+typedef int (*ENGINE_SSL_CLIENT_CERT_PTR)(ENGINE *, SSL *ssl,
+ STACK_OF(X509_NAME) *ca_dn, X509 **pcert, EVP_PKEY **pkey,
+ STACK_OF(X509) **pother, UI_METHOD *ui_method, void *callback_data);
+/* These callback types are for an ENGINE's handler for cipher and digest logic.
+ * These handlers have these prototypes;
+ * int foo(ENGINE *e, const EVP_CIPHER **cipher, const int **nids, int nid);
+ * int foo(ENGINE *e, const EVP_MD **digest, const int **nids, int nid);
+ * Looking at how to implement these handlers in the case of cipher support, if
+ * the framework wants the EVP_CIPHER for 'nid', it will call;
+ * foo(e, &p_evp_cipher, NULL, nid); (return zero for failure)
+ * If the framework wants a list of supported 'nid's, it will call;
+ * foo(e, NULL, &p_nids, 0); (returns number of 'nids' or -1 for error)
+ */
+/* Returns to a pointer to the array of supported cipher 'nid's. If the second
+ * parameter is non-NULL it is set to the size of the returned array. */
+typedef int (*ENGINE_CIPHERS_PTR)(ENGINE *, const EVP_CIPHER **, const int **, int);
+typedef int (*ENGINE_DIGESTS_PTR)(ENGINE *, const EVP_MD **, const int **, int);
+typedef int (*ENGINE_PKEY_METHS_PTR)(ENGINE *, EVP_PKEY_METHOD **, const int **, int);
+typedef int (*ENGINE_PKEY_ASN1_METHS_PTR)(ENGINE *, EVP_PKEY_ASN1_METHOD **, const int **, int);