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)

1 files changed, 33 insertions, 16 deletions

diff --git a/core/vm/evm.go b/core/vm/evm.go
index 71efcfa45..9296cc7ca 100644
--- a/core/vm/evm.go
+++ b/core/vm/evm.go
@@ -33,7 +33,20 @@ type (
 	GetHashFunc func(uint64) common.Hash
 )
 
-// Context provides the EVM with auxiliary information. Once provided it shouldn't be modified.
+// run runs the given contract and takes care of running precompiles with a fallback to the byte code interpreter.
+func run(evm *EVM, snapshot int, contract *Contract, input []byte) ([]byte, error) {
+	if contract.CodeAddr != nil {
+		precompiledContracts := PrecompiledContracts
+		if p := precompiledContracts[*contract.CodeAddr]; p != nil {
+			return RunPrecompiledContract(p, input, contract)
+		}
+	}
+
+	return evm.interpreter.Run(snapshot, contract, input)
+}
+
+// Context provides the EVM with auxiliary information. Once provided
+// it shouldn't be modified.
 type Context struct {
 	// CanTransfer returns whether the account contains
 	// sufficient ether to transfer the value
@@ -55,7 +68,13 @@ type Context struct {
 	Difficulty  *big.Int       // Provides information for DIFFICULTY
 }
 
-// EVM provides information about external sources for the EVM
+// EVM is the Ethereum Virtual Machine base object and provides
+// the necessary tools to run a contract on the given state with
+// the provided context. It should be noted that any error
+// generated through any of the calls should be considered a
+// revert-state-and-consume-all-gas operation, no checks on
+// specific errors should ever be performed. The interpreter makes
+// sure that any errors generated are to be considered faulty code.
 //
 // The EVM should never be reused and is not thread safe.
 type EVM struct {
@@ -68,6 +87,8 @@ type EVM struct {
 
 	// chainConfig contains information about the current chain
 	chainConfig *params.ChainConfig
+	// chain rules contains the chain rules for the current epoch
+	chainRules params.Rules
 	// virtual machine configuration options used to initialise the
 	// evm.
 	vmConfig Config
@@ -79,21 +100,23 @@ type EVM struct {
 	abort int32
 }
 
-// NewEVM retutrns a new EVM evmironment.
+// NewEVM retutrns a new EVM evmironment. The returned EVM is not thread safe
+// and should only ever be used *once*.
 func NewEVM(ctx Context, statedb StateDB, chainConfig *params.ChainConfig, vmConfig Config) *EVM {
 	evm := &EVM{
 		Context:     ctx,
 		StateDB:     statedb,
 		vmConfig:    vmConfig,
 		chainConfig: chainConfig,
+		chainRules:  chainConfig.Rules(ctx.BlockNumber),
 	}
 
 	evm.interpreter = NewInterpreter(evm, vmConfig)
 	return evm
 }
 
-// Cancel cancels any running EVM operation. This may be called concurrently and it's safe to be
-// called multiple times.
+// Cancel cancels any running EVM operation. This may be called concurrently and
+// it's safe to be called multiple times.
 func (evm *EVM) Cancel() {
 	atomic.StoreInt32(&evm.abort, 1)
 }
@@ -134,13 +157,12 @@ func (evm *EVM) Call(caller ContractRef, addr common.Address, input []byte, gas
 	contract := NewContract(caller, to, value, gas)
 	contract.SetCallCode(&addr, evm.StateDB.GetCodeHash(addr), evm.StateDB.GetCode(addr))
 
-	ret, err = evm.interpreter.Run(contract, input)
+	ret, err = run(evm, snapshot, contract, input)
 	// When an error was returned by the EVM or when setting the creation code
 	// above we revert to the snapshot and consume any gas remaining. Additionally
 	// when we're in homestead this also counts for code storage gas errors.
 	if err != nil {
 		contract.UseGas(contract.Gas)
-
 		evm.StateDB.RevertToSnapshot(snapshot)
 	}
 	return ret, contract.Gas, err
@@ -175,10 +197,9 @@ func (evm *EVM) CallCode(caller ContractRef, addr common.Address, input []byte,
 	contract := NewContract(caller, to, value, gas)
 	contract.SetCallCode(&addr, evm.StateDB.GetCodeHash(addr), evm.StateDB.GetCode(addr))
 
-	ret, err = evm.interpreter.Run(contract, input)
+	ret, err = run(evm, snapshot, contract, input)
 	if err != nil {
 		contract.UseGas(contract.Gas)
-
 		evm.StateDB.RevertToSnapshot(snapshot)
 	}
 
@@ -210,10 +231,9 @@ func (evm *EVM) DelegateCall(caller ContractRef, addr common.Address, input []by
 	contract := NewContract(caller, to, nil, gas).AsDelegate()
 	contract.SetCallCode(&addr, evm.StateDB.GetCodeHash(addr), evm.StateDB.GetCode(addr))
 
-	ret, err = evm.interpreter.Run(contract, input)
+	ret, err = run(evm, snapshot, contract, input)
 	if err != nil {
 		contract.UseGas(contract.Gas)
-
 		evm.StateDB.RevertToSnapshot(snapshot)
 	}
 
@@ -253,8 +273,7 @@ func (evm *EVM) Create(caller ContractRef, code []byte, gas uint64, value *big.I
 	contract := NewContract(caller, AccountRef(contractAddr), value, gas)
 	contract.SetCallCode(&contractAddr, crypto.Keccak256Hash(code), code)
 
-	ret, err = evm.interpreter.Run(contract, nil)
-
+	ret, err = run(evm, snapshot, contract, nil)
 	// check whether the max code size has been exceeded
 	maxCodeSizeExceeded := len(ret) > params.MaxCodeSize
 	// if the contract creation ran successfully and no errors were returned
@@ -275,10 +294,8 @@ func (evm *EVM) Create(caller ContractRef, code []byte, gas uint64, value *big.I
 	// when we're in homestead this also counts for code storage gas errors.
 	if maxCodeSizeExceeded ||
 		(err != nil && (evm.ChainConfig().IsHomestead(evm.BlockNumber) || err != ErrCodeStoreOutOfGas)) {
+		contract.UseGas(contract.Gas)
 		evm.StateDB.RevertToSnapshot(snapshot)
-
-		// Nothing should be returned when an error is thrown.
-		return nil, contractAddr, 0, err
 	}
 	// If the vm returned with an error the return value should be set to nil.
 	// This isn't consensus critical but merely to for behaviour reasons such as