stack.go 2.43 KB
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// Copyright 2014 The go-ethereum Authors
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// This file is part of the go-ethereum library.
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//
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// The go-ethereum library is free software: you can redistribute it and/or modify
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// it under the terms of the GNU Lesser General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
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// The go-ethereum library is distributed in the hope that it will be useful,
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// but WITHOUT ANY WARRANTY; without even the implied warranty of
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// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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// GNU Lesser General Public License for more details.
//
// You should have received a copy of the GNU Lesser General Public License
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// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
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package vm
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import (
	"fmt"
	"math/big"
)

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// Stack is an object for basic stack operations. Items popped to the stack are
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// expected to be changed and modified. stack does not take care of adding newly
// initialised objects.
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type Stack struct {
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	data []*big.Int
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}

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func newstack() *Stack {
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	return &Stack{data: make([]*big.Int, 0, 1024)}
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}

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// Data returns the underlying big.Int array.
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func (st *Stack) Data() []*big.Int {
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	return st.data
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}

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func (st *Stack) push(d *big.Int) {
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	// NOTE push limit (1024) is checked in baseCheck
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	//stackItem := new(big.Int).Set(d)
	//st.data = append(st.data, stackItem)
	st.data = append(st.data, d)
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}
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func (st *Stack) pushN(ds ...*big.Int) {
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	st.data = append(st.data, ds...)
}
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func (st *Stack) pop() (ret *big.Int) {
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	ret = st.data[len(st.data)-1]
	st.data = st.data[:len(st.data)-1]
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	return
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}

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func (st *Stack) len() int {
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	return len(st.data)
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}

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func (st *Stack) swap(n int) {
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	st.data[st.len()-n], st.data[st.len()-1] = st.data[st.len()-1], st.data[st.len()-n]
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}

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func (st *Stack) dup(pool *intPool, n int) {
	st.push(pool.get().Set(st.data[st.len()-n]))
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}

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func (st *Stack) peek() *big.Int {
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	return st.data[st.len()-1]
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}

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// Back returns the n'th item in stack
func (st *Stack) Back(n int) *big.Int {
	return st.data[st.len()-n-1]
}

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func (st *Stack) require(n int) error {
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	if st.len() < n {
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		return fmt.Errorf("stack underflow (%d <=> %d)", len(st.data), n)
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	}
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	return nil
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}

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// Print dumps the content of the stack
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func (st *Stack) Print() {
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	fmt.Println("### stack ###")
	if len(st.data) > 0 {
		for i, val := range st.data {
			fmt.Printf("%-3d  %v\n", i, val)
		}
	} else {
		fmt.Println("-- empty --")
	}
	fmt.Println("#############")
}