如何用Go实现BitSet？

Question

I didn't find a BitSet package in Go, so I tried to implement it. I'd like to use a array of uint64 to store the bits.

I need the number of bits to allocate the uint64 array. With Java, I can define a constructor that takes an integer. While Go doesn't provide constructor, how can I properly initialize the BitSet 'object' when user call new()?

Answer 1

Declare bitSet as a private struct:

type bitSet struct {
  len int
  array []uint64
}

Expose the interface BitSet:

type BitSet interface {
  Has(pos int) bool
  Add(pos int) bool
  Len() int
}

Also expose a function NewBitSet:

func NewBitSet(len int) BitSet {
  return &bitSet{len, make(uint64, (len+7) / 8) }
}

This is a Go way for encapsulation: share an interface, not the implementation.