unary.go

package bits

import (
	"github.com/icza/bitio"
)

// ReadUnary decodes and returns an unary coded integer, whose value is
// represented by the number of leading zeros before a one.
//
// Examples of unary coded binary on the left and decoded decimal on the right:
//
//	1       => 0
//	01      => 1
//	001     => 2
//	0001    => 3
//	00001   => 4
//	000001  => 5
//	0000001 => 6
func (br *Reader) ReadUnary() (x uint64, err error) {
	for {
		bit, err := br.Read(1)
		if err != nil {
			return 0, err
		}
		if bit == 1 {
			break
		}
		x++
	}
	return x, nil
}

// WriteUnary encodes x as an unary coded integer, whose value is represented by
// the number of leading zeros before a one.
//
// Examples of unary coded binary on the left and decoded decimal on the right:
//
//	0 => 1
//	1 => 01
//	2 => 001
//	3 => 0001
//	4 => 00001
//	5 => 000001
//	6 => 0000001
func WriteUnary(bw *bitio.Writer, x uint64) error {
	for ; x > 8; x -= 8 {
		if err := bw.WriteByte(0x0); err != nil {
			return err
		}
	}

	bits := uint64(1)
	n := byte(x + 1)
	if err := bw.WriteBits(bits, n); err != nil {
		return err
	}
	return nil
}