ifstream :: ifstream可以读取的最大文件大小是多少 [英] ifstream:: What is the maximum file size that a ifstream can read

问题描述

我试图使用ifstream读取一个3GB的数据文件，它给我错误的文件大小，而当我读取一个600MB的文件，它给了我正确的结果。除了错误的文件大小，我也无法使用ifstream读取整个文件。

I tried to read a 3GB data file using ifstream and it gives me wrong file size, whereas when I read a 600MB file, it gives me the correct result. In addition to wrong file size, I am also unable to read the entire file using ifstream.

这里是我使用的代码

        std::wstring name;
        name.assign(fileName.begin(), fileName.end());
        __stat64 buf;
        if (_wstat64(name.c_str(), &buf) != 0)
            std::cout << -1; // error, could use errno to find out more

        std::cout << " Windows file size : " << buf.st_size << std::endl;;


        std::ifstream fs(fileName.c_str(), std::ifstream::in | std::ifstream::binary);
        fs.seekg(0, std::ios_base::end);

        std::cout << " ifstream  file size: " << fs.tellg() << std::endl;

3GB文件的输出为

 Windows file size : 3147046042
 ifstream  file size: -1147921254

而600 MB文件的输出为

Whereas the output for 600 MB file was

 Windows file size : 678761111
 ifstream  file size: 678761111

为了防万一，我还测试了5GB文件和300 MB文件，

Just in case, I also tested for 5GB file and 300 MB file,

5GB文件的输出为

Windows file size : 5430386900
 ifstream  file size: 1135419604

300MB文件的输出为

The output for 300MB file was

Windows file size : 318763632
 ifstream  file size: 318763632

$ b

It looks to me like it is reaching some limit.

我使用Visual Studio 2010在Windows机器上测试代码，该机器有大量的内存和磁盘空格。

I am testing the code using Visual Studio 2010 on a Windows Machine which has plenty of memory and disk space.

我试图读取一些大文件。

I am trying to read some large files. Which is a good stream reader to use if ifstream can't read large files?

推荐答案

我想你想说：

std::cout << " ifstream  file size: " << fs.tellg().seekpos() << std::endl;

至少对于我放置的一个6GB文件，它可以正常工作。但我正在使用Visual Studio 2012进行编译。甚至您的原始代码在该环境下也正常工作。

At least that works correctly for a 6GB file I have laying around. But I'm compiling with Visual Studio 2012. And even your original code works fine too on that environment.

所以我怀疑这是std库中的一个错误VS 2010在VS 2012中得到修复。无论是在操作符重载为pos_type的错误或如果该类不是64位感知是未知的。我必须安装VS 2010来验证，但这可能是问题。

So I suspect that this is an bug in the std library on VS 2010 that got fixed in VS 2012. Whether it's a bug in the operator overloading for the pos_type or if that class isn't 64-bit aware is unknown. I'd have to install VS 2010 to validate, but that is likely the problem.

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