multihash

Documentation

Overview

Package multihash is the Go implementation of https://github.com/multiformats/multihash, or self-describing hashes.

Index

• Constants
• Variables
• func AppCode(code uint64) bool
• func Encode(buf []byte, code uint64) ([]byte, error)
• func EncodeName(buf []byte, name string) ([]byte, error)
• func ValidCode(code uint64) bool
• type DecodedMultihash
  • func Decode(buf []byte) (*DecodedMultihash, error)
• type ErrInconsistentLen
  • func (e ErrInconsistentLen) Error() string
• type Multihash
  • func Cast(buf []byte) (Multihash, error)
  • func FromB58String(s string) (m Multihash, err error)
  • func FromHexString(s string) (Multihash, error)
  • func Sum(data []byte, code uint64, length int) (Multihash, error)
  • func (m Multihash) B58String() string
  • func (m *Multihash) HexString() string
  • func (m *Multihash) String() string
• type Reader
  • func NewReader(r io.Reader) Reader
• type Writer
  • func NewWriter(w io.Writer) Writer

Constants

const (
	ID         = 0x00
	SHA1       = 0x11
	SHA2_256   = 0x12
	SHA2_512   = 0x13
	SHA3_224   = 0x17
	SHA3_256   = 0x16
	SHA3_384   = 0x15
	SHA3_512   = 0x14
	SHA3       = SHA3_512
	KECCAK_224 = 0x1A
	KECCAK_256 = 0x1B
	KECCAK_384 = 0x1C
	KECCAK_512 = 0x1D

	SHAKE_128 = 0x18
	SHAKE_256 = 0x19

	BLAKE2B_MIN = 0xb201
	BLAKE2B_MAX = 0xb240
	BLAKE2S_MIN = 0xb241
	BLAKE2S_MAX = 0xb260

	DBL_SHA2_256 = 0x56

	MURMUR3 = 0x22
)

constants

Variables

var (
	ErrUnknownCode      = errors.New("unknown multihash code")
	ErrTooShort         = errors.New("multihash too short. must be > 3 bytes")
	ErrTooLong          = errors.New("multihash too long. must be < 129 bytes")
	ErrLenNotSupported  = errors.New("multihash does not yet support digests longer than 127 bytes")
	ErrInvalidMultihash = errors.New("input isn't valid multihash")

	ErrVarintBufferShort = errors.New("uvarint: buffer too small")
	ErrVarintTooLong     = errors.New("uvarint: varint too big (max 64bit)")
)

errors

var Codes = map[uint64]string{
	ID:           "id",
	SHA1:         "sha1",
	SHA2_256:     "sha2-256",
	SHA2_512:     "sha2-512",
	SHA3_224:     "sha3-224",
	SHA3_256:     "sha3-256",
	SHA3_384:     "sha3-384",
	SHA3_512:     "sha3-512",
	DBL_SHA2_256: "dbl-sha2-256",
	MURMUR3:      "murmur3",
	KECCAK_224:   "keccak-224",
	KECCAK_256:   "keccak-256",
	KECCAK_384:   "keccak-384",
	KECCAK_512:   "keccak-512",
	SHAKE_128:    "shake-128",
	SHAKE_256:    "shake-256",
}

Codes maps a hash code to it's name

var DefaultLengths = map[uint64]int{
	ID:           -1,
	SHA1:         20,
	SHA2_256:     32,
	SHA2_512:     64,
	SHA3_224:     28,
	SHA3_256:     32,
	SHA3_384:     48,
	SHA3_512:     64,
	DBL_SHA2_256: 32,
	KECCAK_224:   28,
	KECCAK_256:   32,
	MURMUR3:      4,
	KECCAK_384:   48,
	KECCAK_512:   64,
	SHAKE_128:    32,
	SHAKE_256:    64,
}

DefaultLengths maps a hash code to it's default length

var ErrSumNotSupported = errors.New("Function not implemented. Complain to lib maintainer.")

ErrSumNotSupported is returned when the Sum function code is not implemented

var Names = map[string]uint64{
	"id":           ID,
	"sha1":         SHA1,
	"sha2-256":     SHA2_256,
	"sha2-512":     SHA2_512,
	"sha3":         SHA3_512,
	"sha3-224":     SHA3_224,
	"sha3-256":     SHA3_256,
	"sha3-384":     SHA3_384,
	"sha3-512":     SHA3_512,
	"dbl-sha2-256": DBL_SHA2_256,
	"murmur3":      MURMUR3,
	"keccak-224":   KECCAK_224,
	"keccak-256":   KECCAK_256,
	"keccak-384":   KECCAK_384,
	"keccak-512":   KECCAK_512,
	"shake-128":    SHAKE_128,
	"shake-256":    SHAKE_256,
}

Names maps the name of a hash to the code

Functions

func AppCode

func AppCode(code uint64) bool

AppCode checks whether a multihash code is part of the App range.

func Encode

func Encode(buf []byte, code uint64) ([]byte, error)

Encode a hash digest along with the specified function code. Note: the length is derived from the length of the digest itself.

func EncodeName

func EncodeName(buf []byte, name string) ([]byte, error)

EncodeName is like Encode() but providing a string name instead of a numeric code. See Names for allowed values.

func ValidCode

func ValidCode(code uint64) bool

ValidCode checks whether a multihash code is valid.

Types

type DecodedMultihash

type DecodedMultihash struct {
	Code   uint64
	Name   string
	Length int    // Length is just int as it is type of len() opearator
	Digest []byte // Digest holds the raw multihash bytes
}

DecodedMultihash represents a parsed multihash and allows easy access to the different parts of a multihash.

func Decode

func Decode(buf []byte) (*DecodedMultihash, error)

Decode parses multihash bytes into a DecodedMultihash.

type ErrInconsistentLen

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

ErrInconsistentLen is returned when a decoded multihash has an inconsistent length

func (ErrInconsistentLen) Error

func (e ErrInconsistentLen) Error() string

type Multihash

type Multihash []byte

Multihash is byte slice with the following form: <hash function code><digest size><hash function output>. See the spec for more information.

func Cast

func Cast(buf []byte) (Multihash, error)

Cast casts a buffer onto a multihash, and returns an error if it does not work.

func FromB58String

func FromB58String(s string) (m Multihash, err error)

FromB58String parses a B58-encoded multihash.

func FromHexString

func FromHexString(s string) (Multihash, error)

FromHexString parses a hex-encoded multihash.

func Sum

func Sum(data []byte, code uint64, length int) (Multihash, error)

Sum obtains the cryptographic sum of a given buffer. The length parameter indicates the length of the resulting digest and passing a negative value use default length values for the selected hash function.

func (Multihash) B58String

func (m Multihash) B58String() string

B58String returns the B58-encoded representation of a multihash.

func (*Multihash) HexString

func (m *Multihash) HexString() string

HexString returns the hex-encoded representation of a multihash.

func (*Multihash) String

func (m *Multihash) String() string

String is an alias to HexString().

type Reader

type Reader interface {
	io.Reader

	ReadMultihash() (Multihash, error)
}

Reader is an io.Reader wrapper that exposes a function to read a whole multihash, parse it, and return it.

func NewReader

func NewReader(r io.Reader) Reader

NewReader wraps an io.Reader with a multihash.Reader

type Writer

type Writer interface {
	io.Writer

	WriteMultihash(Multihash) error
}

Writer is an io.Writer wrapper that exposes a function to write a whole multihash.

func NewWriter

func NewWriter(w io.Writer) Writer

NewWriter wraps an io.Writer with a multihash.Writer