931388b687
* Virtual machine for the NEO blockhain. * fixed big.Int numeric operation pointer issue. * added appcall * Added README for vm package. * removed main.go * started VM cli (prompt) integration * added support for printing the stack. * moved cli to vm package * fixed vet errors * updated readme * added more test for VM and fixed some edge cases. * bumped version -> 0.37.0
123 lines
2.3 KiB
Go
123 lines
2.3 KiB
Go
package vm
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import "encoding/binary"
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// Context represent 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 raw program script.
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prog []byte
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// Breakpoints
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breakPoints []int
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}
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// NewContext return a new Context object.
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func NewContext(b []byte) *Context {
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return &Context{
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ip: -1,
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prog: b,
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breakPoints: []int{},
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}
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}
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// Next return the next instruction to execute.
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func (c *Context) Next() Opcode {
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c.ip++
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return Opcode(c.prog[c.ip])
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}
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// IP returns the absosulute 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, Opcode) {
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if c.ip < 0 {
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return c.ip, Opcode(0x00)
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}
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return c.ip, Opcode(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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return &Context{
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ip: c.ip,
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prog: c.prog,
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breakPoints: c.breakPoints,
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}
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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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func (c *Context) readUint32() uint32 {
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start, end := c.IP(), c.IP()+4
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if end > len(c.prog) {
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return 0
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}
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val := binary.LittleEndian.Uint32(c.prog[start:end])
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c.ip += 4
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return val
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}
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func (c *Context) readUint16() uint16 {
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start, end := c.IP(), c.IP()+2
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if end > len(c.prog) {
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return 0
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}
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val := binary.LittleEndian.Uint16(c.prog[start:end])
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c.ip += 2
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return val
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}
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func (c *Context) readByte() byte {
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return c.readBytes(1)[0]
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}
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func (c *Context) readBytes(n int) []byte {
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start, end := c.IP(), c.IP()+n
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if end > len(c.prog) {
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return nil
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}
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out := make([]byte, n)
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copy(out, c.prog[start:end])
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c.ip += n
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return out
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}
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func (c *Context) readVarBytes() []byte {
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n := c.readByte()
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return c.readBytes(int(n))
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}
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