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// 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]
}
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