emit: use io.BinWriter instead of bytes.Buffer

pkg/core/blockchain.go

@@ -1,7 +1,6 @@
 package core
 
 import (
-	"bytes"
 	"fmt"
 	"math"
 	"math/big"
@@ -1486,11 +1485,8 @@ func ScriptFromWitness(hash util.Uint160, witness *transaction.Witness) ([]byte,
 	verification := witness.VerificationScript
 
 	if len(verification) == 0 {
-		bb := new(bytes.Buffer)
+		bb := io.NewBufBinWriter()
-		err := emit.AppCall(bb, hash, false)
+		emit.AppCall(bb.BinWriter, hash, false)
-		if err != nil {
-			return nil, err
-		}
 		verification = bb.Bytes()
 	} else if h := witness.ScriptHash(); hash != h {
 		return nil, errors.New("witness hash mismatch")

pkg/rpc/txBuilder.go

@@ -1,7 +1,6 @@
 package rpc
 
 import (
-	"bytes"
 	"errors"
 	"fmt"
 	"strconv"
@@ -113,22 +112,12 @@ func GetInvocationScript(tx *transaction.Transaction, wif *keys.WIF) ([]byte, er
 func CreateDeploymentScript(avm []byte, contract *ContractDetails) ([]byte, error) {
 	var props smartcontract.PropertyState
 
-	script := new(bytes.Buffer)
+	script := io.NewBufBinWriter()
-	if err := emit.Bytes(script, []byte(contract.Description)); err != nil {
+	emit.Bytes(script.BinWriter, []byte(contract.Description))
-		return nil, err
+	emit.Bytes(script.BinWriter, []byte(contract.Email))
-	}
+	emit.Bytes(script.BinWriter, []byte(contract.Author))
-	if err := emit.Bytes(script, []byte(contract.Email)); err != nil {
+	emit.Bytes(script.BinWriter, []byte(contract.Version))
-		return nil, err
+	emit.Bytes(script.BinWriter, []byte(contract.ProjectName))
-	}
-	if err := emit.Bytes(script, []byte(contract.Author)); err != nil {
-		return nil, err
-	}
-	if err := emit.Bytes(script, []byte(contract.Version)); err != nil {
-		return nil, err
-	}
-	if err := emit.Bytes(script, []byte(contract.ProjectName)); err != nil {
-		return nil, err
-	}
 	if contract.HasStorage {
 		props |= smartcontract.HasStorage
 	}
@@ -138,31 +127,21 @@ func CreateDeploymentScript(avm []byte, contract *ContractDetails) ([]byte, erro
 	if contract.IsPayable {
 		props |= smartcontract.IsPayable
 	}
-	if err := emit.Int(script, int64(props)); err != nil {
+	emit.Int(script.BinWriter, int64(props))
-		return nil, err
+	emit.Int(script.BinWriter, int64(contract.ReturnType))
-	}
-	if err := emit.Int(script, int64(contract.ReturnType)); err != nil {
-		return nil, err
-	}
 	params := make([]byte, len(contract.Parameters))
 	for k := range contract.Parameters {
 		params[k] = byte(contract.Parameters[k])
 	}
-	if err := emit.Bytes(script, params); err != nil {
+	emit.Bytes(script.BinWriter, params)
-		return nil, err
+	emit.Bytes(script.BinWriter, avm)
-	}
+	emit.Syscall(script.BinWriter, "Neo.Contract.Create")
-	if err := emit.Bytes(script, avm); err != nil {
-		return nil, err
-	}
-	if err := emit.Syscall(script, "Neo.Contract.Create"); err != nil {
-		return nil, err
-	}
 	return script.Bytes(), nil
 }
 
 // expandArrayIntoScript pushes all FuncParam parameters from the given array
 // into the given buffer in reverse order.
-func expandArrayIntoScript(script *bytes.Buffer, slice []Param) error {
+func expandArrayIntoScript(script *io.BinWriter, slice []Param) error {
 	for j := len(slice) - 1; j >= 0; j-- {
 		fp, err := slice[j].GetFuncParam()
 		if err != nil {
@@ -174,33 +153,25 @@ func expandArrayIntoScript(script *bytes.Buffer, slice []Param) error {
 			if err != nil {
 				return err
 			}
-			if err := emit.Bytes(script, str); err != nil {
+			emit.Bytes(script, str)
-				return err
-			}
 		case String:
 			str, err := fp.Value.GetString()
 			if err != nil {
 				return err
 			}
-			if err := emit.String(script, str); err != nil {
+			emit.String(script, str)
-				return err
-			}
 		case Hash160:
 			hash, err := fp.Value.GetUint160FromHex()
 			if err != nil {
 				return err
 			}
-			if err := emit.Bytes(script, hash.BytesBE()); err != nil {
+			emit.Bytes(script, hash.BytesBE())
-				return err
-			}
 		case Hash256:
 			hash, err := fp.Value.GetUint256()
 			if err != nil {
 				return err
 			}
-			if err := emit.Bytes(script, hash.BytesBE()); err != nil {
+			emit.Bytes(script, hash.BytesBE())
-				return err
-			}
 		case PublicKey:
 			str, err := fp.Value.GetString()
 			if err != nil {
@@ -210,17 +181,13 @@ func expandArrayIntoScript(script *bytes.Buffer, slice []Param) error {
 			if err != nil {
 				return err
 			}
-			if err := emit.Bytes(script, key.Bytes()); err != nil {
+			emit.Bytes(script, key.Bytes())
-				return err
-			}
 		case Integer:
 			val, err := fp.Value.GetInt()
 			if err != nil {
 				return err
 			}
-			if err := emit.Int(script, int64(val)); err != nil {
+			emit.Int(script, int64(val))
-				return err
-			}
 		case Boolean:
 			str, err := fp.Value.GetString()
 			if err != nil {
@@ -228,14 +195,11 @@ func expandArrayIntoScript(script *bytes.Buffer, slice []Param) error {
 			}
 			switch str {
 			case "true":
-				err = emit.Int(script, 1)
+				emit.Int(script, 1)
 			case "false":
-				err = emit.Int(script, 0)
+				emit.Int(script, 0)
 			default:
-				err = errors.New("wrong boolean value")
+				return errors.New("wrong boolean value")
-			}
-			if err != nil {
-				return err
 			}
 		default:
 			return fmt.Errorf("parameter type %v is not supported", fp.Type)
@@ -247,44 +211,32 @@ func expandArrayIntoScript(script *bytes.Buffer, slice []Param) error {
 // CreateFunctionInvocationScript creates a script to invoke given contract with
 // given parameters.
 func CreateFunctionInvocationScript(contract util.Uint160, params Params) ([]byte, error) {
-	script := new(bytes.Buffer)
+	script := io.NewBufBinWriter()
 	for i := len(params) - 1; i >= 0; i-- {
 		switch params[i].Type {
 		case stringT:
-			if err := emit.String(script, params[i].String()); err != nil {
+			emit.String(script.BinWriter, params[i].String())
-				return nil, err
-			}
 		case numberT:
 			num, err := params[i].GetInt()
 			if err != nil {
 				return nil, err
 			}
-			if err := emit.String(script, strconv.Itoa(num)); err != nil {
+			emit.String(script.BinWriter, strconv.Itoa(num))
-				return nil, err
-			}
 		case arrayT:
 			slice, err := params[i].GetArray()
 			if err != nil {
 				return nil, err
 			}
-			err = expandArrayIntoScript(script, slice)
+			err = expandArrayIntoScript(script.BinWriter, slice)
-			if err != nil {
-				return nil, err
-			}
-			err = emit.Int(script, int64(len(slice)))
-			if err != nil {
-				return nil, err
-			}
-			err = emit.Opcode(script, opcode.PACK)
 			if err != nil {
 				return nil, err
 			}
+			emit.Int(script.BinWriter, int64(len(slice)))
+			emit.Opcode(script.BinWriter, opcode.PACK)
 		}
 	}
 
-	if err := emit.AppCall(script, contract, false); err != nil {
+	emit.AppCall(script.BinWriter, contract, false)
-		return nil, err
-	}
 	return script.Bytes(), nil
 }
 
@@ -293,13 +245,11 @@ func CreateFunctionInvocationScript(contract util.Uint160, params Params) ([]byt
 // expects one array of FuncParams and expands it onto the stack as independent
 // elements.
 func CreateInvocationScript(contract util.Uint160, funcParams []Param) ([]byte, error) {
-	script := new(bytes.Buffer)
+	script := io.NewBufBinWriter()
-	err := expandArrayIntoScript(script, funcParams)
+	err := expandArrayIntoScript(script.BinWriter, funcParams)
 	if err != nil {
 		return nil, err
 	}
-	if err = emit.AppCall(script, contract, false); err != nil {
+	emit.AppCall(script.BinWriter, contract, false)
-		return nil, err
-	}
 	return script.Bytes(), nil
 }

pkg/smartcontract/contract.go

@@ -1,11 +1,11 @@
 package smartcontract
 
 import (
-	"bytes"
 	"fmt"
 	"sort"
 
 	"github.com/CityOfZion/neo-go/pkg/crypto/keys"
+	"github.com/CityOfZion/neo-go/pkg/io"
 	"github.com/CityOfZion/neo-go/pkg/vm/emit"
 	"github.com/CityOfZion/neo-go/pkg/vm/opcode"
 )
@@ -22,22 +22,14 @@ func CreateMultiSigRedeemScript(m int, publicKeys keys.PublicKeys) ([]byte, erro
 		return nil, fmt.Errorf("public key count %d exceeds maximum of length 1024", len(publicKeys))
 	}
 
-	buf := new(bytes.Buffer)
+	buf := io.NewBufBinWriter()
-	if err := emit.Int(buf, int64(m)); err != nil {
+	emit.Int(buf.BinWriter, int64(m))
-		return nil, err
-	}
 	sort.Sort(publicKeys)
 	for _, pubKey := range publicKeys {
-		if err := emit.Bytes(buf, pubKey.Bytes()); err != nil {
+		emit.Bytes(buf.BinWriter, pubKey.Bytes())
-			return nil, err
-		}
-	}
-	if err := emit.Int(buf, int64(len(publicKeys))); err != nil {
-		return nil, err
-	}
-	if err := emit.Opcode(buf, opcode.CHECKMULTISIG); err != nil {
-		return nil, err
 	}
+	emit.Int(buf.BinWriter, int64(len(publicKeys)))
+	emit.Opcode(buf.BinWriter, opcode.CHECKMULTISIG)
 
 	return buf.Bytes(), nil
 }

pkg/vm/emit/emit.go

@@ -1,146 +1,135 @@
 package emit
 
 import (
-	"bytes"
 	"encoding/binary"
 	"errors"
 	"fmt"
-	"io"
 	"math/big"
 
+	"github.com/CityOfZion/neo-go/pkg/io"
 	"github.com/CityOfZion/neo-go/pkg/util"
 	"github.com/CityOfZion/neo-go/pkg/vm/opcode"
 )
 
 // Instruction emits a VM Instruction with data to the given buffer.
-func Instruction(w *bytes.Buffer, op opcode.Opcode, b []byte) error {
+func Instruction(w *io.BinWriter, op opcode.Opcode, b []byte) {
-	if err := w.WriteByte(byte(op)); err != nil {
+	w.WriteB(byte(op))
-		return err
+	w.WriteBytes(b)
-	}
-	_, err := w.Write(b)
-	return err
 }
 
 // Opcode emits a single VM Instruction without arguments to the given buffer.
-func Opcode(w io.ByteWriter, op opcode.Opcode) error {
+func Opcode(w *io.BinWriter, op opcode.Opcode) {
-	return w.WriteByte(byte(op))
+	w.WriteB(byte(op))
 }
 
 // Bool emits a bool type the given buffer.
-func Bool(w io.ByteWriter, ok bool) error {
+func Bool(w *io.BinWriter, ok bool) {
 	if ok {
-		return Opcode(w, opcode.PUSHT)
+		Opcode(w, opcode.PUSHT)
+		return
 	}
-	return Opcode(w, opcode.PUSHF)
+	Opcode(w, opcode.PUSHF)
 }
 
 // Int emits a int type to the given buffer.
-func Int(w *bytes.Buffer, i int64) error {
+func Int(w *io.BinWriter, i int64) {
-	if i == -1 {
+	switch {
-		return Opcode(w, opcode.PUSHM1)
+	case i == -1:
-	}
+		Opcode(w, opcode.PUSHM1)
-	if i == 0 {
+	case i == 0:
-		return Opcode(w, opcode.PUSHF)
+		Opcode(w, opcode.PUSHF)
-	}
+	case i > 0 && i < 16:
-	if i > 0 && i < 16 {
 		val := opcode.Opcode(int(opcode.PUSH1) - 1 + int(i))
-		return Opcode(w, val)
+		Opcode(w, val)
-	}
+	default:
-
 		bInt := big.NewInt(i)
 		val := IntToBytes(bInt)
-	return Bytes(w, val)
+		Bytes(w, val)
+	}
 }
 
 // String emits a string to the given buffer.
-func String(w *bytes.Buffer, s string) error {
+func String(w *io.BinWriter, s string) {
-	return Bytes(w, []byte(s))
+	Bytes(w, []byte(s))
 }
 
 // Bytes emits a byte array to the given buffer.
-func Bytes(w *bytes.Buffer, b []byte) error {
+func Bytes(w *io.BinWriter, b []byte) {
-	var (
+	var n = len(b)
-		err error
-		n   = len(b)
-	)
 
-	if n <= int(opcode.PUSHBYTES75) {
+	switch {
-		return Instruction(w, opcode.Opcode(n), b)
+	case n <= int(opcode.PUSHBYTES75):
-	} else if n < 0x100 {
+		Instruction(w, opcode.Opcode(n), b)
-		err = Instruction(w, opcode.PUSHDATA1, []byte{byte(n)})
+		return
-	} else if n < 0x10000 {
+	case n < 0x100:
+		Instruction(w, opcode.PUSHDATA1, []byte{byte(n)})
+	case n < 0x10000:
 		buf := make([]byte, 2)
 		binary.LittleEndian.PutUint16(buf, uint16(n))
-		err = Instruction(w, opcode.PUSHDATA2, buf)
+		Instruction(w, opcode.PUSHDATA2, buf)
-	} else {
+	default:
 		buf := make([]byte, 4)
 		binary.LittleEndian.PutUint32(buf, uint32(n))
-		err = Instruction(w, opcode.PUSHDATA4, buf)
+		Instruction(w, opcode.PUSHDATA4, buf)
 	}
-	if err != nil {
+	w.WriteBytes(b)
-		return err
-	}
-	_, err = w.Write(b)
-	return err
 }
 
 // Syscall emits the syscall API to the given buffer.
 // Syscall API string cannot be 0.
-func Syscall(w *bytes.Buffer, api string) error {
+func Syscall(w *io.BinWriter, api string) {
-	if len(api) == 0 {
+	if w.Err != nil {
-		return errors.New("syscall api cannot be of length 0")
+		return
+	} else if len(api) == 0 {
+		w.Err = errors.New("syscall api cannot be of length 0")
+		return
 	}
 	buf := make([]byte, len(api)+1)
 	buf[0] = byte(len(api))
 	copy(buf[1:], api)
-	return Instruction(w, opcode.SYSCALL, buf)
+	Instruction(w, opcode.SYSCALL, buf)
 }
 
 // Call emits a call Instruction with label to the given buffer.
-func Call(w *bytes.Buffer, op opcode.Opcode, label int16) error {
+func Call(w *io.BinWriter, op opcode.Opcode, label int16) {
-	return Jmp(w, op, label)
+	Jmp(w, op, label)
 }
 
 // Jmp emits a jump Instruction along with label to the given buffer.
-func Jmp(w *bytes.Buffer, op opcode.Opcode, label int16) error {
+func Jmp(w *io.BinWriter, op opcode.Opcode, label int16) {
-	if !isInstructionJmp(op) {
+	if w.Err != nil {
-		return fmt.Errorf("opcode %s is not a jump or call type", op.String())
+		return
+	} else if !isInstructionJmp(op) {
+		w.Err = fmt.Errorf("opcode %s is not a jump or call type", op.String())
+		return
 	}
 	buf := make([]byte, 2)
 	binary.LittleEndian.PutUint16(buf, uint16(label))
-	return Instruction(w, op, buf)
+	Instruction(w, op, buf)
 }
 
 // AppCall emits an appcall, if tailCall is true, tailCall opcode will be
 // emitted instead.
-func AppCall(w *bytes.Buffer, scriptHash util.Uint160, tailCall bool) error {
+func AppCall(w *io.BinWriter, scriptHash util.Uint160, tailCall bool) {
 	op := opcode.APPCALL
 	if tailCall {
 		op = opcode.TAILCALL
 	}
-	return Instruction(w, op, scriptHash.BytesBE())
+	Instruction(w, op, scriptHash.BytesBE())
 }
 
 // AppCallWithOperationAndData emits an appcall with the given operation and data.
-func AppCallWithOperationAndData(w *bytes.Buffer, scriptHash util.Uint160, operation string, data []byte) error {
+func AppCallWithOperationAndData(w *io.BinWriter, scriptHash util.Uint160, operation string, data []byte) {
-	if err := Bytes(w, data); err != nil {
+	Bytes(w, data)
-		return err
+	String(w, operation)
-	}
+	AppCall(w, scriptHash, false)
-	if err := String(w, operation); err != nil {
-		return err
-	}
-	return AppCall(w, scriptHash, false)
 }
 
 // AppCallWithOperation emits an appcall with the given operation.
-func AppCallWithOperation(w *bytes.Buffer, scriptHash util.Uint160, operation string) error {
+func AppCallWithOperation(w *io.BinWriter, scriptHash util.Uint160, operation string) {
-	if err := Bool(w, false); err != nil {
+	Bool(w, false)
-		return err
+	String(w, operation)
-	}
+	AppCall(w, scriptHash, false)
-	if err := String(w, operation); err != nil {
-		return err
-	}
-	return AppCall(w, scriptHash, false)
 }
 
 func isInstructionJmp(op opcode.Opcode) bool {

pkg/vm/emit/emit_test.go

@@ -1,33 +1,33 @@
 package emit
 
 import (
-	"bytes"
 	"encoding/binary"
 	"testing"
 
+	"github.com/CityOfZion/neo-go/pkg/io"
 	"github.com/CityOfZion/neo-go/pkg/vm/opcode"
 	"github.com/stretchr/testify/assert"
 )
 
 func TestEmitInt(t *testing.T) {
 	t.Run("1-byte int", func(t *testing.T) {
-		buf := new(bytes.Buffer)
+		buf := io.NewBufBinWriter()
-		Int(buf, 10)
+		Int(buf.BinWriter, 10)
 		result := buf.Bytes()
 		assert.EqualValues(t, opcode.PUSH10, result[0])
 	})
 
 	t.Run("2-byte int", func(t *testing.T) {
-		buf := new(bytes.Buffer)
+		buf := io.NewBufBinWriter()
-		Int(buf, 100)
+		Int(buf.BinWriter, 100)
 		result := buf.Bytes()
 		assert.EqualValues(t, opcode.PUSHBYTES1, result[0])
 		assert.EqualValues(t, 100, result[1])
 	})
 
 	t.Run("4-byte int", func(t *testing.T) {
-		buf := new(bytes.Buffer)
+		buf := io.NewBufBinWriter()
-		Int(buf, 1000)
+		Int(buf.BinWriter, 1000)
 		result := buf.Bytes()
 		assert.EqualValues(t, opcode.PUSHBYTES2, result[0])
 		assert.EqualValues(t, 1000, binary.LittleEndian.Uint16(result[1:3]))
@@ -35,18 +35,18 @@ func TestEmitInt(t *testing.T) {
 }
 
 func TestEmitBool(t *testing.T) {
-	buf := new(bytes.Buffer)
+	buf := io.NewBufBinWriter()
-	Bool(buf, true)
+	Bool(buf.BinWriter, true)
-	Bool(buf, false)
+	Bool(buf.BinWriter, false)
 	result := buf.Bytes()
 	assert.Equal(t, opcode.Opcode(result[0]), opcode.PUSH1)
 	assert.Equal(t, opcode.Opcode(result[1]), opcode.PUSH0)
 }
 
 func TestEmitString(t *testing.T) {
-	buf := new(bytes.Buffer)
+	buf := io.NewBufBinWriter()
 	str := "City Of Zion"
-	String(buf, str)
+	String(buf.BinWriter, str)
 	assert.Equal(t, buf.Len(), len(str)+1)
 	assert.Equal(t, buf.Bytes()[1:], []byte(str))
 }
@@ -58,9 +58,9 @@ func TestEmitSyscall(t *testing.T) {
 		"Neo.Runtime.Whatever",
 	}
 
-	buf := new(bytes.Buffer)
+	buf := io.NewBufBinWriter()
 	for _, syscall := range syscalls {
-		Syscall(buf, syscall)
+		Syscall(buf.BinWriter, syscall)
 		result := buf.Bytes()
 		assert.Equal(t, opcode.Opcode(result[0]), opcode.SYSCALL)
 		assert.Equal(t, result[1], uint8(len(syscall)))
@@ -70,8 +70,8 @@ func TestEmitSyscall(t *testing.T) {
 }
 
 func TestEmitCall(t *testing.T) {
-	buf := new(bytes.Buffer)
+	buf := io.NewBufBinWriter()
-	Call(buf, opcode.JMP, 100)
+	Call(buf.BinWriter, opcode.JMP, 100)
 	result := buf.Bytes()
 	assert.Equal(t, opcode.Opcode(result[0]), opcode.JMP)
 	label := binary.LittleEndian.Uint16(result[1:3])

pkg/vm/vm_test.go

@@ -8,6 +8,8 @@ import (
 	"math/rand"
 	"testing"
 
+	"github.com/CityOfZion/neo-go/pkg/io"
+
 	"github.com/CityOfZion/neo-go/pkg/crypto/hash"
 	"github.com/CityOfZion/neo-go/pkg/crypto/keys"
 	"github.com/CityOfZion/neo-go/pkg/util"
@@ -31,9 +33,9 @@ func TestInteropHook(t *testing.T) {
 	v := New()
 	v.RegisterInteropGetter(fooInteropGetter)
 
-	buf := new(bytes.Buffer)
+	buf := io.NewBufBinWriter()
-	emit.Syscall(buf, "foo")
+	emit.Syscall(buf.BinWriter, "foo")
-	emit.Opcode(buf, opcode.RET)
+	emit.Opcode(buf.BinWriter, opcode.RET)
 	v.Load(buf.Bytes())
 	runVM(t, v)
 	assert.Equal(t, 1, v.estack.Len())
@@ -44,12 +46,12 @@ func TestInteropHookViaID(t *testing.T) {
 	v := New()
 	v.RegisterInteropGetter(fooInteropGetter)
 
-	buf := new(bytes.Buffer)
+	buf := io.NewBufBinWriter()
 	fooid := InteropNameToID([]byte("foo"))
 	var id = make([]byte, 4)
 	binary.LittleEndian.PutUint32(id, fooid)
-	_ = emit.Syscall(buf, string(id))
+	emit.Syscall(buf.BinWriter, string(id))
-	_ = emit.Opcode(buf, opcode.RET)
+	emit.Opcode(buf.BinWriter, opcode.RET)
 	v.Load(buf.Bytes())
 	runVM(t, v)
 	assert.Equal(t, 1, v.estack.Len())
@@ -131,10 +133,10 @@ func TestBytesToPublicKey(t *testing.T) {
 }
 
 func TestPushBytes1to75(t *testing.T) {
-	buf := new(bytes.Buffer)
+	buf := io.NewBufBinWriter()
 	for i := 1; i <= 75; i++ {
 		b := randomBytes(i)
-		emit.Bytes(buf, b)
+		emit.Bytes(buf.BinWriter, b)
 		vm := load(buf.Bytes())
 		err := vm.Step()
 		require.NoError(t, err)