 by an <b>index</b>, an integer guaranteed to be unique within structures for the lifetime of the program. Applications using exdata typically call <b>CRYPTO_get_ex_new_index</b> at startup, and store the result in a global variable, or write a wrapper function to provide lazy evaluation. The <b>class_index</b> should be one of the <b>CRYPTO_EX_INDEX_xxx</b> values. The <b>argl</b> and <b>argp</b> parameters are saved to be passed to the callbacks but are otherwise not used. In order to transparently manipu