From 58374e28d95c03d8b0e6d9035c0fb92fad3e865e Mon Sep 17 00:00:00 2001
From: Martin Holst Swende <martin@swende.se>
Date: Sat, 11 Aug 2018 23:03:54 +0200
Subject: core, state: initial implementation of Eip-1283

---
 core/vm/gas_table.go | 59 +++++++++++++++++++++++++++++++++++++++++++++++++++-
 core/vm/interface.go |  1 +
 core/vm/noop.go      |  1 +
 3 files changed, 60 insertions(+), 1 deletion(-)

(limited to 'core/vm')

diff --git a/core/vm/gas_table.go b/core/vm/gas_table.go
index f9eea319e..aee6d6f6d 100644
--- a/core/vm/gas_table.go
+++ b/core/vm/gas_table.go
@@ -17,9 +17,11 @@
 package vm
 
 import (
+	"bytes"
 	"github.com/ethereum/go-ethereum/common"
 	"github.com/ethereum/go-ethereum/common/math"
 	"github.com/ethereum/go-ethereum/params"
+	"math/big"
 )
 
 // memoryGasCosts calculates the quadratic gas for memory expansion. It does so
@@ -115,7 +117,7 @@ func gasReturnDataCopy(gt params.GasTable, evm *EVM, contract *Contract, stack *
 	return gas, nil
 }
 
-func gasSStore(gt params.GasTable, evm *EVM, contract *Contract, stack *Stack, mem *Memory, memorySize uint64) (uint64, error) {
+func gasSStoreOld(gt params.GasTable, evm *EVM, contract *Contract, stack *Stack, mem *Memory, memorySize uint64) (uint64, error) {
 	var (
 		y, x = stack.Back(1), stack.Back(0)
 		val  = evm.StateDB.GetState(contract.Address(), common.BigToHash(x))
@@ -137,6 +139,61 @@ func gasSStore(gt params.GasTable, evm *EVM, contract *Contract, stack *Stack, m
 	}
 }
 
+func gasSStore(gt params.GasTable, evm *EVM, contract *Contract, stack *Stack, mem *Memory, memorySize uint64) (uint64, error) {
+	var (
+		y, x = stack.Back(1), stack.Back(0)
+		current  = evm.StateDB.GetState(contract.Address(), common.BigToHash(x))
+	)
+	//1. If current value equals new value (this is a no-op), 200 gas is deducted.
+	//2. If current value does not equal new value
+	//  2.1 If original value equals current value (this storage slot has not been changed by the current execution context)
+	//    2.1.1 If original value is 0, 20000 gas is deducted.
+	//	  2.1.2 Otherwise, 5000 gas is deducted. If new value is 0, add 15000 gas to refund counter.
+	//	2.2 If original value does not equal current value (this storage slot is dirty), 200 gas is deducted. Apply both of the following clauses.
+	//	  2.2.1 If original value is not 0
+	//      2.2.1.1 If current value is 0 (also means that new value is not 0), remove 15000 gas from refund counter. We can prove that refund counter will never go below 0.
+	//      2.2.1.2 If new value is 0 (also means that current value is not 0), add 15000 gas to refund counter.
+	//	  2.2.2 If original value equals new value (this storage slot is reset)
+	//      2.2.2.1 If original value is 0, add 19800 gas to refund counter.
+	//	    2.2.2.2 Otherwise, add 4800 gas to refund counter.
+	new := common.BigToHash(y)
+	if current == new {
+		// 1. current == new
+		return 200, nil
+	}
+	// Todo, get this value
+	original := common.Hash{}
+
+	// 2
+	if original == current { // 2.1
+		if original == (common.Hash{}){ // 2.1.1
+			return 20000, nil
+		}
+		// 2.1.2
+		if new == (common.Hash{}){
+			evm.StateDB.AddRefund(15000)
+		}
+		return 5000, nil
+	}
+	// 2.2
+	if original != (common.Hash{}){ // 2.2.1
+		if current == (common.Hash{}){ // 2.2.1.1
+			evm.StateDB.SubRefund(15000)
+		}else{
+			// 2.2.1.2
+			evm.StateDB.AddRefund(15000)
+		}
+	}
+	if original == new { // 2.2.2
+		if original == (common.Hash{}){
+			evm.StateDB.AddRefund(19800)
+		}else{
+			evm.StateDB.AddRefund(4800)
+		}
+	}
+	return 200, nil
+}
+
 func makeGasLog(n uint64) gasFunc {
 	return func(gt params.GasTable, evm *EVM, contract *Contract, stack *Stack, mem *Memory, memorySize uint64) (uint64, error) {
 		requestedSize, overflow := bigUint64(stack.Back(1))
diff --git a/core/vm/interface.go b/core/vm/interface.go
index d176f5b39..a5a3ff3e3 100644
--- a/core/vm/interface.go
+++ b/core/vm/interface.go
@@ -40,6 +40,7 @@ type StateDB interface {
 	GetCodeSize(common.Address) int
 
 	AddRefund(uint64)
+	SubRefund(uint64)
 	GetRefund() uint64
 
 	GetState(common.Address, common.Hash) common.Hash
diff --git a/core/vm/noop.go b/core/vm/noop.go
index b71ead0d7..c7ed2e451 100644
--- a/core/vm/noop.go
+++ b/core/vm/noop.go
@@ -56,6 +56,7 @@ func (NoopStateDB) GetCode(common.Address) []byte
 func (NoopStateDB) SetCode(common.Address, []byte)                                     {}
 func (NoopStateDB) GetCodeSize(common.Address) int                                     { return 0 }
 func (NoopStateDB) AddRefund(uint64)                                                   {}
+func (NoopStateDB) SubRefund(uint64)                                                   {}
 func (NoopStateDB) GetRefund() uint64                                                  { return 0 }
 func (NoopStateDB) GetState(common.Address, common.Hash) common.Hash                   { return common.Hash{} }
 func (NoopStateDB) SetState(common.Address, common.Hash, common.Hash)                  {}
-- 
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