335 lines
8.6 KiB
Go
335 lines
8.6 KiB
Go
package vm
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import (
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"encoding/binary"
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"encoding/json"
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"errors"
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"fmt"
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"math/big"
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"github.com/nspcc-dev/neo-go/pkg/crypto/hash"
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"github.com/nspcc-dev/neo-go/pkg/smartcontract/callflag"
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"github.com/nspcc-dev/neo-go/pkg/smartcontract/nef"
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"github.com/nspcc-dev/neo-go/pkg/util"
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"github.com/nspcc-dev/neo-go/pkg/vm/invocations"
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"github.com/nspcc-dev/neo-go/pkg/vm/opcode"
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"github.com/nspcc-dev/neo-go/pkg/vm/stackitem"
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)
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// Context represents the current execution context of the VM.
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type Context struct {
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// Instruction pointer.
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ip int
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// The next instruction pointer.
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nextip int
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// The raw program script.
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prog []byte
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// Breakpoints.
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breakPoints []int
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// Evaluation stack pointer.
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estack *Stack
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static *slot
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local slot
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arguments slot
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// Exception context stack.
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tryStack Stack
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// Script hash of the prog.
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scriptHash util.Uint160
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// Caller's contract script hash.
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callingScriptHash util.Uint160
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// Call flags this context was created with.
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callFlag callflag.CallFlag
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// retCount specifies the number of return values.
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retCount int
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// NEF represents a NEF file for the current contract.
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NEF *nef.File
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// invTree is an invocation tree (or branch of it) for this context.
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invTree *invocations.Tree
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// onUnload is a callback that should be called after current context unloading
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// if no exception occurs.
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onUnload ContextUnloadCallback
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}
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// ContextUnloadCallback is a callback method used on context unloading from istack.
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type ContextUnloadCallback func(commit bool) error
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var errNoInstParam = errors.New("failed to read instruction parameter")
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// NewContext returns a new Context object.
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func NewContext(b []byte) *Context {
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return NewContextWithParams(b, -1, 0)
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}
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// NewContextWithParams creates new Context objects using script, parameter count,
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// return value count and initial position in script.
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func NewContextWithParams(b []byte, rvcount int, pos int) *Context {
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return &Context{
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prog: b,
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retCount: rvcount,
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nextip: pos,
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}
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}
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// Estack returns the evaluation stack of c.
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func (c *Context) Estack() *Stack {
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return c.estack
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}
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// NextIP returns the next instruction pointer.
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func (c *Context) NextIP() int {
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return c.nextip
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}
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// Jump unconditionally moves the next instruction pointer to the specified location.
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func (c *Context) Jump(pos int) {
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if pos < 0 || pos >= len(c.prog) {
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panic("instruction offset is out of range")
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}
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c.nextip = pos
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}
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// Next returns the next instruction to execute with its parameter if any.
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// The parameter is not copied and shouldn't be written to. After its invocation,
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// the instruction pointer points to the instruction returned.
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func (c *Context) Next() (opcode.Opcode, []byte, error) {
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var err error
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c.ip = c.nextip
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if c.ip >= len(c.prog) {
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return opcode.RET, nil, nil
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}
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var instrbyte = c.prog[c.ip]
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instr := opcode.Opcode(instrbyte)
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if !opcode.IsValid(instr) {
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return instr, nil, fmt.Errorf("incorrect opcode %s", instr.String())
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}
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c.nextip++
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var numtoread int
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switch instr {
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case opcode.PUSHDATA1:
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if c.nextip >= len(c.prog) {
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err = errNoInstParam
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} else {
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numtoread = int(c.prog[c.nextip])
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c.nextip++
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}
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case opcode.PUSHDATA2:
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if c.nextip+1 >= len(c.prog) {
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err = errNoInstParam
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} else {
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numtoread = int(binary.LittleEndian.Uint16(c.prog[c.nextip : c.nextip+2]))
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c.nextip += 2
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}
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case opcode.PUSHDATA4:
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if c.nextip+3 >= len(c.prog) {
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err = errNoInstParam
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} else {
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var n = binary.LittleEndian.Uint32(c.prog[c.nextip : c.nextip+4])
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if n > stackitem.MaxSize {
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return instr, nil, errors.New("parameter is too big")
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}
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numtoread = int(n)
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c.nextip += 4
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}
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case opcode.JMP, opcode.JMPIF, opcode.JMPIFNOT, opcode.JMPEQ, opcode.JMPNE,
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opcode.JMPGT, opcode.JMPGE, opcode.JMPLT, opcode.JMPLE,
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opcode.CALL, opcode.ISTYPE, opcode.CONVERT, opcode.NEWARRAYT,
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opcode.ENDTRY,
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opcode.INITSSLOT, opcode.LDSFLD, opcode.STSFLD, opcode.LDARG, opcode.STARG, opcode.LDLOC, opcode.STLOC:
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numtoread = 1
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case opcode.INITSLOT, opcode.TRY, opcode.CALLT:
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numtoread = 2
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case opcode.JMPL, opcode.JMPIFL, opcode.JMPIFNOTL, opcode.JMPEQL, opcode.JMPNEL,
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opcode.JMPGTL, opcode.JMPGEL, opcode.JMPLTL, opcode.JMPLEL,
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opcode.ENDTRYL,
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opcode.CALLL, opcode.SYSCALL, opcode.PUSHA:
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numtoread = 4
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case opcode.TRYL:
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numtoread = 8
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default:
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if instr <= opcode.PUSHINT256 {
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numtoread = 1 << instr
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} else {
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// No parameters, can just return.
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return instr, nil, nil
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}
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}
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if c.nextip+numtoread-1 >= len(c.prog) {
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err = errNoInstParam
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}
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if err != nil {
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return instr, nil, err
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}
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parameter := c.prog[c.nextip : c.nextip+numtoread]
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c.nextip += numtoread
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return instr, parameter, nil
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}
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// IP returns the current instruction offset in the context script.
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func (c *Context) IP() int {
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return c.ip
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}
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// LenInstr returns the number of instructions loaded.
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func (c *Context) LenInstr() int {
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return len(c.prog)
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}
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// CurrInstr returns the current instruction and opcode.
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func (c *Context) CurrInstr() (int, opcode.Opcode) {
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return c.ip, opcode.Opcode(c.prog[c.ip])
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}
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// NextInstr returns the next instruction and opcode.
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func (c *Context) NextInstr() (int, opcode.Opcode) {
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op := opcode.RET
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if c.nextip < len(c.prog) {
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op = opcode.Opcode(c.prog[c.nextip])
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}
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return c.nextip, op
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}
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// Copy returns an new exact copy of c.
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func (c *Context) Copy() *Context {
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ctx := new(Context)
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*ctx = *c
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return ctx
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}
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// GetCallFlags returns the calling flags which the context was created with.
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func (c *Context) GetCallFlags() callflag.CallFlag {
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return c.callFlag
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}
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// Program returns the loaded program.
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func (c *Context) Program() []byte {
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return c.prog
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}
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// ScriptHash returns a hash of the script in the current context.
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func (c *Context) ScriptHash() util.Uint160 {
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if c.scriptHash.Equals(util.Uint160{}) {
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c.scriptHash = hash.Hash160(c.prog)
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}
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return c.scriptHash
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}
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// Value implements the stackitem.Item interface.
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func (c *Context) Value() interface{} {
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return c
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}
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// Dup implements the stackitem.Item interface.
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func (c *Context) Dup() stackitem.Item {
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return c
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}
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// TryBool implements the stackitem.Item interface.
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func (c *Context) TryBool() (bool, error) { panic("can't convert Context to Bool") }
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// TryBytes implements the stackitem.Item interface.
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func (c *Context) TryBytes() ([]byte, error) {
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return nil, errors.New("can't convert Context to ByteArray")
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}
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// TryInteger implements the stackitem.Item interface.
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func (c *Context) TryInteger() (*big.Int, error) {
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return nil, errors.New("can't convert Context to Integer")
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}
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// Type implements the stackitem.Item interface.
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func (c *Context) Type() stackitem.Type { panic("Context cannot appear on evaluation stack") }
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// Convert implements the stackitem.Item interface.
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func (c *Context) Convert(_ stackitem.Type) (stackitem.Item, error) {
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panic("Context cannot be converted to anything")
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}
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// Equals implements the stackitem.Item interface.
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func (c *Context) Equals(s stackitem.Item) bool {
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return c == s
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}
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func (c *Context) atBreakPoint() bool {
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for _, n := range c.breakPoints {
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if n == c.nextip {
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return true
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}
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}
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return false
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}
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func (c *Context) String() string {
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return "execution context"
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}
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// IsDeployed returns whether this context contains a deployed contract.
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func (c *Context) IsDeployed() bool {
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return c.NEF != nil
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}
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// DumpStaticSlot returns json formatted representation of the given slot.
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func (c *Context) DumpStaticSlot() string {
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return dumpSlot(c.static)
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}
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// DumpLocalSlot returns json formatted representation of the given slot.
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func (c *Context) DumpLocalSlot() string {
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return dumpSlot(&c.local)
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}
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// DumpArgumentsSlot returns json formatted representation of the given slot.
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func (c *Context) DumpArgumentsSlot() string {
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return dumpSlot(&c.arguments)
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}
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// dumpSlot returns json formatted representation of the given slot.
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func dumpSlot(s *slot) string {
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if s == nil || *s == nil {
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return "[]"
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}
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b, _ := json.MarshalIndent(s, "", " ")
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return string(b)
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}
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// getContextScriptHash returns script hash of the invocation stack element
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// number n.
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func (v *VM) getContextScriptHash(n int) util.Uint160 {
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istack := v.Istack()
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if istack.Len() <= n {
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return util.Uint160{}
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}
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element := istack.Peek(n)
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ctx := element.value.(*Context)
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return ctx.ScriptHash()
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}
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// PushContextScriptHash pushes the script hash of the
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// invocation stack element number n to the evaluation stack.
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func (v *VM) PushContextScriptHash(n int) error {
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h := v.getContextScriptHash(n)
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v.Estack().PushItem(stackitem.NewByteArray(h.BytesBE()))
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return nil
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}
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func (c *Context) HasTryBlock() bool {
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for i := 0; i < c.tryStack.Len(); i++ {
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eCtx := c.tryStack.Peek(i).Value().(*exceptionHandlingContext)
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if eCtx.State == eTry {
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return true
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}
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}
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return false
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}
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