How Do You Properly Clear and Reset a StringStream in C ?

Clearing and Resetting StringStream

In C , a stringstream is an input/output buffer associated with a string object. It allows for manipulation of strings using stream operations.

Problem Statement:

Consider the following code:

<code class="cpp">stringstream parser;

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

parser << 6; // Doesn't put 6 into parser
short bottom = 0;
parser >> bottom;</code>

The issue arises when attempting to reuse the stringstream after clearing its contents using parser.str("").

Solution:

To properly clear a stringstream, you need to perform two steps:

1. Reset the underlying string to an empty string using parser.str(std::string()).
2. Clear any fail and eof flags using parser.clear().

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

Explanation:

The first >> operation reads the integer 5 from the stringstream and sets the eof bit because the end of the string has been reached. The subsequent attempt to read 6 fails because the eof bit is still set. By resetting the underlying string and clearing the flags, you restore the stream to its initial configuration and allow subsequent operations to succeed.

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