forked from Shiloh/githaven
117 lines
2.5 KiB
Go
117 lines
2.5 KiB
Go
// Copyright (c) 2017 Couchbase, 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 vellum
|
|
|
|
import (
|
|
"hash"
|
|
"hash/fnv"
|
|
)
|
|
|
|
type registryCell struct {
|
|
addr int
|
|
node *builderNode
|
|
}
|
|
|
|
type registry struct {
|
|
table []registryCell
|
|
tableSize uint
|
|
mruSize uint
|
|
hasher hash.Hash64
|
|
}
|
|
|
|
func newRegistry(tableSize, mruSize int) *registry {
|
|
nsize := tableSize * mruSize
|
|
rv := ®istry{
|
|
table: make([]registryCell, nsize),
|
|
tableSize: uint(tableSize),
|
|
mruSize: uint(mruSize),
|
|
hasher: fnv.New64a(),
|
|
}
|
|
return rv
|
|
}
|
|
|
|
func (r *registry) Reset() {
|
|
for i := 0; i < len(r.table); i++ {
|
|
r.table[i] = registryCell{}
|
|
}
|
|
r.hasher.Reset()
|
|
}
|
|
|
|
func (r *registry) entry(node *builderNode) (bool, int, *registryCell) {
|
|
if len(r.table) == 0 {
|
|
return false, 0, nil
|
|
}
|
|
bucket := r.hash(node)
|
|
start := r.mruSize * uint(bucket)
|
|
end := start + r.mruSize
|
|
rc := registryCache(r.table[start:end])
|
|
return rc.entry(node)
|
|
}
|
|
|
|
const fnvPrime = 1099511628211
|
|
|
|
func (r *registry) hash(b *builderNode) int {
|
|
var final uint64
|
|
if b.final {
|
|
final = 1
|
|
}
|
|
|
|
var h uint64 = 14695981039346656037
|
|
h = (h ^ final) * fnvPrime
|
|
h = (h ^ b.finalOutput) * fnvPrime
|
|
for _, t := range b.trans {
|
|
h = (h ^ uint64(t.in)) * fnvPrime
|
|
h = (h ^ t.out) * fnvPrime
|
|
h = (h ^ uint64(t.addr)) * fnvPrime
|
|
}
|
|
return int(h % uint64(r.tableSize))
|
|
}
|
|
|
|
type registryCache []registryCell
|
|
|
|
func (r registryCache) entry(node *builderNode) (bool, int, *registryCell) {
|
|
if len(r) == 1 {
|
|
if r[0].node != nil && r[0].node.equiv(node) {
|
|
return true, r[0].addr, nil
|
|
}
|
|
r[0].node = node
|
|
return false, 0, &r[0]
|
|
}
|
|
for i := range r {
|
|
if r[i].node != nil && r[i].node.equiv(node) {
|
|
addr := r[i].addr
|
|
r.promote(i)
|
|
return true, addr, nil
|
|
}
|
|
}
|
|
// no match
|
|
last := len(r) - 1
|
|
r[last].node = node // discard LRU
|
|
r.promote(last)
|
|
return false, 0, &r[0]
|
|
|
|
}
|
|
|
|
func (r registryCache) promote(i int) {
|
|
for i > 0 {
|
|
r.swap(i-1, i)
|
|
i--
|
|
}
|
|
}
|
|
|
|
func (r registryCache) swap(i, j int) {
|
|
r[i], r[j] = r[j], r[i]
|
|
}
|