cbda064842
This commit contains the entire btcscript repository along with several changes needed to move all of the files into the txscript directory in order to prepare it for merging. This does NOT update btcd or any of the other packages to use the new location as that will be done separately. - All import paths in the old btcscript test files have been changed to the new location - All references to btcscript as the package name have been chagned to txscript This is ongoing work toward #214.
370 lines
7.8 KiB
Go
370 lines
7.8 KiB
Go
// Copyright (c) 2013-2015 Conformal Systems LLC.
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// Use of this source code is governed by an ISC
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// license that can be found in the LICENSE file.
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package txscript
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import (
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"encoding/hex"
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"math/big"
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)
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// asInt converts a byte array to a bignum by treating it as a little endian
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// number with sign bit.
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func asInt(v []byte) (*big.Int, error) {
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// Only 32bit numbers allowed.
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if len(v) > 4 {
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return nil, ErrStackNumberTooBig
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}
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if len(v) == 0 {
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return big.NewInt(0), nil
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}
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negative := false
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origlen := len(v)
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msb := v[len(v)-1]
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if msb&0x80 == 0x80 {
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negative = true
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// remove sign bit
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msb &= 0x7f
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}
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// trim leading 0 bytes
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for ; msb == 0; msb = v[len(v)-1] {
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v = v[:len(v)-1]
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if len(v) == 0 {
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break
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}
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}
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// reverse bytes with a copy since stack is immutable.
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intArray := make([]byte, len(v))
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for i := range v {
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intArray[len(v)-i-1] = v[i]
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}
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// IFF the value is negative and no 0 bytes were trimmed,
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// the leading byte needs to be sign corrected
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if negative && len(intArray) == origlen {
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intArray[0] &= 0x7f
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}
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num := new(big.Int).SetBytes(intArray)
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if negative {
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num = num.Neg(num)
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}
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return num, nil
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}
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// fromInt provies a Big.Int in little endian format with the high bit of the
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// msb donating sign.
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func fromInt(v *big.Int) []byte {
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negative := false
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if v.Sign() == -1 {
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negative = true
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}
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// Int.Bytes() trims leading zeros for us, so we don't have to.
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b := v.Bytes()
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if len(b) == 0 {
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return []byte{}
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}
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arr := make([]byte, len(b))
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for i := range b {
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arr[len(b)-i-1] = b[i]
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}
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// if would otherwise be negative, add a zero byte
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if arr[len(arr)-1]&0x80 == 0x80 {
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arr = append(arr, 0)
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}
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if negative {
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arr[len(arr)-1] |= 0x80
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}
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return arr
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}
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// asBool gets the boolean value of the byte array.
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func asBool(t []byte) bool {
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for i := range t {
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if t[i] != 0 {
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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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// fromBool converts a boolean into the appropriate byte array.
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func fromBool(v bool) []byte {
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if v {
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return []byte{1}
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}
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return []byte{0}
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}
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// Stack represents a stack of immutable objects to be used with bitcoin scripts
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// Objects may be shared, therefore in usage if a value is to be changed it
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// *must* be deep-copied first to avoid changing other values on the stack.
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type Stack struct {
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stk [][]byte
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}
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// PushByteArray adds the given back array to the top of the stack.
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func (s *Stack) PushByteArray(so []byte) {
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s.stk = append(s.stk, so)
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}
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// PushInt converts the provided bignum to a suitable byte array then pushes
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// it onto the top of the stack.
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func (s *Stack) PushInt(val *big.Int) {
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s.PushByteArray(fromInt(val))
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}
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// PushBool converts the provided boolean to a suitable byte array then pushes
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// it onto the top of the stack.
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func (s *Stack) PushBool(val bool) {
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s.PushByteArray(fromBool(val))
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}
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// PopByteArray pops the value off the top of the stack and returns it.
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func (s *Stack) PopByteArray() ([]byte, error) {
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return s.nipN(0)
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}
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// PopInt pops the value off the top of the stack, converts it into a bignum and
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// returns it.
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func (s *Stack) PopInt() (*big.Int, error) {
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so, err := s.PopByteArray()
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if err != nil {
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return nil, err
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}
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return asInt(so)
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}
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// PopBool pops the value off the top of the stack, converts it into a bool and
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// returns it.
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func (s *Stack) PopBool() (bool, error) {
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so, err := s.PopByteArray()
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if err != nil {
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return false, err
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}
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return asBool(so), nil
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}
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// PeekByteArray returns the nth item on the stack without removing it.
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func (s *Stack) PeekByteArray(idx int) (so []byte, err error) {
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sz := len(s.stk)
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if idx < 0 || idx >= sz {
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return nil, ErrStackUnderflow
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}
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return s.stk[sz-idx-1], nil
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}
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// PeekInt returns the nth item on the stack as a bignum without removing it.
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func (s *Stack) PeekInt(idx int) (i *big.Int, err error) {
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so, err := s.PeekByteArray(idx)
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if err != nil {
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return nil, err
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}
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return asInt(so)
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}
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// PeekBool returns the nth item on the stack as a bool without removing it.
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func (s *Stack) PeekBool(idx int) (i bool, err error) {
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so, err := s.PeekByteArray(idx)
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if err != nil {
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return false, err
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}
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return asBool(so), nil
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}
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// nipN is an internal function that removes the nth item on the stack and
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// returns it.
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func (s *Stack) nipN(idx int) (so []byte, err error) {
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sz := len(s.stk)
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if idx < 0 || idx > sz-1 {
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err = ErrStackUnderflow
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return
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}
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so = s.stk[sz-idx-1]
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if idx == 0 {
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s.stk = s.stk[:sz-1]
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} else if idx == sz-1 {
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s1 := make([][]byte, sz-1, sz-1)
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copy(s1, s.stk[1:])
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s.stk = s1
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} else {
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s1 := s.stk[sz-idx : sz]
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s.stk = s.stk[:sz-idx-1]
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s.stk = append(s.stk, s1...)
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}
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return
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}
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// NipN removes the Nth object on the stack
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func (s *Stack) NipN(idx int) error {
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_, err := s.nipN(idx)
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return err
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}
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// Tuck copies the item at the top of the stack and inserts it before the 2nd
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// to top item. e.g.: 2,1 -> 2,1,2
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func (s *Stack) Tuck() error {
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so2, err := s.PopByteArray()
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if err != nil {
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return err
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}
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so1, err := s.PopByteArray()
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if err != nil {
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return err
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}
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s.PushByteArray(so2) // stack 2
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s.PushByteArray(so1) // stack 1,2
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s.PushByteArray(so2) // stack 2,1,2
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return nil
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}
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// Depth returns the number of items on the stack.
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func (s *Stack) Depth() (sz int) {
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sz = len(s.stk)
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return
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}
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// DropN removes the top N items from the stack.
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// e.g.
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// DropN(1): 1,2,3 -> 1,2
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// DropN(2): 1,2,3 -> 1
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func (s *Stack) DropN(n int) error {
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if n < 1 {
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return ErrStackInvalidArgs
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}
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for ; n > 0; n-- {
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_, err := s.PopByteArray()
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if err != nil {
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return err
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}
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}
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return nil
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}
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// DupN duplicates the top N items on the stack.
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// e.g.
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// DupN(1): 1,2,3 -> 1,2,3,3
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// DupN(2): 1,2,3 -> 1,2,3,2,3
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func (s *Stack) DupN(n int) error {
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if n < 1 {
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return ErrStackInvalidArgs
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}
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// Iteratively duplicate the value n-1 down the stack n times.
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// this leaves us with an in-order duplicate of the top N items on the
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// stack.
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for i := n; i > 0; i-- {
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so, err := s.PeekByteArray(n - 1)
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if err != nil {
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return err
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}
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s.PushByteArray(so)
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}
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return nil
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}
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// RotN rotates the top 3N items on the stack to the left
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// e.g.
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// RotN(1): 1,2,3 -> 2,3,1
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func (s *Stack) RotN(n int) error {
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if n < 1 {
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return ErrStackInvalidArgs
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}
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entry := 3*n - 1
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// Nip the 3n-1th item from the stack to the top n times to rotate
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// them up to the head of the stack.
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for i := n; i > 0; i-- {
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so, err := s.nipN(entry)
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if err != nil {
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return err
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}
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s.PushByteArray(so)
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}
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return nil
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}
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// SwapN swaps the top N items on the stack with those below them.
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// E.g.:
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// SwapN(1): 1,2 -> 2,1
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// SwapN(2): 1,2,3,4 -> 3,4,1,2
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func (s *Stack) SwapN(n int) error {
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if n < 1 {
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return ErrStackInvalidArgs
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}
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entry := 2*n - 1
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for i := n; i > 0; i-- {
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// swap 2n-1th entry to topj
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so, err := s.nipN(entry)
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if err != nil {
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return err
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}
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s.PushByteArray(so)
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}
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return nil
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}
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// OverN copies N items N spaces back to the top of the stack.
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// e.g.:
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// OverN(1): 1,2 -> 1,2,1
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// OverN(2): 1,2,3,4 -> 1,2,3,4,1,2
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func (s *Stack) OverN(n int) error {
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if n < 1 {
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return ErrStackInvalidArgs
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}
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// Copy 2n-1th entry to top of the stack
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entry := 2*n - 1
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for ; n > 0; n-- {
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so, err := s.PeekByteArray(entry)
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if err != nil {
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return err
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}
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s.PushByteArray(so)
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// 4,1,2,3,4, now code original 3rd entry to top.
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}
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return nil
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}
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// PickN copies the item N items back in the stack to the top.
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// e.g.:
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// PickN(1): 1,2,3 -> 1,2,3,2
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// PickN(2): 1,2,3 -> 1,2,3,1
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func (s *Stack) PickN(n int) error {
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so, err := s.PeekByteArray(n)
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if err != nil {
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return err
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}
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s.PushByteArray(so)
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return nil
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}
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// RollN moves the item N items back in the stack to the top.
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// e.g.:
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// RollN(1): 1,2,3 -> 1,3,2
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// RollN(2): 1,2,3 -> 2,3,1
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func (s *Stack) RollN(n int) error {
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so, err := s.nipN(n)
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if err != nil {
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return err
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}
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s.PushByteArray(so)
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return nil
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}
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// String returns the stack in a readable format.
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func (s *Stack) String() string {
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var result string
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for _, stack := range s.stk {
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result += hex.Dump(stack)
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}
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return result
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}
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