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