neoneo-go/pkg/vm/emit.go

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package vm
import (
"bytes"
"encoding/binary"
"errors"
"fmt"
"io"
"math/big"
"github.com/CityOfZion/neo-go/pkg/util"
)
// Emit a VM Instruction with data to the given buffer.
func Emit(w *bytes.Buffer, op Instruction, b []byte) error {
if err := w.WriteByte(byte(op)); err != nil {
return err
}
_, err := w.Write(b)
return err
}
// EmitOpcode emits a single VM Instruction the given buffer.
func EmitOpcode(w io.ByteWriter, op Instruction) error {
return w.WriteByte(byte(op))
}
// EmitBool emits a bool type the given buffer.
func EmitBool(w io.ByteWriter, ok bool) error {
if ok {
return EmitOpcode(w, PUSHT)
}
return EmitOpcode(w, PUSHF)
}
// EmitInt emits a int type to the given buffer.
func EmitInt(w *bytes.Buffer, i int64) error {
if i == -1 {
return EmitOpcode(w, PUSHM1)
}
if i == 0 {
return EmitOpcode(w, PUSHF)
}
if i > 0 && i < 16 {
val := Instruction(int(PUSH1) - 1 + int(i))
return EmitOpcode(w, val)
}
bInt := big.NewInt(i)
val := util.ArrayReverse(bInt.Bytes())
return EmitBytes(w, val)
}
// EmitString emits a string to the given buffer.
func EmitString(w *bytes.Buffer, s string) error {
return EmitBytes(w, []byte(s))
}
// EmitBytes emits a byte array to the given buffer.
func EmitBytes(w *bytes.Buffer, b []byte) error {
var (
err error
n = len(b)
)
if n <= int(PUSHBYTES75) {
return Emit(w, Instruction(n), b)
} else if n < 0x100 {
err = Emit(w, PUSHDATA1, []byte{byte(n)})
} else if n < 0x10000 {
buf := make([]byte, 2)
binary.LittleEndian.PutUint16(buf, uint16(n))
err = Emit(w, PUSHDATA2, buf)
} else {
buf := make([]byte, 4)
binary.LittleEndian.PutUint32(buf, uint32(n))
err = Emit(w, PUSHDATA4, buf)
}
if err != nil {
return err
}
_, err = w.Write(b)
return err
}
// EmitSyscall emits the syscall API to the given buffer.
// Syscall API string cannot be 0.
func EmitSyscall(w *bytes.Buffer, api string) error {
if len(api) == 0 {
return errors.New("syscall api cannot be of length 0")
}
buf := make([]byte, len(api)+1)
buf[0] = byte(len(api))
copy(buf[1:], []byte(api))
return Emit(w, SYSCALL, buf)
}
// EmitCall emits a call Instruction with label to the given buffer.
func EmitCall(w *bytes.Buffer, op Instruction, label int16) error {
return EmitJmp(w, op, label)
}
// EmitJmp emits a jump Instruction along with label to the given buffer.
func EmitJmp(w *bytes.Buffer, op Instruction, label int16) error {
if !isInstructionJmp(op) {
return fmt.Errorf("opcode %s is not a jump or call type", op.String())
}
buf := make([]byte, 2)
binary.LittleEndian.PutUint16(buf, uint16(label))
return Emit(w, op, buf)
}
// EmitAppCall emits an appcall, if tailCall is true, tailCall opcode will be
// emitted instead.
func EmitAppCall(w *bytes.Buffer, scriptHash util.Uint160, tailCall bool) error {
op := APPCALL
if tailCall {
op = TAILCALL
}
return Emit(w, op, scriptHash.Bytes())
}
// EmitAppCallWithOperationAndData emits an appcall with the given operation and data.
func EmitAppCallWithOperationAndData(w *bytes.Buffer, scriptHash util.Uint160, operation string, data []byte) error {
if err := EmitBytes(w, data); err != nil {
return err
}
if err := EmitString(w, operation); err != nil {
return err
}
return EmitAppCall(w, scriptHash, false)
}
// EmitAppCallWithOperation emits an appcall with the given operation.
func EmitAppCallWithOperation(w *bytes.Buffer, scriptHash util.Uint160, operation string) error {
if err := EmitBool(w, false); err != nil {
return err
}
if err := EmitString(w, operation); err != nil {
return err
}
return EmitAppCall(w, scriptHash, false)
}
func isInstructionJmp(op Instruction) bool {
if op == JMP || op == JMPIFNOT || op == JMPIF || op == CALL {
return true
}
return false
}