typedef char * (*X509V3_EXT_I2S)(struct v3_ext_method *method, char *ext);
typedef char * (*X509V3_EXT_S2I)(struct v3_ext_method *method, struct v3_ext_ctx *ctx, char *str);
typedef int (*X509V3_EXT_I2R)(struct v3_ext_method *method, char *ext, BIO *out);
typedef char * (*X509V3_EXT_I2S)(struct v3_ext_method *method, char *ext);
typedef char * (*X509V3_EXT_S2I)(struct v3_ext_method *method, struct v3_ext_ctx *ctx, char *str);
typedef int (*X509V3_EXT_I2R)(struct v3_ext_method *method, char *ext, BIO *out);