bitset

bitset.go

package bitset

import "fmt"

const (
	chunkSize uint = 8
	allSet uint64 = 1<<8 - 1
	allReset uint64 = 0
)

type Bitset struct {
	storage []byte
	size uint
}

func NewBitset(size uint) (*Bitset, error) {
	if size == 0 {
		return nil, fmt.Errorf("Cannot create a 0 size bitset")
	}
	storeSize := size / chunkSize
	if size % chunkSize != 0 {
		storeSize++
	}
	storage := make([]byte, storeSize)
	return &Bitset{storage: storage, size: size}, nil
}

func (b *Bitset) SetAll() {
	for i := range b.storage {
		b.storage[i] = byte(allSet)
	}
}

func (b *Bitset) ResetAll() {
	for i := range b.storage {
		b.storage[i] = byte(allReset)
	}
}

func (b *Bitset) Set(position uint) error {
	if position > b.size {
		return fmt.Errorf("Index exceeding bitset size")
	}
	index := position / chunkSize
	indexPos := position % chunkSize
	mask := 1 << indexPos
	b.storage[index] = b.storage[index] | byte(mask)
	return nil
}

func (b *Bitset) Get(position uint) (bool, error) {
	if position > b.size {
		return false, fmt.Errorf("Index exceeding bitset size")
	}
	index := position / chunkSize
	indexPos := position % chunkSize
	return (b.storage[index] >> indexPos) & 0x1 == 1, nil
}