The ___ARESTRA___ file format
-----------------------------

Growing media file with special appendix.

By default appendix starts 4096 bytes from file end, rest padded with zeroes.
File is not initially full sized so appendix moves as file increases.

Appendix starts with magic "___ARESTRA__2".  Looks like the '2' was changed
later modifying the original format's magic "___ARESTRA___".

All fields little endian unless noted otherwise.

Appendix layout:

offset  length  data
---------------------
0       13      "___ARESTRA__2"
13      4       file size
17      4       total size of completed chunks
27      8*n     n start/end pairs. Chunks up to current file size which have
                not yet been completely finished. During downloading these
                chunks may be half full but on exit they are split so only 
                completely empty ranges are saved. Start/end are inclusive.

x       8       0x00/0x00 pair, hardcoded, chunk list terminator
x + 8   1       0x01 ?
x + 9   1       paused flag (0x01 == paused, 0x00 == active)
x + 10  4       0x00000080 ?
x + 14  4       0x00000000 ?
x + 18  4       0x000000F8 ?
x + 22  2       t_len, remaining data after this field
x + 24  t_len   sequence of TLVs. It seems all types are always present even
                if they are empty.


TLV:
0       1       type
1       2       size of following data
3       size    data


TLV types (hex):

01  string, keywords
02  string, title
03  string, artist
04  string, album 
05  string, genre
06  string, year
08  unknown, zero length?
09  string, comment? url? 
0A  string, comment?
0D  sequence of 17 byte source data
0F  hash, 20 bytes
13  unknown, zero length?


Source data:

0   4   user's outside ip (big endian)
4   2   user's port
6   4   supernode ip (big endian)
10  2   supernode port
12  4   user's inside ip  (reserved space, zero or outside ip) (big endian)
16  1   0x00, hardcoded


------

chunking samples:

(during download)
file size: 3969024
appendix start: 1048576
total downloaded: 457728
chunk: 786432 - 1048575
chunk: 524288 - 786431
chunk: 195584 - 262143

(after incomplete exit)
file size: 3969024
appendix start: 1835008
total downloaded: 1055010
chunk: 1674752 - 1835007
chunk: 1318576 - 1572863
chunk: 1147904 - 1310719
chunk: 951922 - 1048575
chunk: 680448 - 786431

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