1=pod
2
3=head1 NAME
4
5 BIO_new_CMS - CMS streaming filter BIO
6
7=head1 SYNOPSIS
8
9 #include <openssl/cms.h>
10
11 BIO *BIO_new_CMS(BIO *out, CMS_ContentInfo *cms);
12
13=head1 DESCRIPTION
14
15BIO_new_CMS() returns a streaming filter BIO chain based on B<cms>. The output
16of the filter is written to B<out>. Any data written to the chain is
17automatically translated to a BER format CMS structure of the appropriate type.
18
19=head1 NOTES
20
21The chain returned by this function behaves like a standard filter BIO. It
22supports non blocking I/O. Content is processed and streamed on the fly and not
23all held in memory at once: so it is possible to encode very large structures.
24After all content has been written through the chain BIO_flush() must be called
25to finalise the structure.
26
27The B<CMS_STREAM> flag must be included in the corresponding B<flags>
28parameter of the B<cms> creation function.
29
30If an application wishes to write additional data to B<out> BIOs should be
31removed from the chain using BIO_pop() and freed with BIO_free() until B<out>
32is reached. If no additional data needs to be written BIO_free_all() can be
33called to free up the whole chain.
34
35Any content written through the filter is used verbatim: no canonical
36translation is performed.
37
38It is possible to chain multiple BIOs to, for example, create a triple wrapped
39signed, enveloped, signed structure. In this case it is the applications
40responsibility to set the inner content type of any outer CMS_ContentInfo
41structures.
42
43Large numbers of small writes through the chain should be avoided as this will
44produce an output consisting of lots of OCTET STRING structures. Prepending
45a BIO_f_buffer() buffering BIO will prevent this.
46
47=head1 BUGS
48
49There is currently no corresponding inverse BIO: i.e. one which can decode
50a CMS structure on the fly.
51
52=head1 RETURN VALUES
53
54BIO_new_CMS() returns a BIO chain when successful or NULL if an error
55occurred. The error can be obtained from ERR_get_error(3).
56
57=head1 SEE ALSO
58
59L<ERR_get_error(3)|ERR_get_error(3)>, L<CMS_sign(3)|CMS_sign(3)>,
60L<CMS_encrypt(3)|CMS_encrypt(3)>
61
62=head1 HISTORY
63
64BIO_new_CMS() was added to OpenSSL 1.0.0
65
66=cut
67