From a58704679ff80cb7a48001fd7d1634b620ee7f8a Mon Sep 17 00:00:00 2001
From: lmittmann <3458786+lmittmann@users.noreply.github.com>
Date: Mon, 13 May 2024 10:05:02 +0200
Subject: [PATCH] added `Address` and `Hash` zero values (#145)

* added `Address` and `Hash` zero values

* cleanup

---------

Co-authored-by: lmittmann <lmittmann@users.noreply.github.com>
---
 util.go            | 6 ++++++
 w3types/message.go | 4 +---
 w3vm/util.go       | 9 ++-------
 w3vm/vm.go         | 8 ++++----
 4 files changed, 13 insertions(+), 14 deletions(-)

diff --git a/util.go b/util.go
index a31aa248..4f3c8fb5 100644
--- a/util.go
+++ b/util.go
@@ -19,6 +19,12 @@ var (
 	BigMaxUint256 = new(big.Int).Sub(new(big.Int).Lsh(Big1, 256), Big1)
 )
 
+// Zero Values.
+var (
+	Addr0 common.Address
+	Hash0 common.Hash
+)
+
 // A returns an address from a hexstring or panics if the hexstring does not
 // represent a valid address.
 //
diff --git a/w3types/message.go b/w3types/message.go
index 03ac5fc5..a046874b 100644
--- a/w3types/message.go
+++ b/w3types/message.go
@@ -10,8 +10,6 @@ import (
 	"github.com/ethereum/go-ethereum/core/types"
 )
 
-var addr0 = common.Address{}
-
 // Message represents a transaction without the signature.
 //
 // If no input data is given, but Func is not null, the input data is
@@ -119,7 +117,7 @@ type message struct {
 // MarshalJSON implements the [json.Marshaler].
 func (msg *Message) MarshalJSON() ([]byte, error) {
 	var enc message
-	if msg.From != addr0 {
+	if msg.From != (common.Address{}) {
 		enc.From = &msg.From
 	}
 	enc.To = msg.To
diff --git a/w3vm/util.go b/w3vm/util.go
index 11a58c17..1b78439f 100644
--- a/w3vm/util.go
+++ b/w3vm/util.go
@@ -13,6 +13,7 @@ import (
 	"github.com/ethereum/go-ethereum/core/tracing"
 	"github.com/ethereum/go-ethereum/core/types"
 	"github.com/holiman/uint256"
+	"github.com/lmittmann/w3"
 	"github.com/lmittmann/w3/internal/crypto"
 	w3hexutil "github.com/lmittmann/w3/internal/hexutil"
 	"github.com/lmittmann/w3/internal/mod"
@@ -20,12 +21,6 @@ import (
 	"github.com/lmittmann/w3/w3types"
 )
 
-// zero values
-var (
-	addr0 common.Address
-	hash0 common.Hash
-)
-
 // RandA returns a random address.
 func RandA() (addr common.Address) {
 	rand.Read(addr[:])
@@ -73,7 +68,7 @@ func nilToZero[T any](ptr *T) *T {
 
 // zeroHashFunc implements a [vm.GetHashFunc] that always returns the zero hash.
 func zeroHashFunc(uint64) common.Hash {
-	return hash0
+	return w3.Hash0
 }
 
 ////////////////////////////////////////////////////////////////////////////////////////////////////
diff --git a/w3vm/vm.go b/w3vm/vm.go
index d2017bbf..dbbb5ef9 100644
--- a/w3vm/vm.go
+++ b/w3vm/vm.go
@@ -58,7 +58,7 @@ func New(opts ...Option) (*VM, error) {
 
 	// set DB
 	db := newDB(vm.opts.fetcher)
-	vm.db, _ = gethState.New(hash0, db, nil)
+	vm.db, _ = gethState.New(w3.Hash0, db, nil)
 	for addr, acc := range vm.opts.preState {
 		vm.db.SetNonce(addr, acc.Nonce)
 		if acc.Balance != nil {
@@ -126,7 +126,7 @@ func (v *VM) apply(msg *w3types.Message, isCall bool, hooks *tracing.Hooks) (*Re
 		GasRefund: result.RefundedGas,
 		GasLimit:  result.UsedGas + v.db.GetRefund(),
 		Output:    result.ReturnData,
-		Logs:      v.db.GetLogs(txHash, 0, hash0),
+		Logs:      v.db.GetLogs(txHash, 0, w3.Hash0),
 	}
 
 	if err := result.Err; err != nil {
@@ -224,14 +224,14 @@ func (vm *VM) Code(addr common.Address) ([]byte, error) {
 func (vm *VM) StorageAt(addr common.Address, slot common.Hash) (common.Hash, error) {
 	val := vm.db.GetState(addr, slot)
 	if vm.db.Error() != nil {
-		return hash0, fmt.Errorf("%w: failed to fetch storage of %s at %s", ErrFetch, addr, slot)
+		return w3.Hash0, fmt.Errorf("%w: failed to fetch storage of %s at %s", ErrFetch, addr, slot)
 	}
 	return val, nil
 }
 
 func (v *VM) buildMessage(msg *w3types.Message, skipAccChecks bool) (*core.Message, *vm.TxContext, error) {
 	nonce := msg.Nonce
-	if !skipAccChecks && nonce == 0 && msg.From != addr0 {
+	if !skipAccChecks && nonce == 0 && msg.From != w3.Addr0 {
 		var err error
 		nonce, err = v.Nonce(msg.From)
 		if err != nil {