How to Read Entire Stream into a Std::String

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

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), {});

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

There's just a type mismatch. ifstream is just a typedef:

typedef basic_ifstream<char> ifstream;

So if you want to use a different underlying type, you just have to tell it:

std::basic_ifstream<uint8_t> stream(path, std::ios::in | std::ios::binary);    
auto eos = std::istreambuf_iterator<uint8_t>();
auto buffer = std::vector<uint8_t>(std::istreambuf_iterator<uint8_t>(stream), eos);

That works for me.

Or, since Dietmar says this might be a little sketchy, you could do something like:

auto stream = std::ifstream(...);
std::vector<uint8_t> data;

std::for_each(std::istreambuf_iterator<char>(stream),
              std::istreambuf_iterator<char>(),
              [&data](const char c){
                  data.push_back(c);
              });

Reading directly from an std::istream into an std::string

std::string has a resize function you could use, or a constructor that'll do the same:

boost::uint16_t len;
is.read((char*)&len, 2);

std::string str(len, '\0');
is.read(&str[0], len);

This is untested, and I don't know if strings are mandated to have contiguous storage.

Read whole ASCII file into C++ std::string

Update: Turns out that this method, while following STL idioms well, is actually surprisingly inefficient! Don't do this with large files. (See: http://insanecoding.blogspot.com/2011/11/how-to-read-in-file-in-c.html)

You can make a streambuf iterator out of the file and initialize the string with it:

#include <string>
#include <fstream>
#include <streambuf>

std::ifstream t("file.txt");
std::string str((std::istreambuf_iterator<char>(t)),
                 std::istreambuf_iterator<char>());

Not sure where you're getting the t.open("file.txt", "r") syntax from. As far as I know that's not a method that std::ifstream has. It looks like you've confused it with C's fopen.

Edit: Also note the extra parentheses around the first argument to the string constructor. These are essential. They prevent the problem known as the "most vexing parse", which in this case won't actually give you a compile error like it usually does, but will give you interesting (read: wrong) results.

Following KeithB's point in the comments, here's a way to do it that allocates all the memory up front (rather than relying on the string class's automatic reallocation):

#include <string>
#include <fstream>
#include <streambuf>

std::ifstream t("file.txt");
std::string str;

t.seekg(0, std::ios::end);   
str.reserve(t.tellg());
t.seekg(0, std::ios::beg);

str.assign((std::istreambuf_iterator<char>(t)),
            std::istreambuf_iterator<char>());

How to convert ostream into a string

void func (ostream& stream) {
    /* Needs to convert stream into string */
    std::stringstream ss;
    ss << stream.rdbuf();
    std::string myString = ss.str();
}

How do I read a file in C++ and write contents into a string?

Don't use << to append something in a string.

Rather than:

while (getline(shaderFile, line)) {
    sourceCode << line;
}

Consider:

while (getline(shaderFile, line)) {
    sourceCode += line;
}

---

Related Topics