defined key type will return its data as is. If a key type does not
implement this function, error EOPNOTSUPP will result.
- As much of the data as can be fitted into the buffer will be copied to
- userspace if the buffer pointer is not NULL.
-
- On a successful return, the function will always return the amount of data
- available rather than the amount copied.
+ If the specified buffer is too small, then the size of the buffer required
+ will be returned. Note that in this case, the contents of the buffer may
+ have been overwritten in some undefined way.
+ Otherwise, on success, the function will return the amount of data copied
+ into the buffer.
* Instantiate a partially constructed key::