/// <summary>
/// Creats two threads which will fill up our queue with urls to photos.
/// </summary>
private void CreatePhotoUrlsFetchers()
{
pictures_urls = new Queue <Uri>(number_of_photos);
next_page_index = number_of_photos / 2; // middle.
next_page_index -= (next_page_index % number_of_pictures_in_page); // make sure we're a multiple of number_of_pictures_in_page.
prev_page_index = next_page_index; // BuildPicturesList method will remove number_of_pictures_in_page from prev_page_index as it starts.
next_page_index -= number_of_pictures_in_page; // BuildPicturesList method will add number_of_pictures_in_page to next_page_index as it starts.
mutex = new Mutex();
semaphore = new Semaphore(0, 600); // Should be enough.
// Create two threads which will enter photos urls to queue.
producer_one = new Thread(new ParameterizedThreadStart(BuildPicturesList));
delegate_GetNexPrevPictureUrl next_method = new delegate_GetNexPrevPictureUrl(GetNextPicturesPageIndex);
producer_one.Start(next_method);
producer_two = new Thread(new ParameterizedThreadStart(BuildPicturesList));
delegate_GetNexPrevPictureUrl prev_method = new delegate_GetNexPrevPictureUrl(GetPrevPicturesPageIndex);
producer_two.Start(prev_method);
}
/// <summary>
/// Adds picture URLs to queue, At the moment two threads are scanning the user's "Photos of You" album,
/// both starts from the 'middle' of the album one advances forward the other backwards,
/// this way the queue will fill up much quicker.
/// </summary>
/// <param name="next_prev_pic_page_url">Method which navigates to a photos page.</param>
private void BuildPicturesList(object next_prev_pic_page_url)
{
try
{
// Casting given parameter.
delegate_GetNexPrevPictureUrl getNexPrevPictureUrl = next_prev_pic_page_url as delegate_GetNexPrevPictureUrl;
List <string> pictures_srcs; // list of picture URLs for the current page.
int current_page_index = getNexPrevPictureUrl(); // Starting position. we navigate both forward and backwards.
do
{
pictures_srcs = GetPicturedSrcs(current_page_index); // Get all photo URLs in current page.
if (pictures_srcs.Count == 0)
{
break;
}
mutex.WaitOne(); // TODD: check if queue is thread safe, if so mutex isn't needed.
foreach (string picture_src in pictures_srcs)
{
pictures_urls.Enqueue(new Uri(picture_src));
}
mutex.ReleaseMutex();
semaphore.Release(pictures_srcs.Count); // one for each image.
current_page_index = getNexPrevPictureUrl(); // Either move forward or backwards depending on the given next_prev_pic_page_url param.
} while (pictures_srcs.Count > 0 && current_page_index >= 0); // index must be positive or equal to zero and we must have some pictures.
}
catch (ThreadAbortException ex)
{
}
// We can logout once the queue is filled by both threads, Facebook doesn't check credentials when acssesing a photo directly.
// But for the time being stay logged.
}
