In OpenSSL, given a certificate, how can I get a string representation of the signature algorithm?

X509_get_开发者_StackOverflow社区signature_type() returns an int. I need to convert this to a string.

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Signature algorithm string name I receive by this way:

X509 *certificate;
char alg[256];
...
OBJ_obj2txt(alg, sizeof(alg), certificate->sig_alg->algorithm, 0);

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OBJ_nid2ln() perhaps? There's also OBJ_nid2sn() for a few signature types which have short names.