bitvector

Documentation

Index

• Variables
• type BitNumbering
• type BitVector
  • func NewBitVector(buf []byte, bytePacking BitNumbering) *BitVector
  • func (v *BitVector) Extend(val byte, count uint, order BitNumbering)
  • func (v *BitVector) Get(idx uint) (byte, error)
  • func (v *BitVector) Iterator(order BitNumbering) func(uint) byte
  • func (v *BitVector) Push(val byte)
  • func (v *BitVector) Take(index uint, count uint, order BitNumbering) (out byte)

Variables

var (
	// ErrOutOfRange - the index passed is out of range for the BitVector
	ErrOutOfRange = errors.New("index out of range")
)

Types

type BitNumbering

type BitNumbering int

BitNumbering indicates the ordering of bits, either least-significant bit in position 0, or most-significant bit in position 0.

It it used in 3 ways with BitVector: 1. Ordering of bits within the Buf []byte structure 2. What order to add bits when using Extend() 3. What order to read bits when using Take()

https://en.wikipedia.org/wiki/Bit_numbering

const (
	// LSB0 - bit ordering starts with the low-order bit
	LSB0 BitNumbering = iota

	// MSB0 - bit ordering starts with the high-order bit
	MSB0
)

type BitVector

type BitVector struct {
	Buf []byte

	// BytePacking is the bit ordering within bytes
	BytePacking BitNumbering

	// Len is the logical number of bits in the vector.
	// The last byte in Buf may have undefined bits if Len is not a multiple of 8
	Len uint
}

BitVector is used to manipulate ordered collections of bits

func NewBitVector

func NewBitVector(buf []byte, bytePacking BitNumbering) *BitVector

NewBitVector constructs a new BitVector from a slice of bytes.

The bytePacking parameter is required to know how to interpret the bit ordering within the bytes.

func (*BitVector) Extend

func (v *BitVector) Extend(val byte, count uint, order BitNumbering)

Extend adds up to 8 bits to the receiver

Given a byte b == 0b11010101 v.Extend(b, 4, LSB0) would add < 1, 0, 1, 0 > v.Extend(b, 4, MSB0) would add < 1, 1, 0, 1 >

Panics if count is out of range

func (*BitVector) Get

func (v *BitVector) Get(idx uint) (byte, error)

Get returns a single bit as a byte -- either 0 or 1

func (*BitVector) Iterator

func (v *BitVector) Iterator(order BitNumbering) func(uint) byte

Iterator returns a function, which when invoked, returns the number of bits requested, and increments an internal cursor.

When the end of the BitVector is reached, it returns zeroes indefinitely

Panics if count is out of range

func (*BitVector) Push

func (v *BitVector) Push(val byte)

Push adds a single bit to the BitVector.

Although it takes a byte, only the low-order bit is used, so just use 0 or 1.

func (*BitVector) Take

func (v *BitVector) Take(index uint, count uint, order BitNumbering) (out byte)

Take reads up to 8 bits at the given index.

Given a BitVector < 1, 1, 0, 1, 0, 1, 0, 1 > v.Take(0, 4, LSB0) would return 0b00001011 v.Take(0, 4, MSB0) would return 0b11010000

Panics if count is out of range