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=pod
=head1 NAME
BIO_new_CMS - CMS streaming filter BIO
=head1 SYNOPSIS
#include <openssl/cms.h>
BIO *BIO_new_CMS(BIO *out, CMS_ContentInfo *cms);
=head1 DESCRIPTION
BIO_new_CMS() returns a streaming filter BIO chain based on B<cms>. The output
of the filter is written to B<out>. Any data written to the chain is
automatically translated to a BER format CMS structure of the appropriate type.
=head1 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 B<CMS_STREAM> flag must be included in the corresponding B<flags>
parameter of the B<cms> creation function.
If an application wishes to write additional data to B<out> BIOs should be
removed from the chain using BIO_pop() and freed with BIO_free() until B<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.
=head1 BUGS
There is currently no corresponding inverse BIO: i.e. one which can decode
a CMS structure on the fly.
=head1 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).
=head1 SEE ALSO
L<ERR_get_error(3)|ERR_get_error(3)>, L<CMS_sign(3)|CMS_sign(3)>,
L<CMS_encrypt(3)|CMS_encrypt(3)>
=head1 HISTORY
BIO_new_CMS() was added to OpenSSL 1.0.0
=cut
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