c++ istream转换为std::string

std::istreambuf_iterator<char> eos;
std::string s(std::istreambuf_iterator<char>(stream), eos);
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(could be a one-liner if not for MVP)

post-2011 edit, this approach is now spelled

std::string s(std::istreambuf_iterator<char>(stream), {});
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I'm late to the party, but here is a fairly efficient solution:

std::string gulp(std::istream &in)
{
    std::string ret;
    char buffer[4096];
    while (in.read(buffer, sizeof(buffer)))
        ret.append(buffer, sizeof(buffer));
    ret.append(buffer, in.gcount());
    return ret;
}

I did some benchmarking, and it turns out that the std::istreambuf_iterator technique (used by the accepted answer) is actually much slower. On gcc 4.4.5 with -O3, it's about a 4.5x difference on my machine, and the gap becomes wider with lower optimization settings.

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You can try using something from algorithms. I have to get ready for work but here's a very quick stab at things (there's got to be a better way):

copy( istreambuf_iterator<char>(stream), istreambuf_iterator<char>(), back_inserter(s) );
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You could do

std::string s;
std::ostringstream os;
os<<stream.rdbuf();
s=os.str();

but I don't know if it's more efficient.

Alternative version:

std::string s;
std::ostringstream os;
stream>>os.rdbuf();
s=os.str();

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Well, if you are looking for a simple and 'readable' way to do it. I would recomend add/use some high level framework on your project. For that I's always use Poco and Boost on all my projects. In this case, with Poco:

    string text;
    FileStream fstream(TEXT_FILE_PATH);
    StreamCopier::copyToString(fstream, text);

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Perhaps this 1 line C++11 solution:

std::vector<char> s{std::istreambuf_iterator<char>{in},{}};