loading a private rsa key with libgcrypt

[Juergen Lueters]

Hi,

i have a project in which a private rsa key has to used in order to sign
a string. I would like to use libgcrypt. 
After reading the documentation i have found  the procedure
"gcry_ac_key_init". Unfortunaltely i can not find out how to prepare a
private rsa-key-file (file.pem) in a way usable for that function.

Is there any documentation or example code which shows how to load a pem
file and transform it into a suitable data set?

Regards

-- 
Juergen Lueters <jlueters at intranet-engineering.de>