Question

我是c ++的新手并且是我自己学习的，所以我有一个应该从文件路径读取指定文件的程序，理论上做一个精确的副本。我的问题是我总是关闭（如字节数，例如，一个173 kb的文件是177kb），从我看到的文件越大，我越关闭。那么为什么我错了，有更好的方法吗？

int main()
{

   //I was monitering memory usage, some reason if i wrote to console to fast, I couldn't moniter memory
   system("pause");
   ifstream inputFile;

   inputFile.open("C:\\Users\\Tallennar\\Documents\\Tables.docx", ios::in | ios::binary);

   ofstream outputFile;
   outputFile.open("word.docx", ios::binary);

   char buffer[257] = { ' ' };//one extra for \0

   if (!inputFile)
       printf("failed to open input file");

   if (!outputFile)
       printf("failed to open outputfile \n");

   //gets my file size
   inputFile.seekg(0, ios::end);
   size_t fileSize = inputFile.tellg();
   inputFile.seekg(0, ios::beg);

   //some math to see how many times I need to loop
   int leftOverFromIterations = fileSize % 256;
   int fileSizeIterations = (fileSize - leftOverFromIterations) / 256;

   int bufferSize = sizeof(buffer);

   //loops through to print to output file
   for (int i = 0; i <= fileSizeIterations; i++)
   {
       inputFile.read(buffer, bufferSize);

       //so i dont get funny chars
       buffer[256] = '\0';
       outputFile.write(buffer, bufferSize);

       //for me to see what is getting printed
       std::cout << buffer;
   }
   //since not every file is divisible by 256, get the 
   //   leftovers from the above for loop
   inputFile.read(buffer, leftOverFromIterations);

   //close files
   inputFile.close();
   outputFile.close();
   system("pause");
   return 0;
}

Answer 1

几个问题：

for循环运行次数过多，应使用i < fileSizeIterations。
您正在使用\0覆盖缓冲区的最后一个字符。您应该将bufferSize设置为小于数组大小的1，因此您不会读入null所需的字符。或者您应该使用std::string而不是C风格的字符串。
您没有将剩菜复制到输出文件。

您还应避免在整个代码中使用256进行硬编码，并在那里使用bufferSize。

int main()
{
    //I was monitering memory usage, some reason if i wrote to console to fast, I couldn't moniter memory
    system("pause");
    ifstream inputFile;


    inputFile.open("C:\\Users\\Tallennar\\Documents\\Tables.docx", ios::in | ios::binary);

    ofstream outputFile;
    outputFile.open("word.docx", ios::binary);

    char buffer[257] = { ' ' };//one extra for \0

    if (!inputFile)
        printf("failed to open input file");

    if (!outputFile)
        printf("failed to open outputfile \n");

    //gets my file size
    inputFile.seekg(0, ios::end);
    size_t fileSize = inputFile.tellg();
    inputFile.seekg(0, ios::beg);

    int bufferSize = sizeof(buffer)-1;

    //some math to see how many times I need to loop
    int leftOverFromIterations = fileSize % bufferSize;
    int fileSizeIterations = (fileSize - leftOverFromIterations) / bufferSize;

    //loops through to print to output file
    for (int i = 0; i < fileSizeIterations; i++)
        {
            inputFile.read(buffer, bufferSize);

            //so i dont get funny chars
            buffer[bufferSize] = '\0';
            outputFile.write(buffer, bufferSize);

            //for me to see what is getting printed
            std::cout << buffer;
        }
    //since not every file is divisible by bufferSize, get the 
    //  leftovers from the above for loop
    inputFile.read(buffer, leftOverFromIterations);

    //so i dont get funny chars    
    buffer[leftOverFromIterations] = '\0';
    outputFile.write(buffer, leftOverFromIterations);

    //for me to see what is getting printed
    std::cout << buffer;

    //close files
    inputFile.close();
    outputFile.close();
    system("pause");
    return 0;
}

Answer 2

为什么不使用getline()呢？更容易混淆。

int main()
{

   //I was monitering memory usage, some reason if i wrote to console to fast, I couldn't moniter memory
   system("pause");
   ifstream inputFile;

   inputFile.open("C:\\Users\\Tallennar\\Documents\\Tables.docx", ios::in | ios::binary);

   ofstream outputFile;
   outputFile.open("word.docx", ios::binary);


   if (!inputFile)
   {
       printf("failed to open input file");
       return 0;  //if you didn't open the file don't continue
   }

   if (!outputFile)
   {
       printf("failed to open outputfile \n");
       return 0;  //if you didn't open the file don't continue
   }

   string line;
   while(getline(inputFile, line ))
   {
      outputFile << line;
   }

   inputFile.close();
   outputFile.close();
   system("pause");
   return 0;
}

注意：我在您的if语句中添加了return 0;，因此如果它无法打开文件就会停止。

免责声明：我没有运行此代码，因为我没有可以处理手头文件的编译器。

我的文件未正确复制

2 个答案: