core: refactor genesis handling

This commit solves several issues concerning the genesis block:

* Genesis/ChainConfig loading was handled by cmd/geth code. This left
  library users in the cold. They could specify a JSON-encoded
  string and overwrite the config, but didn't get any of the additional
  checks performed by geth.
* Decoding and writing of genesis JSON was conflated in
  WriteGenesisBlock. This made it a lot harder to embed the genesis
  block into the forthcoming config file loader. This commit changes
  things so there is a single Genesis type that represents genesis
  blocks. All uses of Write*Genesis* are changed to use the new type
  instead.
* If the chain config supplied by the user was incompatible with the
  current chain (i.e. the chain had already advanced beyond a scheduled
  fork), it got overwritten. This is not an issue in practice because
  previous forks have always had the highest total difficulty. It might
  matter in the future though. The new code reverts the local chain to
  the point of the fork when upgrading configuration.

The change to genesis block data removes compression library
dependencies from package core.

1 files changed, 9 insertions, 25 deletions

diff --git a/core/chain_makers.go b/core/chain_makers.go
index f63496fdc..5bf1ece25 100644
--- a/core/chain_makers.go
+++ b/core/chain_makers.go
@@ -30,19 +30,6 @@ import (
 	"github.com/ethereum/go-ethereum/pow"
 )
 
-/*
- * TODO: move this to another package.
- */
-
-// MakeChainConfig returns a new ChainConfig with the ethereum default chain settings.
-func MakeChainConfig() *params.ChainConfig {
-	return &params.ChainConfig{
-		HomesteadBlock: big.NewInt(0),
-		DAOForkBlock:   nil,
-		DAOForkSupport: true,
-	}
-}
-
 // So we can deterministically seed different blockchains
 var (
 	canonicalSeed = 1
@@ -154,7 +141,7 @@ func (b *BlockGen) OffsetTime(seconds int64) {
 	if b.header.Time.Cmp(b.parent.Header().Time) <= 0 {
 		panic("block time out of range")
 	}
-	b.header.Difficulty = CalcDifficulty(MakeChainConfig(), b.header.Time.Uint64(), b.parent.Time().Uint64(), b.parent.Number(), b.parent.Difficulty())
+	b.header.Difficulty = CalcDifficulty(b.config, b.header.Time.Uint64(), b.parent.Time().Uint64(), b.parent.Number(), b.parent.Difficulty())
 }
 
 // GenerateChain creates a chain of n blocks. The first block's
@@ -170,14 +157,13 @@ func (b *BlockGen) OffsetTime(seconds int64) {
 // values. Inserting them into BlockChain requires use of FakePow or
 // a similar non-validating proof of work implementation.
 func GenerateChain(config *params.ChainConfig, parent *types.Block, db ethdb.Database, n int, gen func(int, *BlockGen)) ([]*types.Block, []types.Receipts) {
+	if config == nil {
+		config = params.TestChainConfig
+	}
 	blocks, receipts := make(types.Blocks, n), make([]types.Receipts, n)
 	genblock := func(i int, h *types.Header, statedb *state.StateDB) (*types.Block, types.Receipts) {
 		b := &BlockGen{parent: parent, i: i, chain: blocks, header: h, statedb: statedb, config: config}
-
 		// Mutate the state and block according to any hard-fork specs
-		if config == nil {
-			config = MakeChainConfig()
-		}
 		if daoBlock := config.DAOForkBlock; daoBlock != nil {
 			limit := new(big.Int).Add(daoBlock, params.DAOForkExtraRange)
 			if h.Number.Cmp(daoBlock) >= 0 && h.Number.Cmp(limit) < 0 {
@@ -226,7 +212,7 @@ func makeHeader(config *params.ChainConfig, parent *types.Block, state *state.St
 		Root:       state.IntermediateRoot(config.IsEIP158(parent.Number())),
 		ParentHash: parent.Hash(),
 		Coinbase:   parent.Coinbase(),
-		Difficulty: CalcDifficulty(MakeChainConfig(), time.Uint64(), new(big.Int).Sub(time, big.NewInt(10)).Uint64(), parent.Number(), parent.Difficulty()),
+		Difficulty: CalcDifficulty(config, time.Uint64(), new(big.Int).Sub(time, big.NewInt(10)).Uint64(), parent.Number(), parent.Difficulty()),
 		GasLimit:   CalcGasLimit(parent),
 		GasUsed:    new(big.Int),
 		Number:     new(big.Int).Add(parent.Number(), common.Big1),
@@ -238,14 +224,12 @@ func makeHeader(config *params.ChainConfig, parent *types.Block, state *state.St
 // chain. Depending on the full flag, if creates either a full block chain or a
 // header only chain.
 func newCanonical(n int, full bool) (ethdb.Database, *BlockChain, error) {
-	// Create the new chain database
-	db, _ := ethdb.NewMemDatabase()
-	evmux := &event.TypeMux{}
-
 	// Initialize a fresh chain with only a genesis block
-	genesis, _ := WriteTestNetGenesisBlock(db)
+	gspec := new(Genesis)
+	db, _ := ethdb.NewMemDatabase()
+	genesis := gspec.MustCommit(db)
 
-	blockchain, _ := NewBlockChain(db, MakeChainConfig(), pow.FakePow{}, evmux, vm.Config{})
+	blockchain, _ := NewBlockChain(db, params.AllProtocolChanges, pow.FakePow{}, new(event.TypeMux), vm.Config{})
 	// Create and inject the requested chain
 	if n == 0 {
 		return db, blockchain, nil