Implement OperandStack for Runtime

runtime/OperandStack.c

@@ -0,0 +1,29 @@
+#include "OperandStack.h"
+
+int OStackSize(OperandStack* stack) {
+    return stack->top;
+}
+
+int OStackPush(OperandStack* stack, int operand) {
+    if (OStackSize(stack) >= TYPE_STACK_SIZE) {
+        // Stack overflow
+        return -1;
+    }
+
+    stack->operands[stack->top] = operand;
+    stack->top++;
+
+    return 0;
+}
+
+int OStackPop(OperandStack* stack, int* result) {
+    if (OStackSize(stack) == 0) {
+        // Stack underflow
+        return -1;
+    }
+
+    *result = stack->operands[stack->top - 1];
+    stack->top--;
+
+    return 0;
+}