std::strstreambuf:: str

Calls freeze() , then returns a copy of start pointer of the get area, std::streambuf::eback() .

The start of the get area, for all writeable std::strstreambuf objects constructed through the interface provided by std::strstream , is also the start of the put area.

Parameters

(none)

Return value

A copy of eback() , which may be a null pointer.

Notes

This function is typically called through the std::strstream interface.

The call to freeze() guarantees that the returned pointer remains valid until the next explicit call to freeze ( false ) : otherwise (on a dynamic buffer) any output operation could trigger buffer reallocation which would invalidate the pointer. It also causes a memory leak in the destructor of std::strstreambuf , unless freeze ( false ) is called before the buffer (or, more commonly, the std:: strstream that manages it) is destroyed.

Example

#include <iostream>
#include <strstream>
 
int main()
{
    std::strstream dyn; // dynamically-allocated read/write buffer
    dyn << "Test: " << 1.23 << std::ends;
    std::strstreambuf* buf = dyn.rdbuf();
    std::cout << "R/W buffer holds [" << buf->str() // or dyn.str()
              << "]\n";
    dyn.freeze(false); // after calling .str() on a dynamic strstream
 
    char arr[10];
    std::ostrstream user(arr, 10); // fixed-size write-only buffer
    buf = user.rdbuf();
    user << 1.23 << std::ends;
    std::cout << "Write-only buffer holds [" << buf->str() // or user.str()
              << "]\n";
 
    std::istrstream lit("1 2 3"); // fixed-size read-only buffer
    buf = lit.rdbuf();
    std::cout << "Read-only buffer holds [" << buf->str() // or lit.str()
              << "]\n";
}

R/W buffer holds [Test: 1.23]
Write-only buffer holds [1.23]
Read-only buffer holds [1 2 31 2 3]

See also