path: root/vm/closure.go

package vm

import (
    "math/big"

    "github.com/ethereum/go-ethereum/ethutil"
    "github.com/ethereum/go-ethereum/state"
)

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

type Closure struct {
    caller  ClosureRef
    object  ClosureRef
    Code    []byte
    message *state.Message

    Gas, UsedGas, Price *big.Int

    Args []byte
}

// Create a new closure for the given data items
func NewClosure(msg *state.Message, caller ClosureRef, object ClosureRef, code []byte, gas, price *big.Int) *Closure {
    c := &Closure{message: msg, 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 *Closure) GetValue(x uint64) *ethutil.Value {
    return c.GetRangeValue(x, 1)
}

func (c *Closure) GetOp(x uint64) OpCode {
    return OpCode(c.GetByte(x))
}

func (c *Closure) GetByte(x uint64) byte {
    if x < uint64(len(c.Code)) {
        return c.Code[x]
    }

    return 0
}

func (c *Closure) GetBytes(x, y int) []byte {
    if x >= len(c.Code) || y >= len(c.Code) {
        return nil
    }

    return c.Code[x : x+y]
}

func (c *Closure) GetRangeValue(x, y uint64) *ethutil.Value {
    if x >= uint64(len(c.Code)) || y >= uint64(len(c.Code)) {
        return ethutil.NewValue(0)
    }

    partial := c.Code[x : x+y]

    return ethutil.NewValue(partial)
}

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

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

    return ret
}

/*
 * Gas functions
 */
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)
}

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

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

func (self *Closure) SetCode(code []byte) {
    self.Code = code
}