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07-file.md

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代码总览

file.h/file.cc/file_test.cc.

proto与文件之间的读写转, 和对文件(夹)的一些操作.

功能/知识

1. 方法GetProtoFromFile()

  • 打开文件读取protobuf消息.若是二进制文件(由文件名后缀判定), 优先调用二进制文件读取方法; 若是文本文件, 优先调用文本文件读取方法.
  • std::equal, 判断两个vector string或者[]是否相等. 注意短链可以匹配的上长链. 一个demo: 
    // equal algorithm example
#include <algorithm>  // std::equal
#include <iostream>   // std::cout
#include <string>     //std::string
int main() {
std::string str1 = "abcdefg";
std::string str2 = "abcdefg";
std::string str3 = "abcd";
std::string str4 = "efg";
// yes
if (std::equal(str1.begin(), str1.end(), str2.begin())) {
    std::cout << "yes" << std::endl;
} else {
    std::cout << "false" << std::endl;
}
// yes
if (std::equal(str3.begin(), str3.end(), str1.begin())) {
    std::cout << "yes" << std::endl;
} else {
    std::cout << "false" << std::endl;
}
// false
if (std::equal(str1.begin(), str1.end(), str3.begin())) {
    std::cout << "yes" << std::endl;
} else {
    std::cout << "false" << std::endl;
}
// yes
if (std::equal(str4.rbegin(), str4.rend(), str1.rbegin())) {
    std::cout << "yes" << std::endl;
} else {
    std::cout << "false" << std::endl;
}
}

2. 方法PathExists()

  • 判断目录或文件是否存在.
  • stat可以用来判断文件是否存在, 如: 
    #include <sys/stat.h>
#include <sys/types.h>
#include <iostream>
using namespace std;
int main()
{
struct stat info;
cout<<stat("test15.cc",&info)<<endl; //存在 0，不存在 -1.
//不管存在与否，info都会有很多字段（有值的那种）可以参考https://blog.csdn.net/natpan/article/details/81453209
cout<<"st_dev is:"<<info.st_dev<<endl;
cout<<"st_ino is:"<<info.st_ino<<endl;
cout<<"st_mode is:"<<info.st_mode<<endl;
cout<<"st_nlink is:"<<info.st_nlink<<endl;
cout<<"st_uid si:"<<info.st_uid<<endl;
cout<<"st_gid is:"<<info.st_gid<<endl;
cout<<"st_rdev is:"<<info.st_rdev<<endl;
cout<<"st_size is:"<<info.st_size<<endl;
cout<<"st_blksize is:"<<info.st_blksize<<endl;
cout<<"st_atime is:"<<info.st_atime<<endl;
cout<<"st_mtime is:"<<info.st_mtime<<endl;
cout<<"st_ctime is :"<<info.st_ctime<<endl;
}

3. 函数DirectoryExists()

  • 判断目录是否存在. 注意目录和文件的字段st_mode是不一样的. 一个demo: 
    #include <sys/stat.h>
#include <sys/types.h>
#include <iostream>
using namespace std;
int main()
{
struct stat info;
cout<<stat("test15.cc",&info)<<endl; 
cout<<"st_mode is:"<<info.st_mode<<endl; // st_mode is:33204
cout<<stat("/home/shiqiang/",&info)<<endl; 
cout<<"st_mode is:"<<info.st_mode<<endl;  // st_mode is:16877
}

4. 方法Glob()

  • 用正则的方法查找文件. demo: 
    #include <iostream>
#include <vector>
#include <string>
#include <glob.h>
std::vector<std::string> Glob(const std::string &pattern) {
glob_t globs = {};
std::vector<std::string> results;
if (glob(pattern.c_str(), GLOB_TILDE, nullptr, &globs) == 0) {
    for (size_t i = 0; i < globs.gl_pathc; ++i) {
    results.emplace_back(globs.gl_pathv[i]);
    std::cout<<results.at(results.size()-1)<<std::endl;
    }
}
globfree(&globs);
return results;
}

int main()
{
// 输入的是正则规则
Glob("test*.cc"); 
}

5. 方法EnsureDirectory()

  • 确保文件夹存在, 如果文件夹不存在就创建它.
  • 一个使用mkdir的demo如下： 
    #include <iostream>
#include <string>
#include <vector>
#include <sys/stat.h>
int main() { 
    std::string directory_path = "/home/shiqiang/temp_ws/shishisfile/";
    for (size_t i = 1; i < directory_path.size(); ++i) {
    if (directory_path[i] == '/') {
        directory_path[i] = 0;
        std::cout<<"directory_path:"<<directory_path.c_str()<<std::endl;
        if (mkdir(directory_path.c_str(), S_IRWXU) != 0) {  //如果没有成创建
        if (errno != EEXIST) {  //如果没有成功创建的原因不是因为文件夹已经存在
            return 0;
        }
        }
        directory_path[i] = '/';
    }
    }
}

6. 方法CopyDir()

  • 作用是拷贝目录.
  • 用struct dirent和readdir()的一个demo： 
    #include <sys/stat.h>
#include <iostream>
#include <string>
#include <vector>
#include <dirent.h>

int main() {
std::string from="./";
DIR *directory = opendir(from.c_str());
struct dirent *entry;
while ((entry = readdir(directory)) != nullptr) {
    std::cout<<"d_name: "<<entry->d_name<<", d_type: "<<(int)entry->d_type<<std::endl; //文件和目录的d_type是不一样的
}
closedir(directory);
return 0;
}

7. 方法GetCurrentPath()

  • 获取当前路径. 一个demo: 
    #include <unistd.h>
#include <iostream>
#include <string>
    int main() {
    char tmp[4096];
    getcwd(tmp,sizeof(tmp));
    std::cout<<tmp<<std::endl;
    return 0;
}