Simple, efficient bitmaps in Go with atomic operation support.

go get github.com/KarpelesLab/bitmap

// Create a new bitmap with capacity for n bits
bitmap.New(n int) Bitmap
// Non-atomic operations
Get(bit int) bool
Set(bit int, value bool)
Toggle(bit int)
// Atomic operations (thread-safe)
GetAtomic(bit int) bool
SetAtomic(bit int, value bool)
ToggleAtomic(bit int)

package main
import "github.com/KarpelesLab/bitmap"
func main() {
    m := bitmap.New(128)
    m.Set(42, true)
    if m.Get(42) {
        // bit 42 is set
    }
    // Thread-safe operations
    m.SetAtomic(100, true)
    m.ToggleAtomic(100)
}

There are already a few bitmap implementations in Go available out there, however they have some shortfalls and/or are too complex for what a bitmap should do.

• boljen's go-bitmap has separate implementations for Bitmap/Concurrent/Threadsafe, and complexifies a lot what should be very simple.
• ShawnMilo's bitmap has a nice feel but lacks atomic methods and adds string methods using json/gzip/base64 (?)
• Roaring Bitmaps are simply too complex for what I need bitmaps for. You should however definitely use that if you store more than 200k bits or so in total.