path: root/ethvm/closure.go

package ethvm

// TODO Re write VM to use values instead of big integers?

import (
    "github.com/ethereum/eth-go/ethstate"
    "github.com/ethereum/eth-go/ethutil"
    "math/big"
)

type ClosureRef interface {
    ReturnGas(*big.Int, *big.Int)
    Address() []byte
    GetStorage(*big.Int) *ethutil.Value
    SetStorage(*big.Int, *ethutil.Value)
}

// Basic inline closure object which implement the 'closure' interface
type Closure struct {
    caller ClosureRef
    object *ethstate.StateObject
    Code   []byte

    Gas, UsedGas, Price *big.Int

    Args []byte
}

// Create a new closure for the given data items
func NewClosure(caller ClosureRef, object *ethstate.StateObject, code []byte, gas, price *big.Int) *Closure {
    c := &Closure{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
}

// Retuns the x element in data slice
func (c *Closure) GetStorage(x *big.Int) *ethutil.Value {
    m := c.object.GetStorage(x)
    if m == nil {
        return ethutil.EmptyValue()
    }

    return m
}

func (c *Closure) Get(x *big.Int) *ethutil.Value {
    return c.Gets(x, big.NewInt(1))
}

func (c *Closure) Gets(x, y *big.Int) *ethutil.Value {
    if x.Int64() >= int64(len(c.Code)) || y.Int64() >= int64(len(c.Code)) {
        return ethutil.NewValue(0)
    }

    partial := c.Code[x.Int64() : x.Int64()+y.Int64()]

    return ethutil.NewValue(partial)
}

func (c *Closure) SetStorage(x *big.Int, val *ethutil.Value) {
    c.object.SetStorage(x, val)
}

func (c *Closure) Address() []byte {
    return c.object.Address()
}

func (c *Closure) Call(vm *Vm, args []byte) ([]byte, *big.Int, error) {
    c.Args = args

    ret, err := vm.RunClosure(c)

    return ret, c.UsedGas, err
}

func (c *Closure) Return(ret []byte) []byte {
    // Return the remaining gas to the caller
    c.caller.ReturnGas(c.Gas, c.Price)

    return ret
}

func (c *Closure) 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 *Closure) ReturnGas(gas, price *big.Int) {
    // Return the gas to the closure
    c.Gas.Add(c.Gas, gas)
    c.UsedGas.Sub(c.UsedGas, gas)
}

func (c *Closure) Object() *ethstate.StateObject {
    return c.object
}

func (c *Closure) Caller() ClosureRef {
    return c.caller
}