file.field.inc

<?php
/**
 * @file
 * Field module functionality for the File module.
 */

/**
 * Implements hook_field_info().
 */
function file_field_info() {
  return array(
    'file' => array(
      'label' => t('File'),
      'description' => t('This field stores the ID of a file as an integer value.'),
      'settings' => array(
        'display_field' => 0,
        'display_default' => 0,
        'uri_scheme' => config_get('system.core', 'file_default_scheme'),
      ),
      'instance_settings' => array(
        'file_extensions' => 'txt',
        'file_directory' => '',
        'max_filesize' => '',
        'description_field' => 0,
      ),
      'default_widget' => 'file_generic',
      'default_formatter' => 'file_default',
      'default_token_formatter' => 'file_url_plain',
    ),
  );
}

/**
 * Implements hook_field_settings_form().
 */
function file_field_settings_form($field, $instance, $has_data) {
  $defaults = field_info_field_settings($field['type']);
  $settings = array_merge($defaults, $field['settings']);

  $form['#attached']['js'][] = backdrop_get_path('module', 'file') . '/js/file.js';

  $form['display_field'] = array(
    '#type' => 'checkbox',
    '#title' => t('Enable <em>Display</em> field'),
    '#default_value' => $settings['display_field'],
    '#description' => t('This option allows users to choose if the uploaded files should be shown or hidden when viewing the content.'),
  );
  $form['display_default'] = array(
    '#type' => 'checkbox',
    '#title' => t('Files displayed by default'),
    '#default_value' => $settings['display_default'],
    '#description' => t('This option sets the default behavior for uploaded files for this field. Users are still allowed to change this setting individually for each file before saving their content.'),
    '#states' => array(
      'visible' => array(
        'input[name="field[settings][display_field]"]' => array('checked' => TRUE),
      ),
    ),
  );

  $scheme_options = array();
  foreach (file_get_stream_wrappers(STREAM_WRAPPERS_WRITE_VISIBLE) as $scheme => $stream_wrapper) {
    $scheme_options[$scheme] = $stream_wrapper['name'];
  }
  $form['uri_scheme'] = array(
    '#type' => 'radios',
    '#title' => t('Upload destination'),
    '#options' => $scheme_options,
    '#default_value' => $settings['uri_scheme'],
    '#description' => t('Select where the final files should be stored. Private file storage has significantly more overhead than public files, but allows restricted access to files within this field.'),
    '#disabled' => $has_data,
  );

  return $form;
}

/**
 * Implements hook_field_instance_settings_form().
 */
function file_field_instance_settings_form($field, $instance) {
  $settings = $instance['settings'];

  $form['file_directory'] = array(
    '#type' => 'textfield',
    '#title' => t('File directory'),
    '#default_value' => $settings['file_directory'],
    '#field_prefix' => $field['settings']['uri_scheme'] == 'public' ? config_get('system.core', 'file_public_path') . '/' : '',
    '#description' => t('Optional subdirectory within the upload destination where files will be stored. Do not include preceding or trailing slashes.'),
    '#element_validate' => array('_file_generic_settings_file_directory_validate'),
    '#weight' => 3,
  );

  // Make the extension list a little more human-friendly by comma-separation.
  $extensions = str_replace(' ', ', ', $settings['file_extensions']);
  $form['file_extensions'] = array(
    '#type' => 'textfield',
    '#title' => t('Allowed file extensions'),
    '#default_value' => $extensions,
    '#description' => t('Separate extensions with a space or comma and do not include the leading dot.'),
    '#element_validate' => array('_file_generic_settings_extensions'),
    '#weight' => 1,
    '#maxlength' => 512,
    // By making this field required, we prevent a potential security issue
    // that would allow files of any type to be uploaded.
    '#required' => TRUE,
  );

  $form['max_filesize'] = array(
    '#type' => 'textfield',
    '#title' => t('Maximum upload size'),
    '#default_value' => $settings['max_filesize'],
    '#description' => t('Enter a value like "512" (bytes), "80 KB" (kilobytes) or "50 MB" (megabytes) in order to restrict the allowed file size. If left empty the file sizes will be limited only by PHP\'s maximum post and file upload sizes (current limit <strong>%limit</strong>).', array('%limit' => format_size(file_upload_max_size()))),
    '#size' => 10,
    '#element_validate' => array('_file_generic_settings_max_filesize'),
    '#weight' => 5,
  );

  $form['description_field'] = array(
    '#type' => 'checkbox',
    '#title' => t('Show <em>File display title</em> field'),
    '#description' => t('This text will be used in links to the uploaded file. When not available, the filename will be used.'),
    '#default_value' => isset($settings['description_field']) ? $settings['description_field'] : '',
    '#parents' => array('instance', 'settings', 'description_field'),
    '#weight' => 11,
  );

  return $form;
}

/**
 * Render API callback: Validates the 'Maximum upload size' field.
 *
 * Ensures that a size has been entered and that it can be parsed by
 * parse_size().
 *
 * This function is assigned as an #element_validate callback in
 * file_field_instance_settings_form().
 */
function _file_generic_settings_max_filesize($element, &$form_state) {
  if (!empty($element['#value']) && !is_numeric(parse_size($element['#value']))) {
    form_error($element, t('The "!name" option must contain a valid value. You may either leave the text field empty or enter a string like "512" (bytes), "80 KB" (kilobytes) or "50 MB" (megabytes).', array('!name' => t($element['title']))));
  }
}

/**
 * Render API callback: Validates the allowed file extensions field.
 *
 * This function is assigned as an #element_validate callback in
 * file_field_instance_settings_form().
 *
 * This doubles as a convenience clean-up function and a validation routine.
 * Commas are allowed by the end-user, but ultimately the value will be stored
 * as a space-separated list for compatibility with file_validate_extensions().
 */
function _file_generic_settings_extensions($element, &$form_state) {
  if (!empty($element['#value'])) {
    $extensions = preg_replace('/([, ]+\.?)/', ' ', trim(strtolower($element['#value'])));
    $extensions = array_filter(explode(' ', $extensions));
    $extensions = implode(' ', array_unique($extensions));
    if (!preg_match('/^([a-z0-9]+([.][a-z0-9])* ?)+$/', $extensions)) {
      form_error($element, t('The list of allowed extensions is not valid, be sure to exclude leading dots and to separate extensions with a comma or space.'));
    }
    else {
      form_set_value($element, $extensions, $form_state);
    }
  }
}

/**
 * Render API callback: Validates the file destination field.
 *
 * Removes slashes from the beginning and end of the destination value and
 * ensures that the file directory path is not included at the beginning of the
 * value.
 *
 * This function is assigned as an #element_validate callback in
 * file_field_instance_settings_form().
 */
function _file_generic_settings_file_directory_validate($element, &$form_state) {
  // Strip slashes from the beginning and end of $widget['file_directory'].
  $value = trim($element['#value'], '\\/');
  form_set_value($element, $value, $form_state);
}

/**
 * Implements hook_field_load().
 */
function file_field_load($entity_type, $entities, $field, $instances, $langcode, &$items, $age) {

  $fids = array();
  foreach ($entities as $id => $entity) {
    // Load the files from the files table.
    foreach ($items[$id] as $delta => $item) {
      if (!empty($item['fid'])) {
        $fids[] = $item['fid'];
      }
    }
  }
  $files = file_load_multiple($fids);

  foreach ($entities as $id => $entity) {
    foreach ($items[$id] as $delta => $item) {
      // If the file does not exist, mark the entire item as empty.
      if (empty($item['fid']) || !isset($files[$item['fid']])) {
        $items[$id][$delta] = NULL;
      }
      else {
        $items[$id][$delta] = array_merge((array) $files[$item['fid']], $item);
      }
    }
  }
}

/**
 * Implements hook_field_prepare_view().
 */
function file_field_prepare_view($entity_type, $entities, $field, $instances, $langcode, &$items) {
  // Remove files specified to not be displayed.
  foreach ($entities as $id => $entity) {
    foreach ($items[$id] as $delta => $item) {
      if (!file_field_displayed($item, $field)) {
        unset($items[$id][$delta]);
      }
    }
    // Ensure consecutive deltas.
    $items[$id] = array_values($items[$id]);
  }
}

/**
 * Implements hook_field_insert().
 */
function file_field_insert($entity_type, $entity, $field, $instance, $langcode, &$items) {
  // Add a new usage of each uploaded file.
  foreach ($items as $item) {
    if ($file = file_load($item['fid'])) {
      file_usage_add($file, 'file', $entity_type, $entity->id());
    }
  }
}

/**
 * Implements hook_field_update().
 *
 * Checks for files that have been removed from the object.
 */
function file_field_update($entity_type, $entity, $field, $instance, $langcode, &$items) {
  $id = $entity->id();

  // On new revisions, all files are considered to be a new usage and no
  // deletion of previous file usages are necessary.
  if (!empty($entity->revision)) {
    foreach ($items as $item) {
      if ($file = file_load($item['fid'])) {
        file_usage_add($file, 'file', $entity_type, $id);
      }
    }
    return;
  }

  // Build a display of the current FIDs.
  $current_fids = array();
  foreach ($items as $item) {
    $current_fids[] = $item['fid'];
  }

  // Compare the original field values with the ones that are being saved.
  $original = $entity->original;
  $original_fids = array();
  if (!empty($original->{$field['field_name']}[$langcode])) {
    foreach ($original->{$field['field_name']}[$langcode] as $original_item) {
      $original_fids[] = $original_item['fid'];
      if (isset($original_item['fid']) && !in_array($original_item['fid'], $current_fids)) {
        // Decrement the file usage count by 1.
        if ($file = file_load($original_item['fid'])) {
          file_usage_delete($file, 'file', $entity_type, $id);
        }
      }
    }
  }

  // Add new usage entries for newly added files.
  foreach ($items as $item) {
    if (!in_array($item['fid'], $original_fids)) {
      if ($file = file_load($item['fid'])) {
        file_usage_add($file, 'file', $entity_type, $id);
      }
    }
  }
}

/**
 * Implements hook_field_delete().
 */
function file_field_delete($entity_type, $entity, $field, $instance, $langcode, &$items) {
  list($id, $vid, $bundle) = entity_extract_ids($entity_type, $entity);

  // Delete all file usages within this entity.
  foreach ($items as $delta => $item) {
    if ($file = file_load($item['fid'])) {
      file_usage_delete($file, 'file', $entity_type, $id, 0);
    }
  }
}

/**
 * Implements hook_field_delete_revision().
 */
function file_field_delete_revision($entity_type, $entity, $field, $instance, $langcode, &$items) {
  foreach ($items as $delta => $item) {
    // Decrement the file usage count by 1.
    if ($file = file_load($item['fid'])) {
      file_usage_delete($file, 'file', $entity_type, $entity->id());
    }
  }
}

/**
 * Implements hook_field_is_empty().
 */
function file_field_is_empty($item, $field) {
  return empty($item['fid']);
}

/**
 * Determines whether a file should be displayed when outputting field content.
 *
 * @param $item
 *   A field item array.
 * @param $field
 *   A field array.
 *
 * @return
 *   Boolean TRUE if the file will be displayed, FALSE if the file is hidden.
 */
function file_field_displayed($item, $field) {
  if (!empty($field['settings']['display_field'])) {
    return (bool) $item['display'];
  }
  return TRUE;
}

/**
 * Implements hook_field_formatter_info().
 */
function file_field_formatter_info() {
  return array(
    'file_default' => array(
      'label' => t('Generic file'),
      'field types' => array('file'),
      'description' => t('Create a simple link to the file. The link is prefixed by a file type icon and the name of the file is used as the link text'),
    ),
    'file_table' => array(
      'label' => t('Table of files'),
      'field types' => array('file'),
      'description' => t('Build a two-column table where the first column contains a generic link to the file and the second column displays the size of the file.'),
    ),
    'file_url_plain' => array(
      'label' => t('URL to file'),
      'field types' => array('file'),
      'description' => t('Display a plain text URL to the file.'),
    ),
    'file_rendered' => array(
      'label' => t('Rendered file'),
      'description' => t('Display the file in a specific view mode'),
      'field types' => array('file', 'image'),
      'settings' => array(
        'file_view_mode' => 'default',
      ),
      'file formatter' => array(
        'hidden' => TRUE,
      ),
    ),
    'file_download_link' => array(
      'label' => t('Download link'),
      'description' => t('Displays a link that will force the browser to download the file.'),
      'field types' => array('file', 'image'),
      'settings' => array(
        'text' => t('Download [file:name]'),
      ),
    ),
    'file_audio' => array(
      'label' => t('Audio'),
      'description' => t('Render the file using an HTML5 audio tag.'),
      'field types' => array('file'),
      'settings' => array(
        'controls' => TRUE,
        'autoplay' => FALSE,
        'loop' => FALSE,
        'preload' => '',
        'multiple_file_behavior' => 'tags',
      ),
      'file formatter' => array(
        'mime types' => array('audio/*'),
      ),
    ),
    'file_video' => array(
      'label' => t('Video'),
      'description' => t('Render the file using an HTML5 video tag.'),
      'field types' => array('file'),
      'settings' => array(
        'controls' => TRUE,
        'autoplay' => FALSE,
        'loop' => FALSE,
        'muted' => FALSE,
        'width' => NULL,
        'height' => NULL,
        'preload' => '',
        'multiple_file_behavior' => 'tags',
      ),
      'file formatter' => array(
        'mime types' => array('video/*'),
      ),
    ),
  );
}

/**
 * Implements hook_field_formatter_settings_form().
 */
function file_field_formatter_settings_form($field, $instance, $view_mode, $form, &$form_state) {
  $display = $instance['display'][$view_mode];
  $settings = $display['settings'];
  $element = array();

  if ($display['type'] == 'file_rendered') {
    $element['file_view_mode'] = array(
      '#title'   => t('View mode'),
      '#type'    => 'select',
      '#options' => file_view_mode_labels(),
      '#default_value' => $settings['file_view_mode'],
      // Never empty, so no #empty_option
    );
  }
  elseif ($display['type'] == 'file_download_link') {
    $element['text'] = array(
      '#type' => 'textfield',
      '#title' => t('Link text'),
      '#description' => t('This field supports tokens.'),
      '#default_value' => $settings['text'],
      '#required' => TRUE,
    );
  }
  elseif ($display['type'] == 'file_audio') {
    $element['controls'] = array(
      '#title' => t('Show audio controls'),
      '#type' => 'checkbox',
      '#default_value' => $settings['controls'],
    );
    $element['autoplay'] = array(
      '#title' => t('Autoplay'),
      '#type' => 'checkbox',
      '#default_value' => $settings['autoplay'],
    );
    $element['loop'] = array(
      '#title' => t('Loop'),
      '#type' => 'checkbox',
      '#default_value' => $settings['loop'],
    );
    $element['preload'] = array(
      '#title' => t('Preload'),
      '#type' => 'select',
      '#default_value' => $settings['preload'],
      '#options' => backdrop_map_assoc(array('none', 'auto', 'metadata')),
      '#empty_option' => 'unspecified',
    );
    $element['multiple_file_behavior'] = array(
      '#title' => t('Display of multiple files'),
      '#type' => 'radios',
      '#options' => array(
        'tags' => t('Use multiple @tag tags, each with a single source', array('@tag' => '<audio>')),
        'sources' => t('Use multiple sources within a single @tag tag', array('@tag' => '<audio>')),
      ),
      '#default_value' => $settings['multiple_file_behavior'],
      // Hide this setting in the manage file display configuration.
      '#access' => !empty($field),
    );

  }
  elseif ($display['type'] == 'file_video') {
    $element['controls'] = array(
      '#title' => t('Show video controls'),
      '#type' => 'checkbox',
      '#default_value' => $settings['controls'],
    );
    $element['autoplay'] = array(
      '#title' => t('Autoplay'),
      '#type' => 'checkbox',
      '#default_value' => $settings['autoplay'],
    );
    $element['loop'] = array(
      '#title' => t('Loop'),
      '#type' => 'checkbox',
      '#default_value' => $settings['loop'],
    );
    $element['muted'] = array(
      '#title' => t('Muted'),
      '#type' => 'checkbox',
      '#default_value' => $settings['muted'],
    );
    $element['width'] = array(
      '#type' => 'textfield',
      '#title' => t('Width'),
      '#default_value' => $settings['width'],
      '#size' => 5,
      '#maxlength' => 5,
      '#field_suffix' => t('pixels'),
    );
    $element['height'] = array(
      '#type' => 'textfield',
      '#title' => t('Height'),
      '#default_value' => $settings['height'],
      '#size' => 5,
      '#maxlength' => 5,
      '#field_suffix' => t('pixels'),
    );
    $element['preload'] = array(
      '#title' => t('Preload'),
      '#type' => 'select',
      '#default_value' => $settings['preload'],
      '#options' => backdrop_map_assoc(array('none', 'auto', 'metadata')),
      '#empty_option' => 'unspecified',
    );
    $element['multiple_file_behavior'] = array(
      '#title' => t('Display of multiple files'),
      '#type' => 'radios',
      '#options' => array(
        'tags' => t('Use multiple @tag tags, each with a single source', array('@tag' => '<video>')),
        'sources' => t('Use multiple sources within a single @tag tag', array('@tag' => '<video>')),
      ),
      '#default_value' => $settings['multiple_file_behavior'],
      // Hide this setting in the manage file display configuration.
      '#access' => !empty($field),
    );
  }

  return $element;
}

/**
 * Implements hook_field_formatter_settings_summary().
 */
function file_field_formatter_settings_summary($field, $instance, $view_mode) {
  $display = $instance['display'][$view_mode];
  $settings = $display['settings'];
  $summary = array();

  if ($display['type'] === 'file_rendered') {
    $view_mode_label = file_view_mode_label($settings['file_view_mode'], t('Unknown'));
    $summary[] = t('View mode: %mode', array('%mode' => $view_mode_label));
  }
  elseif ($display['type'] == 'file_download_link') {
    $summary[] = t('Link text: %text', array('%text' => $settings['text']));
  }
  elseif ($display['type'] === 'file_audio') {
    if (isset($settings['controls'])) {
      $summary[] = t('Controls: %controls', array('%controls' => $settings['controls'] ? 'visible' : 'hidden'));
    }
    if (isset($settings['autoplay'])) {
      $summary[] = t('Autoplay: %autoplay', array('%autoplay' => $settings['autoplay'] ? t('yes') : t('no')));
    }
    if (isset($settings['loop'])) {
      $summary[] = t('Loop: %loop', array('%loop' => $settings['loop'] ? t('yes') : t('no')));
    }
    if (!empty($settings['preload'])) {
      $summary[] = t('Preload: %preload', array('%preload' => $settings['preload']));
    }
    if (isset($settings['multiple_file_behavior'])) {
      $summary[] = t('Multiple files: %multiple', array('%multiple' => $settings['multiple_file_behavior']));
    }
  }
  elseif ($display['type'] === 'file_video') {
    if (isset($settings['controls'])) {
      $summary[] = t('Controls: %controls', array('%controls' => $settings['controls'] ? 'visible' : 'hidden'));
    }
    if (isset($settings['autoplay'])) {
      $summary[] = t('Autoplay: %autoplay', array('%autoplay' => $settings['autoplay'] ? t('yes') : t('no')));
    }
    if (isset($settings['loop'])) {
      $summary[] = t('Loop: %loop', array('%loop' => $settings['loop'] ? t('yes') : t('no')));
    }
    if (isset($settings['muted'])) {
      $summary[] = t('Muted: %muted', array('%muted' => $settings['muted'] ? t('yes') : t('no')));
    }
    if ($settings['width'] && $settings['height']) {
      $summary[] = t('Size: %width x %height', array('%width' => $settings['width'], '%height' => $settings['height']));
    }
    if (!empty($settings['preload'])) {
      $summary[] = t('Preload: %preload', array('%preload' => $settings['preload']));
    }
    if (isset($settings['multiple_file_behavior'])) {
      $summary[] = t('Multiple files: %multiple', array('%multiple' => $settings['multiple_file_behavior']));
    }
  }

  return implode('<br />', $summary);
}

/**
 * Implements hook_field_widget_info().
 */
function file_field_widget_info() {
  return array(
    'file_generic' => array(
      'label' => t('File'),
      'field types' => array('file'),
      'settings' => array(
        'progress_indicator' => 'throbber',
      ),
      'behaviors' => array(
        'multiple values' => FIELD_BEHAVIOR_CUSTOM,
        'default value' => FIELD_BEHAVIOR_NONE,
      ),
    ),
  );
}

/**
 * Implements hook_field_widget_settings_form().
 */
function file_field_widget_settings_form($field, $instance) {
  $widget = $instance['widget'];
  $settings = $widget['settings'];

  $form['progress_indicator'] = array(
    '#type' => 'radios',
    '#title' => t('Progress indicator'),
    '#options' => array(
      'throbber' => t('Throbber'),
      'bar' => t('Bar with progress meter'),
    ),
    '#default_value' => $settings['progress_indicator'],
    '#description' => t('The throbber display does not show the status of uploads but takes up less space. The progress bar is helpful for monitoring progress on large uploads.'),
    '#weight' => 16,
  );

  return $form;
}

/**
 * Implements hook_field_widget_form().
 */
function file_field_widget_form(&$form, &$form_state, $field, $instance, $langcode, $items, $delta, $element) {

  $defaults = array(
    'fid' => 0,
    'display' => !empty($field['settings']['display_default']),
    'description' => '',
  );

  // Load the items for form rebuilds from the field state as they might not be
  // in $form_state['values'] because of validation limitations. Also, they are
  // only passed in as $items when editing existing entities.
  $field_state = field_form_get_state($element['#field_parents'], $field['field_name'], $langcode, $form_state);
  if (isset($field_state['items'])) {
    $items = $field_state['items'];
  }

  // Essentially we use the managed_file type, extended with some enhancements.
  $element_info = element_info('managed_file');
  $element += array(
    '#type' => 'managed_file',
    '#upload_location' => file_field_widget_uri($field, $instance),
    '#upload_validators' => file_field_widget_upload_validators($field, $instance),
    '#value_callback' => 'file_field_widget_value',
    '#process' => array_merge($element_info['#process'], array('file_field_widget_process')),
    '#progress_indicator' => $instance['widget']['settings']['progress_indicator'],
    // Allows this field to return an array instead of a single value.
    '#extended' => TRUE,
  );

  if ($field['cardinality'] == 1) {
    // Set the default value.
    $element['#default_value'] = !empty($items) ? $items[0] : $defaults;
    // If there's only one field, return it as delta 0.
    if (empty($element['#default_value']['fid'])) {
      $element['#description'] = theme('file_upload_help', array('description' => $element['#description'], 'upload_validators' => $element['#upload_validators']));
    }
    $elements = array($element);
  }
  else {
    // If there are multiple values, add an element for each existing one.
    foreach ($items as $item) {
      $elements[$delta] = $element;
      $elements[$delta]['#default_value'] = $item;
      $elements[$delta]['#weight'] = $delta;
      $delta++;
    }
    // And then add one more empty row for new uploads except when this is a
    // programmed form as it is not necessary.
    if (($field['cardinality'] == FIELD_CARDINALITY_UNLIMITED || $delta < $field['cardinality']) && empty($form_state['programmed'])) {
      $elements[$delta] = $element;
      $elements[$delta]['#default_value'] = $defaults;
      $elements[$delta]['#weight'] = $delta;
      $elements[$delta]['#required'] = ($element['#required'] && $delta == 0);
    }
    // The group of elements all-together need some extra functionality
    // after building up the full list (like draggable table rows).
    $elements['#file_upload_delta'] = $delta;
    $elements['#theme'] = 'file_widget_multiple';
    $elements['#theme_wrappers'] = array('fieldset');
    $elements['#process'] = array('file_field_widget_process_multiple');
    $elements['#title'] = $element['#title'];
    $elements['#description'] = $element['#description'];
    $elements['#field_name'] = $element['#field_name'];
    $elements['#language'] = $element['#language'];
    $elements['#display_field'] = $field['settings']['display_field'];

    // Add some properties that will eventually be added to the file upload
    // field. These are added here so that they may be referenced through a
    // hook_form_alter().
    $elements['#file_upload_title'] = t('Add a new file');
    $elements['#file_upload_description'] = theme('file_upload_help', array('description' => '', 'upload_validators' => $elements[0]['#upload_validators']));
  }

  return $elements;
}

/**
 * Retrieves the upload validators for a file field.
 *
 * @param $field
 *   A field array.
 *
 * @return
 *   An array suitable for passing to file_save_upload() or the file field
 *   element's '#upload_validators' property.
 */
function file_field_widget_upload_validators($field, $instance) {
  // Cap the upload size according to the PHP limit.
  $max_filesize = parse_size(file_upload_max_size());
  if (!empty($instance['settings']['max_filesize']) && parse_size($instance['settings']['max_filesize']) < $max_filesize) {
    $max_filesize = parse_size($instance['settings']['max_filesize']);
  }

  $validators = array();

  // There is always a file size limit due to the PHP server limit.
  $validators['file_validate_size'] = array($max_filesize);

  // Add the extension check if necessary.
  if (!empty($instance['settings']['file_extensions'])) {
    $validators['file_validate_extensions'] = array($instance['settings']['file_extensions']);
  }

  return $validators;
}

/**
 * Determines the URI for a file field instance.
 *
 * @param $field
 *   A field array.
 * @param $instance
 *   A field instance array.
 * @param $data
 *   An array of token objects to pass to token_replace().
 *
 * @return
 *   A file directory URI with tokens replaced.
 *
 * @see token_replace()
 */
function file_field_widget_uri($field, $instance, $data = array()) {
  $destination = trim($instance['settings']['file_directory'], '/');

  // Replace tokens.
  $destination = token_replace($destination, $data);

  return $field['settings']['uri_scheme'] . '://' . $destination;
}

/**
 * Render API callback: Retrieves the value for the file_generic field element.
 *
 * This function is assigned as a #value callback in file_field_widget_form().
 */
function file_field_widget_value($element, $input, $form_state) {
  if ($input) {
    // Checkboxes lose their value when empty.
    // If the display field is present make sure its unchecked value is saved.
    $field = field_widget_field($element, $form_state);
    if (empty($input['display'])) {
      $input['display'] = !empty($field['settings']['display_field']) ? 0 : 1;
    }
  }

  // We depend on the managed file element to handle uploads.
  $return = file_managed_file_value($element, $input, $form_state);

  // Ensure that all the required properties are returned even if empty.
  $return += array(
    'fid' => 0,
    'display' => 1,
    'description' => '',
  );

  return $return;
}

/**
 * Render API callback: Processes a file_generic field element.
 *
 * Expands the file_generic type to include the description and display fields.
 *
 * This function is assigned as a #process callback in file_field_widget_form().
 */
function file_field_widget_process($element, &$form_state, $form) {
  $item = $element['#value'];
  $item['fid'] = $element['fid']['#value'];

  $field = field_widget_field($element, $form_state);
  $instance = field_widget_instance($element, $form_state);
  $settings = $instance['widget']['settings'];

  $element['#theme'] = 'file_widget';

  // Add the display field if enabled.
  if (!empty($field['settings']['display_field'])) {
    $element['display'] = array(
      '#type' => empty($item['fid']) ? 'hidden' : 'checkbox',
      '#title' => t('Include file in display'),
      '#value' => isset($item['display']) ? $item['display'] : $field['settings']['display_default'],
      '#attributes' => array('class' => array('file-display')),
    );
  }
  else {
    $element['display'] = array(
      '#type' => 'hidden',
      '#value' => '1',
    );
  }

  // Add the description field if enabled.
  if (!empty($instance['settings']['description_field']) && $item['fid']) {
    $element['description'] = array(
      '#type' => 'textfield',
      '#title' => t('File display title'),
      '#description' => t('This text will be used in links to the uploaded file.'),
      '#value' => isset($item['description']) ? $item['description'] : '',
      '#maxlength' => 500,
    );
  }

  // Adjust the Ajax settings so that on upload and remove of any individual
  // file, the entire group of file fields is updated together.
  if ($field['cardinality'] != 1) {
    $parents = array_slice($element['#array_parents'], 0, -1);
    $new_path = 'file/ajax/' . implode('/', $parents) . '/' . $form['form_build_id']['#value'];
    // Token here is not generated with backdrop_token() as it does not need to
    // be session-based.
    $token = backdrop_hmac_base64($new_path, backdrop_get_private_key() . backdrop_get_hash_salt());
    $new_path .= '/' . $token;
    $field_element = backdrop_array_get_nested_value($form, $parents);
    $new_wrapper = $field_element['#id'] . '-ajax-wrapper';
    foreach (element_children($element) as $key) {
      if (isset($element[$key]['#ajax']['path'])) {
        $element[$key]['#ajax']['path'] = $new_path;
        $element[$key]['#ajax']['wrapper'] = $new_wrapper;
      }
    }
    unset($element['#prefix'], $element['#suffix']);
  }

  // Add another submit handler to the upload and remove buttons, to implement
  // functionality needed by the field widget. This submit handler, along with
  // the rebuild logic in file_field_widget_form() requires the entire field,
  // not just the individual item, to be valid.
  foreach (array('upload_button', 'remove_button') as $key) {
    $element[$key]['#submit'][] = 'file_field_widget_submit';
    $element[$key]['#limit_validation_errors'] = array(array_slice($element['#parents'], 0, -1));
  }

  return $element;
}

/**
 * Render API callback: Processes a group of file_generic field elements.
 *
 * Adds the weight field to each row so it can be ordered and adds a new Ajax
 * wrapper around the entire group so it can be replaced all at once.
 *
 * This function is assigned as a #process callback in file_field_widget_form().
 */
function file_field_widget_process_multiple($element, &$form_state, $form) {
  $element_children = element_children($element, TRUE);
  $count = count($element_children);

  foreach ($element_children as $delta => $key) {
    if ($key != $element['#file_upload_delta']) {
      $description = _file_field_get_description_from_element($element[$key]);
      $element[$key]['_weight'] = array(
        '#type' => 'weight',
        '#title' => $description ? t('Weight for @title', array('@title' => $description)) : t('Weight for new file'),
        '#title_display' => 'invisible',
        '#delta' => $count,
        '#default_value' => $delta,
      );
    }
    else {
      // The title needs to be assigned to the upload field so that validation
      // errors include the correct widget label.
      $element[$key]['#title'] = $element['#title'];
      $element[$key]['_weight'] = array(
        '#type' => 'hidden',
        '#default_value' => $delta,
      );
    }
  }

  // Add a new wrapper around all the elements for Ajax replacement.
  $element['#prefix'] = '<div id="' . $element['#id'] . '-ajax-wrapper">';
  $element['#suffix'] = '</div>';

  return $element;
}

/**
 * Retrieves the file description from a field field element.
 *
 * This helper function is used by file_field_widget_process_multiple().
 *
 * @param $element
 *   The element being processed.
 *
 * @return
 *   A description of the file suitable for use in the administrative interface.
 */
function _file_field_get_description_from_element($element) {
  // Use the actual file description, if it's available.
  if (!empty($element['#default_value']['description'])) {
    return $element['#default_value']['description'];
  }
  // Otherwise, fall back to the filename.
  if (!empty($element['#default_value']['filename'])) {
    return $element['#default_value']['filename'];
  }
  // This is probably a newly uploaded file; no description is available.
  return FALSE;
}

/**
 * Form submission handler for upload/remove button of file_field_widget_form().
 *
 * This runs in addition to and after file_managed_file_submit().
 *
 * @see file_managed_file_submit()
 * @see file_field_widget_form()
 * @see file_field_widget_process()
 */
function file_field_widget_submit($form, &$form_state) {
  // During the form rebuild, file_field_widget_form() will create field item
  // widget elements using re-indexed deltas, so clear out $form_state['input']
  // to avoid a mismatch between old and new deltas. The rebuilt elements will
  // have #default_value set appropriately for the current state of the field,
  // so nothing is lost in doing this.
  $parents = array_slice($form_state['triggering_element']['#parents'], 0, -2);
  backdrop_array_set_nested_value($form_state['input'], $parents, NULL);

  $button = $form_state['triggering_element'];

  // Go one level up in the form, to the widgets container.
  $element = backdrop_array_get_nested_value($form, array_slice($button['#array_parents'], 0, -1));
  $field_name = $element['#field_name'];
  $langcode = $element['#language'];
  $parents = $element['#field_parents'];

  $submitted_values = backdrop_array_get_nested_value($form_state['values'], array_slice($button['#parents'], 0, -2));
  foreach ($submitted_values as $delta => $submitted_value) {
    if (!$submitted_value['fid']) {
      unset($submitted_values[$delta]);
    }
  }

  // Re-index deltas after removing empty items.
  $submitted_values = array_values($submitted_values);

  // Update form_state values.
  backdrop_array_set_nested_value($form_state['values'], array_slice($button['#parents'], 0, -2), $submitted_values);

  // Update items.
  $field_state = field_form_get_state($parents, $field_name, $langcode, $form_state);
  $field_state['items'] = $submitted_values;
  field_form_set_state($parents, $field_name, $langcode, $form_state, $field_state);
}

/**
 * Implements hook_field_formatter_prepare_view().
 */
function file_field_formatter_prepare_view($entity_type, $entities, $field, $instances, $langcode, &$items, $displays) {
  // File and image fields set item values to NULL if a file cannot be loaded.
  // Remove those empty items so we can simply iterate through $items normally
  // in file_field_formatter_view().
  foreach (array_keys($entities) as $id) {
    $items[$id] = array_filter($items[$id]);
  }
}

/**
 * Implements hook_field_formatter_view().
 */
function file_field_formatter_view($entity_type, $entity, $field, $instance, $langcode, $items, $display) {
  $element = array();
  $settings = isset($display['settings']) ? $display['settings'] : array();

  switch ($display['type']) {
    case 'file_default':
      foreach ($items as $delta => $item) {
        $element[$delta] = array(
          '#theme' => 'file_link',
          '#file' => (object) $item,
        );
      }
      break;

    case 'file_url_plain':
      foreach ($items as $delta => $item) {
        $element[$delta] = array('#markup' => empty($item['uri']) ? '' : file_create_url($item['uri']));
      }
      break;

    case 'file_table':
      if (!empty($items)) {
        // Display all values in a single element..
        $element[0] = array(
          '#theme' => 'file_formatter_table',
          '#items' => $items,
        );
      }
      break;

    case 'file_rendered':
      foreach ($items as $delta => $item) {
        // Protect ourselves from recursive rendering.
        static $recursive_render_depth = array();
        if (!empty($item)) {
          // The repeat-rendering protection may be disabled if necessary.
          if (config_get('file.settings', 'protect_repeated_render')) {
            // Protect ourselves from repeated rendering.
            static $repeated_render_depth = array();
            $repeated_render_id = $entity_type . $field['field_name'] . $item['fid'];
            if (isset($repeated_render_depth[$repeated_render_id])) {
              $repeated_render_depth[$repeated_render_id]++;
            }
            else {
              $repeated_render_depth[$repeated_render_id] = 1;
            }

            if ($repeated_render_depth[$repeated_render_id] > 10) {
              watchdog(
                'file_entity',
                'Repeated rendering detected when rendering entity %entity_type: %entity_id, using the %field_name field. Aborting rendering.',
                array(
                  '%entity_type' => 'file',
                  '%entity_id' => $item['fid'],
                  '%field_name' => $field['field_name'],
                ),
                WATCHDOG_ERROR
              );
              return $element;
            }
          }

          $file = file_load($item['fid']);
          if (isset($item['display'])) {
            $file->display = $item['display'];
          }
          if (isset($item['description'])) {
            $file->description = $item['description'];
          }

          // Add some references to the referencing entity.
          // @see https://www.drupal.org/node/2333107
          $file->referencing_entity = $entity;
          $file->referencing_entity_type = $entity_type;
          $file->referencing_field = $field['field_name'];

          // Untranslatable fields are rendered with no language code, fall back
          // to the content language in that case.
          $element[$delta] = file_view($file, $settings['file_view_mode'], $langcode !== LANGUAGE_NONE ? $langcode : NULL);
        }
        else {
          $variables = array(
            '%referencing_entity_type' => $entity_type,
            '%field_name' => $field['field_name'],
            '%entity_type' => 'file',
          );
          $message = 'In the %referencing_entity_type, the %field_name field refers to a %entity_type which does not exist. Aborting the render for it.';
          watchdog('file', $message, $variables, WATCHDOG_ERROR);
        }
      }
      break;

    case 'file_download_link':
      // Prevent 'empty' fields from causing a WSOD.
      $items = array_filter($items);
      foreach ($items as $delta => $item) {
        if (!empty($item['fid']) && ($file = file_load($item['fid'])) && file_access('download', $file)) {
          $element[$delta] = array(
            '#theme' => 'file_download_link',
            '#file' => $file,
            '#text' => $settings['text'],
          );
        }
      }
      break;

    case 'file_audio':
      $multiple_file_behavior = $settings['multiple_file_behavior'];

      // Build an array of sources for each <audio> element.
      $source_lists = array();
      if ($multiple_file_behavior == 'tags') {
        foreach ($items as $delta => $item) {
          if (file_get_mimetype_type($item) == 'audio') {
            $source_lists[$delta] = array($item);
          }
        }
      }
      else {
        foreach ($items as $delta => $item) {
          if (file_get_mimetype_type($item) == 'audio') {
            $source_lists[0][$delta] = $item;
          }
        }
      }

      // Render each source list as an <audio> element.
      foreach ($source_lists as $delta => $sources) {
        $element[$delta] = array(
          '#theme' => 'file_audio',
          '#files' => $sources,
          '#controls' => $settings['controls'],
          '#autoplay' => $settings['autoplay'],
          '#loop' => $settings['loop'],
          '#preload' => $settings['preload'],
        );
      }
      break;

    case 'file_video':
      $multiple_file_behavior = $settings['multiple_file_behavior'];

      // Build an array of sources for each <video> element.
      $source_lists = array();
      if ($multiple_file_behavior == 'tags') {
        foreach ($items as $delta => $item) {
          if (file_get_mimetype_type($item) == 'video') {
            $source_lists[$delta] = array($item);
          }
        }
      }
      else {
        foreach ($items as $delta => $item) {
          if (file_get_mimetype_type($item) == 'video') {
            $source_lists[0][$delta] = $item;
          }
        }
      }

      // Render each source list as an <video> element.
      foreach ($source_lists as $delta => $sources) {
        $element[$delta] = array(
          '#theme' => 'file_video',
          '#files' => $sources,
          '#controls' => $settings['controls'],
          '#autoplay' => $settings['autoplay'],
          '#loop' => $settings['loop'],
          '#muted' => $settings['muted'],
          '#width' => $settings['width'],
          '#height' => $settings['height'],
          '#preload' => $settings['preload'],
        );
      }
      break;

  }

  return $element;
}