consensus, core/*, params: metropolis preparation refactor

This commit is a preparation for the upcoming metropolis hardfork. It
prepares the state, core and vm packages such that integration with
metropolis becomes less of a hassle.

* Difficulty calculation requires header instead of individual
  parameters
* statedb.StartRecord renamed to statedb.Prepare and added Finalise
  method required by metropolis, which removes unwanted accounts from
  the state (i.e. selfdestruct)
* State keeps record of destructed objects (in addition to dirty
  objects)
* core/vm pre-compiles may now return errors
* core/vm pre-compiles gas check now take the full byte slice as argument
  instead of just the size
* core/vm now keeps several hard-fork instruction tables instead of a
  single instruction table and removes the need for hard-fork checks in
  the instructions
* core/vm contains a empty restruction function which is added in
  preparation of metropolis write-only mode operations
* Adds the bn256 curve
* Adds and sets the metropolis chain config block parameters (2^64-1)

2 files changed, 62 insertions, 25 deletions

diff --git a/params/config.go b/params/config.go
index bc63a45b9..5fb414d62 100644
--- a/params/config.go
+++ b/params/config.go
@@ -26,28 +26,32 @@ import (
 var (
 	// MainnetChainConfig is the chain parameters to run a node on the main network.
 	MainnetChainConfig = &ChainConfig{
-		ChainId:        MainNetChainID,
-		HomesteadBlock: MainNetHomesteadBlock,
-		DAOForkBlock:   MainNetDAOForkBlock,
-		DAOForkSupport: true,
-		EIP150Block:    MainNetHomesteadGasRepriceBlock,
-		EIP150Hash:     MainNetHomesteadGasRepriceHash,
-		EIP155Block:    MainNetSpuriousDragon,
-		EIP158Block:    MainNetSpuriousDragon,
-		Ethash:         new(EthashConfig),
+		ChainId:         MainNetChainID,
+		HomesteadBlock:  MainNetHomesteadBlock,
+		DAOForkBlock:    MainNetDAOForkBlock,
+		DAOForkSupport:  true,
+		EIP150Block:     MainNetHomesteadGasRepriceBlock,
+		EIP150Hash:      MainNetHomesteadGasRepriceHash,
+		EIP155Block:     MainNetSpuriousDragon,
+		EIP158Block:     MainNetSpuriousDragon,
+		MetropolisBlock: MainNetMetropolisBlock,
+
+		Ethash: new(EthashConfig),
 	}
 
 	// TestnetChainConfig contains the chain parameters to run a node on the Ropsten test network.
 	TestnetChainConfig = &ChainConfig{
-		ChainId:        big.NewInt(3),
-		HomesteadBlock: big.NewInt(0),
-		DAOForkBlock:   nil,
-		DAOForkSupport: true,
-		EIP150Block:    big.NewInt(0),
-		EIP150Hash:     common.HexToHash("0x41941023680923e0fe4d74a34bdac8141f2540e3ae90623718e47d66d1ca4a2d"),
-		EIP155Block:    big.NewInt(10),
-		EIP158Block:    big.NewInt(10),
-		Ethash:         new(EthashConfig),
+		ChainId:         big.NewInt(3),
+		HomesteadBlock:  big.NewInt(0),
+		DAOForkBlock:    nil,
+		DAOForkSupport:  true,
+		EIP150Block:     big.NewInt(0),
+		EIP150Hash:      common.HexToHash("0x41941023680923e0fe4d74a34bdac8141f2540e3ae90623718e47d66d1ca4a2d"),
+		EIP155Block:     big.NewInt(10),
+		EIP158Block:     big.NewInt(10),
+		MetropolisBlock: TestNetMetropolisBlock,
+
+		Ethash: new(EthashConfig),
 	}
 
 	// RinkebyChainConfig contains the chain parameters to run a node on the Rinkeby test network.
@@ -68,15 +72,15 @@ var (
 
 	// AllProtocolChanges contains every protocol change (EIPs)
 	// introduced and accepted by the Ethereum core developers.
-	// TestChainConfig is like AllProtocolChanges but has chain ID 1.
 	//
 	// This configuration is intentionally not using keyed fields.
 	// This configuration must *always* have all forks enabled, which
 	// means that all fields must be set at all times. This forces
 	// anyone adding flags to the config to also have to set these
 	// fields.
-	AllProtocolChanges = &ChainConfig{big.NewInt(1337), big.NewInt(0), nil, false, big.NewInt(0), common.Hash{}, big.NewInt(0), big.NewInt(0), new(EthashConfig), nil}
-	TestChainConfig    = &ChainConfig{big.NewInt(1), big.NewInt(0), nil, false, big.NewInt(0), common.Hash{}, big.NewInt(0), big.NewInt(0), new(EthashConfig), nil}
+	AllProtocolChanges = &ChainConfig{big.NewInt(1337), big.NewInt(0), nil, false, big.NewInt(0), common.Hash{}, big.NewInt(0), big.NewInt(0), big.NewInt(0), new(EthashConfig), nil}
+	TestChainConfig    = &ChainConfig{big.NewInt(1), big.NewInt(0), nil, false, big.NewInt(0), common.Hash{}, big.NewInt(0), big.NewInt(0), nil, new(EthashConfig), nil}
+	TestRules          = TestChainConfig.Rules(new(big.Int))
 )
 
 // ChainConfig is the core config which determines the blockchain settings.
@@ -95,8 +99,10 @@ type ChainConfig struct {
 	EIP150Block *big.Int    `json:"eip150Block,omitempty"` // EIP150 HF block (nil = no fork)
 	EIP150Hash  common.Hash `json:"eip150Hash,omitempty"`  // EIP150 HF hash (fast sync aid)
 
-	EIP155Block *big.Int `json:"eip155Block,omitempty"` // EIP155 HF block
-	EIP158Block *big.Int `json:"eip158Block,omitempty"` // EIP158 HF block
+	EIP155Block *big.Int `json:"eip155Block"` // EIP155 HF block
+	EIP158Block *big.Int `json:"eip158Block"` // EIP158 HF block
+
+	MetropolisBlock *big.Int `json:"metropolisBlock"` // Metropolis switch block (nil = no fork, 0 = alraedy on homestead)
 
 	// Various consensus engines
 	Ethash *EthashConfig `json:"ethash,omitempty"`
@@ -141,6 +147,7 @@ func (c *ChainConfig) String() string {
 		c.EIP150Block,
 		c.EIP155Block,
 		c.EIP158Block,
+		c.MetropolisBlock,
 		engine,
 	)
 }
@@ -251,6 +258,13 @@ func configNumEqual(x, y *big.Int) bool {
 	return x.Cmp(y) == 0
 }
 
+func (c *ChainConfig) IsMetropolis(num *big.Int) bool {
+	if c.MetropolisBlock == nil || num == nil {
+		return false
+	}
+	return num.Cmp(c.MetropolisBlock) >= 0
+}
+
 // ConfigCompatError is raised if the locally-stored blockchain is initialised with a
 // ChainConfig that would alter the past.
 type ConfigCompatError struct {
@@ -281,3 +295,22 @@ func newCompatError(what string, storedblock, newblock *big.Int) *ConfigCompatEr
 func (err *ConfigCompatError) Error() string {
 	return fmt.Sprintf("mismatching %s in database (have %d, want %d, rewindto %d)", err.What, err.StoredConfig, err.NewConfig, err.RewindTo)
 }
+
+// Rules wraps ChainConfig and is merely syntatic sugar or can be used for functions
+// that do not have or require information about the block.
+//
+// Rules is a one time interface meaning that it shouldn't be used in between transition
+// phases.
+type Rules struct {
+	ChainId                                   *big.Int
+	IsHomestead, IsEIP150, IsEIP155, IsEIP158 bool
+	IsMetropolis                              bool
+}
+
+func (c *ChainConfig) Rules(num *big.Int) Rules {
+	chainId := c.ChainId
+	if chainId == nil {
+		chainId = new(big.Int)
+	}
+	return Rules{ChainId: new(big.Int).Set(chainId), IsHomestead: c.IsHomestead(num), IsEIP150: c.IsEIP150(num), IsEIP155: c.IsEIP155(num), IsEIP158: c.IsEIP158(num), IsMetropolis: c.IsMetropolis(num)}
+}
diff --git a/params/util.go b/params/util.go
index bf833d510..d4d43d047 100644
--- a/params/util.go
+++ b/params/util.go
@@ -17,6 +17,7 @@
 package params
 
 import (
+	"math"
 	"math/big"
 
 	"github.com/ethereum/go-ethereum/common"
@@ -38,6 +39,9 @@ var (
 	TestNetSpuriousDragon = big.NewInt(10)
 	MainNetSpuriousDragon = big.NewInt(2675000)
 
-	TestNetChainID = big.NewInt(3) // Testnet default chain ID
-	MainNetChainID = big.NewInt(1) // Mainnet default chain ID
+	TestNetMetropolisBlock = big.NewInt(math.MaxInt64)
+	MainNetMetropolisBlock = big.NewInt(math.MaxInt64)
+
+	TestNetChainID = big.NewInt(3) // Test net default chain ID
+	MainNetChainID = big.NewInt(1) // main net default chain ID
 )