Deprecated - Drupal core

I think, there is a bug in includes/file.inc. Sorry, I post it here, but I did not find a Bugtracker for Drupal-Core:

Starting in line 196:

  if ($_FILES["files"]["name"][$source] && is_uploaded_file($_FILES["files"]["tmp_name"][$source])) {

    // Check for file upload errors and return FALSE if a
    // lower level system error occurred.
    switch ($_FILES["files"]["error"][$source]) {

      // @see http://php.net/manual/en/features.file-upload.errors.php
      case UPLOAD_ERR_OK:
        break;

      case UPLOAD_ERR_INI_SIZE:
      case UPLOAD_ERR_FORM_SIZE:
        drupal_set_message(t('The file %file could not be saved, because it exceeds the maximum allowed size for uploads.', array('%file' => $source)), 'error');
        return 0;

      case UPLOAD_ERR_PARTIAL:
      case UPLOAD_ERR_NO_FILE:
        drupal_set_message(t('The file %file could not be saved, because the upload did not complete.', array('%file' => $source)), 'error');
        return 0;

      // Unknown error
      default:
        drupal_set_message(t('The file %file could not be saved. An unknown error has occurred.', array('%file' => $source)),'error');
        return 0;
    }

The if-clause checks, if there was a file uploaded. If no file was uploaded, then it ommits the following switch-case-block.

I need to write the code to make a dynamic view based on the date.
So i have to access the database, but i want to use the standard code of drupal.
Which classes are used for accessing the database? Is there a class that retrieve parameters of a node from the db?

Sorry to bother you with such a trivial question but I'm getting nowhere searching the forums or browsing the API docs ...
Is there a Drupal variable of some kind available that simply indicates whether the current user is logged in or not?
Better still, is there a document somewhere that details this and all similar variables?

Thanks

What's the meaning of this column?

Hi. Looking at search module, i can see this piece of code.

 // Construct the search form.
    $output = drupal_get_form('search_form', NULL, $keys, $type);
    $output .= $results;

So, the search results is always showing the search form before the results of the search. Is there any way to override this function in order to show the search form in other place of the page?. (For example, after the results list)
Thank you.

Hello,

I am sorry if i am at a wrong place. But someone please help me.

I have developed a small java shop web application.

I want that to be integrated into my existing drupal site?

i.e I need to implement a Shop GUI on Drupal, but relying on outside services to call.

how should i do this?