如何在Windows上查看超过4GB的kg（）文件？ [英] How can I seekg() files over 4GB on Windows?

问题描述

我在Windows 7，64位和NTFS。
我建立一个必须是32位的DLL。我有一个非常简单的例程，我想在C ++中实现。我正在读一个大文件：

  unsigned long p; 
 ifstream source（file）; 
 streampos pp（p）; 
 source.seekg（pp）; 
 

对于超过4GB的文件，我尝试使用unsigned long long，但它不工作。
我做错了什么？我使用的是GNU GCC，是否可以试用MSVC Express 2008/2010？

更新：
$ b

似乎我的GCC有问题。现在我使用MSVC测试你的建议，它似乎是工作。 MSVC使用_int64表示streampos / streamoff对象，我稍后将使用GCC检查。

解决方案

相对寻找，即使用 seekg 的双参数重载。

  //开始寻找从头开始
 source.seekg（some_pos，std :: ios :: beg）; 
 
 //然后从那个位置寻找更多的东西
 source.seekg（some_offset，std :: ios :: cur）; 
  

I am on Windows 7, 64bit and NTFS. I am building a DLL that must be 32 bit. I have a very simple routine that I'd like to implement in C++. I'm reading a large file using:

unsigned long p;
ifstream source(file);
streampos pp(p);
source.seekg(pp);

For files over 4GB I tried using unsigned long long but it's not working. What am I doing wrong? I'm using GNU GCC, would it be of any use trying MSVC Express 2008/2010?

Update:

There seems that something is wrong with my GCC. Right now I'm testing your proposals using MSVC and it seems that is working. MSVC uses an _int64 to represent streampos/streamoff objects, I will check later with GCC.

解决方案

You may have to use a number of relative seeks instead, i.e. use the two-argument overload of seekg.

// Start with seeking from the beginning
source.seekg(some_pos, std::ios::beg);

// Then seek some more from that position
source.seekg(some_offset, std::ios::cur);

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