c文件读写

快来打我* 2023-07-04 03:24 64阅读 0赞

关于c 里面的 open 可以参考[链接][Link 1]

#include <string>
    #include <sys/types.h>
    #include <sys/stat.h>
    #include <fcntl.h>
    #include <unistd.h>
    
    struct feature_data {
      int score;
      std::string query;
      feature_data() : score(0), query("") {}
    };
    
    struct  PhraseDictHeader {
      size_t header_size;
      int phrase_num;
      int offset;
    };
    
    void test_darts() {
      std::vector<const char*> sorted_keys;
      std::vector<size_t> sorted_keylens;
      std::vector<int> sorted_values;
      std::vector<size_t> values;
      std::vector<std::pair<std::string, int32_t>> inputs_darts;
      std::vector<feature_data> phrase_features;
      size_t offset = 0;
      for (uint32_t i = 0; i < inputs_darts.size(); i++) {
        sorted_keys.push_back(inputs_darts[i].first.c_str());
        sorted_keylens.push_back(inputs_darts[i].first.length());
        sorted_values.push_back(values.size());
        values.push_back(offset);
        offset += sizeof(uint16_t) + sizeof(feature_data);
        //LOG(INFO) << inputs_darts[i] << "\t" << sorted_values.back() << "\t" << offset;
      }
      cout << "inputs_darts size:" << inputs_darts.size() << endl;
      std::string filename = "output.txt";
      // #include <sys/types.h>    #include <sys/stat.h>    #include <fcntl.h>
      int fd = ::open(filename.c_str(), O_WRONLY | O_CREAT | O_TRUNC, 0644);
      if (fd < 0) {
        cout << "open file error!"  << endl;
        return;
      }
      // bzero() 会将内存块（字符串）的前n个字节清零;
      PhraseDictHeader header;
      bzero(&header, sizeof(header));
      header.header_size = sizeof(header);
      header.phrase_num = values.size();
      header.offset =  offset;
      cout << "header_size:" << header.header_size << endl;
      // write 头文件 #include <unistd.h>
      ::write(fd, &header, sizeof(PhraseDictHeader));
      for (size_t i = 0; i < values.size(); ++i) {
        ::write(fd, &values[i], sizeof(size_t));
      }
      for (uint32_t i = 0; i < inputs_darts.size(); i++) {
        uint16_t byte = sizeof(feature_data);
        ::write(fd, &byte, sizeof(uint16_t));
        ::write(fd, &phrase_features[inputs_darts[i].second], sizeof(feature_data));
      }
      // 关闭文件
      close(fd);
    
      int fr =  ::open(filename.c_str(), O_RDONLY, 0644);
      PhraseDictHeader header2;
      ::read(fr, &header2, sizeof(PhraseDictHeader));
      cout << "header2 size:" << header2.header_size << endl;
      close(fr);
    }
    int main() {
      test_darts();
      return 0;
    }

[Link 1]: http://c.biancheng.net/cpp/html/238.html