sha256

Documentation

Overview

Package sha256 provides functions to export the middle state of internal sha256.digest and set the state. It also provides functions to serialize and deserialize between text and sha256.digest.

Index

• Variables
• func GetHashStateText(digest hash.Hash) (string, error)
• func NewHashWithStateText(stateCipherText string) (digest hash.Hash, err error)
• func SetHashState(digest hash.Hash, state *State) error
• type State
  • func DecodeStringToState(cipherText string) (*State, error)
  • func GetHashState(digest hash.Hash) (*State, error)
  • func (s *State) EncodeToString() (string, error)

Examples

• GetHashStateText
• NewHashWithStateText

Variables

var ErrDigestType = errors.New("digest must be type of *sha256.digest")

ErrDigestType hash.Hash has many implementation types, but, here, we only reflect sha256.digest type.

Functions

func GetHashStateText

func GetHashStateText(digest hash.Hash) (string, error)

GetHashStateText is also a helper method, it will return text representation of hash or unexpected error.

Example

// When you need to save the middle state of hash to use sometime in
// the future, just call GetHashStateText() function simply.
// When you need this hash with the state, you can call NewHashWithState()
// function, see the next example. It seems like serialize and deserialize.

hash := sha256.New()
if _, err := hash.Write([]byte("hello world")); err != nil {
	// you should handle the unexpected error
	return
}
fmt.Println(hex.EncodeToString(hash.Sum(nil)))
hashStateText, err := GetHashStateText(hash)
if err == nil {
	fmt.Println(hashStateText)
}

Output:

b94d27b9934d3e08a52e52d7da7dabfac484efe37a5380ee9088f7ace2efcde9
MP+BAwEBBVN0YXRlAf+CAAEEAQFIAf+EAAEBWAH/hgABAk54AQQAAQNMZW4BBgAAABn/gwEBAQlbOF11aW50MzIB/4QAAQYBEAAAGv+FAQEBCVs2NF11aW50OAH/hgABBgH/gAAAc/+CAQj8agnmZ/y7Z66F/Dxu83L8pU/1OvxRDlJ//JsFaIz8H4PZq/xb4M0ZAUBoZWxsbyB3b3JsZAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAARYBCwA=

func NewHashWithStateText

func NewHashWithStateText(stateCipherText string) (digest hash.Hash, err error)

NewHashWithStateText is a helper method, directly generate *sha256.digest by stateCipherText. Maybe, it will raise an error, return value err will represent it. If successfully, digest returned will be available.

Example

// When you saved the middle state of hash, you can recover it at
// any time.

stateText := "MP+BAwEBBXN0YXRlAf+CAAEEAQFIAf+EAAEBWAH/hgABAk54AQQAAQNMZW4BBgAAABn/gwEBAQlbOF11aW50MzIB/4QAAQYBEAAAGv+FAQEBCVs2NF11aW50OAH/hgABBgH/gAAAc/+CAQj8agnmZ/y7Z66F/Dxu83L8pU/1OvxRDlJ//JsFaIz8H4PZq/xb4M0ZAUBzb21ldGhpbmcAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAARIBCQA="
hash, _ := NewHashWithStateText(stateText)
fmt.Println(hex.EncodeToString(hash.Sum(nil)))

Output:

3fc9b689459d738f8c88a3a48aa9e33542016b7a4052e001aaa536fca74813cb

func SetHashState

func SetHashState(digest hash.Hash, state *State) error

SetHashState will be used to set sha256.digest state. This method will help us implement continuous hash.

Types

type State

type State struct {

	// H is corresponding to sha256.digest.h
	H [8]uint32

	// X is corresponding to sha256.digest.x
	X [64]byte

	// Nx is corresponding to sha256.digest.nx
	Nx int

	// Len is corresponding to sha256.digest.len
	Len uint64
}

State is a representation of *sha256.digest

func DecodeStringToState

func DecodeStringToState(cipherText string) (*State, error)

DecodeStringToState decodes string that is encoded by base64, and then decodes it to a *state. When something goes wrong, it will return an error, otherwise err is nil.

func GetHashState

func GetHashState(digest hash.Hash) (*State, error)

GetHashState will return sha256.digest internal state. This is an unsafe method, so you should use it with caution. If reflect successfully, it will return a *State.

func (*State) EncodeToString

func (s *State) EncodeToString() (string, error)

EncodeToString encodes state to string by base64 encode. If there are anything wrong, it will return an error to represent it.