创建创世块的代码解析
在cmd的geth目录下的main.go中
init函数先于main函数执行，做命令的初始化，其中比较重要的有三个地方，app.Action=geth,app.Commands中consoleCommand，以及App.Before指向的匿名函数
func init() {
// Initialize the CLI app and start Geth
app.Action = geth
app.HideVersion = true // we have a command to print the version
app.Copyright = "Copyright 2013-2018 The go-ethereum Authors"
app.Commands = []cli.Command{
// See chaincmd.go:
initCommand,
importCommand,
exportCommand,
importPreimagesCommand,
exportPreimagesCommand,
copydbCommand,
removedbCommand,
dumpCommand,
// See monitorcmd.go:
monitorCommand,
// See accountcmd.go:
accountCommand,
walletCommand,
// See consolecmd.go:
consoleCommand,
attachCommand,
javascriptCommand,
// See misccmd.go:
makecacheCommand,
makedagCommand,
versionCommand,
bugCommand,
licenseCommand,
// See config.go
dumpConfigCommand,
}
sort.Sort(cli.CommandsByName(app.Commands))
app.Flags = append(app.Flags, nodeFlags...)
app.Flags = append(app.Flags, rpcFlags...)
app.Flags = append(app.Flags, consoleFlags...)
app.Flags = append(app.Flags, debug.Flags...)
app.Flags = append(app.Flags, whisperFlags...)
app.Before = func(ctx *cli.Context) error {
runtime.GOMAXPROCS(runtime.NumCPU())
if err := debug.Setup(ctx); err != nil {
return err
}
// Start system runtime metrics collection
go metrics.CollectProcessMetrics(3 * time.Second)
utils.SetupNetwork(ctx)
return nil
}
app.After = func(ctx *cli.Context) error {
debug.Exit()
console.Stdin.Close() // Resets terminal mode.
return nil
}
}
main函数中的内容比较简单，这里不多做任何解释。
func main() {
if err := app.Run(os.Args); err != nil {
fmt.Fprintln(os.Stderr, err)
os.Exit(1)
}
}
通过gopkg.in/urfave/cli.v1包中的代码来衔接到cmd/geth/chaincmd包中的代码，APP包中中HandleAction函数action的类型是「func(*Context) error」，此时将执行a(context)方法，那么此时调用那个Action呢，就是我们前面提到的App.init()初始化命令时的initCommand，接下来我们来看看cmd/geth/chaincmd中的initCommand：
var (
initCommand = cli.Command{
Action: utils.MigrateFlags(initGenesis),
Name: "init",
Usage: "Bootstrap and initialize a new genesis block",
ArgsUsage: "<genesisPath>",
Flags: []cli.Flag{
utils.DataDirFlag,
utils.LightModeFlag,
},
Category: "BLOCKCHAIN COMMANDS",
Description: `
The init command initializes a new genesis block and definition for the network.
This is a destructive action and changes the network in which you will be
participating.
It expects the genesis file as argument.`,
}
这允许使用现有的配置功能。当所有标志被迁移时，该功能可以被删除，并且必须改变现有的配置功能，即使用本地标志
func MigrateFlags(action func(ctx *cli.Context) error) func(*cli.Context) error {
return func(ctx *cli.Context) error {
for _, name := range ctx.FlagNames() {
if ctx.IsSet(name) {
ctx.GlobalSet(name, ctx.String(name))
}
}
return action(ctx)
}
}
根据给定的JSon格式文件初始化创世块
func initGenesis(ctx *cli.Context) error {
// Make sure we have a valid genesis JSON
genesisPath := ctx.Args().First()
if len(genesisPath) == 0 {
utils.Fatalf("Must supply path to genesis JSON file")
}
file, err := os.Open(genesisPath)
if err != nil {
utils.Fatalf("Failed to read genesis file: %v", err)
}
defer file.Close()
genesis := new(core.Genesis)
if err := json.NewDecoder(file).Decode(genesis); err != nil {
utils.Fatalf("invalid genesis file: %v", err)
}
// Open an initialise both full and light databases
stack := makeFullNode(ctx)
for _, name := range []string{"chaindata", "lightchaindata"} {
chaindb, err := stack.OpenDatabase(name, 0, 0)
if err != nil {
utils.Fatalf("Failed to open database: %v", err)
}
_, hash, err := core.SetupGenesisBlock(chaindb, genesis)
if err != nil {
utils.Fatalf("Failed to write genesis block: %v", err)
}
log.Info("Successfully wrote genesis state", "database", name, "hash", hash)
}
return nil
}
将初始创世块存储
chaindb, err := stack.OpenDatabase(name, 0, 0)
if err != nil {
utils.Fatalf("Failed to open database: %v", err)
}
涉及到的Core层次的代码
genesis := new(core.Genesis)
_, hash, err := core.SetupGenesisBlock(chaindb, genesis)
if err != nil {
utils.Fatalf("Failed to write genesis block: %v", err)
}
创世块的数据结构
type Genesis struct {
Config *params.ChainConfig `json:"config"`
Nonce uint64 `json:"nonce"`
Timestamp uint64 `json:"timestamp"`
ExtraData []byte `json:"extraData"`
GasLimit uint64 `json:"gasLimit" gencodec:"required"`
Difficulty *big.Int `json:"difficulty" gencodec:"required"`
Mixhash common.Hash `json:"mixHash"`
Coinbase common.Address `json:"coinbase"`
Alloc GenesisAlloc `json:"alloc" gencodec:"required"`
// These fields are used for consensus tests. Please don't use them
// in actual genesis blocks.
Number uint64 `json:"number"`
GasUsed uint64 `json:"gasUsed"`
ParentHash common.Hash `json:"parentHash"`
}
检查创世块的相关处理逻辑，符合逻辑写创世块，或者反馈控制台相应的问题
func SetupGenesisBlock(db ethdb.Database, genesis *Genesis) (*params.ChainConfig, common.Hash, error) {
if genesis != nil && genesis.Config == nil {
return params.AllProtocolChanges, common.Hash{}, errGenesisNoConfig
}
// Just commit the new block if there is no stored genesis block.
stored := GetCanonicalHash(db, 0) //获取genesis对应的区块
if (stored == common.Hash{}) { //如果没有区块 最开始启动geth会进入这里。
if genesis == nil {
//如果genesis是nil 而且stored也是nil 那么使用主网络
// 如果是test dev rinkeby 那么genesis不为空 会设置为各自的genesis
log.Info("Writing default main-net genesis block")
genesis = DefaultGenesisBlock()
} else { // 否则使用配置的区块
log.Info("Writing custom genesis block")
}
// 写入数据库
block, err := genesis.Commit(db)
return genesis.Config, block.Hash(), err
}
// Check whether the genesis block is already written.
if genesis != nil { //如果genesis存在而且区块也存在 那么对比这两个区块是否相同
block, _ := genesis.ToBlock()
hash := block.Hash()
if hash != stored {
return genesis.Config, block.Hash(), &GenesisMismatchError{stored, hash}
}
}
// Get the existing chain configuration.
// 获取当前存在的区块链的genesis配置
newcfg := genesis.configOrDefault(stored)
// 获取当前的区块链的配置
storedcfg, err := GetChainConfig(db, stored)
if err != nil {
if err == ErrChainConfigNotFound {
// This case happens if a genesis write was interrupted.
log.Warn("Found genesis block without chain config")
err = WriteChainConfig(db, stored, newcfg)
}
return newcfg, stored, err
}
// Special case: don't change the existing config of a non-mainnet chain if no new
// config is supplied. These chains would get AllProtocolChanges (and a compat error)
// if we just continued here.
// 特殊情况：如果没有提供新的配置，请不要更改非主网链的现有配置。
// 如果我们继续这里，这些链会得到AllProtocolChanges（和compat错误）。
if genesis == nil && stored != params.MainnetGenesisHash {
return storedcfg, stored, nil // 如果是私有链接会从这里退出。
}
// Check config compatibility and write the config. Compatibility errors
// are returned to the caller unless we're already at block zero.
// 检查配置的兼容性,除非我们在区块0,否则返回兼容性错误.
height := GetBlockNumber(db, GetHeadHeaderHash(db))
if height == missingNumber {
return newcfg, stored, fmt.Errorf("missing block number for head header hash")
}
compatErr := storedcfg.CheckCompatible(newcfg, height)
// 如果区块已经写入数据了,那么就不能更改genesis配置了
if compatErr != nil && height != 0 && compatErr.RewindTo != 0 {
return newcfg, stored, compatErr
}
// 如果是主网络会从这里退出。
return newcfg, stored, WriteChainConfig(db, stored, newcfg)
}
ToBlock, 这个方法使用genesis的数据，使用基于内存的数据库，然后创建了一个block并返回。
// ToBlock creates the block and state of a genesis specification.
func (g *Genesis) ToBlock() (*types.Block, *state.StateDB) {
db, _ := ethdb.NewMemDatabase()
statedb, _ := state.New(common.Hash{}, state.NewDatabase(db))
for addr, account := range g.Alloc {
statedb.AddBalance(addr, account.Balance)
statedb.SetCode(addr, account.Code)
statedb.SetNonce(addr, account.Nonce)
for key, value := range account.Storage {
statedb.SetState(addr, key, value)
}
}
root := statedb.IntermediateRoot(false)
head := &types.Header{
Number: new(big.Int).SetUint64(g.Number),
Nonce: types.EncodeNonce(g.Nonce),
Time: new(big.Int).SetUint64(g.Timestamp),
ParentHash: g.ParentHash,
Extra: g.ExtraData,
GasLimit: new(big.Int).SetUint64(g.GasLimit),
GasUsed: new(big.Int).SetUint64(g.GasUsed),
Difficulty: g.Difficulty,
MixDigest: g.Mixhash,
Coinbase: g.Coinbase,
Root: root,
}
if g.GasLimit == 0 {
head.GasLimit = params.GenesisGasLimit
}
if g.Difficulty == nil {
head.Difficulty = params.GenesisDifficulty
}
return types.NewBlock(head, nil, nil, nil), statedb
}
Commit方法和MustCommit方法, Commit方法把给定的genesis的block和state写入数据库， 这个block被认为是规范的区块链头。
// Commit writes the block and state of a genesis specification to the database.
// The block is committed as the canonical head block.
func (g *Genesis) Commit(db ethdb.Database) (*types.Block, error) {
block, statedb := g.ToBlock()
if block.Number().Sign() != 0 {
return nil, fmt.Errorf("can't commit genesis block with number > 0")
}
if _, err := statedb.CommitTo(db, false); err != nil {
return nil, fmt.Errorf("cannot write state: %v", err)
}
// 写入总难度
if err := WriteTd(db, block.Hash(), block.NumberU64(), g.Difficulty); err != nil {
return nil, err
}
// 写入区块
if err := WriteBlock(db, block); err != nil {
return nil, err
}
// 写入区块收据
if err := WriteBlockReceipts(db, block.Hash(), block.NumberU64(), nil); err != nil {
return nil, err
}
// 写入 headerPrefix + num (uint64 big endian) + numSuffix -> hash
if err := WriteCanonicalHash(db, block.Hash(), block.NumberU64()); err != nil {
return nil, err
}
// 写入 "LastBlock" -> hash
if err := WriteHeadBlockHash(db, block.Hash()); err != nil {
return nil, err
}
// 写入 "LastHeader" -> hash
if err := WriteHeadHeaderHash(db, block.Hash()); err != nil {
return nil, err
}
config := g.Config
if config == nil {
config = params.AllProtocolChanges
}
// 写入 ethereum-config-hash -> config
return block, WriteChainConfig(db, block.Hash(), config)
}
// MustCommit writes the genesis block and state to db, panicking on error.
// The block is committed as the canonical head block.
func (g *Genesis) MustCommit(db ethdb.Database) *types.Block {
block, err := g.Commit(db)
if err != nil {
panic(err)
}
return block
}
返回各种模式的默认Genesis
// DefaultGenesisBlock returns the Ethereum main net genesis block.
func DefaultGenesisBlock() *Genesis {
return &Genesis{
Config: params.MainnetChainConfig,
Nonce: 66,
ExtraData: hexutil.MustDecode("0x11bbe8db4e347b4e8c937c1c8370e4b5ed33adb3db69cbdb7a38e1e50b1b82fa"),
GasLimit: 5000,
Difficulty: big.NewInt(17179869184),
Alloc: decodePrealloc(mainnetAllocData),
}
}
// DefaultTestnetGenesisBlock returns the Ropsten network genesis block.
func DefaultTestnetGenesisBlock() *Genesis {
return &Genesis{
Config: params.TestnetChainConfig,
Nonce: 66,
ExtraData: hexutil.MustDecode("0x3535353535353535353535353535353535353535353535353535353535353535"),
GasLimit: 16777216,
Difficulty: big.NewInt(1048576),
Alloc: decodePrealloc(testnetAllocData),
}
}
// DefaultRinkebyGenesisBlock returns the Rinkeby network genesis block.
func DefaultRinkebyGenesisBlock() *Genesis {
return &Genesis{
Config: params.RinkebyChainConfig,
Timestamp: 1492009146,
ExtraData: hexutil.MustDecode("0x52657370656374206d7920617574686f7269746168207e452e436172746d616e42eb768f2244c8811c63729a21a3569731535f067ffc57839b00206d1ad20c69a1981b489f772031b279182d99e65703f0076e4812653aab85fca0f00000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"),
GasLimit: 4700000,
Difficulty: big.NewInt(1),
Alloc: decodePrealloc(rinkebyAllocData),
}
}
// DevGenesisBlock returns the 'geth --dev' genesis block.
func DevGenesisBlock() *Genesis {
return &Genesis{
Config: params.AllProtocolChanges,
Nonce: 42,
GasLimit: 4712388,
Difficulty: big.NewInt(131072),
Alloc: decodePrealloc(devAllocData),
}
}
GitHub地址：
https://github.com/guoshijiang/go-ethereum-code-analysis
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