int CMS_uncompress(CMS_ContentInfo *cms, BIO *dcont, BIO *out, unsigned int flags);
CMS_uncompress() extracts and uncompresses the content from a CMS CompressedData structure cms. data is a BIO to write the content to and flags is an optional set of flags.
The dcont parameter is used in the rare case where the compressed content is detached. It will normally be set to NULL.
The only currently supported compression algorithm is zlib: if the structure indicates the use of any other algorithm an error is returned.
If zlib support is not compiled into OpenSSL then CMS_uncompress() will always return an error.
The following flags can be passed in the flags parameter.
If the CMS_TEXT flag is set MIME headers for type text/plain are deleted from the content. If the content is not of type text/plain then an error is returned.
CMS_uncompress() returns either 1 for success or 0 for failure. The error can be obtained from ERR_get_error(3)
The lack of single pass processing and the need to hold all data in memory as mentioned in CMS_verify() also applies to CMS_decompress().