126 lines
4.3 KiB
C++
126 lines
4.3 KiB
C++
#ifndef BPT_MEMORYRIVER_HPP
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#define BPT_MEMORYRIVER_HPP
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#include <fstream>
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#include <iostream>
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#include <stack>
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using std::fstream;
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using std::ifstream;
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using std::ofstream;
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using std::string;
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template <class T, const int info_len = 2>
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class MemoryRiver {
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private:
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/* your code here */
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fstream file;
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string file_name;
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const int sizeofT = sizeof(T);
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std::stack<int> free_mem;
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int total_mem = 0;
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public:
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MemoryRiver() = default;
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~MemoryRiver() {
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file.open(file_name, std::ios::binary | std ::ios::out | std::ios::in);
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file.seekp(info_len * sizeof(int), std::ios::beg);
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// std::cerr << "pos1 " << info_len * sizeof(int) << std::endl;
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file.write(reinterpret_cast<char *>(&total_mem), sizeof(int));
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int tmp = free_mem.size();
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file.write(reinterpret_cast<char *>(&tmp), sizeof(int));
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file.seekp((info_len + 2) * sizeof(int) + total_mem * sizeofT,
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std::ios::beg);
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// std::cerr << "pos2 " << (info_len + 2) * sizeof(int) + total_mem * sizeofT
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// << std::endl;
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while (!free_mem.empty()) {
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tmp = free_mem.top();
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file.write(reinterpret_cast<char *>(&tmp), sizeof(int));
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free_mem.pop();
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}
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file.close();
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}
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bool operator=(const MemoryRiver &) = delete;
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MemoryRiver(const string &file_name) : file_name(file_name) {
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file.open(file_name, std::ios::binary | std ::ios::out | std::ios::in);
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file.seekg(info_len * sizeof(int), std::ios::beg);
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file.read(reinterpret_cast<char *>(&total_mem), sizeof(int));
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int free_mem_size = 0;
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file.read(reinterpret_cast<char *>(&free_mem_size), sizeof(int));
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file.seekg((info_len + 2) * sizeof(int) + total_mem * sizeofT,
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std::ios::beg);
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while (free_mem_size-- > 0) {
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int tmp;
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file.read(reinterpret_cast<char *>(&tmp), sizeof(int));
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free_mem.push(tmp);
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fprintf(stderr,"get %d\n",tmp);
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}
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file.close();
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}
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void initialise(string FN = "") {
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if (FN != "") file_name = FN;
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file.open(file_name, std::ios::binary | std ::ios::out);
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file.seekp(0, std::ios::beg);
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int tmp = 0;
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for (int i = 0; i < info_len; ++i)
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file.write(reinterpret_cast<char *>(&tmp), sizeof(int));
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file.close();
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}
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// 读出第n个int的值赋给tmp，1_base
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void get_info(int &tmp, int n) {
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if (n > info_len) return;
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file.open(file_name, std::ios::binary | std ::ios::out | std::ios::in);
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file.seekg((n - 1) * sizeof(int), std::ios::beg);
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// std::cerr << "pos " << (n - 1) * sizeof(int) << std::endl;
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file.read(reinterpret_cast<char *>(&tmp), sizeof(int));
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file.close();
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}
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// 将tmp写入第n个int的位置，1_base
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void write_info(int tmp, int n) {
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if (n > info_len) return;
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file.open(file_name, std::ios::binary | std ::ios::out | std::ios::in);
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file.seekp((n - 1) * sizeof(int), std::ios::beg);
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file.write(reinterpret_cast<const char *>(&tmp), sizeof(int));
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file.close();
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}
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// 在文件合适位置写入类对象t，并返回写入的位置索引index
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// 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
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int write(T &t) {
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int index = -1;
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if (!free_mem.empty()) {
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index = free_mem.top();
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free_mem.pop();
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} else
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index = ++total_mem;
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update(t, index);
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return index;
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}
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// 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
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void update(T &t, const int index) {
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file.open(file_name, std::ios::binary | std ::ios::out | std::ios::in);
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file.seekp((info_len + 2) * sizeof(int) + (index - 1) * sizeofT,
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std::ios::beg);
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file.write(reinterpret_cast<char *>(&t), sizeofT);
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file.close();
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}
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// 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
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void read(T &t, const int index) {
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file.open(file_name, std::ios::binary | std ::ios::out | std::ios::in);
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file.seekg((info_len + 2) * sizeof(int) + (index - 1) * sizeofT,
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std::ios::beg);
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file.read(reinterpret_cast<char *>(&t), sizeofT);
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file.close();
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}
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// 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
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void Delete(int index) { free_mem.push(index); }
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};
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#endif // BPT_MEMORYRIVER_HPP
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