BIO_new_CMS() returns a streaming filter BIO chain based on cms. The output of the filter is written to
out. Any data written to the chain
is automatically translated to a BER format CMS structure of the
appropriate type.
NOTES
The chain returned by this function behaves like a standard filter
BIO. It supports non blocking I/O. Content is processed and streamed
on the fly and not all held in memory at once: so it is possible to
encode very large structures. After all content has been written
through the chain BIO_flush() must be called to finalise the
structure.
The CMS_STREAM flag must be included
in the corresponding flags parameter
of the cms creation function.
If an application wishes to write additional data to out BIOs should be removed from the chain
using BIO_pop() and freed with BIO_free() until out is reached. If no additional data needs to
be written BIO_free_all() can be called to free up the whole chain.
Any content written through the filter is used verbatim: no canonical
translation is performed.
It is possible to chain multiple BIOs to, for example, create a
triple wrapped signed, enveloped, signed structure. In this case it
is the applications responsibility to set the inner content type of
any outer CMS_ContentInfo structures.
Large numbers of small writes through the chain should be avoided as
this will produce an output consisting of lots of OCTET STRING
structures. Prepending a BIO_f_buffer() buffering BIO will prevent
this.
BUGS
There is currently no corresponding inverse BIO: i.e. one which can
decode a CMS structure on the fly.
RETURN VALUES
BIO_new_CMS() returns a BIO chain when successful or NULL if an error
occurred. The error can be obtained from ERR_get_error(3).
