Sync.m

NSArray *documentPaths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
NSString *documentsDirectoryPath = [documentPaths objectAtIndex:0];

NSString *checksum = nil;
BOOL initialSync = YES;
if([this isUpdatePending]){
    NSString *filePath = [documentsDirectoryPath stringByAppendingPathComponent:@"updated.db"];
    NSData *contents = [NSData dataWithContentsOfFile:filePath];
    checksum = [contents MD5HexDigest];
    initialSync = NO;
}else if([this hasPerformedInitialSync]){
    NSString *filePath = [documentsDirectoryPath stringByAppendingPathComponent:@"database.db"];
    NSData *contents = [NSData dataWithContentsOfFile:filePath];
    checksum = [contents MD5HexDigest];
    initialSync = NO;
}