On Friday 27 February 2009 14:00:38 j16sdiz at freenetproject.org wrote:
> Author: j16sdiz
> Date: 2009-02-27 14:00:37 +0000 (Fri, 27 Feb 2009)
> New Revision: 25853
>
> Modified:
> trunk/freenet/devnotes/specs/metadata-v0.txt
> Log:
> some (incomplete) doc update
>
> Modified: trunk/freenet/devnotes/specs/metadata-v0.txt
> ===================================================================
> --- trunk/freenet/devnotes/specs/metadata-v0.txt 2009-02-27 14:00:05 UTC
(rev 25852)
> +++ trunk/freenet/devnotes/specs/metadata-v0.txt 2009-02-27 14:00:37 UTC
(rev 25853)
> @@ -11,6 +11,7 @@
> size, metadata of any conceivable size, ZIP manifests and ordinary
> manifests. Limits will be imposed at the client level. Comments?
>
> +All numbers are in java big-endian.
>
> 8 bytes - magic number for freenet metadata
> Wasted bytes, just being paranoid.
> @@ -19,78 +20,73 @@
> 0 for now.
>
> 1 byte - document type
> -0 = simple redirect (including splitfiles)
> -1 = multi-level metadata (fetch this key, then use it as metadata)
> -2 = ordinary manifest
> -3 = ZIP manifest
> -4 = reserved for use in ZIP manifests, see below
> -5+ = available
> + 0 = SIMPLE_REDIRECT - simple redirect (including splitfiles)
> + 1 = MULTI_LEVEL_METADATA - multi-level metadata (fetch this key,
then use it as metadata)
> + 2 = SIMPLE_MANIFEST - ordinary manifest
> + 3 = ARCHIVE_MANIFEST - ZIP/TAR manifest
> + 4 = ARCHIVE_INTERNAL_REDIRECT - reserved for use in ZIP/TAR manifests,
see below
>
> -If multi-level metadata:
> +If documentType == MULTI_LEVEL_METADATA:
> 1 byte - number of levels (must decrease by 1 on each level!)
> 1 byte - document type of final metadata
> 8 bytes - length of final data
>
> -For a simple redirect, multi-level metadata, or a ZIP manifest:
> +If documentType == SIMPLE_REDIRECT or SIMPLE_MANIFEST or ARCHIVE_MANIFEST
or ARCHIVE_INTERNAL_REDIRECT
> + 2 bytes - flags
> + bit 0 = FLAGS_SPLITFILE - splitfile
> + bit 1 = FLAGS_DBR - DBR (splitfile + DBR *is* valid, not
supported)
> + bit 2 = FLAGS_NO_MIME - no MIME type
> + bit 3 = FLAGS_COMPRESSED_MIME - compressed MIME type
> + bit 4 = FLAGS_EXTRA_METADATA - has extra metadata fields (ignored)
> + bit 5 = FLAGS_FULL_KEYS - redirects as full keys (invalid if
splitfile)
> + bit 6 = FLAGS_SPLIT_USE_LENGTHS - reserved/unused
> + bit 7 = FLAGS_COMPRESSED - compressed splitfile
>
> -2 bytes - flags
> -bit 0 = splitfile
> -bit 1 = DBR (splitfile + DBR *is* valid)
> -bit 2 = no MIME type
> -bit 3 = compressed MIME type
> -bit 4 = has extra metadata fields
> -bit 5 = redirects as full keys (invalid if splitfile)
> -bit 6 = unused
> -bit 7 = compressed splitfile (might work with normal redirects but there
> -is no point as single blocks are transparently gzipped anyway)
> +If documentType == ARCHIVE_MANIFEST:
> + 2 bytes - ARCHIVE_TYPE
> + 0 = ZIP ("application/zip", "application/x-zip") /* eventually get rid
of ZIP support at some point */
> + 1 = TAR ("application/x-tar")
>
> -If a ZIP manifest:
> -2 bytes - archive ID (initially 0 = ZIP. We may in future support 1 =
> -tar, with the compressed splitfile bit set, and then a codec specified
> -below, for tar.gz, tar.bz2 etc)
> +If flags |= FLAGS_SPLITFILE:
> + 8 bytes - real content length (compressed size, signed number)
>
> -If a splitfile:
> -8 bytes - real content length (uncompressed)
> -Note no 2GB limit. :)
> +If flags |= FLAGS_COMPRESSED:
> + 2 bytes - COMPRESSOR_TYPE
> + 0 = GZIP
> + 1 = BZIP2
> + 2 = LZMA
> + 8 bytes - decompressed content length (signed number)
>
> -If compressed:
> -2 bytes - codec ID
> -Initially we only support gzip (0).
> -8 bytes - decompressed content length
> +If _NOT_ flags |= FLAGS_NO_MIME:
> + If flags |= FLAGS_COMPRESSED_MIME:
> + 2 bytes - compressedMIMEValue (base MIME type IDs)
> + See DefaultMIMETypes.java for the look up table
>
> -If has a MIME type:
> -If raw:
> -1 byte - length (N)
> -N bytes - string
> + If compressedMIMEValue & 0x7fff == 0x7fff:
Surely the opposite - if the top bit is set, ...
> + 2 bytes - compressedMIMEParams
> + else
> + 1 byte - length (N)
> + N bytes - MIME Type (UTF-8 String)
>
> -If compressed:
> -2 bytes - base MIME type ID; index into lookup table; last bit is not
> - part of the lookup index, and defines whether parameters are necessary.
> -2 bytes - if parameters are expected, parameters ID (mostly charset= for
> - text/ types; other types may define other parameters)
> +If flags |= DBR: (not supported yet)
> + 4 bytes - period, in seconds
> + 4 bytes - offset, in seconds
Probably will never be supported... imho it's a bad idea.
>
> +If flags |= FLAGS_EXTRA_METADATA: (ignored)
> + 2 bytes - number of extra metadata fields
> + For each extra metadata field:
> + 2 bytes - metadata field type
> + 1 byte - length
> + N bytes - metadata field specific information
>
> -If DBR:
> -4 bytes - period, in seconds
> -4 bytes - offset, in seconds
>
> -If has extra metadata fields:
> -2 bytes - number of extra metadata fields
> +If (!(flags |= FLAGS_SPLITFILE) && ((documentType == SIMPLE_REDIRECT) ||
(documentType == ARCHIVE_MANIFEST)):
> + If FLAGS_FULL_KEYS
> + 1 byte - length of binary key
> + N bytes - binary key (this is just a compressed FreenetURI, see
FreenetURI.java)
> + Else
> + 5+32+32 bytes - raw binary form of a CHK
I thought full keys were allowed in SIMPLE_REDIRECT ??
>
> -For each:
> -2 bytes - metadata field type
> -1 byte - length
> -N bytes - metadata field specific information
> -
> -
> -For a simple redirect:
> -
> -If bit 5 is set above:
> -1 byte - length of binary key
> -N bytes - binary key (this is just a compressed FreenetURI)
> -Else:
> -<fixed number yet to be determined> bytes - raw binary form of a CHK
> -
> For a splitfile redirect:
> 2 bytes - algorithm ID
> 0 = no redundancy. Invalid unless bit 6 or 5 above is set.
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