如何将整个流读入 std: : string？

我试图将整个流(多行)读入一个字符串。

我在用这个代码，它能用，但是它冒犯了我的风格感... 肯定有更简单的方法吧？也许用弦流？

void Obj::loadFromStream(std::istream & stream)
{
std::string s;


std::streampos p = stream.tellg();  // remember where we are


stream.seekg(0, std::ios_base::end); // go to the end
std::streamoff sz = stream.tellg() - p;  // work out the size
stream.seekg(p);        // restore the position


s.resize(sz);          // resize the string
stream.read(&s[0], sz);  // and finally, read in the data.

实际上，对字符串的 const引用也可以做到这一点，这可能会使事情变得更简单..。

const std::string &s(... a miracle occurs here...)
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小开

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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最佳答案

How about 

std::istreambuf_iterator<char> eos;
std::string s(std::istreambuf_iterator<char>(stream), eos);

(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), {});
小开

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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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.

小开

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},{}};
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What about to use getline with delimiter? The next code helps me to read whole std::cin into string on ubuntu with g++-10.

#include <iostream>
#include <string>


using namespace std;


int main() {
string s;


getline(cin, s, {}); //the whole stream into variable s


return 0;
}

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