1 files changed, 73 insertions, 0 deletions
diff --git a/openssl/doc/crypto/CMS_compress.pod b/openssl/doc/crypto/CMS_compress.pod
new file mode 100644
index 000000000..0a0715271
--- /dev/null
+++ b/openssl/doc/crypto/CMS_compress.pod
@@ -0,0 +1,73 @@
+=pod
+
+=head1 NAME
+
+CMS_compress - create a CMS CompressedData structure
+
+=head1 SYNOPSIS
+
+ #include <openssl/cms.h>
+
+ CMS_ContentInfo *CMS_compress(BIO *in, int comp_nid, unsigned int flags);
+
+=head1 DESCRIPTION
+
+CMS_compress() creates and returns a CMS CompressedData structure. B<comp_nid>
+is the compression algorithm to use or B<NID_undef> to use the default
+algorithm (zlib compression). B<in> is the content to be compressed.
+B<flags> is an optional set of flags.
+
+=head1 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 B<CMS_TEXT> flag is set MIME headers for type B<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 B<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 B<CMS_BINARY> is set then
+B<CMS_TEXT> is ignored.
+
+If the B<CMS_STREAM> flag is set a partial B<CMS_ContentInfo> structure is
+returned suitable for streaming I/O: no data is read from the BIO B<in>.
+
+The compressed data is included in the CMS_ContentInfo structure, unless
+B<CMS_DETACHED> is set in which case it is omitted. This is rarely used in
+practice and is not supported by SMIME_write_CMS().
+
+=head1 NOTES
+
+If the flag B<CMS_STREAM> is set the returned B<CMS_ContentInfo> structure is
+B<not> complete and outputting its contents via a function that does not
+properly finalize the B<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 B<BIO> directly using
+BIO_new_CMS().
+
+Additional compression parameters such as the zlib compression level cannot
+currently be set.
+
+=head1 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).
+
+=head1 SEE ALSO
+
+L<ERR_get_error(3)|ERR_get_error(3)>, L<CMS_uncompress(3)|CMS_uncompress(3)>
+
+=head1 HISTORY
+
+CMS_compress() was added to OpenSSL 0.9.8
+The B<CMS_STREAM> flag was first supported in OpenSSL 1.0.0.
+
+=cut