/**
* Checks if the table of the specified database is locked.
*
* @param db name of database
* @param ctx database context
* @return result of check
*/
public static boolean locked(final String db, final Context ctx) {
final IOFile table = MetaData.file(ctx.globalopts.dbpath(db), DATATBL);
if (!table.exists()) return false;
try (final RandomAccessFile file = new RandomAccessFile(table.file(), "rw")) {
return file.getChannel().tryLock() == null;
} catch (final ClosedChannelException ex) {
return false;
} catch (final OverlappingFileLockException | IOException ex) {
return true;
}
}
/**
* Reads a block from disk.
*
* @param b block to fetch
*/
private void readBlock(final int b) {
if (!bm.cursor(b)) return;
final Buffer bf = bm.current();
try {
if (bf.dirty) writeBlock(bf);
bf.pos = b;
if (b >= blocks) {
blocks = b + 1;
} else {
file.seek(bf.pos * IO.BLOCKSIZE);
file.readFully(bf.data);
}
} catch (final IOException ex) {
Util.stack(ex);
}
}
/**
* Writes the specified block to disk and resets the dirty flag.
*
* @param bf buffer to write
* @throws IOException I/O exception
*/
private void writeBlock(final Buffer bf) throws IOException {
file.seek(bf.pos * IO.BLOCKSIZE);
file.write(bf.data);
bf.dirty = false;
}
/**
* Acquires a lock on the file. Does nothing if the correct lock has already been acquired.
* Otherwise, releases an existing lock.
*
* @param shared shared/exclusive lock
* @return success flag
* @throws IOException I/O exception
*/
private boolean lck(final boolean shared) throws IOException {
if (fl != null && shared == fl.isShared()) return true;
if (fl != null) fl.release();
fl = file.getChannel().tryLock(0, Long.MAX_VALUE, shared);
return fl != null;
}
@Override
public synchronized void close() throws IOException {
flush();
file.close();
}
