Resetting a String Stream

Resetting a string stream in C++ is straightforward. You can use the str() method to set new content for the stream, which also resets the stream position to the beginning.

This method takes a std::string as an argument and replaces the current content with the new string. Here’s an example:

1#include <iostream>
2#include <sstream>
3
4int main() {
5  std::ostringstream Stream;
6  Stream << "Initial content";
7  std::cout << "Stream: "
8    << Stream.str() << "\n";
9
10  Stream.str("New content");  
11  std::cout << "Stream: "
12    << Stream.str() << "\n";
13}

1Stream: Initial content
2Stream: New content

When you call Stream.str("New content"), it sets the stream's content to "New content" and moves the output position to the beginning.

Clearing the Stream

If you want to clear the stream without setting new content, you can pass an empty string to the str() method:

1Stream.str("");

Alternatively, you can clear the stream state using the clear() method, which resets the stream's error state flags:

1Stream.clear();

However, clear() does not remove the content of the stream. It only resets the state flags. To completely reset the stream (content and state), you should use both methods:

1Stream.str("");
2Stream.clear();

This combination ensures that the stream is empty and ready for new operations.

Practical Example

Here’s a practical example where you might want to reset a string stream:

1#include <iostream>
2#include <sstream>
3
4void ProcessData(const std::string& data) {
5  std::ostringstream Stream;
6  Stream << data;
7  std::cout << "Processed: "
8    << Stream.str() << "\n";
9
10  Stream.str("");  
11  Stream.clear();
12
13  // New data processing
14  Stream << "Additional data";
15  std::cout << "Processed: "
16    << Stream.str() << "\n";
17}
18
19int main() {
20  ProcessData("First data");
21}

1Processed: First data
2Processed: Additional data

In this example, we reset the stream before processing new data to ensure the old data does not interfere with new operations.