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, 8 insertions, 10 deletions

diff --git a/accounts/abi/bind/backends/simulated.go b/accounts/abi/bind/backends/simulated.go
index 2f5719c78..3d7e96bf6 100644
--- a/accounts/abi/bind/backends/simulated.go
+++ b/accounts/abi/bind/backends/simulated.go
@@ -37,9 +37,6 @@ import (
 	"github.com/ethereum/go-ethereum/pow"
 )
 
-// Default chain configuration which sets homestead phase at block 0 (i.e. no frontier)
-var chainConfig = &params.ChainConfig{HomesteadBlock: big.NewInt(0), EIP150Block: new(big.Int), EIP158Block: new(big.Int)}
-
 // This nil assignment ensures compile time that SimulatedBackend implements bind.ContractBackend.
 var _ bind.ContractBackend = (*SimulatedBackend)(nil)
 
@@ -60,11 +57,12 @@ type SimulatedBackend struct {
 
 // NewSimulatedBackend creates a new binding backend using a simulated blockchain
 // for testing purposes.
-func NewSimulatedBackend(accounts ...core.GenesisAccount) *SimulatedBackend {
+func NewSimulatedBackend(alloc core.GenesisAlloc) *SimulatedBackend {
 	database, _ := ethdb.NewMemDatabase()
-	core.WriteGenesisBlockForTesting(database, accounts...)
-	blockchain, _ := core.NewBlockChain(database, chainConfig, new(pow.FakePow), new(event.TypeMux), vm.Config{})
-	backend := &SimulatedBackend{database: database, blockchain: blockchain}
+	genesis := core.Genesis{Config: params.AllProtocolChanges, Alloc: alloc}
+	genesis.MustCommit(database)
+	blockchain, _ := core.NewBlockChain(database, genesis.Config, new(pow.FakePow), new(event.TypeMux), vm.Config{})
+	backend := &SimulatedBackend{database: database, blockchain: blockchain, config: genesis.Config}
 	backend.rollback()
 	return backend
 }
@@ -90,7 +88,7 @@ func (b *SimulatedBackend) Rollback() {
 }
 
 func (b *SimulatedBackend) rollback() {
-	blocks, _ := core.GenerateChain(chainConfig, b.blockchain.CurrentBlock(), b.database, 1, func(int, *core.BlockGen) {})
+	blocks, _ := core.GenerateChain(b.config, b.blockchain.CurrentBlock(), b.database, 1, func(int, *core.BlockGen) {})
 	b.pendingBlock = blocks[0]
 	b.pendingState, _ = state.New(b.pendingBlock.Root(), b.database)
 }
@@ -253,7 +251,7 @@ func (b *SimulatedBackend) callContract(ctx context.Context, call ethereum.CallM
 	evmContext := core.NewEVMContext(msg, block.Header(), b.blockchain)
 	// Create a new environment which holds all relevant information
 	// about the transaction and calling mechanisms.
-	vmenv := vm.NewEVM(evmContext, statedb, chainConfig, vm.Config{})
+	vmenv := vm.NewEVM(evmContext, statedb, b.config, vm.Config{})
 	gaspool := new(core.GasPool).AddGas(math.MaxBig256)
 	ret, gasUsed, _, err := core.NewStateTransition(vmenv, msg, gaspool).TransitionDb()
 	return ret, gasUsed, err
@@ -274,7 +272,7 @@ func (b *SimulatedBackend) SendTransaction(ctx context.Context, tx *types.Transa
 		panic(fmt.Errorf("invalid transaction nonce: got %d, want %d", tx.Nonce(), nonce))
 	}
 
-	blocks, _ := core.GenerateChain(chainConfig, b.blockchain.CurrentBlock(), b.database, 1, func(number int, block *core.BlockGen) {
+	blocks, _ := core.GenerateChain(b.config, b.blockchain.CurrentBlock(), b.database, 1, func(number int, block *core.BlockGen) {
 		for _, tx := range b.pendingBlock.Transactions() {
 			block.AddTx(tx)
 		}