implement inter-chunk structure generation

src/util/listutil.hpp

@@ -1,15 +1,20 @@
 #pragma once
 
 #include <algorithm>
-#include <queue>
 #include <string>
 #include <vector>
 
 namespace util {
     template <class T>
-    bool contains(const std::vector<T>& vec, const T& value) {
+    inline bool contains(const std::vector<T>& vec, const T& value) {
         return std::find(vec.begin(), vec.end(), value) != vec.end();
     }
 
+    template <class T>
+    inline void concat(std::vector<T>& a, const std::vector<T>& b) {
+        a.reserve(a.size() + b.size());
+        a.insert(a.end(), b.begin(), b.end());
+    }
+
     std::string to_string(const std::vector<std::string>& vec);
 }