1 files changed, 65 insertions, 0 deletions
diff --git a/vm/stack.go b/vm/stack.go
new file mode 100644
index 000000000..c5c2774db
--- /dev/null
+++ b/vm/stack.go
@@ -0,0 +1,65 @@
+package vm
+
+import (
+	"fmt"
+	"math/big"
+)
+
+func newStack() *stack {
+	return &stack{}
+}
+
+type stack struct {
+	data []*big.Int
+	ptr  int
+}
+
+func (st *stack) push(d *big.Int) {
+	stackItem := new(big.Int).Set(d)
+	if len(st.data) > st.ptr {
+		st.data[st.ptr] = stackItem
+	} else {
+		st.data = append(st.data, stackItem)
+	}
+	st.ptr++
+}
+
+func (st *stack) pop() (ret *big.Int) {
+	st.ptr--
+	ret = st.data[st.ptr]
+	return
+}
+
+func (st *stack) len() int {
+	return st.ptr
+}
+
+func (st *stack) swap(n int) {
+	st.data[st.len()-n], st.data[st.len()-1] = st.data[st.len()-1], st.data[st.len()-n]
+}
+
+func (st *stack) dup(n int) {
+	st.push(st.data[st.len()-n])
+}
+
+func (st *stack) peek() *big.Int {
+	return st.data[st.len()-1]
+}
+
+func (st *stack) require(n int) {
+	if st.len() < n {
+		panic(fmt.Sprintf("stack underflow (%d <=> %d)", len(st.data), n))
+	}
+}
+
+func (st *stack) Print() {
+	fmt.Println("### stack ###")
+	if len(st.data) > 0 {
+		for i, val := range st.data {
+			fmt.Printf("%-3d  %v\n", i, val)
+		}
+	} else {
+		fmt.Println("-- empty --")
+	}
+	fmt.Println("#############")
+}