std::ostrstream::freeze (3) - Linux Manuals

std::ostrstream::freeze: std::ostrstream::freeze

NAME

std::ostrstream::freeze - std::ostrstream::freeze

Synopsis

void freeze(bool flag = true);

If the stream is using a dynamically-allocated array for output, disables (flag == true) or enables (flag == false) automatic allocation/deallocation of the buffer. Effectively calls rdbuf()->freeze(flag)

Notes

After a call to str(), dynamic streams become frozen automatically. A call to freeze(false) is required before exiting the scope in which this ostrstream object was created. otherwise the destructor will leak memory. Also, additional output to a frozen stream may be truncated once it reaches the end of the allocated buffer.

Parameters

flag - desired status

Return value

(none)

Example

// Run this code

  #include <strstream>
  #include <iostream>

  int main()
  {
      std::ostrstream dyn; // dynamically-allocated output buffer
      dyn << "Test: " << 1.23; // note: no std::ends to demonstrate appending
      std::cout << "The output stream contains \"";
      std::cout.write(dyn.str(), dyn.pcount()) << "\"\n";
      // the stream is now frozen due to str()
      dyn << " More text"; // output to a frozen stream may be truncated
      std::cout << "The output stream contains \"";
      std::cout.write(dyn.str(), dyn.pcount()) << "\"\n";
      dyn.freeze(false); // freeze(false) must be called or the destructor will leak

      std::ostrstream dyn2; // dynamically-allocated output buffer
      dyn2 << "Test: " << 1.23; // note: no std::ends
      std::cout << "The output stream contains \"";
      std::cout.write(dyn2.str(), dyn2.pcount()) << "\"\n";
      dyn2.freeze(false); // unfreeze the stream after str()
      dyn2 << " More text" << std::ends; // output will not be truncated (buffer grows)
      std::cout << "The output stream contains \"" << dyn2.str() << "\"\n";
      dyn2.freeze(false); // freeze(false) must be called or the destructor will leak
  }

Possible output:

  The output stream contains "Test: 1.23"
  The output stream contains "Test: 1.23 More "
  The output stream contains "Test: 1.23"
  The output stream contains "Test: 1.23 More text"