1CMS_COMPRESS(3)                     OpenSSL                    CMS_COMPRESS(3)
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NAME

6       CMS_compress - create a CMS CompressedData structure
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SYNOPSIS

9        #include <openssl/cms.h>
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11        CMS_ContentInfo *CMS_compress(BIO *in, int comp_nid, unsigned int flags);
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DESCRIPTION

14       CMS_compress() creates and returns a CMS CompressedData structure.
15       comp_nid is the compression algorithm to use or NID_undef to use the
16       default algorithm (zlib compression). in is the content to be
17       compressed.  flags is an optional set of flags.
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NOTES

20       The only currently supported compression algorithm is zlib using the
21       NID NID_zlib_compression.
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23       If zlib support is not compiled into OpenSSL then CMS_compress() will
24       return an error.
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26       If the CMS_TEXT flag is set MIME headers for type text/plain are
27       prepended to the data.
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29       Normally the supplied content is translated into MIME canonical format
30       (as required by the S/MIME specifications) if CMS_BINARY is set no
31       translation occurs. This option should be used if the supplied data is
32       in binary format otherwise the translation will corrupt it. If
33       CMS_BINARY is set then CMS_TEXT is ignored.
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35       If the CMS_STREAM flag is set a partial CMS_ContentInfo structure is
36       returned suitable for streaming I/O: no data is read from the BIO in.
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38       The compressed data is included in the CMS_ContentInfo structure,
39       unless CMS_DETACHED is set in which case it is omitted. This is rarely
40       used in practice and is not supported by SMIME_write_CMS().
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NOTES

43       If the flag CMS_STREAM is set the returned CMS_ContentInfo structure is
44       not complete and outputting its contents via a function that does not
45       properly finalize the CMS_ContentInfo structure will give unpredictable
46       results.
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48       Several functions including SMIME_write_CMS(), i2d_CMS_bio_stream(),
49       PEM_write_bio_CMS_stream() finalize the structure. Alternatively
50       finalization can be performed by obtaining the streaming ASN1 BIO
51       directly using BIO_new_CMS().
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53       Additional compression parameters such as the zlib compression level
54       cannot currently be set.
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RETURN VALUES

57       CMS_compress() returns either a CMS_ContentInfo structure or NULL if an
58       error occurred. The error can be obtained from ERR_get_error(3).
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SEE ALSO

61       ERR_get_error(3), CMS_uncompress(3)
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HISTORY

64       The CMS_STREAM flag was added in OpenSSL 1.0.0.
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67       Copyright 2008-2016 The OpenSSL Project Authors. All Rights Reserved.
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69       Licensed under the OpenSSL license (the "License").  You may not use
70       this file except in compliance with the License.  You can obtain a copy
71       in the file LICENSE in the source distribution or at
72       <https://www.openssl.org/source/license.html>.
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761.1.1q                            2023-07-20                   CMS_COMPRESS(3)
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