Package intervals provides a fast insertion-sort based solution to the merge overlapping intervals problem.
An Interval represents a range of the form [Start, End), which contains
all x in Start <= x < End. x can be any type that is ordered,
including the various sizes of int, uint, float types, uintptr and
string.
The Intervals type is a slice of Interval as maintained by the Insert()
method, which keeps them in ascending order and with any two overlapping
Interval merged. Two Interval overlap if the End of one is >= the
Start from the next one.
An example use case for this might be trying to do a concurrent download,
such as chunks of a large file from S3. You could kick off n goroutines,
each waiting to download 1/n of the file, and use something like
sync.WaitGroup to wait until they are all done until you start to use
them. However, that would require waiting until the last byte is received
before start sending the first byte. If you want to start streaming the
answer from the beginning as soon as the relevant chunks are written to
disk, you could maintain a done Intervals[int64] and done.Insert() the
byte range written after each successful Write(), start streaming as soon
as done.Search(0) returns true, up to the whatever the returned Interval's
End - 1 is.
The overhead of Insert() is very low, with the worst case of Insert()ing
10,000 non-overlapping intervals only taking 147ns on my Apple Mac M1:
$ go test -cpu=1 -bench=.
goos: darwin
goarch: arm64
pkg: github.com/die-net/intervals
BenchmarkInsertNonOverlapping/1 115100521 10.30 ns/op
BenchmarkInsertNonOverlapping/10 45857023 26.01 ns/op
BenchmarkInsertNonOverlapping/100 29844249 39.27 ns/op
BenchmarkInsertNonOverlapping/1000 21177404 57.57 ns/op
BenchmarkInsertNonOverlapping/10000 8115252 147.0 ns/op
BenchmarkInsertOverlapping/1 91738153 12.94 ns/op
BenchmarkInsertOverlapping/10 52171077 23.19 ns/op
BenchmarkInsertOverlapping/100 54989328 22.00 ns/op
BenchmarkInsertOverlapping/1000 47051826 25.75 ns/op
BenchmarkInsertOverlapping/10000 36945717 32.76 ns/op
PASS
And there's 100% test coverage, with a bunch of weird corner cases tested.
Copyright 2021-2024 Aaron Hopkins and contributors
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.