Description of the feature:
Add an API like
gnutls_hmac_copy() (or so) that copies the state of an HMAC.
Applications that this feature may be relevant to:
Required for https://gitlab.gnome.org/GNOME/glib/merge_requests/903 which is a reimplementation of GHmac using GnuTLS.
Is this feature implemented in other libraries (and which)
Yes, it's implemented in OpenSSL too:
int HMAC_CTX_copy(HMAC_CTX *dctx, HMAC_CTX *sctx);