl *Bloom) HasTS(entry []byte) bool {
bl.Mtx.Lock()
defer bl.Mtx.Unlock()
return bl.Has(entry)
}
// AddIfNotHas
// Only Add entry if it's not present in the bloomfilter
// returns true if entry was added
// returns false if entry was allready registered in the bloomfilter
func (bl Bloom) AddIfNotHas(entry []byte) (added bool) {
if bl.Has(entry) {
return added
}
bl.Add(entry)
return true
}
// AddIfNotHasTS
// Tread safe: Only Add entry if it's not present in the bloomfilter
// returns true if entry was added
// returns false if entry was allready registered in the bloomfilter
func (bl *Bloom) AddIfNotHasTS(entry []byte) (added bool) {
bl.Mtx.Lock()
defer bl.Mtx.Unlock()
return bl.AddIfNotHas(entry)
}
// Size
// make Bloom filter with as bitset of size sz
func (bl *Bloom) Size(sz uint64) {
bl.bitset = make([]uint64, sz>>6)
}
// Clear
// resets the Bloom filter
func (bl *Bloom) Clear() {
bs := bl.bitset
for i := range bs {
bs[i] = 0
}
}
// Set
// set the bit[idx] of bitsit
func (bl *Bloom) set(idx uint64) {
// ommit unsafe
// *(*uint8)(unsafe.Pointer(uintptr(unsafe.Pointer(&bl.bitset[idx>>6])) + uintptr((idx%64)>>3))) |= mask[idx%8]
bl.bitset[idx>>6] |= 1 << (idx % 64)
}
// IsSet
// check if bit[idx] of bitset is set
// returns true/false
func (bl *Bloom) isSet(idx uint64) bool {
// ommit unsafe
// return (((*(*uint8)(unsafe.Pointer(uintptr(unsafe.Pointer(&bl.bitset[idx>>6])) + uintptr((idx%64)>>3)))) >> (idx % 8)) & 1) == 1
return bl.bitset[idx>>6]&(1<<(idx%64)) != 0
}
// JSONMarshal
// returns JSON-object (type bloomJSONImExport) as []byte
func (bl Bloom) JSONMarshal() []byte {
bloomImEx := bloomJSONImExport{}
bloomImEx.SetLocs = uint64(bl.setLocs)
bloomImEx.FilterSet = make([]byte, len(bl.bitset)<<3)
for i := range bloomImEx.FilterSet {
bloomImEx.FilterSet[i] = *(*byte)(unsafe.Pointer(uintptr(unsafe.Pointer(&bl.bitset[0])) + uintptr(i)))
}
data, err := json.Marshal(bloomImEx)
if err != nil {
log.Fatal("json.Marshal failed: ", err)
}
return data
}
// // alternative hashFn
// func (bl Bloom) fnv64a(b *[]byte) (l, h uint64) {
// h64 := fnv.New64a()
// h64.Write(*b)
// hash := h64.Sum64()
// h = hash >> 32
// l = hash << 32 >> 32
// return l, h
// }
//
// // <-- http://partow.net/programming/hashfunctions/index.html
// // citation: An algorithm proposed by Donald E. Knuth in The Art Of Computer Programming Volume 3,
// // under the topic of sorting and search chapter 6.4.
// // modified to fit with boolset-length
// func (bl Bloom) DEKHash(b *[]byte) (l, h uint64) {
// hash := uint64(len(*b))
// for _, c := range *b {
// hash = ((hash << 5) ^ (hash >> bl.shift)) ^ uint64(c)
// }
// h = hash >> bl.shift
// l = hash << bl.sizeExp >> bl.sizeExp
// return l, h
// }