107 lines
2.5 KiB
Go
107 lines
2.5 KiB
Go
// Copyright 2023-2024 The NATS Authors
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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 stree
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// Node with 10 children
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// This node size is for the particular case that a part of the subject is numeric
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// in nature, i.e. it only needs to satisfy the range 0-9 without wasting bytes
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// Order of struct fields for best memory alignment (as per govet/fieldalignment)
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type node10 struct {
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child [10]node
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meta
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key [10]byte
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}
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func newNode10(prefix []byte) *node10 {
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nn := &node10{}
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nn.setPrefix(prefix)
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return nn
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}
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// Currently we do not keep node10 sorted or use bitfields for traversal so just add to the end.
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// TODO(dlc) - We should revisit here with more detailed benchmarks.
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func (n *node10) addChild(c byte, nn node) {
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if n.size >= 10 {
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panic("node10 full!")
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}
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n.key[n.size] = c
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n.child[n.size] = nn
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n.size++
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}
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func (n *node10) findChild(c byte) *node {
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for i := uint16(0); i < n.size; i++ {
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if n.key[i] == c {
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return &n.child[i]
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}
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}
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return nil
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}
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func (n *node10) isFull() bool { return n.size >= 10 }
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func (n *node10) grow() node {
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nn := newNode16(n.prefix)
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for i := 0; i < 10; i++ {
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nn.addChild(n.key[i], n.child[i])
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}
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return nn
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}
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// Deletes a child from the node.
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func (n *node10) deleteChild(c byte) {
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for i, last := uint16(0), n.size-1; i < n.size; i++ {
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if n.key[i] == c {
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// Unsorted so just swap in last one here, else nil if last.
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if i < last {
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n.key[i] = n.key[last]
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n.child[i] = n.child[last]
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n.key[last] = 0
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n.child[last] = nil
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} else {
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n.key[i] = 0
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n.child[i] = nil
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}
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n.size--
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return
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}
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}
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}
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// Shrink if needed and return new node, otherwise return nil.
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func (n *node10) shrink() node {
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if n.size > 4 {
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return nil
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}
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nn := newNode4(nil)
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for i := uint16(0); i < n.size; i++ {
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nn.addChild(n.key[i], n.child[i])
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}
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return nn
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}
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// Iterate over all children calling func f.
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func (n *node10) iter(f func(node) bool) {
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for i := uint16(0); i < n.size; i++ {
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if !f(n.child[i]) {
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return
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}
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}
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}
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// Return our children as a slice.
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func (n *node10) children() []node {
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return n.child[:n.size]
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}
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