How to Effectively Reset a Stringstream in C ?

Resetting a Stringstream Effectively

In C , stringstreams are a valuable tool for manipulating and parsing strings. To reset a stringstream, developers use the str() method to clear the underlying string. However, this approach may not fully reset the stream.

The Case Study

Consider the following code snippet:

<code class="cpp">stringstream parser;

parser << 5;
short top = 0;
parser >> top;
parser.str(""); // Attempting to reset parser

parser << 6; // Fails to insert 6 into parser
short bottom = 0;
parser >> bottom;</code>

The intention is to reset the parser stream and assign a new value to it. However, the code unexpectedly fails to insert 6 into the parser.

Understanding the Error

The root of the problem lies in the incomplete reset. The str() method only clears the underlying string, while the error flags (such as eof and fail) remain set. Subsequent operations, like reading from the stream, will fail due to these flags.

Proper Resetting Technique

To effectively reset a stringstream, it is crucial to not only clear the string but also reset the error flags. This can be achieved using the clear() method:

<code class="cpp">parser.str( std::string() );
parser.clear();</code>

By calling both str() and clear(), the string is reset to an empty string, and any error flags are cleared, ensuring that subsequent operations will succeed.

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