DISCUSSION In addition to supporting RP9
as the preferred application container
format (.rp9 files), the RetroPlatform
player software supports snapshot files to
store saved session state snapshots.
An .rp9-snapshot file contains as much
data as possible about the saved machine.
This includes copies of disk image files
(local host folders mounted in the guest are
not included),
system memory, a preview thumbnail of the
saved system, a description and a timestamp.
A snapshot can be saved, run and deleted
without referencing or affecting the content
of the disk image files in the original RP9
package (unless the configuration referenced
data stored in host folders). Because data
is duplicated in each snapshot, snapshots
are independent of each other. Changes are
applied to the original RP9 file only after
a snapshot is run and only if changes are
explicitly committed when closing the
session. If the session is closed without
committing disk changes, both the snapshot
used to start the session and the original
RP9 file are left unchanged.
For each filename.rp9 file there can be
multiple filename.number.rp9-snapshot files.
For example:
- Asteroid Invader II (Acme Games, 1986, Amiga).rp9
- Asteroid Invader II (Acme Games, 1986, Amiga).1.rp9-snapshot
- Asteroid Invader II (Acme Games, 1986, Amiga).2.rp9-snapshot
- etc.
There is no dependency between snapshots.
The only dependency is between a snapshot
and the corresponding RP9 file, which must
exist and have the same root name. The numbering of snapshot files
does not need to be sequential (snapshot
files may be deleted in any order). The
player can sort snapshots by their internal
timestamp. If moving or copying snapshots
for preservation purposes, it is important
to keep together the .rp9-snapshot file(s)
with the corresponding .rp9 file.
Unlike RP9 files, snapshot files contain
plugin-specific session data, therefore
cross-engine portability is not to be
expected.
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