diff options
author | Dr. Stephen Henson <steve@openssl.org> | 2008-04-09 17:04:36 +0000 |
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committer | Dr. Stephen Henson <steve@openssl.org> | 2008-04-09 17:04:36 +0000 |
commit | 360bb61d860f9ce7e48b2bb85d3ef9f521f95ab9 (patch) | |
tree | da48e6c85caf5dbcdaa7d88826205067e5d0c7a6 /doc/crypto/CMS_compress.pod | |
parent | 847e551f39c2a218e36f95d93d45b72ec4446a2a (diff) |
Add CMS_compress() docs.
Diffstat (limited to 'doc/crypto/CMS_compress.pod')
-rw-r--r-- | doc/crypto/CMS_compress.pod | 70 |
1 files changed, 70 insertions, 0 deletions
diff --git a/doc/crypto/CMS_compress.pod b/doc/crypto/CMS_compress.pod new file mode 100644 index 0000000000..f2550b4947 --- /dev/null +++ b/doc/crypto/CMS_compress.pod @@ -0,0 +1,70 @@ +=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 +algorithms (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 this 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(). + +=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 0.9.9. + +=cut |