std::ostrstream::freeze

 

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ostrstream::freeze

ostrstream::pcount

 

void freeze( bool flag = true );		(deprecated in C++98) (removed in C++26)

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 <iostream>
#include <strstream>
 
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"

See also

freeze

sets/clears the frozen state of the buffer (public member function of std::strstreambuf)