How to Reset and Reuse ostringstream for Optimal App Performance?

Reusing ostringstream for Efficient App Performance

Allocations in applications can be resource-intensive, especially when dealing with data streams like ostringstream. To optimize performance, it's beneficial to avoid excessive allocations. One way to achieve this is by resetting an ostringstream to its initial state for reuse.

Resetting the Object to Its Initial State

There are two common approaches to reset an ostringstream and reuse its underlying buffer:

• clear() and str() Sequence:

<code class="cpp">s.clear();
s.str("");</code>

This sequence effectively clears the internal error flags and assigns an empty string to the stringstream object.

• Manual Clear and Seek:

<code class="cpp">s.clear();
s.seekp(0); // Reset output position
s.seekg(0); // Reset input position</code>

This method manually clears any internal error flags and seeks both the output and input positions to the beginning of the buffer.

Preventing Reallocations with seekp()

In some cases, you may want to avoid reallocations altogether. By overwriting the existing data in the output buffer instead of assigning a new string with str(), you can prevent additional memory allocation:

<code class="cpp">s.clear();
s.seekp(0);
s &lt;&lt; "b";</code>

Using std::ends for C-Compatible Strings

If you need to use the stringstream output in C functions, consider using std::ends to terminate the string with a null character:

<code class="cpp">s.clear();
s &lt;&lt; "hello";
s.seekp(0);
s &lt;&lt; "b" &lt;&lt; std::ends;</code>

Additional Notes:

• assert() statements are used in the examples to verify the expected behavior.
• std::ends is a relic of the deprecated std::strstream, which allowed writing directly to a stack-allocated char array. While std::strstream is no longer recommended, std::ends remains useful in certain scenarios, as demonstrated above.

The above is the detailed content of How to Reset and Reuse ostringstream for Optimal App Performance?. For more information, please follow other related articles on the PHP Chinese website!