115 lines
2.6 KiB
Go
115 lines
2.6 KiB
Go
// Copyright (c) 2017 Couchbase, Inc.
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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package vellum
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type registryCell struct {
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addr int
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node *builderNode
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}
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type registry struct {
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builderNodePool *builderNodePool
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table []registryCell
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tableSize uint
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mruSize uint
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}
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func newRegistry(p *builderNodePool, tableSize, mruSize int) *registry {
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nsize := tableSize * mruSize
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rv := ®istry{
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builderNodePool: p,
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table: make([]registryCell, nsize),
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tableSize: uint(tableSize),
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mruSize: uint(mruSize),
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}
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return rv
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}
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func (r *registry) Reset() {
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var empty registryCell
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for i := range r.table {
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r.builderNodePool.Put(r.table[i].node)
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r.table[i] = empty
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}
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}
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func (r *registry) entry(node *builderNode) (bool, int, *registryCell) {
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if len(r.table) == 0 {
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return false, 0, nil
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}
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bucket := r.hash(node)
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start := r.mruSize * uint(bucket)
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end := start + r.mruSize
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rc := registryCache(r.table[start:end])
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return rc.entry(node, r.builderNodePool)
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}
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const fnvPrime = 1099511628211
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func (r *registry) hash(b *builderNode) int {
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var final uint64
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if b.final {
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final = 1
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}
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var h uint64 = 14695981039346656037
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h = (h ^ final) * fnvPrime
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h = (h ^ b.finalOutput) * fnvPrime
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for _, t := range b.trans {
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h = (h ^ uint64(t.in)) * fnvPrime
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h = (h ^ t.out) * fnvPrime
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h = (h ^ uint64(t.addr)) * fnvPrime
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}
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return int(h % uint64(r.tableSize))
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}
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type registryCache []registryCell
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func (r registryCache) entry(node *builderNode, pool *builderNodePool) (bool, int, *registryCell) {
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if len(r) == 1 {
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if r[0].node != nil && r[0].node.equiv(node) {
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return true, r[0].addr, nil
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}
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pool.Put(r[0].node)
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r[0].node = node
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return false, 0, &r[0]
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}
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for i := range r {
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if r[i].node != nil && r[i].node.equiv(node) {
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addr := r[i].addr
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r.promote(i)
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return true, addr, nil
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}
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}
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// no match
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last := len(r) - 1
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pool.Put(r[last].node)
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r[last].node = node // discard LRU
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r.promote(last)
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return false, 0, &r[0]
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}
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func (r registryCache) promote(i int) {
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for i > 0 {
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r.swap(i-1, i)
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i--
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}
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}
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func (r registryCache) swap(i, j int) {
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r[i], r[j] = r[j], r[i]
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}
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