varint

README

go-varint

Varint helpers that enforce minimal encoding.

Table of Contents

• Install
• Contribute
• License

Install

go get github.com/multiformats/go-varint

Contribute

Contributions welcome. Please check out the issues.

Check out our contributing document for more information on how we work, and about contributing in general. Please be aware that all interactions related to multiformats are subject to the IPFS Code of Conduct.

Small note: If editing the README, please conform to the standard-readme specification.

License

MIT © 2019 Protocol Labs

Documentation

Index

• Constants
• Variables
• func FromUvarint(buf []byte) (uint64, int, error)
• func PutUvarint(buf []byte, x uint64) int
• func ReadUvarint(r io.ByteReader) (uint64, error)
• func ToUvarint(num uint64) []byte
• func UvarintSize(num uint64) int

Constants

const (
	// MaxLenUvarint63 is the maximum number of bytes representing an uvarint in
	// this encoding, supporting a maximum value of 2^63 (uint63), aka
	// MaxValueUvarint63.
	MaxLenUvarint63 = 9

	// MaxValueUvarint63 is the maximum encodable uint63 value.
	MaxValueUvarint63 = (1 << 63) - 1
)

Variables

var (
	ErrOverflow   = errors.New("varints larger than uint63 not supported")
	ErrUnderflow  = errors.New("varints malformed, could not reach the end")
	ErrNotMinimal = errors.New("varint not minimally encoded")
)

Functions

func FromUvarint

func FromUvarint(buf []byte) (uint64, int, error)

FromUvarint reads an unsigned varint from the beginning of buf, returns the varint, and the number of bytes read.

func PutUvarint

func PutUvarint(buf []byte, x uint64) int

PutUvarint is an alias for binary.PutUvarint.

This is provided for convenience so users of this library can avoid built-in varint functions and easily audit code for uses of those functions.

Make sure that x is smaller or equal to MaxValueUvarint63, otherwise this function will produce values that may be rejected by readers.

func ReadUvarint

func ReadUvarint(r io.ByteReader) (uint64, error)

ReadUvarint reads a unsigned varint from the given reader.

func ToUvarint

func ToUvarint(num uint64) []byte

ToUvarint converts an unsigned integer to a varint-encoded []byte

func UvarintSize

func UvarintSize(num uint64) int

UvarintSize returns the size (in bytes) of `num` encoded as a unsigned varint.

This may return a size greater than MaxUvarintLen63, which would be an illegal value, and would be rejected by readers.