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Signextend

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This commit is contained in:
obscuren 2014-11-01 02:14:55 +01:00
parent c8438979a9
commit 3f90f7c898
2 changed files with 18 additions and 0 deletions
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4
ethutil/big.go
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@ -34,6 +34,10 @@ func BigD(data []byte) *big.Int {
return n
}
func BitTest(num *big.Int, i int) bool {
return num.Bit(i) > 0
}
// To256
//
// "cast" the big int to a 256 big int (i.e., limit to)

14
vm/vm_debug.go
View File

@ -392,6 +392,20 @@ func (self *DebugVm) RunClosure(closure *Closure) (ret []byte, err error) {
self.Printf(" = %v", base)
stack.Push(base)
case SIGNEXTEND:
back := stack.Pop().Uint64()
if back.Cmp(big.NewInt(31)) < 0 {
bit := uint(back*8 + 7)
num := stack.Pop()
mask := new(big.Int).Lsh(ethutil.Big1, bit)
mask.Sub(mask, ethutil.Big1)
if ethutil.BitTest(num, int(bit)) {
num.Or(num, mask.Not(mask))
} else {
num.And(num, mask)
}
stack.Push(num)
}
case NOT:
base.Sub(Pow256, stack.Pop()).Sub(base, ethutil.Big1)