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std::ostrstream::freeze

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< cpp‎ | io‎ | ostrstream
Revision as of 07:42, 1 August 2013 by P12bot (Talk | contribs)

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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()->pcount()

Contents

[edit] 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.

[edit] Parameters

flag - desired status

[edit] Return value

(none)

[edit] Example

#include <strstream>
#include <iostream>
 
int main()
{
    std::ostrstream dyn; // dynamically-allocated output buffer
    dyn << "Test: " << 1.23;
    std::cout << "The output stream contains \"" << dyn.str() << "\"\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 \"" << dyn.str() << "\"\n\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;
    std::cout << "The output stream contains \"" << dyn2.str() << "\"\n";
    dyn2.freeze(false);   // unfreeze the stream after str()
    dyn2 << " More text"; // output will not be truncated (the underlying buffer may grow)
    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"

[edit] See also

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