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nyaa-pantsu/vendor/github.com/RoaringBitmap/roaring/README.md

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roaring [![Build Status](https://travis-ci.org/RoaringBitmap/roaring.png)](https://travis-ci.org/RoaringBitmap/roaring) [![Coverage Status](https://coveralls.io/repos/github/RoaringBitmap/roaring/badge.svg?branch=master)](https://coveralls.io/github/RoaringBitmap/roaring?branch=master) [![GoDoc](https://godoc.org/github.com/RoaringBitmap/roaring?status.svg)](https://godoc.org/github.com/RoaringBitmap/roaring) [![Go Report Card](https://goreportcard.com/badge/RoaringBitmap/roaring)](https://goreportcard.com/report/github.com/RoaringBitmap/roaring)
=============
This is a go port of the Roaring bitmap data structure.
Roaring is used by [Apache Spark](https://spark.apache.org/), [Apache Kylin](http://kylin.io), [Netflix Atlas](https://github.com/Netflix/atlas), [LinkedIn Pinot](https://github.com/linkedin/pinot/wiki), [Druid.io](http://druid.io/), [Whoosh](https://pypi.python.org/pypi/Whoosh/), [Pilosa](https://www.pilosa.com/),
and [Apache Lucene](http://lucene.apache.org/) (as well as supporting systems
such as Solr and Elastic).
Roaring bitmaps are found to work well in many important applications:
> Use Roaring for bitmap compression whenever possible. Do not use other bitmap compression methods ([Wang et al., SIGMOD 2017](http://db.ucsd.edu/wp-content/uploads/2017/03/sidm338-wangA.pdf))
The ``roaring`` Go library is used by
* [Cloud Torrent](https://github.com/jpillora/cloud-torrent): a self-hosted remote torrent client
* [runv](https://github.com/hyperhq/runv): an Hypervisor-based runtime for the Open Containers Initiative
There are also [Java](https://github.com/RoaringBitmap/RoaringBitmap) and [C/C++](https://github.com/RoaringBitmap/CRoaring) versions. The Java, C, C++ and Go version are binary compatible: e.g, you can save bitmaps
from a Java program and load them back in Go, and vice versa. We have a [format specification](https://github.com/RoaringBitmap/RoaringFormatSpec).
This code is licensed under Apache License, Version 2.0 (ASL2.0).
Copyright 2016 by the authors.
### References
- Samy Chambi, Daniel Lemire, Owen Kaser, Robert Godin,
Better bitmap performance with Roaring bitmaps,
Software: Practice and Experience Volume 46, Issue 5, pages 709–719, May 2016
http://arxiv.org/abs/1402.6407 This paper used data from http://lemire.me/data/realroaring2014.html
- Daniel Lemire, Gregory Ssi-Yan-Kai, Owen Kaser, Consistently faster and smaller compressed bitmaps with Roaring, Software: Practice and Experience (accepted in 2016, to appear) http://arxiv.org/abs/1603.06549
### Dependencies
Dependencies are fetched automatically by giving the `-t` flag to `go get`.
they include
- github.com/smartystreets/goconvey/convey
- github.com/willf/bitset
- github.com/mschoch/smat
Note that the smat library requires Go 1.6 or better.
#### Installation
- go get -t github.com/RoaringBitmap/roaring
### Example
Here is a simplified but complete example:
```go
package main
import (
"fmt"
"github.com/RoaringBitmap/roaring"
"bytes"
)
func main() {
// example inspired by https://github.com/fzandona/goroar
fmt.Println("==roaring==")
rb1 := roaring.BitmapOf(1, 2, 3, 4, 5, 100, 1000)
fmt.Println(rb1.String())
rb2 := roaring.BitmapOf(3, 4, 1000)
fmt.Println(rb2.String())
rb3 := roaring.NewBitmap()
fmt.Println(rb3.String())
fmt.Println("Cardinality: ", rb1.GetCardinality())
fmt.Println("Contains 3? ", rb1.Contains(3))
rb1.And(rb2)
rb3.Add(1)
rb3.Add(5)
rb3.Or(rb1)
// prints 1, 3, 4, 5, 1000
i := rb3.Iterator()
for i.HasNext() {
fmt.Println(i.Next())
}
fmt.Println()
// next we include an example of serialization
buf := new(bytes.Buffer)
rb1.WriteTo(buf) // we omit error handling
newrb:= roaring.NewBitmap()
newrb.ReadFrom(buf)
if rb1.Equals(newrb) {
fmt.Println("I wrote the content to a byte stream and read it back.")
}
}
```
If you wish to use serialization and handle errors, you might want to
consider the following sample of code:
```go
rb := BitmapOf(1, 2, 3, 4, 5, 100, 1000)
buf := new(bytes.Buffer)
size,err:=rb.WriteTo(buf)
if err != nil {
t.Errorf("Failed writing")
}
newrb:= NewBitmap()
size,err=newrb.ReadFrom(buf)
if err != nil {
t.Errorf("Failed reading")
}
if ! rb.Equals(newrb) {
t.Errorf("Cannot retrieve serialized version")
}
```
Given N integers in [0,x), then the serialized size in bytes of
a Roaring bitmap should never exceed this bound:
`` 8 + 9 * ((long)x+65535)/65536 + 2 * N ``
That is, given a fixed overhead for the universe size (x), Roaring
bitmaps never use more than 2 bytes per integer. You can call
``BoundSerializedSizeInBytes`` for a more precise estimate.
### Documentation
Current documentation is available at http://godoc.org/github.com/RoaringBitmap/roaring
### Goroutine safety
In general, it should not generally be considered safe to access
the same bitmaps using different goroutines--they are left
unsynchronized for performance. Should you want to access
a Bitmap from more than one goroutine, you should
provide synchronization. Typically this is done by using channels to pass
the *Bitmap around (in Go style; so there is only ever one owner),
or by using `sync.Mutex` to serialize operations on Bitmaps.
### Coverage
We test our software. For a report on our test coverage, see
https://coveralls.io/github/RoaringBitmap/roaring?branch=master
### Benchmark
Type
go test -bench Benchmark -run -
### Iterative use
You can use roaring with gore:
- go get -u github.com/motemen/gore
- Make sure that ``$GOPATH/bin`` is in your ``$PATH``.
- go get github/RoaringBitmap/roaring
```go
$ gore
gore version 0.2.6 :help for help
gore> :import github.com/RoaringBitmap/roaring
gore> x:=roaring.New()
gore> x.Add(1)
gore> x.String()
"{1}"
```
### Fuzzy testing
You can help us test further the library with fuzzy testing:
go get github.com/dvyukov/go-fuzz/go-fuzz
go get github.com/dvyukov/go-fuzz/go-fuzz-build
go test -tags=gofuzz -run=TestGenerateSmatCorpus
go-fuzz-build github.com/RoaringBitmap/roaring
go-fuzz -bin=./roaring-fuzz.zip -workdir=workdir/ -timeout=200
Let it run, and if the # of crashers is > 0, check out the reports in
the workdir where you should be able to find the panic goroutine stack
traces.
### Alternative in Go
There is a Go version wrapping the C/C++ implementation https://github.com/RoaringBitmap/gocroaring
For an alternative implementation in Go, see https://github.com/fzandona/goroar
The two versions were written independently.
### Mailing list/discussion group
https://groups.google.com/forum/#!forum/roaring-bitmaps