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segment_tree.go
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/
segment_tree.go
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/*
* Copyright (c) 2024 Yunshan Networks
*
* 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 segmenttree
import (
"runtime"
"sync"
"github.com/Workiva/go-datastructures/bitarray"
)
func intervalToIntegerRange(interval Interval) IntegerRange {
lower, lowerClosed := interval.Lower()
upper, upperClosed := interval.Upper()
return ranged(lower, lowerClosed, upper, upperClosed)
}
type SegmentTree struct {
trees []ImmutableSegmentTree
values []Value
}
func (t *SegmentTree) Query(intervals ...Interval) []Value {
dimension := len(t.trees)
if len(intervals) != dimension || len(t.values) == 0 {
return nil
}
wg := sync.WaitGroup{}
wg.Add(dimension)
results := make([]bitarray.BitArray, dimension)
for d := 0; d < dimension; d++ {
go func(d int) {
results[d] = t.trees[d].query(intervalToIntegerRange(intervals[d]))
wg.Done()
}(d)
}
wg.Wait()
indexBitSet := results[0]
for d := 1; d < len(t.trees); d++ {
indexBitSet = indexBitSet.And(results[d])
}
values := make([]Value, 0, len(t.values))
valueSet := bitarray.NewSparseBitArray()
for iterator := indexBitSet.Blocks(); iterator.Next(); {
blockIndex, block := iterator.Value()
for i := uint64(0); i < 64; i++ {
if 1<<i&block == 0 {
continue
}
index := blockIndex*64 + i
value := t.values[index]
if found, _ := valueSet.GetBit(value.Id()); found {
continue
}
values = append(values, value)
valueSet.SetBit(value.Id())
}
}
return values
}
func (t *SegmentTree) clear() {
for i := 0; i < len(t.trees); i++ {
t.trees[i].clear()
}
}
func New(dimension int, entries ...Entry) (Tree, error) {
if dimension == 0 {
return nil, InvalidDimension
}
values := make([]Value, len(entries))
for i, entry := range entries {
values[i] = entry.Value
if len(entry.Intervals) < dimension {
return nil, InsufficientIntervalLength
}
}
trees := make([]ImmutableSegmentTree, dimension)
for d := 0; d < dimension; d++ {
intervals := make([]IntegerRange, len(entries))
for i, entry := range entries {
intervals[i] = intervalToIntegerRange(entry.Intervals[d])
}
trees[d].init(intervals)
}
tree := &SegmentTree{trees: trees, values: values}
runtime.SetFinalizer(tree, func(t *SegmentTree) {
t.clear()
})
return tree, nil
}