Manual:D2i X509 NAME(3)
d2i_X509_NAME, i2d_X509_NAME - X509_NAME encoding functions
#include <openssl/x509.h> X509_NAME *d2i_X509_NAME(X509_NAME **a, unsigned char **pp, long length); int i2d_X509_NAME(X509_NAME *a, unsigned char **pp);
These functions decode and encode an X509_NAME structure which is the the same as the Name type defined in RFC2459 (and elsewhere) and used for example in certificate subject and issuer names.
Othewise the functions behave in a similar way to d2i_X509() and i2d_X509() described in the d2i_X509(3) manual page.