equity/equity/util/shift.go

   1 package equity
   2
   3 import (
   4         "bytes"
   5         "encoding/binary"
   6         "encoding/hex"
   7         "errors"
   8
   9         "github.com/vapor/protocol/vm"
  10
  11         "github.com/vapor/equity/compiler"
  12 )
  13
  14 const (
  15         firstClauseShift string = "00000000"
  16         endingClauseName string = "ending"
  17 )
  18
  19 // Shift statistics contract clause's offset
  20 func Shift(contract *compiler.Contract) (map[string]string, error) {
  21         clauseMap := make(map[string]string)
  22         if len(contract.Clauses) == 1 {
  23                 clauseMap[contract.Clauses[0].Name] = firstClauseShift
  24                 return clauseMap, nil
  25         }
  26
  27         instructions, err := vm.ParseProgram(contract.Body)
  28         if err != nil {
  29                 return nil, err
  30         }
  31
  32         var jumpifData [][]byte
  33         for i, inst := range instructions {
  34                 if inst.Op.String() == "JUMPIF" {
  35                         if i > 0 && instructions[i-1].Op.String() == "NOP" {
  36                                 continue
  37                         }
  38                         jumpifData = append([][]byte{inst.Data}, jumpifData...)
  39                 }
  40         }
  41
  42         // Check the number of contract's clause
  43         if len(contract.Clauses) != len(jumpifData)+1 {
  44                 return nil, errors.New("the number of contract's clause is not equal to the number of jumpif instruction")
  45         }
  46
  47         for i, clause := range contract.Clauses {
  48                 if i == 0 {
  49                         clauseMap[clause.Name] = firstClauseShift
  50                         continue
  51                 }
  52                 clauseMap[clause.Name] = hex.EncodeToString(jumpifData[i-1])
  53         }
  54
  55         var buffer bytes.Buffer
  56         if err := binary.Write(&buffer, binary.LittleEndian, uint32(len(contract.Body))); err != nil {
  57                 return nil, err
  58         }
  59         clauseMap[endingClauseName] = hex.EncodeToString(buffer.Bytes())
  60
  61         return clauseMap, nil
  62 }