将数据从fstream复制到stringstream，没有缓冲区？ [英] Copy data from fstream to stringstream with no buffer?

问题描述

还有，我可以从 fstream （一个文件）传输数据到 stringstream 内存）？

Is there anyway I can transfer data from an fstream (a file) to a stringstream (a stream in the memory)?

目前，我使用一个缓冲区，但这需要双倍的内存，因为你需要将数据复制到一个缓冲区，然后复制缓冲区到字符串流，直到你删除缓冲区，数据被复制在内存中。

Currently, I'm using a buffer, but this requires double the memory, because you need to copy the data to a buffer, then copy the buffer to the stringstream, and until you delete the buffer, the data is duplicated in the memory.

std::fstream fWrite(fName,std::ios::binary | std::ios::in | std::ios::out);  
    fWrite.seekg(0,std::ios::end); //Seek to the end  
    int fLen = fWrite.tellg(); //Get length of file  
    fWrite.seekg(0,std::ios::beg); //Seek back to beginning  
    char* fileBuffer = new char[fLen];  
    fWrite.read(fileBuffer,fLen);  
    Write(fileBuffer,fLen); //This writes the buffer to the stringstream  
    delete fileBuffer;`

推荐答案

// need to include <algorithm> and <iterator>, and of course <fstream> and <sstream>
ifstream fin("input.txt");
ostringstream sout;
copy(istreambuf_iterator<char>(fin),
     istreambuf_iterator<char>(),
     ostreambuf_iterator<char>(sout));

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