blockchain

README

Blockchain

A simple blockchain implementation.

Install

Fist, use go get to install the latest version of the library:

go get -u github.com/lynn9388/blockchain

Next, include this package in your application:

import "github.com/lynn9388/blockchain"

Example

genesis := GenesisBlock()
bc := NewBlockchain(genesis)
bc.AddBlock(genesis.Header.NewBlock(StringData("lynn9388")))

Documentation

Overview

Package blockchain provides a simple blockchain implementation.

Index

• type Block
  • func NewBlock(prevBlockHeader *BlockHeader, extra []byte, data [][]byte) *Block
  • func NewGenesisBlock() *Block
  • func (b *Block) IsValid(prevBlockHeader *BlockHeader, isExtraValid func([]byte) bool) bool
• type BlockHeader
  • func (bh *BlockHeader) Hash() []byte
  • func (bh *BlockHeader) ToByte() []byte
• type Blockchain
  • func NewBlockchain(dbFile string, genesis *Block) *Blockchain
  • func (bc *Blockchain) AddBlock(b *Block, isExtraValid func([]byte) bool)
• type Iterator
  • func NewIterator(bc *Blockchain, blockHash []byte) *Iterator
  • func (i *Iterator) Prev() *Block

Types

type Block

type Block struct {
	Header *BlockHeader `json:"header"`
	Data   [][]byte     `json:"data"`
}

Block holds batches of valid data/transactions.

func NewBlock

func NewBlock(prevBlockHeader *BlockHeader, extra []byte, data [][]byte) *Block

NewBlock creates a new block. If there is no extra info then extra can be nil (will be converted to empty) or empty. The data can not be nil or empty, because a block without data is invalid.

func NewGenesisBlock

func NewGenesisBlock() *Block

NewGenesisBlock returns the genesis block.

func (*Block) IsValid

func (b *Block) IsValid(prevBlockHeader *BlockHeader, isExtraValid func([]byte) bool) bool

IsValid checks if every fields in a block is valid. isExtraValid can be nil if check extra info is unnecessary.

type BlockHeader

type BlockHeader struct {
	Index      int    `json:"index"`
	Time       int64  `json:"time"`
	PrevHash   []byte `json:"prevHash"`
	MerkleRoot []byte `json:"merkleRoot"`
	Extra      []byte `json:"extra"`
}

BlockHeader holds the metadata of a block

func (*BlockHeader) Hash

func (bh *BlockHeader) Hash() []byte

Hash returns the SHA256 hash of the block header.

func (*BlockHeader) ToByte

func (bh *BlockHeader) ToByte() []byte

ToByte converts the block header to bytes.

type Blockchain

type Blockchain struct {
	DB      *bolt.DB // DB stored the blockchain
	Tips    []*Block // last block of all branches
	BestTip *Block   // last block of longest branch
}

Blockchain implements interactions with a DB.

func NewBlockchain

func NewBlockchain(dbFile string, genesis *Block) *Blockchain

NewBlockchain creates a blockchain from DB file. If the file does not exist then it will be created and initialize a new blockchain with genesis block.

func (*Blockchain) AddBlock

func (bc *Blockchain) AddBlock(b *Block, isExtraValid func([]byte) bool)

AddBlock saves a block into the blockchain if it is valid. isExtraValid can be nil if check extra info is unnecessary.

type Iterator

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

Iterator is used to iterate over blockchain's blocks.

func NewIterator

func NewIterator(bc *Blockchain, blockHash []byte) *Iterator

NewIterator returns a iterator with a start block.

func (*Iterator) Prev

func (i *Iterator) Prev() *Block

Prev returns the block pointed by the iterator and move to the previous block. It will end with genesis block and then return nil.