Amiga Forever Essentials and C64 Forever
Essentials for Android aim
to support the development of
third-party emulation apps and to make it
easier for users to enjoy such apps. In
order to achieve this goal, legal and official ROM and OS files
licensed for use on Android are made
available, with a shared access mechanism
for developers.
Like in other versions of the software,
ROM files are stored in a directory named
"rom", and ADF (Amiga disk image) files are stored
in a directory named "adf". On
Android devices, this is inside the "files"
directory of the
"com.cloanto.amigaforever.essentials"
namespace for Amiga Forever, and
"com.cloanto.c64forever.essentials" for C64
Forever.
When the app is launched, or if a content
rescan is initiated, it copies the system
files to a shared location on the public
"External Storage" (which may be internal or
on SD card) and to the private "Internal
Storage".
The publicly accessible
"external" storage is within
the "/sdcard/" path as returned by
Environment.getExternalStorageDirectory().
The same files are also present on
internal storage, within the "/data/data/"
path as returned byContext.getFilesDir(),
but this space is private (not accessible by
other apps) without root access rights.
Additional information about ROM files:
- Amiga Forever Essentials ROM files
are 512 KB
- The ROM file names are designed for
long-term support and are not expected
to change
- A ROM file beginning with
"AMIROMTYPE1" indicates an XOR encoding
against rom.key, as illustrated in
memory.c of the original
UAE source code (October 1997 and
later versions)
- A rom.key file, if present, is in
the same directory as the ROM files
- Only Amiga ROM files are encoded
(8-bit CBM ROM files are not)
Sample code to locate the "files"
directory on external storage:
private String getExternalDir() {
String dir = "";
File current_dir;
current_dir = this.getExternalFilesDir(null);
if ((current_dir != null) && (Environment.getExternalStorageState().equals(Environment.MEDIA_MOUNTED))) {
dir = current_dir.toString() + "/../../com.cloanto.amigaforever.essentials/files";
}
return dir;
}
Sample code to locate the "files"
directory on internal storage:
private String getInternalDir() {
String dir = getFilesDir().toString() + "/../../com.cloanto.amigaforever.essentials/files";
return dir;
}
The app further writes
an "index.txt" file at the root of each
"files" directory, placing a timestamp in
the first line. This makes it possible to
use the most recent file set, if both
internal and external storage versions are
present:
public void startApplication() {
int external_timestamp = getTimestamp(getExternalDir());
int internal_timestamp = getTimestamp(getInternalDir());
Log.i("DEBUG", "External timestamp: " + external_timestamp);
Log.i("DEBUG", "Internal timestamp: " + internal_timestamp);
}
private int getTimestamp(String directory) {
if (directory.equals("")) { return 0; }
try {
File mypath = new File(directory, "index.txt");
FileInputStream fis = new FileInputStream(mypath);
BufferedReader reader = new BufferedReader(new InputStreamReader(fis));
String timestamp = reader.readLine();
reader.close();
fis.close();
return Integer.parseInt(timestamp);
} catch (Exception e) {
}
return 0;
}
Some tips to improve the user experience:
- Ideally, a default ROM file
should be preselected for each system, so that an emulation session can start without
errors even if the user has not manually
chosen a ROM file
- If something goes wrong and a ROM
cannot be opened for whatever reason
(e.g. Amiga Forever Essentials installed
after emulation app, or previous user
path set to non-existing location, etc.), consider
falling back to a suitable Amiga Forever
Essentials ROM
- To determine the best location of
the ROM and OS files, check
for the presence of one or more files,
not just for the directory (the content
of which may be empty or not accessible)
- Encoded ROMs are best supported
transparently (there is no need to
request the path of the rom.key file, as
it is the same as the ROM files)
- Keeping the "rom" and "adf" paths
independent, and starting from the
autodetected location for each, helps
the user quickly find the correct files
in their respective location (rather
than manually changing directory) when
changing settings
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