CMS_COMPRESS(3)            Library Functions Manual            CMS_COMPRESS(3)

NAME
     CMS_compress - create a CMS CompressedData structure

SYNOPSIS
     #include <openssl/cms.h>

     CMS_ContentInfo *
     CMS_compress(BIO *in, int comp_nid, unsigned int flags);

DESCRIPTION
     CMS_compress() creates and returns a CMS CompressedData structure.

     comp_nid is the compression algorithm to use or NID_undef to use the
     default algorithm.  Currently, the default algorithm NID_zlib_compression
     is the only supported algorithm.  If zlib support is not compiled in,
     CMS_compress() always returns an error.

     in provides the content to be compressed.

     Any of the following flags (OR'ed together) can be passed in the flags
     parameter:

     CMS_TEXT
             Prepend MIME headers for type text/plain to the data.

     CMS_BINARY
             Do not translate the supplied content into MIME canonical format,
             even though that is required by the S/MIME specifications.  This
             option should be used if the supplied data is in binary format.
             Otherwise, the translation will corrupt it.  If CMS_BINARY is
             set, CMS_TEXT is ignored.

     CMS_STREAM
             Return a partial CMS_ContentInfo structure suitable for streaming
             I/O: no data is read from in.  Several functions including
             SMIME_write_CMS(3), i2d_CMS_bio_stream(3), or
             PEM_write_bio_CMS_stream(3) can be used to finalize the
             structure.  Alternatively, finalization can be performed by
             obtaining the streaming ASN1 BIO directly using BIO_new_CMS(3).
             Outputting the contents of the CMS_ContentInfo structure via a
             function that does not properly finalize it will give
             unpredictable results.

     CMS_DETACHED
             Do not include the compressed data in the CMS_ContentInfo
             structure.  This is rarely used in practice and is not supported
             by SMIME_write_CMS(3).

     Additional compression parameters such as the zlib compression level
     cannot currently be set.

RETURN VALUES
     CMS_compress() returns either a CMS_ContentInfo structure or NULL if an
     error occurred.  The error can be obtained from ERR_get_error(3).

SEE ALSO
     CMS_ContentInfo_new(3), CMS_uncompress(3)

STANDARDS
     RFC 3274: Compressed Data Content Type for Cryptographic Message Syntax
     (CMS)

HISTORY
     CMS_compress() first appeared in OpenSSL 0.9.8h and has been available
     since OpenBSD 6.7.

     The CMS_STREAM flag first appeared in OpenSSL 1.0.0.

Linux 6.8.2-arch2-1            November 2, 2019            Linux 6.8.2-arch2-1