1 .\" $NetBSD: CMS_compress.3,v 1.14 2015/06/12 17:01:13 christos Exp $
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135 .\" ========================================================================
137 .IX Title "CMS_compress 3"
138 .TH CMS_compress 3 "2009-12-26" "1.0.1n" "OpenSSL"
139 .\" For nroff, turn off justification. Always turn off hyphenation; it makes
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144 CMS_compress \- create a CMS CompressedData structure
148 .IX Header "SYNOPSIS"
150 \& #include <openssl/cms.h>
152 \& CMS_ContentInfo *CMS_compress(BIO *in, int comp_nid, unsigned int flags);
155 .IX Header "DESCRIPTION"
156 \&\fICMS_compress()\fR creates and returns a \s-1CMS\s0 CompressedData structure. \fBcomp_nid\fR
157 is the compression algorithm to use or \fBNID_undef\fR to use the default
158 algorithm (zlib compression). \fBin\fR is the content to be compressed.
159 \&\fBflags\fR is an optional set of flags.
162 The only currently supported compression algorithm is zlib using the \s-1NID\s0
163 NID_zlib_compression.
165 If zlib support is not compiled into OpenSSL then \fICMS_compress()\fR will return
168 If the \fB\s-1CMS_TEXT\s0\fR flag is set \s-1MIME\s0 headers for type \fBtext/plain\fR are
169 prepended to the data.
171 Normally the supplied content is translated into \s-1MIME\s0 canonical format (as
172 required by the S/MIME specifications) if \fB\s-1CMS_BINARY\s0\fR is set no translation
173 occurs. This option should be used if the supplied data is in binary format
174 otherwise the translation will corrupt it. If \fB\s-1CMS_BINARY\s0\fR is set then
175 \&\fB\s-1CMS_TEXT\s0\fR is ignored.
177 If the \fB\s-1CMS_STREAM\s0\fR flag is set a partial \fBCMS_ContentInfo\fR structure is
178 returned suitable for streaming I/O: no data is read from the \s-1BIO \s0\fBin\fR.
180 The compressed data is included in the CMS_ContentInfo structure, unless
181 \&\fB\s-1CMS_DETACHED\s0\fR is set in which case it is omitted. This is rarely used in
182 practice and is not supported by \fISMIME_write_CMS()\fR.
185 If the flag \fB\s-1CMS_STREAM\s0\fR is set the returned \fBCMS_ContentInfo\fR structure is
186 \&\fBnot\fR complete and outputting its contents via a function that does not
187 properly finalize the \fBCMS_ContentInfo\fR structure will give unpredictable
190 Several functions including \fISMIME_write_CMS()\fR, \fIi2d_CMS_bio_stream()\fR,
191 \&\fIPEM_write_bio_CMS_stream()\fR finalize the structure. Alternatively finalization
192 can be performed by obtaining the streaming \s-1ASN1 \s0\fB\s-1BIO\s0\fR directly using
193 \&\fIBIO_new_CMS()\fR.
195 Additional compression parameters such as the zlib compression level cannot
198 .IX Header "RETURN VALUES"
199 \&\fICMS_compress()\fR returns either a CMS_ContentInfo structure or \s-1NULL\s0 if an error
200 occurred. The error can be obtained from \fIERR_get_error\fR\|(3).
202 .IX Header "SEE ALSO"
203 \&\fIERR_get_error\fR\|(3), \fICMS_uncompress\fR\|(3)
206 \&\fICMS_compress()\fR was added to OpenSSL 0.9.8
207 The \fB\s-1CMS_STREAM\s0\fR flag was first supported in OpenSSL 1.0.0.