如何从内存读取，就像使用iostream的文件？ [英] How can I read from memory just like from a file using iostream?

问题描述

我有简单的文本文件加载到内存。我想从内存读取，就像我从这样的光盘读取：

  ifstream文件; 
 string line; 
 
 file.open（C：\\file.txt）; 
 if（file.is_open（））
 {
 while（file.good（））
 {
 getline（file，line）; 
} 
} 
 file.close（）; 
  

但我有内存中的文件。我有一个在内存中的地址和这个文件的大小。

我必须做的以具有与上述代码中处理文件相同的流畅度吗？

解决方案

我发现一个解决方案适用于VC ++，因为 Nim 解决方案只适用于GCC编译器（非常感谢，谢谢你的回答我发现帮助我的其他答案。）

似乎其他人也有类似的问题。我完全按照这里和这里。 p>

因此，从一个内存中读取一个istream，你必须这样做：

  class membuf：public streambuf 
 {
 public：
 membuf（char * p，size_t n）{
 setg（p，p，p + n） ; 
} 
}; 
 
 int main（）
 {
 char buffer [] =Hello World！\\\
这是下一行\\\
最后一行; 
 membuf mb（buffer，sizeof（buffer））; 
 
 istream istr（& mb）; 
 string line; 
 while（getline（istr，line））
 {
 cout<< line：[<线<< ]<< endl; 
} 
} 
  

EDIT：你有'\r\\\
'新行如Nim所写：

  if（* line.rbegin（）= ='\r'）line.erase（line.end（） -  1）; 
  

---

我试图将此记忆视为 wistream 。有人知道如何这样做吗？我问单独的问题< a>为此。

I have simple text file loaded into memory. I want to read from memory just like I would read from a disc like here:

ifstream file;
string line;

file.open("C:\\file.txt");
if(file.is_open())
{
    while(file.good())
    {
        getline(file,line);         
    }
}   
file.close();

But I have file in memory. I have an address in memory and a size of this file.

What I must do to have the same fluency as with dealing with file in the code above?

解决方案

I found a solution that works on VC++ since Nim solution works only on GCC compiler (big thanks, though. Thanks to your answer I found other answers which helped me!).

It seems that other people have similar problem too. I did exactly as here and here.

So to read from a piece of memory just like form a istream you have to do this:

class membuf : public streambuf
{
    public:
        membuf(char* p, size_t n) {
        setg(p, p, p + n);
    }
};

int main()
{
    char buffer[] = "Hello World!\nThis is next line\nThe last line";  
    membuf mb(buffer, sizeof(buffer));

    istream istr(&mb);
    string line;
    while(getline(istr, line))
    {
        cout << "line:[" << line << "]" << endl;
    }
}

EDIT: And if you have '\r\n' new lines do as Nim wrote:

if (*line.rbegin() == '\r') line.erase(line.end() - 1);

---

I'm trying to treat this memory as as wistream. Does anybody know how to do this? I asked separate question for this.

这篇关于如何从内存读取，就像使用iostream的文件？的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！