core: added basic chain configuration

Added chain configuration options and write out during genesis database
insertion. If no "config" was found, nothing is written to the database.

Configurations are written on a per genesis base. This means
that any chain (which is identified by it's genesis hash) can have their
own chain settings.

core/config.go

@@ -0,0 +1,46 @@
+// Copyright 2016 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 (
+	"errors"
+	"math/big"
+
+	"github.com/ethereum/go-ethereum/core/vm"
+)
+
+var ChainConfigNotFoundErr = errors.New("ChainConfig not found") // general config not found error
+
+// ChainConfig is the core config which determines the blockchain settings.
+//
+// ChainConfig is stored in the database on a per block basis. This means
+// that any network, identified by its genesis block, can have its own
+// set of configuration options.
+type ChainConfig struct {
+	HomesteadBlock *big.Int // homestead switch block
+
+	VmConfig vm.Config `json:"-"`
+}
+
+// IsHomestead returns whether num is either equal to the homestead block or greater.
+func (c *ChainConfig) IsHomestead(num *big.Int) bool {
+	if num == nil {
+		return false
+	}
+
+	return num.Cmp(c.HomesteadBlock) >= 0
+}