Closures and vm based on closures

Status: Work in progress

ethchain/closure.go

@@ -0,0 +1,68 @@
+package ethchain
+
+// TODO Re write VM to use values instead of big integers?
+
+import (
+	"github.com/ethereum/eth-go/ethutil"
+	"math/big"
+)
+
+type Callee interface {
+	ReturnGas(*big.Int, *State)
+}
+
+type ClosureBody interface {
+	Callee
+	ethutil.RlpEncodable
+	GetMem(int64) *ethutil.Value
+}
+
+// Basic inline closure object which implement the 'closure' interface
+type Closure struct {
+	callee Callee
+	object ClosureBody
+	state  *State
+
+	gas *big.Int
+	val *big.Int
+}
+
+// Create a new closure for the given data items
+func NewClosure(callee Callee, object ClosureBody, state *State, gas, val *big.Int) *Closure {
+	return &Closure{callee, object, state, gas, val}
+}
+
+// Retuns the x element in data slice
+func (c *Closure) GetMem(x int64) *ethutil.Value {
+	m := c.object.GetMem(x)
+	if m == nil {
+		return ethutil.EmptyValue()
+	}
+
+	return m
+}
+
+func (c *Closure) Return(ret []byte) []byte {
+	// Return the remaining gas to the callee
+	// If no callee is present return it to
+	// the origin (i.e. contract or tx)
+	if c.callee != nil {
+		c.callee.ReturnGas(c.gas, c.state)
+	} else {
+		c.object.ReturnGas(c.gas, c.state)
+		// TODO incase it's a POST contract we gotta serialise the contract again.
+		// But it's not yet defined
+	}
+
+	return ret
+}
+
+// Implement the Callee interface
+func (c *Closure) ReturnGas(gas *big.Int, state *State) {
+	// Return the gas to the closure
+	c.gas.Add(c.gas, gas)
+}
+
+func (c *Closure) GetGas() *big.Int {
+	return c.gas
+}