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CMS_compress(3)                     OpenSSL                    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 (zlib compression). in is the content to be
       compressed.  flags is an optional set of flags.


NOTES

       The only currently supported compression algorithm is zlib using the
       NID NID_zlib_compression.

       If zlib support is not compiled into OpenSSL then CMS_compress() will
       return an error.

       If the CMS_TEXT flag is set MIME headers for type text/plain are
       prepended to the data.

       Normally the supplied content is translated into MIME canonical format
       (as required by the S/MIME specifications) if CMS_BINARY 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
       CMS_BINARY is set then CMS_TEXT is ignored.

       If the CMS_STREAM flag is set a partial CMS_ContentInfo structure is
       returned suitable for streaming I/O: no data is read from the BIO in.

       The compressed data is included in the CMS_ContentInfo structure,
       unless CMS_DETACHED is set in which case it is omitted. This is rarely
       used in practice and is not supported by SMIME_write_CMS().


NOTES

       If the flag CMS_STREAM is set the returned CMS_ContentInfo structure is
       not complete and outputting its contents via a function that does not
       properly finalize the CMS_ContentInfo structure will give unpredictable
       results.

       Several functions including SMIME_write_CMS(), i2d_CMS_bio_stream(),
       PEM_write_bio_CMS_stream() finalize the structure. Alternatively
       finalization can be performed by obtaining the streaming ASN1 BIO
       directly using BIO_new_CMS().

       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

       ERR_get_error(3), CMS_uncompress(3)


HISTORY

       CMS_compress() was added to OpenSSL 0.9.8 The CMS_STREAM flag was first
       supported in OpenSSL 1.0.0.

1.0.2h                            2016-05-03                   CMS_compress(3)

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