chunked uploading iOS

By the way, here's a quick sample I put together. I haven't tested this fully, so don't just ship this, but I believe the basics are right:

- (void) doTest {

    if ([[DBSession sharedSession] isLinked]) {
        NSLog(@"Running test...");

        // Write a file to the local documents directory
        NSString *text = @"Hello world. Usually something much longer here.";
        NSString *filename = @"working-draft.txt";
        NSString *localDir = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES)[0];
        self.localPath = [localDir stringByAppendingPathComponent:filename];
        [text writeToFile:self.localPath atomically:YES encoding:NSUTF8StringEncoding error:nil];

        self.dbClient = [[DBRestClient alloc] initWithSession:[DBSession sharedSession]];
        self.dbClient.delegate = self;

        // Start the upload. No upload ID known yet
        [self.dbClient uploadFileChunk:nil offset:0 fromPath:self.localPath];

    }


}

- (void)restClient:(DBRestClient *)client uploadedFileChunk:(NSString *)uploadId newOffset:(unsigned long long)offset
          fromFile:(NSString *)localPath expires:(NSDate *)expiresDate {

    NSLog(@"uploadedFileChunk: %@, newOffset: %llu, fromFile: %@, expires: %@", uploadId, offset, localPath, expiresDate);

    NSFileManager *fileManager = [NSFileManager defaultManager];
    NSDictionary *attrs = [fileManager attributesOfItemAtPath:self.localPath error: NULL];

    // in real use, there's probably a dangerous race condition here in checking the size each time, but this is just for demonstration purposes
    if (offset >= [attrs fileSize]) {
        // all data has been uploaded
        NSLog(@"Finishing upload...");
        [self.dbClient uploadFile:@"chunked_uploaded_file.txt" toPath:@"/" withParentRev:nil fromUploadId:uploadId];
    } else {
        // more data to upload
        NSLog(@"Continuing upload...");
        [self.dbClient uploadFileChunk:uploadId offset:offset fromPath:localPath];
    }

}

- (void)restClient:(DBRestClient *)client uploadFileChunkFailedWithError:(NSError *)error {

    NSLog(@"uploadFileChunkFailedWithError: %@", error);
    // TODO: retry

}