/
single_table.go
153 lines (136 loc) · 3.41 KB
/
single_table.go
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package cuckoo
import (
"fmt"
"math/rand"
)
type fingerprint []byte
type singleTable struct {
numBucket uint32
tagsPerBucket uint32
bitsPerItem uint32
tagMask uint32
buckets []fingerprint
}
func (t *singleTable) SizeInTags() uint32 {
return t.numBucket * t.tagsPerBucket
}
func (t *singleTable) Init(numBucket, tagsPerBucket, bitsPerItem uint32) {
t.numBucket = numBucket
t.tagsPerBucket = tagsPerBucket
t.bitsPerItem = bitsPerItem
t.tagMask = (1 << bitsPerItem) - 1
t.buckets = make([]fingerprint, numBucket)
kBytesPerFingerprint := (bitsPerItem*tagsPerBucket + 7) >> 3
var i uint32
for i = 0; i < numBucket; i++ {
t.buckets[i] = make(fingerprint, kBytesPerFingerprint)
}
}
func (t *singleTable) Insert(i uint32, tag uint32, kickout bool) (oldTag uint32, ok bool) {
var j uint32
for j = 0; j < t.tagsPerBucket; j++ {
if t.readTag(i, j) == 0 {
t.writeTag(i, j, tag)
return 0, true
}
}
if !kickout {
return tag, false
}
var r uint32 = uint32(rand.Intn(int(t.tagsPerBucket)))
oldTag = t.readTag(i, r)
t.writeTag(i, r, tag)
return oldTag, false
}
func (t *singleTable) Delete(i uint32, tag uint32) bool {
var j uint32
for j = 0; j < t.tagsPerBucket; j++ {
if t.readTag(i, j) == tag {
t.writeTag(i, j, 0)
return true
}
}
return false
}
func (t *singleTable) Find(i uint32, tag uint32) bool {
var j uint32
for j = 0; j < t.tagsPerBucket; j++ {
if t.readTag(i, j) == tag {
return true
}
}
return false
}
func (t *singleTable) Info() string {
return fmt.Sprintf("SingleHashtable with tag size:%v bits \n"+
"\t\tAssociativity: %v \n"+
"\t\tTotal # of rows: %v\n"+
"\t\tTotal # slots: %v\n",
t.bitsPerItem, t.tagsPerBucket, t.numBucket, t.numBucket*t.tagsPerBucket)
}
func (t *singleTable) String() string {
return SingleTable
}
func (t *singleTable) writeTag(i, j, tag uint32) {
fp := t.buckets[i]
tag = tag & t.tagMask
/* following code only works for little-endian */
if t.bitsPerItem == 2 {
fp[0] |= byte(tag << (2 * j))
} else if t.bitsPerItem == 4 {
pos := j >> 1
if j&1 == 0 {
fp[pos] &= 0xf0
fp[pos] |= byte(tag)
} else {
fp[pos] &= 0x0f
fp[pos] |= byte(tag << 4)
}
} else if t.bitsPerItem == 8 {
fp[j] = byte(tag)
} else if t.bitsPerItem == 12 {
pos := j + (j >> 1)
if j&1 == 0 {
fp[pos] = byte(tag)
fp[pos+1] &= 0xf0
fp[pos+1] |= byte(tag >> 8)
} else {
fp[pos] &= 0x0f
fp[pos] |= byte(tag << 4)
fp[pos+1] = byte(tag >> 4)
}
} else if t.bitsPerItem == 16 {
pos := j << 1
fp[pos] = byte(tag)
fp[pos+1] = byte(tag >> 8)
} else if t.bitsPerItem == 32 {
pos := j << 2
fp[pos] = byte(tag)
fp[pos+1] = byte(tag >> 8)
fp[pos+2] = byte(tag >> 16)
fp[pos+3] = byte(tag >> 24)
}
}
func (t *singleTable) readTag(i, j uint32) uint32 {
/* following code only works for little-endian */
fp := t.buckets[i]
var tag uint32 = 0
if t.bitsPerItem == 2 {
tag = uint32(fp[0] >> (j * 2))
} else if t.bitsPerItem == 4 {
pos := j >> 1
tag = uint32(fp[pos] >> ((j & 1) << 2))
} else if t.bitsPerItem == 8 {
tag = uint32(fp[j])
} else if t.bitsPerItem == 12 {
pos := j + (j >> 1)
tag = (uint32(fp[pos]) | uint32(fp[pos+1])<<8) >> ((j & 1) << 2)
} else if t.bitsPerItem == 16 {
pos := j << 1
tag = uint32(fp[pos]) | uint32(fp[pos+1])<<8
} else if t.bitsPerItem == 32 {
pos := j << 2
tag = uint32(fp[pos]) | uint32(fp[pos+1])<<8 | uint32(fp[pos+2])<<16 | uint32(fp[pos+3])<<24
}
return tag & t.tagMask
}