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Major CHD/chdman update: [Aaron Giles]
The CHD version number has been increased from 4 to 5. This means any
diff CHDs will no longer work. If you absolutely need to keep the
data for any existing ones you have, find both the diff CHD and the
original CHD for the game in question and upgrade using these
commands:

rename diff\game.dif diff\game-old.dif chdman copy -i
diff\game-old.dif -ip roms\game.chd -o diff\game.dif -op roms\game.chd
-c none

Specifics regarding this change:

Defined a new CHD version 5. New features/behaviors of this version:
* support for up to 4 codecs; each block can use 1 of the 4
* new LZMA codec, which tends to do better than zlib overall
* new FLAC codec, primarily used for CDs (but can be applied
anywhere)
* upgraded AVHuff codec now uses FLAC for encoding audio
* new Huffman codec, used to catch more nearly-uncompressable blocks
* compressed CHDs now use a compressed map for significant savings
* CHDs now are aware of a "unit" size; each hunk holds 1 or more
units (in general units map to sectors for hard disks/CDs)
* diff'ing against a parent now diffs at the unit level, greatly
improving compression

Rewrote and modernized chd.c. CHD versions prior to 3 are
unsupported, and version 3/4 CHDs are only supported for reading.
Creating a new CHD now leaves the file open. Added methods to read
and write at the unit and byte level, removing the need to handle
this manually. Added metadata access methods that pass astrings and
dynamic_buffers to simplify the interfaces. A companion class
chd_compressor now implements full multithreaded compression,
analyzing and compressing multiple hunks independently in parallel.
Split the codec implementations out into a separate file chdcodec.*

Updated harddisk.c and cdrom.c to rely on the caching/byte-level
read/ write capabilities of the chd_file class. cdrom.c (and chdman)
now also pad CDs to 4-frame boundaries instead of hunk boundaries,
ensuring that the same SHA1 hashes are produced regardless of the
hunk size.

Rewrote chdman.exe entirely, switching from positional parameters to
proper options. Use "chdman help" to get a list of commands, and
"chdman help " to get help for any particular command. Many
redundant commands were removed now that additional flexibility is
available. Some basic mappings:

Old: chdman -createblankhd New: chdman
createhd -o -chs ,,

Old: chdman -createuncomphd .... New: chdman
createhd -i -o -c none ....

Old: chdman -verifyfix New: chdman verify -i -f

Old: chdman -merge New: chdman copy
-i -ip -o

Old: chdman -diff New: chdman
copy -i -o -op

Old: chdman -update New: chdman copy -i
-o

Added new core file coretmpl.h to hold core template classes. For now
just one class, dynamic_array<> is defined, which acts like an array
of a given object but which can be appended to and/or resized. Also
defines dynamic_buffer as dynamic_array for holding an
arbitrary buffer of bytes. Expect to see these used a lot.

Added new core helper hashing.c/.h which defines classes for each of
the common hashing methods and creator classes to wrap the
computation of these hashes. A future work item is to reimplement the
core emulator hashing code using these.

Split bit buffer helpers out into C++ classes and into their own
public header in bitstream.h.

Updated huffman.c/.h to C++, and changed the interface to make it
more flexible to use in nonstandard ways. Also added huffman
compression of the static tree for slightly better compression rates.

Created flac.c/.h as simplified C++ wrappers around the FLAC
interface. A future work item is to convert the samples sound device
to a modern device and leverage this for reading FLAC files.

Renamed avcomp.* to avhuff.*, updated to C++, and added support for
FLAC as the audio encoding mechanism. The old huffman audio is still
supported for decode only.

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0.130u1
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IMPORTANT NOTE: The CHD format has undergone a change with this
release. The main reason for this change is to include some of the
key metadata into the hashes for the CHDs. This ensures that the
metadata is valid and prevents abuse.

The first impact you will find is that all of your CHD differencing
files are invalid. Just delete your "diff" directory contents
entirely.

The second impact is that all your existing CHDs will warn you that
they have incorrect hashes. This is expected. Your old CHDs should
still work fine, so if you can live with the "bad ROM" warnings, you
don't really need to do anything. However, if this bugs you or you
want to be "clean", you can update your CHDs, using this command
line:

chdman -update

for each one of your CHDs. This will take a while, but will produce
CHDs that match the new checksums posted in the drivers.

Updated CHD format to version 4. Checksums are now computed and
stored separately for raw data and metadata, and metadata is now
checksummed by default. [Aaron Giles]

Updated chdman to support a generic metadata addition system:
chdman -addmetatext []
chdman -addmetabin []
[Aaron Giles]

Changed the CHD verify interfaces to pass back a structure containing
all the necessary data for verification and fixing. [Aaron Giles]