Add RET Opcode

pkg/vm/vm_ops_flow.go

@@ -0,0 +1,25 @@
+package vm
+
+import (
+	"github.com/CityOfZion/neo-go/pkg/vm/stack"
+)
+
+// Flow control
+
+// RET Returns from the current context
+// Returns HALT if there are nomore context's to run
+func RET(op stack.Instruction, ctx *stack.Context, istack *stack.Invocation) (Vmstate, error) {
+
+	// Pop current context from the Inovation stack
+	err := istack.RemoveCurrentContext()
+	if err != nil {
+		return FAULT, err
+	}
+
+	// If there are no-more context's left to ran, then we HALT
+	if istack.Len() == 0 {
+		return HALT, nil
+	}
+
+	return NONE, nil
+}