110 lines
2.3 KiB
Go
110 lines
2.3 KiB
Go
package vm
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import (
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"math"
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"math/big"
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"github.com/ethereum/go-ethereum/ethutil"
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)
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type ContextRef interface {
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ReturnGas(*big.Int, *big.Int)
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Address() []byte
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SetCode([]byte)
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}
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type Context struct {
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caller ContextRef
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object ContextRef
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Code []byte
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Gas, UsedGas, Price *big.Int
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Args []byte
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}
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// Create a new context for the given data items
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func NewContext(caller ContextRef, object ContextRef, code []byte, gas, price *big.Int) *Context {
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c := &Context{caller: caller, object: object, Code: code, Args: nil}
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// Gas should be a pointer so it can safely be reduced through the run
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// This pointer will be off the state transition
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c.Gas = gas //new(big.Int).Set(gas)
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// In most cases price and value are pointers to transaction objects
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// and we don't want the transaction's values to change.
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c.Price = new(big.Int).Set(price)
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c.UsedGas = new(big.Int)
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return c
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}
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func (c *Context) GetOp(n uint64) OpCode {
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return OpCode(c.GetByte(n))
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}
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func (c *Context) GetByte(n uint64) byte {
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if n < uint64(len(c.Code)) {
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return c.Code[n]
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}
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return 0
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}
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func (c *Context) GetBytes(x, y int) []byte {
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return c.GetRangeValue(uint64(x), uint64(y))
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}
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func (c *Context) GetRangeValue(x, size uint64) []byte {
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x = uint64(math.Min(float64(x), float64(len(c.Code))))
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y := uint64(math.Min(float64(x+size), float64(len(c.Code))))
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return ethutil.RightPadBytes(c.Code[x:y], int(size))
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}
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func (c *Context) GetCode(x, size uint64) []byte {
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x = uint64(math.Min(float64(x), float64(len(c.Code))))
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y := uint64(math.Min(float64(x+size), float64(len(c.Code))))
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return ethutil.RightPadBytes(c.Code[x:y], int(size))
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}
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func (c *Context) Return(ret []byte) []byte {
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// Return the remaining gas to the caller
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c.caller.ReturnGas(c.Gas, c.Price)
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return ret
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}
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/*
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* Gas functions
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*/
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func (c *Context) UseGas(gas *big.Int) bool {
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if c.Gas.Cmp(gas) < 0 {
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return false
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}
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// Sub the amount of gas from the remaining
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c.Gas.Sub(c.Gas, gas)
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c.UsedGas.Add(c.UsedGas, gas)
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return true
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}
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// Implement the caller interface
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func (c *Context) ReturnGas(gas, price *big.Int) {
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// Return the gas to the context
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c.Gas.Add(c.Gas, gas)
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c.UsedGas.Sub(c.UsedGas, gas)
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}
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/*
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* Set / Get
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*/
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func (c *Context) Address() []byte {
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return c.object.Address()
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}
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func (self *Context) SetCode(code []byte) {
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self.Code = code
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}
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