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131 .IX Title "CMS_COMPRESS 3"
132 .TH CMS_COMPRESS 3 "2018-09-11" "1.1.1" "OpenSSL"
133 .\" For nroff, turn off justification. Always turn off hyphenation; it makes
134 .\" way too many mistakes in technical documents.
138 CMS_compress \- create a CMS CompressedData structure
140 .IX Header "SYNOPSIS"
142 \& #include <openssl/cms.h>
144 \& CMS_ContentInfo *CMS_compress(BIO *in, int comp_nid, unsigned int flags);
147 .IX Header "DESCRIPTION"
148 \&\fICMS_compress()\fR creates and returns a \s-1CMS\s0 CompressedData structure. \fBcomp_nid\fR
149 is the compression algorithm to use or \fBNID_undef\fR to use the default
150 algorithm (zlib compression). \fBin\fR is the content to be compressed.
151 \&\fBflags\fR is an optional set of flags.
154 The only currently supported compression algorithm is zlib using the \s-1NID\s0
155 NID_zlib_compression.
157 If zlib support is not compiled into OpenSSL then \fICMS_compress()\fR will return
160 If the \fB\s-1CMS_TEXT\s0\fR flag is set \s-1MIME\s0 headers for type \fBtext/plain\fR are
161 prepended to the data.
163 Normally the supplied content is translated into \s-1MIME\s0 canonical format (as
164 required by the S/MIME specifications) if \fB\s-1CMS_BINARY\s0\fR is set no translation
165 occurs. This option should be used if the supplied data is in binary format
166 otherwise the translation will corrupt it. If \fB\s-1CMS_BINARY\s0\fR is set then
167 \&\fB\s-1CMS_TEXT\s0\fR is ignored.
169 If the \fB\s-1CMS_STREAM\s0\fR flag is set a partial \fBCMS_ContentInfo\fR structure is
170 returned suitable for streaming I/O: no data is read from the \s-1BIO\s0 \fBin\fR.
172 The compressed data is included in the CMS_ContentInfo structure, unless
173 \&\fB\s-1CMS_DETACHED\s0\fR is set in which case it is omitted. This is rarely used in
174 practice and is not supported by \fISMIME_write_CMS()\fR.
177 If the flag \fB\s-1CMS_STREAM\s0\fR is set the returned \fBCMS_ContentInfo\fR structure is
178 \&\fBnot\fR complete and outputting its contents via a function that does not
179 properly finalize the \fBCMS_ContentInfo\fR structure will give unpredictable
182 Several functions including \fISMIME_write_CMS()\fR, \fIi2d_CMS_bio_stream()\fR,
183 \&\fIPEM_write_bio_CMS_stream()\fR finalize the structure. Alternatively finalization
184 can be performed by obtaining the streaming \s-1ASN1\s0 \fB\s-1BIO\s0\fR directly using
185 \&\fIBIO_new_CMS()\fR.
187 Additional compression parameters such as the zlib compression level cannot
190 .IX Header "RETURN VALUES"
191 \&\fICMS_compress()\fR returns either a CMS_ContentInfo structure or \s-1NULL\s0 if an error
192 occurred. The error can be obtained from \fIERR_get_error\fR\|(3).
194 .IX Header "SEE ALSO"
195 \&\fIERR_get_error\fR\|(3), \fICMS_uncompress\fR\|(3)
198 The \fB\s-1CMS_STREAM\s0\fR flag was added in OpenSSL 1.0.0.
200 .IX Header "COPYRIGHT"
201 Copyright 2008\-2016 The OpenSSL Project Authors. All Rights Reserved.
203 Licensed under the OpenSSL license (the \*(L"License\*(R"). You may not use
204 this file except in compliance with the License. You can obtain a copy
205 in the file \s-1LICENSE\s0 in the source distribution or at
206 <https://www.openssl.org/source/license.html>.