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.RightPadBytes(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 }