144 lines
5.8 KiB
Plaintext
144 lines
5.8 KiB
Plaintext
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Here's something that might help you... I wrote it quite fast but it should
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be accurate ;) However, there's probably a lot of stuff here that you don't
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need/understant for now... but keep all this, you'll need it soon ;)
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--> This is NOT the "official" Tehcnical stuff....
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File Header:
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offset type/size comment
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------ --------- ---------------------------------
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0 char[8] Signature: 'ziRCONia'
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8 word file header size (from offset 10, not counting this
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word)
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10 word version 0xyyzh (x.yy) (displayed in hex. no conversion)
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z: 0 nothing
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1-0eh revision a to n (-may- be useful...)
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0fh Beta
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12 word number of blocks within file
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14 dword total length of unpacked file
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18 dword file offset where is located the "block offset table"
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22 word dummy... must currently be 0ffffH
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The block offset table is simply N_of_Block dwords which are the
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absolute position of each block in the file. Each of those blocks have
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the following header:
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0 dword unpacked size
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4 dword compressed size
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8 dword XOR check (see note below)
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12 word number of "sub-blocks" (nblk)
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14 word flags (see below)
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16 word number of translation table entry } for compression
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18 word start number of bit } don't mind them
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for now...
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20 sub-block[nblk] Sub-blocks of data info.
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each sub-block has the following info:
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0 dword absolute position in uncompressed file
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4 dword size of uncompressed block
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all "nblk" sub-block info are stored right after the block header.
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Those small blocks are only non-contiguous blocks of the "same type"
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grouped together within one bigger block for better compression.
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- XOR check: instead of implementing a CRC, I coded a XOR check.
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How it works: a dword variable is set to 0, and XORed
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with every complete 4 bytes of the original data of the
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"bigblock". Remaining bytes (i.e, size of bigblock is
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not a multiple of 4) are simply ignored. This is only
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to implement a minimal check of destination when
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decompressing.
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- Flags: this is a 16 bits field:
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15 14 13 12 11 10 9 8
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<20><><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>Ŀ
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<20> 0 <20> 0 <20> 0 <20> 0 <20> 0 <20> 0 <20>Abs16<31> M/S <20>
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<20><><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>
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7 6 5 4 3 2 1 0
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<20><><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>Ŀ
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<20> R <20> T y p e <20> R <20> 8/16<31>Delta<74>Comp.<2E>
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<20><><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>
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bits marked as "0" MUST be 0 (they are reserved for future
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extensions...) Every "1" must be considered as invalid or
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unsupported feature (compressed by a newer version of MMCMP)
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bits marked as "R" are reserved (used during compression processing
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and they don't mean much within the file...) No check should be
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performed on those bits.
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- Comp.: 0: not compressed
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1: compressed
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- Delta: 0: data is not changed
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1: data is Delta (every byte or word is the difference
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between itself and the previous one. First byte or word
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is compared to 0.
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- 8/16: 0: 8 bits compression scheme
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1: 16 bits compression scheme
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- M/S: 0: mono
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1: stereo (not implemented yet) MUST BE 0
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- Abs16 Whithin compression algorithm, 16 bits samples are
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converted to deltas and transformed a bit so there's
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no negative numbers. However, some trackers already
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convert data to deltas, but there's still the little
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transformation to do.
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0: don't do it
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1: do it
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Note: This bit IS NOT checked if Delta bit is 1, but
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should be 0 in this case. May only be set if
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Delta bit is 0.
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- Type: This field doesn't really serve any purpose ;) but
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helping identify type of data in this block. There's
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no strict identifier but the following block types are
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used by MMCMP (warning: do not expect the following to
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always be true... data of different types for us (e.g
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instrument header and sample header) may be interpreted
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as the same type of block (they are contiguous, or
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similar, etc...) for better compression.) The three
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bits are stored in the order you would expect (MSB at
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left, LSB at right)
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0: Module identifier: the firsts bytes of a module
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(this type must NOT be used for anything else...)
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1: Module header: anything useful in the header, which
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is not in block-type 0 (actually not used by MMCMP)
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2: instrument header
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3: sample header
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4: patterns
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5: sample
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6: no definition yet...
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7: remaining (every part of the module that hasn't
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been thrown into the "block list" (i.e probably
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don't fit under any block types...)
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Note that MMCMP sorting scheme puts block of type 0
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first and type 7 last. This is also some sort of
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priority. As for now, know that block of type 0 is
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UNIQUE and is the FIRST.
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Scanning files:
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1. Check if installed and disable MMTSR
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2. Open module
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3. Check signature. If not 'ziRCONia' jump to 11
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4. read "block offset table" offset field (dword at offset 18)
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(and any other info you would like to read)
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5. jump to this position within the file
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6. read the first entry of the table (position of block 0)
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7. jump to this position within the file
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8. read the block header.
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9. If block-type field is not 0, jump to 6 and read the next entry
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instead. (the first block should be of type 0. If not, there's
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probably no block of this type...)
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10.Read the uncompressed data (it should not have the compressed flag
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set)
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11.reenable MMTSR if installed
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12.Do what you would do with the header info and close module if you
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wish...
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