CMS_compress - create a CMS CompressedData structure
CMS_ContentInfo *CMS_compress(BIO *in, int comp_nid, unsigned int flags);
creates and returns a CMS CompressedData structure.
is the compression algorithm to use or NID_undef
the default algorithm (zlib compression). in
is the content to be
is an optional set of flags.
The only currently supported compression algorithm is zlib using the NID
If zlib support is not compiled into OpenSSL then CMS_compress()
return an error.
If the CMS_TEXT
flag is set MIME headers for type text/plain
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
If the CMS_STREAM
flag is set a partial CMS_ContentInfo
is returned suitable for streaming I/O: no data is read from the BIO
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()
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
Several functions including SMIME_write_CMS()
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.
returns either a CMS_ContentInfo structure or NULL if an
error occurred. The error can be obtained from ERR_get_error(3)
was added to OpenSSL 0.9.8 The CMS_STREAM
first supported in OpenSSL 1.0.0.