upd: 完成前置作业1

docs/homework_requirement/memoryriver.hpp

@@ -0,0 +1,126 @@
+#ifndef BPT_MEMORYRIVER_HPP
+#define BPT_MEMORYRIVER_HPP
+
+#include <fstream>
+#include <iostream>
+#include <stack>
+
+using std::fstream;
+using std::ifstream;
+using std::ofstream;
+using std::string;
+
+template <class T, const int info_len = 2>
+class MemoryRiver {
+ private:
+  /* your code here */
+  fstream file;
+  string file_name;
+  const int sizeofT = sizeof(T);
+  std::stack<int> free_mem;
+  int total_mem = 0;
+
+ public:
+  MemoryRiver() = default;
+  ~MemoryRiver() {
+    file.open(file_name, std::ios::binary | std ::ios::out | std::ios::in);
+    file.seekp(info_len * sizeof(int), std::ios::beg);
+    // std::cerr << "pos1 " << info_len * sizeof(int) << std::endl;
+    file.write(reinterpret_cast<char *>(&total_mem), sizeof(int));
+    int tmp = free_mem.size();
+    file.write(reinterpret_cast<char *>(&tmp), sizeof(int));
+    file.seekp((info_len + 2) * sizeof(int) + total_mem * sizeofT,
+               std::ios::beg);
+    // std::cerr << "pos2 " << (info_len + 2) * sizeof(int) + total_mem * sizeofT
+              // << std::endl;
+    while (!free_mem.empty()) {
+      tmp = free_mem.top();
+      file.write(reinterpret_cast<char *>(&tmp), sizeof(int));
+      free_mem.pop();
+    }
+    file.close();
+  }
+  bool operator=(const MemoryRiver &) = delete;
+
+  MemoryRiver(const string &file_name) : file_name(file_name) {
+    file.open(file_name, std::ios::binary | std ::ios::out | std::ios::in);
+    file.seekg(info_len * sizeof(int), std::ios::beg);
+    file.read(reinterpret_cast<char *>(&total_mem), sizeof(int));
+    int free_mem_size = 0;
+    file.read(reinterpret_cast<char *>(&free_mem_size), sizeof(int));
+    file.seekg((info_len + 2) * sizeof(int) + total_mem * sizeofT,
+               std::ios::beg);
+    while (free_mem_size-- > 0) {
+      int tmp;
+      file.read(reinterpret_cast<char *>(&tmp), sizeof(int));
+      free_mem.push(tmp);
+      fprintf(stderr,"get %d\n",tmp);
+    }
+    file.close();
+  }
+
+  void initialise(string FN = "") {
+    if (FN != "") file_name = FN;
+    file.open(file_name, std::ios::binary | std ::ios::out);
+    file.seekp(0, std::ios::beg);
+    int tmp = 0;
+    for (int i = 0; i < info_len; ++i)
+      file.write(reinterpret_cast<char *>(&tmp), sizeof(int));
+    file.close();
+  }
+
+  // 读出第n个int的值赋给tmp，1_base
+  void get_info(int &tmp, int n) {
+    if (n > info_len) return;
+    file.open(file_name, std::ios::binary | std ::ios::out | std::ios::in);
+    file.seekg((n - 1) * sizeof(int), std::ios::beg);
+    // std::cerr << "pos " << (n - 1) * sizeof(int) << std::endl;
+    file.read(reinterpret_cast<char *>(&tmp), sizeof(int));
+    file.close();
+  }
+
+  // 将tmp写入第n个int的位置，1_base
+  void write_info(int tmp, int n) {
+    if (n > info_len) return;
+    file.open(file_name, std::ios::binary | std ::ios::out | std::ios::in);
+    file.seekp((n - 1) * sizeof(int), std::ios::beg);
+    file.write(reinterpret_cast<const char *>(&tmp), sizeof(int));
+    file.close();
+  }
+
+  // 在文件合适位置写入类对象t，并返回写入的位置索引index
+  // 位置索引意味着当输入正确的位置索引index，在以下三个函数中都能顺利的找到目标对象进行操作
+  int write(T &t) {
+    int index = -1;
+    if (!free_mem.empty()) {
+      index = free_mem.top();
+      free_mem.pop();
+    } else
+      index = ++total_mem;
+    update(t, index);
+    return index;
+  }
+
+  // 用t的值更新位置索引index对应的对象，保证调用的index都是由write函数产生
+  void update(T &t, const int index) {
+    file.open(file_name, std::ios::binary | std ::ios::out | std::ios::in);
+    file.seekp((info_len + 2) * sizeof(int) + (index - 1) * sizeofT,
+               std::ios::beg);
+    file.write(reinterpret_cast<char *>(&t), sizeofT);
+    file.close();
+  }
+
+  // 读出位置索引index对应的T对象的值并赋值给t，保证调用的index都是由write函数产生
+  void read(T &t, const int index) {
+    file.open(file_name, std::ios::binary | std ::ios::out | std::ios::in);
+    file.seekg((info_len + 2) * sizeof(int) + (index - 1) * sizeofT,
+               std::ios::beg);
+    file.read(reinterpret_cast<char *>(&t), sizeofT);
+    file.close();
+  }
+
+  // 删除位置索引index对应的对象(不涉及空间回收时，可忽略此函数)，保证调用的index都是由write函数产生
+  void Delete(int index) { free_mem.push(index); }
+};
+
+#endif  // BPT_MEMORYRIVER_HPP