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Editing: CMS_compress.3
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Always turn off hyphenation; it makes .\" way too many mistakes in technical documents. .if n .ad l .nh .SH "NAME" CMS_compress \- create a CMS CompressedData structure .SH "SYNOPSIS" .IX Header "SYNOPSIS" .Vb 1 \& #include <openssl/cms.h> \& \& CMS_ContentInfo *CMS_compress(BIO *in, int comp_nid, unsigned int flags); .Ve .SH "DESCRIPTION" .IX Header "DESCRIPTION" \&\fBCMS_compress()\fR creates and returns a \s-1CMS\s0 CompressedData structure. \fBcomp_nid\fR is the compression algorithm to use or \fBNID_undef\fR to use the default algorithm (zlib compression). \fBin\fR is the content to be compressed. \&\fBflags\fR is an optional set of flags. .SH "NOTES" .IX Header "NOTES" The only currently supported compression algorithm is zlib using the \s-1NID\s0 NID_zlib_compression. .PP If zlib support is not compiled into OpenSSL then \fBCMS_compress()\fR will return an error. .PP If the \fB\s-1CMS_TEXT\s0\fR flag is set \s-1MIME\s0 headers for type \fBtext/plain\fR are prepended to the data. .PP Normally the supplied content is translated into \s-1MIME\s0 canonical format (as required by the S/MIME specifications) if \fB\s-1CMS_BINARY\s0\fR is set no translation occurs. This option should be used if the supplied data is in binary format otherwise the translation will corrupt it. If \fB\s-1CMS_BINARY\s0\fR is set then \&\fB\s-1CMS_TEXT\s0\fR is ignored. .PP If the \fB\s-1CMS_STREAM\s0\fR flag is set a partial \fBCMS_ContentInfo\fR structure is returned suitable for streaming I/O: no data is read from the \s-1BIO\s0 \fBin\fR. .PP The compressed data is included in the CMS_ContentInfo structure, unless \&\fB\s-1CMS_DETACHED\s0\fR is set in which case it is omitted. This is rarely used in practice and is not supported by \fBSMIME_write_CMS()\fR. .SH "NOTES" .IX Header "NOTES" If the flag \fB\s-1CMS_STREAM\s0\fR is set the returned \fBCMS_ContentInfo\fR structure is \&\fBnot\fR complete and outputting its contents via a function that does not properly finalize the \fBCMS_ContentInfo\fR structure will give unpredictable results. .PP Several functions including \fBSMIME_write_CMS()\fR, \fBi2d_CMS_bio_stream()\fR, \&\fBPEM_write_bio_CMS_stream()\fR finalize the structure. Alternatively finalization can be performed by obtaining the streaming \s-1ASN1\s0 \fB\s-1BIO\s0\fR directly using \&\fBBIO_new_CMS()\fR. .PP Additional compression parameters such as the zlib compression level cannot currently be set. .SH "RETURN VALUES" .IX Header "RETURN VALUES" \&\fBCMS_compress()\fR returns either a CMS_ContentInfo structure or \s-1NULL\s0 if an error occurred. The error can be obtained from \fBERR_get_error\fR\|(3). .SH "SEE ALSO" .IX Header "SEE ALSO" \&\fBERR_get_error\fR\|(3), \fBCMS_uncompress\fR\|(3) .SH "HISTORY" .IX Header "HISTORY" \&\fBCMS_compress()\fR was added to OpenSSL 0.9.8 The \fB\s-1CMS_STREAM\s0\fR flag was first supported in OpenSSL 1.0.0.
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