cmd/evm, core/vm, test: refactored VM and core

* Moved `vm.Transfer` to `core` package and changed execution to call
`env.Transfer` instead of `core.Transfer` directly.
* core/vm: byte code VM moved to jump table instead of switch
* Moved `vm.Transfer` to `core` package and changed execution to call
  `env.Transfer` instead of `core.Transfer` directly.
* Byte code VM now shares the same code as the JITVM
* Renamed Context to Contract
* Changed initialiser of state transition & unexported methods
* Removed the Execution object and refactor `Call`, `CallCode` &
  `Create` in to their own functions instead of being methods.
* Removed the hard dep on the state for the VM. The VM now
  depends on a Database interface returned by the environment. In the
  process the core now depends less on the statedb by usage of the env
* Moved `Log` from package `core/state` to package `core/vm`.

core/vm/contract.go

@@ -0,0 +1,126 @@
+// Copyright 2014 The go-ethereum Authors
+// This file is part of the go-ethereum library.
+//
+// The go-ethereum library is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Lesser General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// The go-ethereum library is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+// GNU Lesser General Public License for more details.
+//
+// You should have received a copy of the GNU Lesser General Public License
+// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
+
+package vm
+
+import (
+	"math/big"
+
+	"github.com/ethereum/go-ethereum/common"
+)
+
+// ContractRef is a reference to the contract's backing object
+type ContractRef interface {
+	ReturnGas(*big.Int, *big.Int)
+	Address() common.Address
+	SetCode([]byte)
+}
+
+// Contract represents an ethereum contract in the state database. It contains
+// the the contract code, calling arguments. Contract implements ContractReg
+type Contract struct {
+	caller ContractRef
+	self   ContractRef
+
+	jumpdests destinations // result of JUMPDEST analysis.
+
+	Code     []byte
+	Input    []byte
+	CodeAddr *common.Address
+
+	value, Gas, UsedGas, Price *big.Int
+
+	Args []byte
+}
+
+// Create a new context for the given data items.
+func NewContract(caller ContractRef, object ContractRef, value, gas, price *big.Int) *Contract {
+	c := &Contract{caller: caller, self: object, Args: nil}
+
+	if parent, ok := caller.(*Contract); ok {
+		// Reuse JUMPDEST analysis from parent context if available.
+		c.jumpdests = parent.jumpdests
+	} else {
+		c.jumpdests = make(destinations)
+	}
+
+	// Gas should be a pointer so it can safely be reduced through the run
+	// This pointer will be off the state transition
+	c.Gas = gas //new(big.Int).Set(gas)
+	c.value = new(big.Int).Set(value)
+	// In most cases price and value are pointers to transaction objects
+	// and we don't want the transaction's values to change.
+	c.Price = new(big.Int).Set(price)
+	c.UsedGas = new(big.Int)
+
+	return c
+}
+
+// GetOp returns the n'th element in the contract's byte array
+func (c *Contract) GetOp(n uint64) OpCode {
+	return OpCode(c.GetByte(n))
+}
+
+// GetByte returns the n'th byte in the contract's byte array
+func (c *Contract) GetByte(n uint64) byte {
+	if n < uint64(len(c.Code)) {
+		return c.Code[n]
+	}
+
+	return 0
+}
+
+// Return returns the given ret argument and returns any remaining gas to the
+// caller
+func (c *Contract) Return(ret []byte) []byte {
+	// Return the remaining gas to the caller
+	c.caller.ReturnGas(c.Gas, c.Price)
+
+	return ret
+}
+
+// UseGas attempts the use gas and subtracts it and returns true on success
+func (c *Contract) UseGas(gas *big.Int) (ok bool) {
+	ok = useGas(c.Gas, gas)
+	if ok {
+		c.UsedGas.Add(c.UsedGas, gas)
+	}
+	return
+}
+
+// ReturnGas adds the given gas back to itself.
+func (c *Contract) ReturnGas(gas, price *big.Int) {
+	// Return the gas to the context
+	c.Gas.Add(c.Gas, gas)
+	c.UsedGas.Sub(c.UsedGas, gas)
+}
+
+// Address returns the contracts address
+func (c *Contract) Address() common.Address {
+	return c.self.Address()
+}
+
+// SetCode sets the code to the contract
+func (self *Contract) SetCode(code []byte) {
+	self.Code = code
+}
+
+// SetCallCode sets the address of the code address and sets the code
+// of the contract according to the backing database.
+func (self *Contract) SetCallCode(addr *common.Address, code []byte) {
+	self.Code = code
+	self.CodeAddr = addr
+}