core/vm/runtime: simplified runtime calling mechanism

Implemented `runtime.Call` which uses - unlike Execute - the given state
for the execution and the address of the contract you wish to execute.
Unlike `Execute`, `Call` requires a config.

core/vm/runtime/runtime.go

@@ -41,6 +41,7 @@ type Config struct {
 	DisableJit  bool // "disable" so it's enabled by default
 	Debug       bool
 
+	State     *state.StateDB
 	GetHashFn func(n uint64) common.Hash
 }
 
@@ -94,12 +95,14 @@ func Execute(code, input []byte, cfg *Config) ([]byte, *state.StateDB, error) {
 	vm.EnableJit = !cfg.DisableJit
 	vm.Debug = cfg.Debug
 
+	if cfg.State == nil {
+		db, _ := ethdb.NewMemDatabase()
+		cfg.State, _ = state.New(common.Hash{}, db)
+	}
 	var (
-		db, _      = ethdb.NewMemDatabase()
-		statedb, _ = state.New(common.Hash{}, db)
-		vmenv      = NewEnv(cfg, statedb)
-		sender     = statedb.CreateAccount(cfg.Origin)
-		receiver   = statedb.CreateAccount(common.StringToAddress("contract"))
+		vmenv    = NewEnv(cfg, cfg.State)
+		sender   = cfg.State.CreateAccount(cfg.Origin)
+		receiver = cfg.State.CreateAccount(common.StringToAddress("contract"))
 	)
 	// set the receiver's (the executing contract) code for execution.
 	receiver.SetCode(code)
@@ -117,5 +120,43 @@ func Execute(code, input []byte, cfg *Config) ([]byte, *state.StateDB, error) {
 	if cfg.Debug {
 		vm.StdErrFormat(vmenv.StructLogs())
 	}
-	return ret, statedb, err
+	return ret, cfg.State, err
+}
+
+// Call executes the code given by the contract's address. It will return the
+// EVM's return value or an error if it failed.
+//
+// Call, unlike Execute, requires a config and also requires the State field to
+// be set.
+func Call(address common.Address, input []byte, cfg *Config) ([]byte, error) {
+	setDefaults(cfg)
+
+	// defer the call to setting back the original values
+	defer func(debug, forceJit, enableJit bool) {
+		vm.Debug = debug
+		vm.ForceJit = forceJit
+		vm.EnableJit = enableJit
+	}(vm.Debug, vm.ForceJit, vm.EnableJit)
+
+	vm.ForceJit = !cfg.DisableJit
+	vm.EnableJit = !cfg.DisableJit
+	vm.Debug = cfg.Debug
+
+	vmenv := NewEnv(cfg, cfg.State)
+
+	sender := cfg.State.GetOrNewStateObject(cfg.Origin)
+	// Call the code with the given configuration.
+	ret, err := vmenv.Call(
+		sender,
+		address,
+		input,
+		cfg.GasLimit,
+		cfg.GasPrice,
+		cfg.Value,
+	)
+
+	if cfg.Debug {
+		vm.StdErrFormat(vmenv.StructLogs())
+	}
+	return ret, err
 }

core/vm/runtime/runtime_test.go

@@ -17,12 +17,15 @@
 package runtime
 
 import (
+	"math/big"
 	"strings"
 	"testing"
 
 	"github.com/ethereum/go-ethereum/accounts/abi"
 	"github.com/ethereum/go-ethereum/common"
+	"github.com/ethereum/go-ethereum/core/state"
 	"github.com/ethereum/go-ethereum/core/vm"
+	"github.com/ethereum/go-ethereum/ethdb"
 )
 
 func TestDefaults(t *testing.T) {
@@ -71,6 +74,49 @@ func TestEnvironment(t *testing.T) {
 	}, nil, nil)
 }
 
+func TestExecute(t *testing.T) {
+	ret, _, err := Execute([]byte{
+		byte(vm.PUSH1), 10,
+		byte(vm.PUSH1), 0,
+		byte(vm.MSTORE),
+		byte(vm.PUSH1), 32,
+		byte(vm.PUSH1), 0,
+		byte(vm.RETURN),
+	}, nil, nil)
+	if err != nil {
+		t.Fatal("didn't expect error", err)
+	}
+
+	num := common.BytesToBig(ret)
+	if num.Cmp(big.NewInt(10)) != 0 {
+		t.Error("Expected 10, got", num)
+	}
+}
+
+func TestCall(t *testing.T) {
+	db, _ := ethdb.NewMemDatabase()
+	state, _ := state.New(common.Hash{}, db)
+	address := common.HexToAddress("0x0a")
+	state.SetCode(address, []byte{
+		byte(vm.PUSH1), 10,
+		byte(vm.PUSH1), 0,
+		byte(vm.MSTORE),
+		byte(vm.PUSH1), 32,
+		byte(vm.PUSH1), 0,
+		byte(vm.RETURN),
+	})
+
+	ret, err := Call(address, nil, &Config{State: state})
+	if err != nil {
+		t.Fatal("didn't expect error", err)
+	}
+
+	num := common.BytesToBig(ret)
+	if num.Cmp(big.NewInt(10)) != 0 {
+		t.Error("Expected 10, got", num)
+	}
+}
+
 func TestRestoreDefaults(t *testing.T) {
 	Execute(nil, nil, &Config{Debug: true})
 	if vm.ForceJit {

core/vm_env.go

@@ -25,6 +25,21 @@ import (
 	"github.com/ethereum/go-ethereum/core/vm"
 )
 
+// GetHashFn returns a function for which the VM env can query block hashes thru
+// up to the limit defined by the Yellow Paper and uses the given block chain
+// to query for information.
+func GetHashFn(ref common.Hash, chain *BlockChain) func(n uint64) common.Hash {
+	return func(n uint64) common.Hash {
+		for block := chain.GetBlock(ref); block != nil; block = chain.GetBlock(block.ParentHash()) {
+			if block.NumberU64() == n {
+				return block.Hash()
+			}
+		}
+
+		return common.Hash{}
+	}
+}
+
 type VMEnv struct {
 	state  *state.StateDB
 	header *types.Header
@@ -32,17 +47,20 @@ type VMEnv struct {
 	depth  int
 	chain  *BlockChain
 	typ    vm.Type
+
+	getHashFn func(uint64) common.Hash
 	// structured logging
 	logs []vm.StructLog
 }
 
 func NewEnv(state *state.StateDB, chain *BlockChain, msg Message, header *types.Header) *VMEnv {
 	return &VMEnv{
-		chain:  chain,
-		state:  state,
-		header: header,
-		msg:    msg,
-		typ:    vm.StdVmTy,
+		chain:     chain,
+		state:     state,
+		header:    header,
+		msg:       msg,
+		typ:       vm.StdVmTy,
+		getHashFn: GetHashFn(header.ParentHash, chain),
 	}
 }
 
@@ -59,13 +77,7 @@ func (self *VMEnv) SetDepth(i int)           { self.depth = i }
 func (self *VMEnv) VmType() vm.Type          { return self.typ }
 func (self *VMEnv) SetVmType(t vm.Type)      { self.typ = t }
 func (self *VMEnv) GetHash(n uint64) common.Hash {
-	for block := self.chain.GetBlock(self.header.ParentHash); block != nil; block = self.chain.GetBlock(block.ParentHash()) {
-		if block.NumberU64() == n {
-			return block.Hash()
-		}
-	}
-
-	return common.Hash{}
+	return self.getHashFn(n)
 }
 
 func (self *VMEnv) AddLog(log *vm.Log) {