5 CMS_compress - create a CMS CompressedData structure
9 #include <openssl/cms.h>
11 CMS_ContentInfo *CMS_compress(BIO *in, int comp_nid, unsigned int flags);
15 CMS_compress() creates and returns a CMS CompressedData structure. B<comp_nid>
16 is the compression algorithm to use or B<NID_undef> to use the default
17 algorithm (zlib compression). B<in> is the content to be compressed.
18 B<flags> is an optional set of flags.
22 The only currently supported compression algorithm is zlib using the NID
25 If zlib support is not compiled into OpenSSL then CMS_compress() will return
28 If the B<CMS_TEXT> flag is set MIME headers for type B<text/plain> are
29 prepended to the data.
31 Normally the supplied content is translated into MIME canonical format (as
32 required by the S/MIME specifications) if B<CMS_BINARY> is set no translation
33 occurs. This option should be used if the supplied data is in binary format
34 otherwise the translation will corrupt it. If B<CMS_BINARY> is set then
35 B<CMS_TEXT> is ignored.
37 If the B<CMS_STREAM> flag is set a partial B<CMS_ContentInfo> structure is
38 returned suitable for streaming I/O: no data is read from the BIO B<in>.
40 The compressed data is included in the CMS_ContentInfo structure, unless
41 B<CMS_DETACHED> is set in which case it is omitted. This is rarely used in
42 practice and is not supported by SMIME_write_CMS().
46 If the flag B<CMS_STREAM> is set the returned B<CMS_ContentInfo> structure is
47 B<not> complete and outputting its contents via a function that does not
48 properly finalize the B<CMS_ContentInfo> structure will give unpredictable
51 Several functions including SMIME_write_CMS(), i2d_CMS_bio_stream(),
52 PEM_write_bio_CMS_stream() finalize the structure. Alternatively finalization
53 can be performed by obtaining the streaming ASN1 B<BIO> directly using
56 Additional compression parameters such as the zlib compression level cannot
61 CMS_compress() returns either a CMS_ContentInfo structure or NULL if an error
62 occurred. The error can be obtained from ERR_get_error(3).
66 L<ERR_get_error(3)>, L<CMS_uncompress(3)>
70 The B<CMS_STREAM> flag was added in OpenSSL 1.0.0.
74 Copyright 2008-2016 The OpenSSL Project Authors. All Rights Reserved.
76 Licensed under the OpenSSL license (the "License"). You may not use
77 this file except in compliance with the License. You can obtain a copy
78 in the file LICENSE in the source distribution or at
79 L<https://www.openssl.org/source/license.html>.