bits

Documentation

Overview

Package bits provides bit access operations and binary decoding algorithms.

Index

• func DecodeZigZag(x uint32) int32
• func EncodeZigZag(x int32) uint32
• func IntN(x uint64, n uint) int64
• func WriteUnary(bw *bitio.Writer, x uint64) error
• type Reader
  • func NewReader(r io.Reader) *Reader
  • func (br *Reader) Read(n uint) (x uint64, err error)
  • func (br *Reader) ReadUnary() (x uint64, err error)

Functions

func DecodeZigZag

func DecodeZigZag(x uint32) int32

DecodeZigZag decodes a ZigZag encoded integer and returns it.

Examples of ZigZag encoded values on the left and decoded values on the right:

0 =>  0
1 => -1
2 =>  1
3 => -2
4 =>  2
5 => -3
6 =>  3

ref: https://developers.google.com/protocol-buffers/docs/encoding

func EncodeZigZag

func EncodeZigZag(x int32) uint32

EncodeZigZag encodes a given integer to ZigZag-encoding.

Examples of integer input on the left and corresponding ZigZag encoded values on the right:

 0 => 0
-1 => 1
 1 => 2
-2 => 3
 2 => 4
-3 => 5
 3 => 6

ref: https://developers.google.com/protocol-buffers/docs/encoding

func IntN

func IntN(x uint64, n uint) int64

IntN returns the signed two's complement of x with the specified integer bit width.

Examples of unsigned (n-bit width) x values on the left and decoded values on the right:

0b011 -> 3
0b010 -> 2
0b001 -> 1
0b000 -> 0
0b111 -> -1
0b110 -> -2
0b101 -> -3
0b100 -> -4

func WriteUnary

func WriteUnary(bw *bitio.Writer, x uint64) error

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

Types

type Reader

type Reader struct {
	// contains filtered or unexported fields
}

A Reader handles bit reading operations. It buffers bits up to the next byte boundary.

func NewReader

func NewReader(r io.Reader) *Reader

NewReader returns a new Reader that reads bits from r.

func (*Reader) Read

func (br *Reader) Read(n uint) (x uint64, err error)

Read reads and returns the next n bits, at most 64. It buffers bits up to the next byte boundary.

func (*Reader) ReadUnary

func (br *Reader) ReadUnary() (x uint64, err error)

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