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Package multihash

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Published: Feb 3, 2020 | License: MIT | Module:


Package multihash is the Go implementation of, or self-describing hashes.




const (
	IDENTITY = 0x00
	// Deprecated: use IDENTITY
	ID         = IDENTITY
	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

	MD5 = 0xd5

	DBL_SHA2_256 = 0x56

	MURMUR3_128 = 0x22
	// Deprecated: use MURMUR3_128

	X11 = 0x1100



var (
	ErrUnknownCode      = errors.New("unknown multihash code")
	ErrTooShort         = errors.New("multihash too short. must be >= 2 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)")


var Codes = map[uint64]string{
	IDENTITY:     "identity",
	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_128:  "murmur3-128",
	KECCAK_224:   "keccak-224",
	KECCAK_256:   "keccak-256",
	KECCAK_384:   "keccak-384",
	KECCAK_512:   "keccak-512",
	SHAKE_128:    "shake-128",
	SHAKE_256:    "shake-256",
	X11:          "x11",
	MD5:          "md5",

Codes maps a hash code to it's name

var DefaultLengths = map[uint64]int{
	IDENTITY:     -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_128:  4,
	KECCAK_384:   48,
	KECCAK_512:   64,
	SHAKE_128:    32,
	SHAKE_256:    64,
	X11:          64,
	MD5:          16,

DefaultLengths maps a hash code to it's default length

var ErrLenTooLarge = errors.New("requested length was too large for digest")
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{
	"identity":     IDENTITY,
	"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,
	"murmur3-128":  MURMUR3_128,
	"keccak-224":   KECCAK_224,
	"keccak-256":   KECCAK_256,
	"keccak-384":   KECCAK_384,
	"keccak-512":   KECCAK_512,
	"shake-128":    SHAKE_128,
	"shake-256":    SHAKE_256,
	"x11":          X11,
	"md5":          MD5,

Names maps the name of a hash to the code

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.



// ignores errors for simplicity - don't do that at home.
buf, _ := hex.DecodeString("0beec7b5ea3f0fdbc95d0dd47f3c5bc275da8a33")
mhbuf, _ := EncodeName(buf, "sha1")
mhhex := hex.EncodeToString(mhbuf)
fmt.Printf("hex: %v\n", mhhex)
hex: 11140beec7b5ea3f0fdbc95d0dd47f3c5bc275da8a33

func RegisterHashFunc

func RegisterHashFunc(code uint64, hashFunc HashFunc) error

RegisterHashFunc adds an entry to the package-level code -> hash func map. The hash function must return at least the requested number of bytes. If it returns more, the hash will be truncated.

func ValidCode

func ValidCode(code uint64) bool

ValidCode checks whether a multihash code is valid.

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.



// ignores errors for simplicity - don't do that at home.
buf, _ := hex.DecodeString("0beec7b5ea3f0fdbc95d0dd47f3c5bc275da8a33")
mhbuf, _ := EncodeName(buf, "sha1")
o, _ := Decode(mhbuf)
mhhex := hex.EncodeToString(o.Digest)
fmt.Printf("obj: %v 0x%x %d %s\n", o.Name, o.Code, o.Length, mhhex)
obj: sha1 0x11 20 0beec7b5ea3f0fdbc95d0dd47f3c5bc275da8a33

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 HashFunc

type HashFunc func(data []byte, length int) (digest []byte, err error)

HashFunc is a hash function that hashes data into digest.

The length is the size the digest will be truncated to. While the hash function isn't responsible for truncating the digest, it may want to error if the length is invalid for the hash function (e.g., truncation would make the hash useless).

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 MHFromBytes

func MHFromBytes(buf []byte) (int, Multihash, error)

MHFromBytes reads a multihash from the given byte buffer, returning the number of bytes read as well as the 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 {

	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 Set

type Set struct {
	// contains filtered or unexported fields

Set is a set of Multihashes, holding one copy per Multihash.

func NewSet

func NewSet() *Set

NewSet creates a new set correctly initialized.

func (*Set) Add

func (s *Set) Add(m Multihash)

Add adds a new multihash to the set.

func (*Set) All

func (s *Set) All() []Multihash

All returns a slice with all the elements in the set.

func (*Set) ForEach

func (s *Set) ForEach(f func(m Multihash) error) error

ForEach runs f(m) with each multihash in the set. If returns immediately if f(m) returns an error.

func (*Set) Has

func (s *Set) Has(m Multihash) bool

Has returns true if the element is in the set.

func (*Set) Len

func (s *Set) Len() int

Len returns the number of elements in the set.

func (*Set) Remove

func (s *Set) Remove(m Multihash)

Remove removes an element from the set.

func (*Set) Visit

func (s *Set) Visit(m Multihash) bool

Visit adds a multihash only if it is not in the set already. Returns true if the multihash was added (was not in the set before).

type Writer

type Writer interface {

	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

Package Files

Documentation was rendered with GOOS=linux and GOARCH=amd64.

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