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#8 in Emulators

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Emulation Manager

This is a command-line based utility for adding and auditing ROMs for MAME, MAME's software list, MAME's extras, the Redump database and the No-Intro database.

That is, given a database of what the ROM files are supposed to be, the ROM files themselves, and where to put them, this will make sure everything winds up with the correct name and in the right place so that the games are playable.

It's also extremely fast, able to audit MAME's entire game set in under 10 seconds, and update from one version to the next in under a minute - even on very modest hardware.


At present, the easiest way to install the latest version of emuman is with Rust's cargo:

cargo install emuman

Getting Started

The first thing to do is populate the manager's database of what the ROMs are supposed to be.

Getting started with MAME

If one has MAME already installed, one can pipe its XML output directly into our init routine, like:

mame -listxml | emuman mame init

But if not, the full driver information is available directly from MAME's download page as mameXXXXlx.zip where XXXX is the latest version number. We can feed our init routine with it like:

emuman mame init mameXXXXlx.zip

No unzipping required. Or for added convenience, one can initialize our database directly from the URL on MAME's website, like:

emuman mame init https://github.com/mamedev/mame/releases/download/mameXXXX/mameXXXXlx.zip

This will download the Zip file, extract the file and perform the database initialization.

Getting started with MAME's software list

Formerly known as MESS, MAME's software list is a database of the software for all the various home consoles, portables, personal computers, etc. that MAME supports. This list is updated every time MAME is updated. However, it isn't available as a single file on MAME's website since it's split into a lot of individual XML files (at least one per system).

One way to get these files is to populate them from the hash directory of an installed version of MAME, like:

emuman sl init mameXXXX/hash/*.xml

These files are also provided in MAME's source code dump, or even straight off the git repository of its source code. Just look for a hash directory with lots of XML files.

Getting started with MAME's extras

In this case, "extras" means things like artwork and snapshots for MAME, courtesy of Progetto-Snaps. These are updated every few versions of MAME. Look to their download page for the latest snapshots downloads. These are distributed as a mix of full packs and updates like pS_XXX_YYYY_ZZZ.zip where XXX is what sort of extra it is ("title", "logo", etc.), YYYY is whether it's a "fullset" or update ("upd"), and ZZZ is the MAME version.

Our manager can be initialized directly from the zipped files like:

emuman extra init pS*.zip

This will look in the Zip files and populate our database with any XML data files it can find.

Getting started with the No-Intro database

No-Intro.org maintains a set of XML data files which can be downloaded individually or in bulk. These are labeled like <Manufacturer> - <Platform> (<datestamp>-<version>).dat and can also be initialized in bulk, like:

emuman nointro init *.dat

These data files are updated regularly, but one doesn't need to reinitialize them all every time; specifying only a single .dat file will update only that platform and leave the rest as-is.

Getting started with the Redump database

Redump.org also maintains a set of XML data files which can be downloaded on a per-system basis. But whereas No-Intro is primarily interested in chip-based media, Redump focuses on optical discs. It's XML data files are named like: <Manufacturer> - <Platform> - Datfile (<game count>) (<data and timestamp>).dat and can also be initialized in bulk, like:

emuman redump init *.dat

As with No-Intro, the Redump files can also be updated separately.

Adding the ROM files

At this point, it's important to detail how this ROM manager differs from every other one out there; instead of packing several ROM files into one Zip file per game, we leave store them as one ROM file per file on disk and (for MAME-related categories) one directory per game.

For instance, instead of packing everything for Mr. Do! in a mrdo.zip file, we will create a mrdo directory and place all its ROM files in that directory, like:


One directory per machine, and one file per ROM.

MAME is extremely lenient about how its ROM files are stored and will accept a directory full of machine sub-directories just as easily as it will accept a directory full of .zip files.

But since MAME shares a many of the same ROMs across many different games, we use hard links to de-duplicate them into only a single file on disk. Using mrdo and mrdofix as an example:

mrdo/           mrdofix/
  f10--1.bin  ⇔   f10--1.bin
  h5-05.bin   ⇔   h5-05.bin
  j10--4.bin  ⇔   j10--4.bin
  j2-u001.bin ⇔   j2-u001.bin
  k5-06.bin   ⇔   k5-06.bin
  n8-07.bin   ⇔   n8-07.bin
  r8-08.bin   ⇔   r8-08.bin
  t02--3.bin  ⇔   t02--3.bin
  u02--2.bin  ⇔   u02--2.bin

Ten of these ROM files are identical between the two versions, so we'll simply hard-link them together (indicated by the ).

Furthermore, using the filesystem's built-in compression (like ZFS' per-filesystem compression setting) enables us to pack them into less space. Having the filesystem be in charge of compression separates concerns and supports compression types that MAME (or other emulators) may not.

Adding ROMs for MAME

Now that the manager knows what the ROMs are supposed to be, we simply need to tell it where to find the ROMs we have and where to put them. Like:

emuman mame repair -r MAMEXXXX/roms/ input_dir1/ input_dir2/ ...

Where the -r flag indicates our ROM destination and the input_dir paths are where our existing ROMs are now. The inputs can be individual files, Zip files (which are scanned for ROMs), directories (which are scanned recursively) or even URLs to remote files (which may also be Zip files, and are downloaded and scanned).

This option was formerly labeled add (which is an alias and may still be used).

Once the target ROM destination has been specified, the manager will reuse that destination next time so we don't have to specify it again.

If the destination directory doesn't exist, it will be created and populated. If it does exist, existing game subdirectories will be scanned and repaired as needed - such as missing files being pulled from our input ROMs, or simple renames being performed.

Once complete, this will generate a full report of any games that have missing or extra files along with a summary.

Adding ROMs for the Software List

This is similar to MAME, but we'll also need to specify what software list to use for the ROMs. Like if we're interested in the Vectrex catalog, try:

emuman sl repair -L vectrex -r MAMEXXXX/software/vectrex/ input_dir/

Where the -L option indicates which software list we're interested in. If unspecified, emuman will provide an interactive list to choose from. As with MAME, this will keep track of the software list root directory (MAMEXXXX/software) so we only need to specify the target once.

But unlike MAME, the software list has a repair-all option which only requires the software list root directory and will attempt to add titles to every single software list, like:

emuman sl repair-all -r MAMEXXXX/software/ input_dir/

The process of adding and repairing ROMs in the output directory from the input files works the same as with MAME and also generates a report when completed.

Adding extras/ROMs for Snapshots, No-Intro and Redump

These are similar to MAME's Software List in that ROMs are organized on a per-system basis and the system should be specified, like:

emuman nointro repair -D "GCE - Vectrex" -r Vectrex/ input_dir/

The -D option indicates which DAT file name to use. Again, if unspecified, emuman will let the user pick one. The difference is that these don't expect a single "root" directory like MAME's Software List; the target directory for each individual DAT file may be different.

Again, as with MAME, the output directory will be repaired using the input files and a final report will be generated once complete.

Also like the software list, there is a repair-all option, like:

emuman nointro repair-all input_dir/

Which will attempt to repair all No-Intro DAT files with defined directories.

Verifying ROM files

Although adding ROMs also performs verification, we may wish to verify them separately. If the target directory has already been defined, this may be as simple as:

emuman mame verify

The other modes have similar verify and verify-all features which verify the ROMs present provide a listing of files that are bad/missing.

Both repairing and verifying work very similarly, the only difference being that verifying only displays reports and doesn't take any input files are make changes to files on disk.

Upgrading from one version to the next

If the only difference is newly added files or simple renames, one can run repair to populate the missing files from external sources and to bring it to the latest version. But when entire games are renamed from one version to the next (for instance, a game gets promoted to the new "parent" set) that's when things get complicated. To fix that problem, the easiest way to upgrade is to use the old set as yet another ROM source, like:

emuman mame repair -r MAMEYYYY/roms/ MAMEXXXX/roms/ changed_roms_dir/

Where XXXX is the previous version and YYYY is the current version. Then just remove the old XXXX version when finished. Since we hard-link files whenever possible and most ROM files don't change from one version to the next, this won't take as much time or space as one might think.

How we make adding/verification fast

The first time adding or verifying the games for MAME, the Software List or anything else won't be especially fast; it may take a half an hour or more to verify hundreds of thousands of ROM and CHD files, even when leveraging a good multi-core CPU.

But because most ROMs don't change from one emulator version to the next, and emulators don't modify ROM files themselves, we can leverage the filesystem's extended attributes to drop calculated hash values alongside the files themselves without modifying their contents in any way. And checking an extended attribute is a lot faster than performing a hash of the entire file.


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