How to read entire stream into a std::string?

Question

I'm trying to read an entire stream (multiple lines) into a string.

I'm using this code, and it works, but it's offending my sense of style... Surely there's an easier way? Maybe using stringstreams?

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

  int p = stream.tellg();  // remember where we are

  stream.seekg(0, std::ios_base::end); // go to the end
  int 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.

EDIT:

Actually, a const reference to a string would do as well, and that may make things easier...

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

Answer 1

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();

Answer 2

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)

Answer 3

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) );

Answer 4

the .ReadToEnd() method in System.IO.StreamReader (.Net) is basically implemented the same way..:

public override string ReadToEnd() {
    StringBuilder builder = new StringBuilder(this.charLen - this.charPos);
    do {
        builder.Append(this.charBuffer, this.charPos, this.charLen - this.charPos);
        this.charPos = this.charLen;
        this.ReadBuffer();
    }
    while (this.charLen > 0);
    return builder.ToString();
}

but i get your point!