1 files changed, 73 insertions, 0 deletions
diff --git a/core/evm.go b/core/evm.go
new file mode 100644
index 000000000..6a5713075
--- /dev/null
+++ b/core/evm.go
@@ -0,0 +1,73 @@
+// 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 core
+
+import (
+	"math/big"
+
+	"github.com/ethereum/go-ethereum/common"
+	"github.com/ethereum/go-ethereum/core/types"
+	"github.com/ethereum/go-ethereum/core/vm"
+)
+
+// BlockFetcher retrieves headers by their hash
+type HeaderFetcher interface {
+	// GetHeader returns the hash corresponding to their hash
+	GetHeader(common.Hash, uint64) *types.Header
+}
+
+// NewEVMContext creates a new context for use in the EVM.
+func NewEVMContext(msg Message, header *types.Header, chain HeaderFetcher) vm.Context {
+	return vm.Context{
+		CanTransfer: CanTransfer,
+		Transfer:    Transfer,
+		GetHash:     GetHashFn(header, chain),
+
+		Origin:      msg.From(),
+		Coinbase:    header.Coinbase,
+		BlockNumber: new(big.Int).Set(header.Number),
+		Time:        new(big.Int).Set(header.Time),
+		Difficulty:  new(big.Int).Set(header.Difficulty),
+		GasLimit:    new(big.Int).Set(header.GasLimit),
+		GasPrice:    new(big.Int).Set(msg.GasPrice()),
+	}
+}
+
+// GetHashFn returns a GetHashFunc which retrieves header hashes by number
+func GetHashFn(ref *types.Header, chain HeaderFetcher) func(n uint64) common.Hash {
+	return func(n uint64) common.Hash {
+		for header := chain.GetHeader(ref.ParentHash, ref.Number.Uint64()-1); header != nil; header = chain.GetHeader(header.ParentHash, header.Number.Uint64()-1) {
+			if header.Number.Uint64() == n {
+				return header.Hash()
+			}
+		}
+
+		return common.Hash{}
+	}
+}
+
+// CanTransfer checks wether there are enough funds in the address' account to make a transfer.
+// This does not take the necessary gas in to account to make the transfer valid.
+func CanTransfer(db vm.StateDB, addr common.Address, amount *big.Int) bool {
+	return db.GetBalance(addr).Cmp(amount) >= 0
+}
+
+// Transfer subtracts amount from sender and adds amount to recipient using the given Db
+func Transfer(db vm.StateDB, sender, recipient common.Address, amount *big.Int) {
+	db.SubBalance(sender, amount)
+	db.AddBalance(recipient, amount)
+}