rpc: move all top*FromStack client functions to a separate file

Some of them are shared between multiple RPC client APIs, so let's keep
them in a separate place for better maintainability.

pkg/rpc/client/helper.go

@@ -0,0 +1,77 @@
+package client
+
+import (
+	"crypto/elliptic"
+	"errors"
+	"fmt"
+
+	"github.com/nspcc-dev/neo-go/pkg/crypto/keys"
+	"github.com/nspcc-dev/neo-go/pkg/rpc/response/result"
+	"github.com/nspcc-dev/neo-go/pkg/vm/stackitem"
+)
+
+// getInvocationError returns an error in case of bad VM state or empty stack.
+func getInvocationError(result *result.Invoke) error {
+	if result.State != "HALT" {
+		return fmt.Errorf("invocation failed: %s", result.FaultException)
+	}
+	if len(result.Stack) == 0 {
+		return errors.New("result stack is empty")
+	}
+	return nil
+}
+
+// topBoolFromStack returns the top boolean value from stack.
+func topBoolFromStack(st []stackitem.Item) (bool, error) {
+	index := len(st) - 1 // top stack element is last in the array
+	result, ok := st[index].Value().(bool)
+	if !ok {
+		return false, fmt.Errorf("invalid stack item type: %s", st[index].Type())
+	}
+	return result, nil
+}
+
+// topIntFromStack returns the top integer value from stack.
+func topIntFromStack(st []stackitem.Item) (int64, error) {
+	index := len(st) - 1 // top stack element is last in the array
+	bi, err := st[index].TryInteger()
+	if err != nil {
+		return 0, err
+	}
+	return bi.Int64(), nil
+}
+
+// topPublicKeysFromStack returns the top array of public keys from stack.
+func topPublicKeysFromStack(st []stackitem.Item) (keys.PublicKeys, error) {
+	index := len(st) - 1 // top stack element is last in the array
+	var (
+		pks keys.PublicKeys
+		err error
+	)
+	items, ok := st[index].Value().([]stackitem.Item)
+	if !ok {
+		return nil, fmt.Errorf("invalid stack item type: %s", st[index].Type())
+	}
+	pks = make(keys.PublicKeys, len(items))
+	for i, item := range items {
+		val, ok := item.Value().([]byte)
+		if !ok {
+			return nil, fmt.Errorf("invalid array element #%d: %s", i, item.Type())
+		}
+		pks[i], err = keys.NewPublicKeyFromBytes(val, elliptic.P256())
+		if err != nil {
+			return nil, err
+		}
+	}
+	return pks, nil
+}
+
+// top string from stack returns the top string from stack.
+func topStringFromStack(st []stackitem.Item) (string, error) {
+	index := len(st) - 1 // top stack element is last in the array
+	bs, err := st[index].TryBytes()
+	if err != nil {
+		return "", err
+	}
+	return string(bs), nil
+}

pkg/rpc/client/native.go

@@ -3,14 +3,12 @@ package client
 // Various non-policy things from native contracts.
 
 import (
-	"crypto/elliptic"
 	"fmt"
 
 	"github.com/nspcc-dev/neo-go/pkg/core/native/nativenames"
 	"github.com/nspcc-dev/neo-go/pkg/core/native/noderoles"
 	"github.com/nspcc-dev/neo-go/pkg/crypto/keys"
 	"github.com/nspcc-dev/neo-go/pkg/smartcontract"
-	"github.com/nspcc-dev/neo-go/pkg/vm/stackitem"
 )
 
 // GetOraclePrice invokes `getPrice` method on a native Oracle contract.
@@ -65,28 +63,3 @@ func (c *Client) GetDesignatedByRole(role noderoles.Role, index uint32) (keys.Pu
 	}
 	return topPublicKeysFromStack(result.Stack)
 }
-
-// topPublicKeysFromStack returns the top array of public keys from stack.
-func topPublicKeysFromStack(st []stackitem.Item) (keys.PublicKeys, error) {
-	index := len(st) - 1 // top stack element is last in the array
-	var (
-		pks keys.PublicKeys
-		err error
-	)
-	items, ok := st[index].Value().([]stackitem.Item)
-	if !ok {
-		return nil, fmt.Errorf("invalid stack item type: %s", st[index].Type())
-	}
-	pks = make(keys.PublicKeys, len(items))
-	for i, item := range items {
-		val, ok := item.Value().([]byte)
-		if !ok {
-			return nil, fmt.Errorf("invalid array element #%d: %s", i, item.Type())
-		}
-		pks[i], err = keys.NewPublicKeyFromBytes(val, elliptic.P256())
-		if err != nil {
-			return nil, err
-		}
-	}
-	return pks, nil
-}

pkg/rpc/client/nep17.go

@@ -1,19 +1,16 @@
 package client
 
 import (
-	"errors"
 	"fmt"
 
 	"github.com/nspcc-dev/neo-go/pkg/core/transaction"
 	"github.com/nspcc-dev/neo-go/pkg/encoding/address"
 	"github.com/nspcc-dev/neo-go/pkg/io"
-	"github.com/nspcc-dev/neo-go/pkg/rpc/response/result"
 	"github.com/nspcc-dev/neo-go/pkg/smartcontract"
 	"github.com/nspcc-dev/neo-go/pkg/smartcontract/callflag"
 	"github.com/nspcc-dev/neo-go/pkg/util"
 	"github.com/nspcc-dev/neo-go/pkg/vm/emit"
 	"github.com/nspcc-dev/neo-go/pkg/vm/opcode"
-	"github.com/nspcc-dev/neo-go/pkg/vm/stackitem"
 	"github.com/nspcc-dev/neo-go/pkg/wallet"
 )
 
@@ -221,32 +218,3 @@ func (c *Client) MultiTransferNEP17(acc *wallet.Account, gas int64, recipients [
 
 	return c.SendRawTransaction(tx)
 }
-
-func topIntFromStack(st []stackitem.Item) (int64, error) {
-	index := len(st) - 1 // top stack element is last in the array
-	bi, err := st[index].TryInteger()
-	if err != nil {
-		return 0, err
-	}
-	return bi.Int64(), nil
-}
-
-func topStringFromStack(st []stackitem.Item) (string, error) {
-	index := len(st) - 1 // top stack element is last in the array
-	bs, err := st[index].TryBytes()
-	if err != nil {
-		return "", err
-	}
-	return string(bs), nil
-}
-
-// getInvocationError returns an error in case of bad VM state or empty stack.
-func getInvocationError(result *result.Invoke) error {
-	if result.State != "HALT" {
-		return fmt.Errorf("invocation failed: %s", result.FaultException)
-	}
-	if len(result.Stack) == 0 {
-		return errors.New("result stack is empty")
-	}
-	return nil
-}

pkg/rpc/client/policy.go

@@ -6,7 +6,6 @@ import (
 	"github.com/nspcc-dev/neo-go/pkg/core/native/nativenames"
 	"github.com/nspcc-dev/neo-go/pkg/smartcontract"
 	"github.com/nspcc-dev/neo-go/pkg/util"
-	"github.com/nspcc-dev/neo-go/pkg/vm/stackitem"
 )
 
 // GetFeePerByte invokes `getFeePerByte` method on a native Policy contract.
@@ -80,13 +79,3 @@ func (c *Client) IsBlocked(hash util.Uint160) (bool, error) {
 	}
 	return topBoolFromStack(result.Stack)
 }
-
-// topBoolFromStack returns the top boolean value from stack
-func topBoolFromStack(st []stackitem.Item) (bool, error) {
-	index := len(st) - 1 // top stack element is last in the array
-	result, ok := st[index].Value().(bool)
-	if !ok {
-		return false, fmt.Errorf("invalid stack item type: %s", st[index].Type())
-	}
-	return result, nil
-}