ostrstream problems

[wey97]

how do you clear or empty an ostrstream?

#include <windows.h>
#include <strstream>

using namespace std;

void main(){

	ostrstream oss;

	oss << "3.14159265359" << ends;

	MessageBox(0, oss.str(), "", 0);


	// now clear out the stream so a new stream can be written


	oss << "1.41421356237" << ends; 

	MessageBox(0, oss.str(), "", 0);

}

[parksie]

#include <iostream>
#include <sstream>

using namespace std;

int main() {
	ostringstream oss;

	oss << "Hi there: " << 5 << " " << 10 << ends;
	cout << oss.str() << endl;

	oss.seekp(0);

	oss << "Again!! " << "blah: " << 5 * 10 << ends;
	cout << oss.str() << endl;

	return 0;
}

....with small modifications to bring you up to the standard

[wey97]

Oh, right. stringstreams are the new standard.

[parksie]

Less memory-leak potential since they return a string, not char* (in the old ones, when you call .str(), it locks the buffer and strange things happen).

Plus, these are all templated (w00t!).

[wey97]

So are you saying oss.str().c_str() may cause a memory leak too?

[parksie]

No, because it returns a constant pointer, and doesn't lock any buffers since it will delete it when the destructor is called.

Hence why you should use the new ones - as Bjarne says, "Resource Initialisation is Acquisition"

[wey97]

Cool.
I guess.

[wey97]

Thanks.

[CornedBee]

What does that mean in easy English parksie?

[parksie]

Originally posted by CornedBee
What does that mean in easy English parksie?

What, the acquisition thing?

It basically means that once you create a representation of something, you have allocated what it is, for example:

class mutex { };

void lockedcode() {
    mutex m; // blocks until it can recieve the mutex

    // some unsafe operation
}

In this code, creating the mutex object tries to acquire the OS's mutex handle, and destroying it releases it again.

[CornedBee]

Ok, I think I understand...