147 lines
2.9 KiB
Go
147 lines
2.9 KiB
Go
package vm
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import (
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"errors"
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"github.com/CityOfZion/neo-go/pkg/io"
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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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// Return value count, -1 is unspecified.
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rvcount int
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// Evaluation stack pointer.
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estack *Stack
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// Alt stack pointer.
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astack *Stack
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}
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// NewContext returns a new Context object.
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func NewContext(b []byte) *Context {
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return &Context{
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prog: b,
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breakPoints: []int{},
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rvcount: -1,
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}
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}
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// Next returns the next instruction to execute with its parameter if any. After
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// its invocation the instruction pointer points to the instruction being
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// returned.
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func (c *Context) Next() (Instruction, []byte, error) {
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c.ip = c.nextip
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if c.ip >= len(c.prog) {
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return RET, nil, nil
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}
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r := io.NewBinReaderFromBuf(c.prog[c.ip:])
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var instrbyte byte
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r.ReadLE(&instrbyte)
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instr := Instruction(instrbyte)
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c.nextip++
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var numtoread int
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switch instr {
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case PUSHDATA1, SYSCALL:
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var n byte
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r.ReadLE(&n)
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numtoread = int(n)
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c.nextip++
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case PUSHDATA2:
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var n uint16
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r.ReadLE(&n)
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numtoread = int(n)
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c.nextip += 2
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case PUSHDATA4:
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var n uint32
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r.ReadLE(&n)
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if n > MaxItemSize {
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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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case JMP, JMPIF, JMPIFNOT, CALL, CALLED, CALLEDT:
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numtoread = 2
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case CALLI:
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numtoread = 4
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case APPCALL, TAILCALL:
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numtoread = 20
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case CALLE, CALLET:
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numtoread = 22
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default:
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if instr >= PUSHBYTES1 && instr <= PUSHBYTES75 {
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numtoread = int(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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parameter := make([]byte, numtoread)
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r.ReadLE(parameter)
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if r.Err != nil {
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return instr, nil, errors.New("failed to read instruction parameter")
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}
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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 absolute instruction without taking 0 into account.
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// If that program starts the ip = 0 but IP() will return 1, cause its
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// the first instruction.
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func (c *Context) IP() int {
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return c.ip + 1
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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, Instruction) {
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return c.ip, Instruction(c.prog[c.ip])
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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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// 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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// Value implements StackItem interface.
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func (c *Context) Value() interface{} {
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return c
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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.ip {
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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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