CMS_compress (3)

Leading comments

Automatically generated by Pod::Man 4.07 (Pod::Simple 3.32)

Standard preamble:
========================================================================

(The comments found at the beginning of the groff file "man3/CMS_compress.3ssl".)

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 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_zlib_compression.

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

If the

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

Normally the supplied content is translated into

canonical format (as required by the S/MIME specifications) if 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 is set then is ignored.

If the

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

The compressed data is included in the CMS_ContentInfo structure, unless

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 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

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 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 flag was first supported in OpenSSL 1.0.0.