core, core/state, trie: EIP158, reprice & skip empty account write

This commit implements EIP158 part 1, 2, 3 & 4

1. If an account is empty it's no longer written to the trie. An empty
  account is defined as (balance=0, nonce=0, storage=0, code=0).
2. Delete an empty account if it's touched
3. An empty account is redefined as either non-existent or empty.
4. Zero value calls and zero value suicides no longer consume the 25k
  reation costs.

params: moved core/config to params

Signed-off-by: Jeffrey Wilcke <jeffrey@ethereum.org>

params/config.go

@@ -0,0 +1,84 @@
+// 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 params
+
+import (
+	"math/big"
+
+	"github.com/ethereum/go-ethereum/common"
+)
+
+// 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 `json:"homesteadBlock"` // Homestead switch block (nil = no fork, 0 = already homestead)
+	DAOForkBlock   *big.Int `json:"daoForkBlock"`   // TheDAO hard-fork switch block (nil = no fork)
+	DAOForkSupport bool     `json:"daoForkSupport"` // Whether the nodes supports or opposes the DAO hard-fork
+
+	// EIP150 implements the Gas price changes (https://github.com/ethereum/EIPs/issues/150)
+	EIP150Block *big.Int    `json:"EIP150Block"` // EIP150 HF block (nil = no fork)
+	EIP150Hash  common.Hash `json:"EIP150Hash"`  // EIP150 HF hash (fast sync aid)
+
+	EIP158Block *big.Int `json:"EIP158Block"` // EIP158 HF block
+}
+
+var TestChainConfig = &ChainConfig{new(big.Int), new(big.Int), true, new(big.Int), common.Hash{}, new(big.Int)}
+
+// IsHomestead returns whether num is either equal to the homestead block or greater.
+func (c *ChainConfig) IsHomestead(num *big.Int) bool {
+	if c.HomesteadBlock == nil || num == nil {
+		return false
+	}
+	return num.Cmp(c.HomesteadBlock) >= 0
+}
+
+// GasTable returns the gas table corresponding to the current phase (homestead or homestead reprice).
+//
+// The returned GasTable's fields shouldn't, under any circumstances, be changed.
+func (c *ChainConfig) GasTable(num *big.Int) GasTable {
+	if num == nil {
+		return GasTableHomestead
+	}
+
+	switch {
+	case c.EIP158Block != nil && num.Cmp(c.EIP158Block) >= 0:
+		return GasTableEIP158
+	case c.EIP150Block != nil && num.Cmp(c.EIP150Block) >= 0:
+		return GasTableHomesteadGasRepriceFork
+	default:
+		return GasTableHomestead
+	}
+}
+
+func (c *ChainConfig) IsEIP150(num *big.Int) bool {
+	if c.EIP150Block == nil || num == nil {
+		return false
+	}
+	return num.Cmp(c.EIP150Block) >= 0
+
+}
+
+func (c *ChainConfig) IsEIP158(num *big.Int) bool {
+	if c.EIP158Block == nil || num == nil {
+		return false
+	}
+	return num.Cmp(c.EIP158Block) >= 0
+
+}