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# Initialization and shutdown.

XML Security Library initialization/shutdown process includes initialization and shutdown of the dependent libraries:

- libxml library;

- libxslt library;

- crypto library (OpenSSL, GnuTLS, GCrypt, NSS, ...);

- xmlsec library (xmlSecInit and xmlSecShutdown functions);

- xmlsec-crypto library (xmlSecCryptoDLLoadLibrary to load xmlsec-crypto library dynamicaly if needed, xmlSecCryptoInit and xmlSecCryptoShutdown functions);

xmlsec-crypto library also provides a convinient functions xmlSecAppCryptoInit and xmlSecAppCryptoShutdown to initialize the crypto library itself but application can do it by itself.

Example 1. Initializing application.

        /* Init libxml and libxslt libraries */
        xmlInitParser();
        LIBXML_TEST_VERSION
        xmlLoadExtDtdDefaultValue = XML_DETECT_IDS | XML_COMPLETE_ATTRS;
        xmlSubstituteEntitiesDefault(1);
    #ifndef XMLSEC_NO_XSLT
        xmlIndentTreeOutput = 1;
    #endif /* XMLSEC_NO_XSLT */

        /* Init xmlsec library */
        if(xmlSecInit() < 0) {
    	fprintf(stderr, "Error: xmlsec initialization failed.\n");
    	return(-1);
        }

        /* Check loaded library version */
        if(xmlSecCheckVersion() != 1) {
    	fprintf(stderr, "Error: loaded xmlsec library version is not compatible.\n");
    	return(-1);
        }

        /* Load default crypto engine if we are supporting dynamic
         * loading for xmlsec-crypto libraries. Use the crypto library
         * name ("openssl", "nss", etc.) to load corresponding
         * xmlsec-crypto library.
         */
    #ifdef XMLSEC_CRYPTO_DYNAMIC_LOADING
        if(xmlSecCryptoDLLoadLibrary(BAD_CAST XMLSEC_CRYPTO) < 0) {
    	fprintf(stderr, "Error: unable to load default xmlsec-crypto library. Make sure\n"
    			"that you have it installed and check shared libraries path\n"
    			"(LD_LIBRARY_PATH) envornment variable.\n");
    	return(-1);
        }
    #endif /* XMLSEC_CRYPTO_DYNAMIC_LOADING */

        /* Init crypto library */
        if(xmlSecCryptoAppInit(NULL) < 0) {
    	fprintf(stderr, "Error: crypto initialization failed.\n");
    	return(-1);
        }

        /* Init xmlsec-crypto library */
        if(xmlSecCryptoInit() < 0) {
    	fprintf(stderr, "Error: xmlsec-crypto initialization failed.\n");
    	return(-1);
        }

Example 2. Shutting down application.

        /* Shutdown xmlsec-crypto library */
        xmlSecCryptoShutdown();

        /* Shutdown crypto library */
        xmlSecCryptoAppShutdown();

        /* Shutdown xmlsec library */
        xmlSecShutdown();

        /* Shutdown libxslt/libxml */
    #ifndef XMLSEC_NO_XSLT
        xsltCleanupGlobals();
    #endif /* XMLSEC_NO_XSLT */
        xmlCleanupParser();