Add pagination to b_manage

src/manage/Paginator.hpp

@@ -0,0 +1,29 @@
+#pragma once
+
+#include <utility>
+
+class Paginator {
+public:
+    Paginator() = default;
+    Paginator(int pageSize, int total) : pageSize(pageSize), total(total)
+    {
+        numPages = (total + pageSize - 1) / pageSize;
+    };
+    ~Paginator() = default;
+    int getPageSize() const { return pageSize; }
+    int getTotal() const { return total; }
+    std::pair<int, int> getOffset(int page) const
+    {
+        if (page > numPages)
+            throw std::out_of_range("page out of range");
+        return { (page - 1) * pageSize, std::min(total - 1, page * pageSize - 1) };
+    }
+    int getPages() const { return numPages; }
+    bool valid(int page) const { return page > 0 && page <= numPages; }
+    bool hasPrev(int page) const { return page > 1; }
+    bool hasNext(int page) const { return page < getPages(); }
+private:
+    int pageSize;
+    int total;
+    int numPages;
+};