From 721748acfd47d4607fbeb30e26c2c333cdc4cffc Mon Sep 17 00:00:00 2001
From: Evgeniy Stratonikov <evgeniy@nspcc.ru>
Date: Wed, 5 May 2021 17:48:40 +0300
Subject: [PATCH 1/2] examples: change NFT contract to use storage iterators

---
 cli/nep11_test.go      |  14 ++--
 examples/nft-nd/nft.go | 145 ++++++++++++++++-------------------------
 2 files changed, 67 insertions(+), 92 deletions(-)

diff --git a/cli/nep11_test.go b/cli/nep11_test.go
index 035561466..e40d5bc05 100644
--- a/cli/nep11_test.go
+++ b/cli/nep11_test.go
@@ -1,6 +1,7 @@
 package main
 
 import (
+	"bytes"
 	"fmt"
 	"io"
 	"io/ioutil"
@@ -233,8 +234,13 @@ func TestNEP11_OwnerOf_BalanceOf_Transfer(t *testing.T) {
 	// tokensOf: good, several tokens
 	tokenID1 := mint(t)
 	e.Run(t, cmdTokensOf...)
-	e.checkNextLine(t, string(tokenID))
-	e.checkNextLine(t, string(tokenID1))
+	fst, snd := tokenID, tokenID1
+	if bytes.Compare(tokenID, tokenID1) == 1 {
+		fst, snd = snd, fst
+	}
+
+	e.checkNextLine(t, string(fst))
+	e.checkNextLine(t, string(snd))
 
 	// tokens: missing contract hash
 	cmdTokens := []string{"neo-go", "wallet", "nep11", "tokens",
@@ -245,8 +251,8 @@ func TestNEP11_OwnerOf_BalanceOf_Transfer(t *testing.T) {
 
 	// tokens: good, several tokens
 	e.Run(t, cmdTokens...)
-	e.checkNextLine(t, string(tokenID))
-	e.checkNextLine(t, string(tokenID1))
+	e.checkNextLine(t, string(fst))
+	e.checkNextLine(t, string(snd))
 
 	// balance check: several tokens, ok
 	e.Run(t, append(cmdCheckBalance, "--token", h.StringLE())...)
diff --git a/examples/nft-nd/nft.go b/examples/nft-nd/nft.go
index aa53bb2c2..eb79c2775 100644
--- a/examples/nft-nd/nft.go
+++ b/examples/nft-nd/nft.go
@@ -23,9 +23,12 @@ import (
 // Prefixes used for contract data storage.
 const (
 	totalSupplyPrefix = "s"
-	accountPrefix     = "a"
-	tokenPrefix       = "t"
-	tokensPrefix      = "ts"
+	// balancePrefix contains map from addresses to balances.
+	balancePrefix = "b"
+	// accountPrefix contains map from address + token id to tokens
+	accountPrefix = "a"
+	// tokenPrefix contains map from token id to it's owner.
+	tokenPrefix = "t"
 )
 
 var (
@@ -63,22 +66,25 @@ func totalSupply(ctx storage.Context) int {
 	return res
 }
 
-// mkAccountKey creates DB key for account specified by concatenating accountPrefix
-// and account address.
-func mkAccountKey(holder interop.Hash160) []byte {
+// mkAccountPrefix creates DB key-prefix for account tokens specified
+// by concatenating accountPrefix and account address.
+func mkAccountPrefix(holder interop.Hash160) []byte {
 	res := []byte(accountPrefix)
 	return append(res, holder...)
 }
 
-// mkStringKey creates DB key for token specified by concatenating tokenPrefix
-// and token ID.
-func mkTokenKey(token []byte) []byte {
-	res := []byte(tokenPrefix)
-	return append(res, token...)
+// mkBalanceKey creates DB key for account specified by concatenating balancePrefix
+// and account address.
+func mkBalanceKey(holder interop.Hash160) []byte {
+	res := []byte(balancePrefix)
+	return append(res, holder...)
 }
 
-func mkTokensKey() []byte {
-	return []byte(tokensPrefix)
+// mkTokenKey creates DB key for token specified by concatenating tokenPrefix
+// and token ID.
+func mkTokenKey(tokenID []byte) []byte {
+	res := []byte(tokenPrefix)
+	return append(res, tokenID...)
 }
 
 // BalanceOf returns the number of tokens owned by specified address.
@@ -87,64 +93,48 @@ func BalanceOf(holder interop.Hash160) int {
 		panic("bad owner address")
 	}
 	ctx := storage.GetReadOnlyContext()
-	tokens := getTokensOf(ctx, holder)
-	return len(tokens)
+	return getBalanceOf(ctx, mkBalanceKey(holder))
 }
 
-// getTokensOf is an internal implementation of TokensOf, tokens are stored
-// as a serialized slice of strings in the DB, so it gets and unwraps them
-// (or returns an empty slice).
-func getTokensOf(ctx storage.Context, holder interop.Hash160) []string {
-	var res = []string{}
-
-	key := mkAccountKey(holder)
-	val := storage.Get(ctx, key)
+// getBalanceOf returns balance of the account using database key.
+func getBalanceOf(ctx storage.Context, balanceKey []byte) int {
+	val := storage.Get(ctx, balanceKey)
 	if val != nil {
-		res = std.Deserialize(val.([]byte)).([]string)
+		return val.(int)
 	}
-	return res
+	return 0
 }
 
-// setTokensOf saves current tokens owned by account if there are any,
-// otherwise it just drops the appropriate key from the DB.
-func setTokensOf(ctx storage.Context, holder interop.Hash160, tokens []string) {
-	key := mkAccountKey(holder)
-	if len(tokens) != 0 {
-		val := std.Serialize(tokens)
-		storage.Put(ctx, key, val)
+// addToBalance adds amount to the account balance. Amount can be negative.
+func addToBalance(ctx storage.Context, holder interop.Hash160, amount int) {
+	key := mkBalanceKey(holder)
+	old := getBalanceOf(ctx, key)
+	old += amount
+	if old > 0 {
+		storage.Put(ctx, key, old)
 	} else {
 		storage.Delete(ctx, key)
 	}
 }
 
-// setTokens saves minted token if it is not saved yet.
-func setTokens(ctx storage.Context, newToken string) {
-	key := mkTokensKey()
-	var tokens = []string{}
-	val := storage.Get(ctx, key)
-	if val != nil {
-		tokens = std.Deserialize(val.([]byte)).([]string)
-	}
-	for i := 0; i < len(tokens); i++ {
-		if util.Equals(tokens[i], newToken) {
-			return
-		}
-	}
-	tokens = append(tokens, newToken)
-	val = std.Serialize(tokens)
-	storage.Put(ctx, key, val)
+// addToken adds token to the account.
+func addToken(ctx storage.Context, holder interop.Hash160, token []byte) {
+	key := mkAccountPrefix(holder)
+	storage.Put(ctx, append(key, token...), token)
+}
+
+// removeToken removes token from the account.
+func removeToken(ctx storage.Context, holder interop.Hash160, token []byte) {
+	key := mkAccountPrefix(holder)
+	storage.Delete(ctx, append(key, token...))
 }
 
 // Tokens returns an iterator that contains all of the tokens minted by the contract.
 func Tokens() iterator.Iterator {
 	ctx := storage.GetReadOnlyContext()
-	var arr = []string{}
-	key := mkTokensKey()
-	val := storage.Get(ctx, key)
-	if val != nil {
-		arr = std.Deserialize(val.([]byte)).([]string)
-	}
-	return iterator.Create(arr)
+	key := []byte(tokenPrefix)
+	iter := storage.Find(ctx, key, storage.RemovePrefix|storage.KeysOnly)
+	return iter
 }
 
 // TokensOf returns an iterator with all tokens held by specified address.
@@ -153,9 +143,9 @@ func TokensOf(holder interop.Hash160) iterator.Iterator {
 		panic("bad owner address")
 	}
 	ctx := storage.GetReadOnlyContext()
-	tokens := getTokensOf(ctx, holder)
-
-	return iterator.Create(tokens)
+	key := mkAccountPrefix(holder)
+	iter := storage.Find(ctx, key, storage.ValuesOnly)
+	return iter
 }
 
 // getOwnerOf returns current owner of the specified token or panics if token
@@ -197,18 +187,11 @@ func Transfer(to interop.Hash160, token []byte, data interface{}) bool {
 	}
 
 	if string(owner) != string(to) {
-		toksOwner := getTokensOf(ctx, owner)
-		toksTo := getTokensOf(ctx, to)
+		addToBalance(ctx, owner, -1)
+		removeToken(ctx, owner, token)
 
-		var newToksOwner = []string{}
-		for _, tok := range toksOwner {
-			if tok != string(token) {
-				newToksOwner = append(newToksOwner, tok)
-			}
-		}
-		toksTo = append(toksTo, string(token))
-		setTokensOf(ctx, owner, newToksOwner)
-		setTokensOf(ctx, to, toksTo)
+		addToBalance(ctx, to, 1)
+		addToken(ctx, to, token)
 		setOwnerOf(ctx, token, to)
 	}
 	postTransfer(owner, to, token, data)
@@ -246,14 +229,12 @@ func OnNEP17Payment(from interop.Hash160, amount int, data interface{}) {
 		tokIn = append(tokIn, std.Serialize(data)...)
 	}
 
-	tokenHash := crypto.Sha256(tokIn)
+	tokenHash := crypto.Ripemd160(tokIn)
 	token := std.Base58Encode(tokenHash)
 
-	toksOf := getTokensOf(ctx, from)
-	toksOf = append(toksOf, token)
-	setTokensOf(ctx, from, toksOf)
+	addToken(ctx, from, []byte(token))
 	setOwnerOf(ctx, []byte(token), from)
-	setTokens(ctx, token)
+	addToBalance(ctx, from, 1)
 
 	total++
 	storage.Put(ctx, []byte(totalSupplyPrefix), total)
@@ -287,20 +268,8 @@ func Update(nef, manifest []byte) {
 // Properties returns properties of the given NFT.
 func Properties(id []byte) map[string]string {
 	ctx := storage.GetReadOnlyContext()
-	var tokens = []string{}
-	key := mkTokensKey()
-	val := storage.Get(ctx, key)
-	if val != nil {
-		tokens = std.Deserialize(val.([]byte)).([]string)
-	}
-	var exists bool
-	for i := 0; i < len(tokens); i++ {
-		if util.Equals(tokens[i], id) {
-			exists = true
-			break
-		}
-	}
-	if !exists {
+	owner := storage.Get(ctx, mkTokenKey(id)).(interop.Hash160)
+	if owner == nil {
 		panic("unknown token")
 	}
 	result := map[string]string{

From 23a4e254363b5a9c31cc9d80d0b3e2c5151a9cba Mon Sep 17 00:00:00 2001
From: Evgeniy Stratonikov <evgeniy@nspcc.ru>
Date: Thu, 29 Apr 2021 17:19:30 +0300
Subject: [PATCH 2/2] interop: remove `System.Iterator.Create`, fix #1935

There are now only storage iterators. Related #1933.
---
 pkg/compiler/syscall_test.go              |  1 -
 pkg/core/interop/interopnames/names.go    |  2 -
 pkg/core/interop/iterator/interop.go      | 38 ++++++++--
 pkg/core/interop/iterator/interop_test.go | 22 +++++-
 pkg/core/interop_system_test.go           |  4 +-
 pkg/core/interops.go                      |  1 -
 pkg/core/native/nonfungible.go            | 30 +++++++-
 pkg/interop/iterator/iterator.go          |  8 ---
 pkg/rpc/response/result/invoke.go         |  5 +-
 pkg/vm/interop.go                         | 85 -----------------------
 pkg/vm/interop_iterators.go               | 71 -------------------
 pkg/vm/vm_test.go                         | 62 -----------------
 12 files changed, 83 insertions(+), 246 deletions(-)
 delete mode 100644 pkg/vm/interop_iterators.go

diff --git a/pkg/compiler/syscall_test.go b/pkg/compiler/syscall_test.go
index a2b02b385..ff4c011b1 100644
--- a/pkg/compiler/syscall_test.go
+++ b/pkg/compiler/syscall_test.go
@@ -65,7 +65,6 @@ func TestSyscallExecution(t *testing.T) {
 		"contract.CreateMultisigAccount":   {interopnames.SystemContractCreateMultisigAccount, []string{"1", pubs}, false},
 		"contract.CreateStandardAccount":   {interopnames.SystemContractCreateStandardAccount, []string{pub}, false},
 		"contract.GetCallFlags":            {interopnames.SystemContractGetCallFlags, nil, false},
-		"iterator.Create":                  {interopnames.SystemIteratorCreate, []string{pubs}, false},
 		"iterator.Next":                    {interopnames.SystemIteratorNext, []string{"iterator.Iterator{}"}, false},
 		"iterator.Value":                   {interopnames.SystemIteratorValue, []string{"iterator.Iterator{}"}, false},
 		"runtime.BurnGas":                  {interopnames.SystemRuntimeBurnGas, []string{"1"}, true},
diff --git a/pkg/core/interop/interopnames/names.go b/pkg/core/interop/interopnames/names.go
index 6d2da3bea..030629ada 100644
--- a/pkg/core/interop/interopnames/names.go
+++ b/pkg/core/interop/interopnames/names.go
@@ -13,7 +13,6 @@ const (
 	SystemContractGetCallFlags          = "System.Contract.GetCallFlags"
 	SystemContractNativeOnPersist       = "System.Contract.NativeOnPersist"
 	SystemContractNativePostPersist     = "System.Contract.NativePostPersist"
-	SystemIteratorCreate                = "System.Iterator.Create"
 	SystemIteratorNext                  = "System.Iterator.Next"
 	SystemIteratorValue                 = "System.Iterator.Value"
 	SystemRuntimeBurnGas                = "System.Runtime.BurnGas"
@@ -53,7 +52,6 @@ var names = []string{
 	SystemContractGetCallFlags,
 	SystemContractNativeOnPersist,
 	SystemContractNativePostPersist,
-	SystemIteratorCreate,
 	SystemIteratorNext,
 	SystemIteratorValue,
 	SystemRuntimeBurnGas,
diff --git a/pkg/core/interop/iterator/interop.go b/pkg/core/interop/iterator/interop.go
index f9efa9d09..6a72e8cf9 100644
--- a/pkg/core/interop/iterator/interop.go
+++ b/pkg/core/interop/iterator/interop.go
@@ -2,22 +2,48 @@ package iterator
 
 import (
 	"github.com/nspcc-dev/neo-go/pkg/core/interop"
-	"github.com/nspcc-dev/neo-go/pkg/vm"
+	"github.com/nspcc-dev/neo-go/pkg/vm/stackitem"
 )
 
-// Create creates an iterator from array-like or map stack item.
-func Create(ic *interop.Context) error {
-	return vm.IteratorCreate(ic.VM)
+type iterator interface {
+	Next() bool
+	Value() stackitem.Item
 }
 
 // Next advances the iterator, pushes true on success and false otherwise.
 func Next(ic *interop.Context) error {
-	return vm.IteratorNext(ic.VM)
+	iop := ic.VM.Estack().Pop().Interop()
+	arr := iop.Value().(iterator)
+	ic.VM.Estack().PushVal(arr.Next())
+
+	return nil
 }
 
 // Value returns current iterator value and depends on iterator type:
 // For slices the result is just value.
 // For maps the result is key-value pair packed in a struct.
 func Value(ic *interop.Context) error {
-	return vm.IteratorValue(ic.VM)
+	iop := ic.VM.Estack().Pop().Interop()
+	arr := iop.Value().(iterator)
+	ic.VM.Estack().PushVal(arr.Value())
+
+	return nil
+}
+
+// IsIterator returns whether stackitem implements iterator interface.
+func IsIterator(item stackitem.Item) bool {
+	_, ok := item.Value().(iterator)
+	return ok
+}
+
+// Values returns an array of up to `max` iterator values. The second
+// return parameter denotes whether iterator is truncated.
+func Values(item stackitem.Item, max int) ([]stackitem.Item, bool) {
+	var result []stackitem.Item
+	arr := item.Value().(iterator)
+	for arr.Next() && max > 0 {
+		result = append(result, arr.Value())
+		max--
+	}
+	return result, arr.Next()
 }
diff --git a/pkg/core/interop/iterator/interop_test.go b/pkg/core/interop/iterator/interop_test.go
index fe830fea8..f8d025be2 100644
--- a/pkg/core/interop/iterator/interop_test.go
+++ b/pkg/core/interop/iterator/interop_test.go
@@ -6,15 +6,31 @@ import (
 
 	"github.com/nspcc-dev/neo-go/pkg/core/interop"
 	"github.com/nspcc-dev/neo-go/pkg/vm"
+	"github.com/nspcc-dev/neo-go/pkg/vm/stackitem"
 	"github.com/stretchr/testify/require"
 )
 
+type testIter struct {
+	index int
+	arr   []int
+}
+
+func (t *testIter) Next() bool {
+	if t.index < len(t.arr) {
+		t.index++
+	}
+	return t.index < len(t.arr)
+}
+
+func (t testIter) Value() stackitem.Item {
+	return stackitem.NewBigInteger(big.NewInt(int64(t.arr[t.index])))
+}
+
 // Iterator is thoroughly tested in VM package, these are smoke tests.
 func TestIterator(t *testing.T) {
 	ic := &interop.Context{VM: vm.New()}
-	full := []byte{4, 8, 15}
-	ic.VM.Estack().PushVal(full)
-	require.NoError(t, Create(ic))
+	full := []int{4, 8, 15}
+	ic.VM.Estack().PushVal(stackitem.NewInterop(&testIter{index: -1, arr: full}))
 
 	res := ic.VM.Estack().Pop().Item()
 	for i := range full {
diff --git a/pkg/core/interop_system_test.go b/pkg/core/interop_system_test.go
index ab3c9da26..f98ecde0f 100644
--- a/pkg/core/interop_system_test.go
+++ b/pkg/core/interop_system_test.go
@@ -338,8 +338,8 @@ func getTestContractState(bc *Blockchain) (*state.Contract, *state.Contract) {
 	emit.Opcodes(w.BinWriter, opcode.DROP)
 	emit.Opcodes(w.BinWriter, opcode.RET)
 	invalidStackOff := w.Len()
-	emit.Opcodes(w.BinWriter, opcode.NEWARRAY0, opcode.DUP, opcode.DUP, opcode.APPEND, opcode.NEWMAP)
-	emit.Syscall(w.BinWriter, interopnames.SystemIteratorCreate)
+	emit.Opcodes(w.BinWriter, opcode.NEWARRAY0, opcode.DUP, opcode.DUP, opcode.APPEND) // recursive array
+	emit.Syscall(w.BinWriter, interopnames.SystemStorageGetReadOnlyContext)            // interop item
 	emit.Opcodes(w.BinWriter, opcode.RET)
 	callT0Off := w.Len()
 	emit.Opcodes(w.BinWriter, opcode.CALLT, 0, 0, opcode.PUSH1, opcode.ADD, opcode.RET)
diff --git a/pkg/core/interops.go b/pkg/core/interops.go
index 07f09cb9e..f5f20e6eb 100644
--- a/pkg/core/interops.go
+++ b/pkg/core/interops.go
@@ -38,7 +38,6 @@ var systemInterops = []interop.Function{
 	{Name: interopnames.SystemContractGetCallFlags, Func: contractGetCallFlags, Price: 1 << 10},
 	{Name: interopnames.SystemContractNativeOnPersist, Func: native.OnPersist, Price: 0, RequiredFlags: callflag.States},
 	{Name: interopnames.SystemContractNativePostPersist, Func: native.PostPersist, Price: 0, RequiredFlags: callflag.States},
-	{Name: interopnames.SystemIteratorCreate, Func: iterator.Create, Price: 1 << 4, ParamCount: 1},
 	{Name: interopnames.SystemIteratorNext, Func: iterator.Next, Price: 1 << 15, ParamCount: 1},
 	{Name: interopnames.SystemIteratorValue, Func: iterator.Value, Price: 1 << 4, ParamCount: 1},
 	{Name: interopnames.SystemRuntimeBurnGas, Func: runtime.BurnGas, Price: 1 << 4, ParamCount: 1},
diff --git a/pkg/core/native/nonfungible.go b/pkg/core/native/nonfungible.go
index c1bf4cc9b..03cd67ef7 100644
--- a/pkg/core/native/nonfungible.go
+++ b/pkg/core/native/nonfungible.go
@@ -19,7 +19,6 @@ import (
 	"github.com/nspcc-dev/neo-go/pkg/smartcontract/callflag"
 	"github.com/nspcc-dev/neo-go/pkg/smartcontract/manifest"
 	"github.com/nspcc-dev/neo-go/pkg/util"
-	"github.com/nspcc-dev/neo-go/pkg/vm"
 	"github.com/nspcc-dev/neo-go/pkg/vm/stackitem"
 )
 
@@ -244,8 +243,8 @@ func (n *nonfungible) tokensOf(ic *interop.Context, args []stackitem.Item) stack
 	for i := range arr {
 		arr[i] = stackitem.NewByteArray(s.Tokens[i])
 	}
-	iter, _ := vm.NewIterator(stackitem.NewArray(arr))
-	return iter
+	iter := newArrayIterator(arr)
+	return stackitem.NewInterop(iter)
 }
 
 func (n *nonfungible) mint(ic *interop.Context, s nftTokenState) {
@@ -382,3 +381,28 @@ func (n *nonfungible) transfer(ic *interop.Context, args []stackitem.Item) stack
 func makeNFTAccountKey(owner util.Uint160) []byte {
 	return append([]byte{prefixNFTAccount}, owner.BytesBE()...)
 }
+
+type arrayWrapper struct {
+	index int
+	value []stackitem.Item
+}
+
+func newArrayIterator(arr []stackitem.Item) *arrayWrapper {
+	return &arrayWrapper{
+		index: -1,
+		value: arr,
+	}
+}
+
+func (a *arrayWrapper) Next() bool {
+	if next := a.index + 1; next < len(a.value) {
+		a.index = next
+		return true
+	}
+
+	return false
+}
+
+func (a *arrayWrapper) Value() stackitem.Item {
+	return a.value[a.index]
+}
diff --git a/pkg/interop/iterator/iterator.go b/pkg/interop/iterator/iterator.go
index 4169bc0ca..33a78d563 100644
--- a/pkg/interop/iterator/iterator.go
+++ b/pkg/interop/iterator/iterator.go
@@ -11,14 +11,6 @@ import "github.com/nspcc-dev/neo-go/pkg/interop/neogointernal"
 // structure is similar in function to Neo .net framework's Iterator.
 type Iterator struct{}
 
-// Create creates an iterator from the given items (array, struct, map, byte
-// array or integer and boolean converted to byte array). A new iterator is set
-// to point at element -1, so to access its first element you need to call Next
-// first. This function uses `System.Iterator.Create` syscall.
-func Create(items interface{}) Iterator {
-	return neogointernal.Syscall1("System.Iterator.Create", items).(Iterator)
-}
-
 // Next advances the iterator returning true if it is was successful (and you
 // can use Key or Value) and false otherwise (and there are no more elements in
 // this Iterator). This function uses `System.Iterator.Next` syscall.
diff --git a/pkg/rpc/response/result/invoke.go b/pkg/rpc/response/result/invoke.go
index 3f077c7ba..cbd2740f0 100644
--- a/pkg/rpc/response/result/invoke.go
+++ b/pkg/rpc/response/result/invoke.go
@@ -4,6 +4,7 @@ import (
 	"encoding/json"
 	"fmt"
 
+	"github.com/nspcc-dev/neo-go/pkg/core/interop/iterator"
 	"github.com/nspcc-dev/neo-go/pkg/core/transaction"
 	"github.com/nspcc-dev/neo-go/pkg/vm"
 	"github.com/nspcc-dev/neo-go/pkg/vm/stackitem"
@@ -63,8 +64,8 @@ func (r Invoke) MarshalJSON() ([]byte, error) {
 			data []byte
 			err  error
 		)
-		if (r.Stack[i].Type() == stackitem.InteropT) && vm.IsIterator(r.Stack[i]) {
-			iteratorValues, truncated := vm.IteratorValues(r.Stack[i], r.maxIteratorResultItems)
+		if (r.Stack[i].Type() == stackitem.InteropT) && iterator.IsIterator(r.Stack[i]) {
+			iteratorValues, truncated := iterator.Values(r.Stack[i], r.maxIteratorResultItems)
 			value := make([]json.RawMessage, len(iteratorValues))
 			for j := range iteratorValues {
 				value[j], err = stackitem.ToJSONWithTypes(iteratorValues[j])
diff --git a/pkg/vm/interop.go b/pkg/vm/interop.go
index 64f1c0f6f..4885f255e 100644
--- a/pkg/vm/interop.go
+++ b/pkg/vm/interop.go
@@ -7,7 +7,6 @@ import (
 
 	"github.com/nspcc-dev/neo-go/pkg/core/interop/interopnames"
 	"github.com/nspcc-dev/neo-go/pkg/smartcontract/callflag"
-	"github.com/nspcc-dev/neo-go/pkg/vm/stackitem"
 )
 
 // interopIDFuncPrice adds an ID to the InteropFuncPrice.
@@ -23,12 +22,6 @@ var defaultVMInterops = []interopIDFuncPrice{
 		Func: runtimeLog, Price: 1 << 15, RequiredFlags: callflag.AllowNotify},
 	{ID: interopnames.ToID([]byte(interopnames.SystemRuntimeNotify)),
 		Func: runtimeNotify, Price: 1 << 15, RequiredFlags: callflag.AllowNotify},
-	{ID: interopnames.ToID([]byte(interopnames.SystemIteratorCreate)),
-		Func: IteratorCreate, Price: 1 << 4},
-	{ID: interopnames.ToID([]byte(interopnames.SystemIteratorNext)),
-		Func: IteratorNext, Price: 1 << 15},
-	{ID: interopnames.ToID([]byte(interopnames.SystemIteratorValue)),
-		Func: IteratorValue, Price: 1 << 4},
 }
 
 func init() {
@@ -70,81 +63,3 @@ func init() {
 		return defaultVMInterops[i].ID < defaultVMInterops[j].ID
 	})
 }
-
-// IsIterator returns whether stackitem implements iterator interface.
-func IsIterator(item stackitem.Item) bool {
-	_, ok := item.Value().(iterator)
-	return ok
-}
-
-// IteratorNext handles syscall System.Enumerator.Next.
-func IteratorNext(v *VM) error {
-	iop := v.Estack().Pop().Interop()
-	arr := iop.Value().(iterator)
-	v.Estack().PushVal(arr.Next())
-
-	return nil
-}
-
-// IteratorValue handles syscall System.Enumerator.Value.
-func IteratorValue(v *VM) error {
-	iop := v.Estack().Pop().Interop()
-	arr := iop.Value().(iterator)
-	v.Estack().Push(&Element{value: arr.Value()})
-
-	return nil
-}
-
-// IteratorValues returns an array of up to `max` iterator values. The second
-// return parameter denotes whether iterator is truncated.
-func IteratorValues(item stackitem.Item, max int) ([]stackitem.Item, bool) {
-	var result []stackitem.Item
-	arr := item.Value().(iterator)
-	for arr.Next() && max > 0 {
-		result = append(result, arr.Value())
-		max--
-	}
-	return result, arr.Next()
-}
-
-// NewIterator creates new iterator from the provided stack item.
-func NewIterator(item stackitem.Item) (stackitem.Item, error) {
-	switch t := item.(type) {
-	case *stackitem.Array, *stackitem.Struct:
-		return stackitem.NewInterop(&arrayWrapper{
-			index: -1,
-			value: t.Value().([]stackitem.Item),
-		}), nil
-	case *stackitem.Map:
-		return NewMapIterator(t), nil
-	default:
-		data, err := t.TryBytes()
-		if err != nil {
-			return nil, fmt.Errorf("non-iterable type %s", t.Type())
-		}
-		return stackitem.NewInterop(&byteArrayWrapper{
-			index: -1,
-			value: data,
-		}), nil
-	}
-}
-
-// IteratorCreate handles syscall System.Iterator.Create.
-func IteratorCreate(v *VM) error {
-	data := v.Estack().Pop().Item()
-	item, err := NewIterator(data)
-	if err != nil {
-		return err
-	}
-
-	v.Estack().Push(&Element{value: item})
-	return nil
-}
-
-// NewMapIterator returns new interop item containing iterator over m.
-func NewMapIterator(m *stackitem.Map) *stackitem.Interop {
-	return stackitem.NewInterop(&mapWrapper{
-		index: -1,
-		m:     m.Value().([]stackitem.MapElement),
-	})
-}
diff --git a/pkg/vm/interop_iterators.go b/pkg/vm/interop_iterators.go
deleted file mode 100644
index 2fc07b5f7..000000000
--- a/pkg/vm/interop_iterators.go
+++ /dev/null
@@ -1,71 +0,0 @@
-package vm
-
-import (
-	"math/big"
-
-	"github.com/nspcc-dev/neo-go/pkg/vm/stackitem"
-)
-
-type (
-	iterator interface {
-		Next() bool
-		Value() stackitem.Item
-	}
-
-	arrayWrapper struct {
-		index int
-		value []stackitem.Item
-	}
-
-	byteArrayWrapper struct {
-		index int
-		value []byte
-	}
-
-	mapWrapper struct {
-		index int
-		m     []stackitem.MapElement
-	}
-)
-
-func (a *arrayWrapper) Next() bool {
-	if next := a.index + 1; next < len(a.value) {
-		a.index = next
-		return true
-	}
-
-	return false
-}
-
-func (a *arrayWrapper) Value() stackitem.Item {
-	return a.value[a.index]
-}
-
-func (a *byteArrayWrapper) Next() bool {
-	if next := a.index + 1; next < len(a.value) {
-		a.index = next
-		return true
-	}
-
-	return false
-}
-
-func (a *byteArrayWrapper) Value() stackitem.Item {
-	return stackitem.NewBigInteger(big.NewInt(int64(a.value[a.index])))
-}
-
-func (m *mapWrapper) Next() bool {
-	if next := m.index + 1; next < len(m.m) {
-		m.index = next
-		return true
-	}
-
-	return false
-}
-
-func (m *mapWrapper) Value() stackitem.Item {
-	return stackitem.NewStruct([]stackitem.Item{
-		m.m[m.index].Key,
-		m.m[m.index].Value,
-	})
-}
diff --git a/pkg/vm/vm_test.go b/pkg/vm/vm_test.go
index 5fcaaa89c..d6d9a4e8a 100644
--- a/pkg/vm/vm_test.go
+++ b/pkg/vm/vm_test.go
@@ -468,68 +468,6 @@ func TestPushData4BigN(t *testing.T) {
 	checkVMFailed(t, vm)
 }
 
-func getIteratorProg(n int) (prog []byte) {
-	prog = []byte{byte(opcode.INITSSLOT), 1, byte(opcode.STSFLD0)}
-	for i := 0; i < n; i++ {
-		prog = append(prog, byte(opcode.LDSFLD0))
-		prog = append(prog, getSyscallProg(interopnames.SystemIteratorNext)...)
-		prog = append(prog, byte(opcode.LDSFLD0))
-		prog = append(prog, getSyscallProg(interopnames.SystemIteratorValue)...)
-	}
-	prog = append(prog, byte(opcode.LDSFLD0))
-	prog = append(prog, getSyscallProg(interopnames.SystemIteratorNext)...)
-
-	return
-}
-
-func checkEnumeratorStack(t *testing.T, vm *VM, arr []stackitem.Item) {
-	require.Equal(t, len(arr)+1, vm.estack.Len())
-	require.Equal(t, stackitem.NewBool(false), vm.estack.Peek(0).value)
-	for i := 0; i < len(arr); i++ {
-		require.Equal(t, arr[i], vm.estack.Peek(i+1).value, "pos: %d", i+1)
-	}
-}
-
-func testIterableCreate(t *testing.T, isByteArray bool) {
-	prog := getSyscallProg(interopnames.SystemIteratorCreate)
-	prog = append(prog, getIteratorProg(2)...)
-
-	vm := load(prog)
-	arr := []stackitem.Item{
-		stackitem.NewBigInteger(big.NewInt(42)),
-		stackitem.NewByteArray([]byte{3, 2, 1}),
-	}
-	if isByteArray {
-		arr[1] = stackitem.Make(7)
-		vm.estack.PushVal([]byte{42, 7})
-	} else {
-		vm.estack.Push(&Element{value: stackitem.NewArray(arr)})
-	}
-
-	runVM(t, vm)
-	checkEnumeratorStack(t, vm, []stackitem.Item{
-		arr[1], stackitem.NewBool(true),
-		arr[0], stackitem.NewBool(true),
-	})
-}
-
-func TestIteratorCreate(t *testing.T) {
-	t.Run("Array", func(t *testing.T) { testIterableCreate(t, false) })
-	t.Run("ByteArray", func(t *testing.T) { testIterableCreate(t, true) })
-	t.Run("Map", func(f *testing.T) {})
-	t.Run("Interop", func(t *testing.T) {
-		v := New()
-		v.Estack().PushVal(stackitem.NewInterop([]byte{42}))
-		require.Error(t, IteratorCreate(v))
-	})
-}
-
-func getSyscallProg(name string) (prog []byte) {
-	buf := io.NewBufBinWriter()
-	emit.Syscall(buf.BinWriter, name)
-	return buf.Bytes()
-}
-
 func getTestCallFlagsFunc(syscall []byte, flags callflag.CallFlag, result interface{}) func(t *testing.T) {
 	return func(t *testing.T) {
 		script := append([]byte{byte(opcode.SYSCALL)}, syscall...)