path: root/core/modules/file/file.module

<?php

/**
 * @file
 * Defines a "managed_file" Form API field and a "file" field for Field module.
 */

use Drupal\Component\Utility\SafeMarkup;
use Drupal\Component\Utility\String;
use Drupal\Core\Field\FieldDefinitionInterface;
use Drupal\Core\Form\FormStateInterface;
use Drupal\Core\Render\Element;
use Drupal\Core\Routing\RouteMatchInterface;
use Drupal\file\Entity\File;
use Drupal\file\FileInterface;
use Drupal\Component\Utility\NestedArray;
use Drupal\Component\Utility\Unicode;
use Drupal\Core\Entity\EntityStorageInterface;
use Drupal\Core\Template\Attribute;
use Drupal\file\FileUsage\FileUsageInterface;

// Load all Field module hooks for File.
require_once __DIR__ . '/file.field.inc';

/**
 * Implements hook_help().
 */
function file_help($route_name, RouteMatchInterface $route_match) {
  switch ($route_name) {
    case 'help.page.file':
      $output = '';
      $output .= '<h3>' . t('About') . '</h3>';
      $output .= '<p>' . t('The File module allows you to create fields that contain files. See the <a href="!field">Field module help</a> and the <a href="!field_ui">Field UI help</a> pages for general information on fields and how to create and manage them. For more information, see the <a href="!file_documentation">online documentation for the File module</a>.', array('!field' => \Drupal::url('help.page', array('name' => 'field')), '!field_ui' => \Drupal::url('help.page', array('name' => 'field_ui')), '!file_documentation' => 'https://drupal.org/documentation/modules/file')) . '</p>';
      $output .= '<h3>' . t('Uses') . '</h3>';
      $output .= '<dl>';
      $output .= '<dt>' . t('Managing and displaying file fields') . '</dt>';
      $output .= '<dd>' . t('The <em>settings</em> and the <em>display</em> of the file field can be configured separately. See the <a href="!field_ui">Field UI help</a> for more information on how to manage fields and their display.', array('!field_ui' => \Drupal::url('help.page', array('name' => 'field_ui')))) . '</dd>';
      $output .= '<dt>' . t('Allowing file extensions') . '</dt>';
      $output .= '<dd>' . t('In the field settings, you can define the allowed file extensions (for example <em>pdf docx psd</em>) for the files that will be uploaded with the file field.') . '</dd>';
      $output .= '<dt>' . t('Storing files ') . '</dt>';
      $output .= '<dd>' . t('Uploaded files can either be stored as <em>public</em> or <em>private</em>, depending on the <a href="!file-system">File system settings</a>. For more information, see the <a href="!system-help">System module help page</a>.', array('!file-system' => \Drupal::url('system.file_system_settings'), '!system-help' => \Drupal::url('help.page', array('name' => 'system')))) . '</dd>';
      $output .= '<dt>' . t('Restricting the maximum file size') . '</dt>';
      $output .= '<dd>' . t('The maximum file size that users can upload is limited by PHP settings of the server, but you can restrict by entering the desired value as the <em>Maximum upload size</em> setting. The maximum file size is automatically displayed to users in the help text of the file field.') . '</dd>';
      $output .= '<dt>' . t('Displaying files and descriptions') . '<dt>';
      $output .= '<dd>' . t('In the field settings, you can allow users to toggle whether individual files are displayed. In the display settings, you can then choose one of the following formats: <ul><li><em>Generic file</em> displays links to the files and adds icons that symbolize the file extensions. If <em>descriptions</em> are enabled and have been submitted, then the description is displayed instead of the file name.</li><li><em>URL to file</em> displays the full path to the file as plain text.</li><li><em>Table of files</em> lists links to the files and the file sizes in a table.</li><li><em>RSS enclosure</em> only displays the first file, and only in a RSS feed, formatted according to the RSS 2.0 syntax for enclosures.</li></ul> A file can still be linked to directly by its URI even if it is not displayed.') . '</dd>';
      $output .= '</dl>';
      return $output;
  }
}

/**
 * Implements hook_element_info().
 *
 * The managed file element may be used anywhere in Drupal.
 */
function file_element_info() {
  $types['managed_file'] = array(
    '#input' => TRUE,
    '#process' => array('file_managed_file_process'),
    '#value_callback' => 'file_managed_file_value',
    '#element_validate' => array('file_managed_file_validate'),
    '#pre_render' => array('file_managed_file_pre_render'),
    '#theme' => 'file_managed_file',
    '#theme_wrappers' => array('form_element'),
    '#progress_indicator' => 'throbber',
    '#progress_message' => NULL,
    '#upload_validators' => array(),
    '#upload_location' => NULL,
    '#size' => 22,
    '#multiple' => FALSE,
    '#extended' => FALSE,
    '#attached' => array(
      'library' => array('file/drupal.file'),
    ),
  );
  return $types;
}

/**
 * Loads file entities from the database.
 *
 * @param array $fids
 *   (optional) An array of entity IDs. If omitted, all entities are loaded.
 * @param $reset
 *   Whether to reset the internal file_load_multiple() cache.
 *
 * @return array
 *   An array of file entities, indexed by fid.
 *
 * @deprecated in Drupal 8.x, will be removed before Drupal 9.0.
 *   Use \Drupal\file\Entity\File::loadMultiple().
 *
 * @see hook_ENTITY_TYPE_load()
 * @see file_load()
 * @see entity_load()
 * @see \Drupal\Core\Entity\Query\EntityQueryInterface
 */
function file_load_multiple(array $fids = NULL, $reset = FALSE) {
  if ($reset) {
    \Drupal::entityManager()->getStorage('file')->resetCache($fids);
  }
  return File::loadMultiple($fids);
}

/**
 * Loads a single file entity from the database.
 *
 * @param $fid
 *   A file ID.
 * @param $reset
 *   Whether to reset the internal file_load_multiple() cache.
 *
 * @return \Drupal\file\FileInterface
 *   A file entity or NULL if the file was not found.
 *
 * @deprecated in Drupal 8.x, will be removed before Drupal 9.0.
 *   Use \Drupal\file\Entity\File::load().
 *
 * @see hook_ENTITY_TYPE_load()
 * @see file_load_multiple()
 */
function file_load($fid, $reset = FALSE) {
  if ($reset) {
    \Drupal::entityManager()->getStorage('file')->resetCache(array($fid));
  }
  return File::load($fid);
}

/**
 * Copies a file to a new location and adds a file record to the database.
 *
 * This function should be used when manipulating files that have records
 * stored in the database. This is a powerful function that in many ways
 * performs like an advanced version of copy().
 * - Checks if $source and $destination are valid and readable/writable.
 * - If file already exists in $destination either the call will error out,
 *   replace the file or rename the file based on the $replace parameter.
 * - If the $source and $destination are equal, the behavior depends on the
 *   $replace parameter. FILE_EXISTS_REPLACE will error out. FILE_EXISTS_RENAME
 *   will rename the file until the $destination is unique.
 * - Adds the new file to the files database. If the source file is a
 *   temporary file, the resulting file will also be a temporary file. See
 *   file_save_upload() for details on temporary files.
 *
 * @param \Drupal\file\FileInterface $source
 *   A file entity.
 * @param $destination
 *   A string containing the destination that $source should be copied to.
 *   This must be a stream wrapper URI.
 * @param $replace
 *   Replace behavior when the destination file already exists:
 *   - FILE_EXISTS_REPLACE - Replace the existing file. If a managed file with
 *       the destination name exists then its database entry will be updated. If
 *       no database entry is found then a new one will be created.
 *   - FILE_EXISTS_RENAME - Append _{incrementing number} until the filename is
 *       unique.
 *   - FILE_EXISTS_ERROR - Do nothing and return FALSE.
 *
 * @return
 *   File object if the copy is successful, or FALSE in the event of an error.
 *
 * @see file_unmanaged_copy()
 * @see hook_file_copy()
 */
function file_copy(FileInterface $source, $destination = NULL, $replace = FILE_EXISTS_RENAME) {
  if (!file_valid_uri($destination)) {
    if (($realpath = drupal_realpath($source->getFileUri())) !== FALSE) {
      \Drupal::logger('file')->notice('File %file (%realpath) could not be copied because the destination %destination is invalid. This is often caused by improper use of file_copy() or a missing stream wrapper.', array('%file' => $source->getFileUri(), '%realpath' => $realpath, '%destination' => $destination));
    }
    else {
      \Drupal::logger('file')->notice('File %file could not be copied because the destination %destination is invalid. This is often caused by improper use of file_copy() or a missing stream wrapper.', array('%file' => $source->getFileUri(), '%destination' => $destination));
    }
    drupal_set_message(t('The specified file %file could not be copied because the destination is invalid. More information is available in the system log.', array('%file' => $source->getFileUri())), 'error');
    return FALSE;
  }

  if ($uri = file_unmanaged_copy($source->getFileUri(), $destination, $replace)) {
    $file = $source->createDuplicate();
    $file->setFileUri($uri);
    $file->setFilename(drupal_basename($uri));
    // If we are replacing an existing file re-use its database record.
    // @todo Do not create a new entity in order to update it, see
    //   https://drupal.org/node/2241865
    if ($replace == FILE_EXISTS_REPLACE) {
      $existing_files = entity_load_multiple_by_properties('file', array('uri' => $uri));
      if (count($existing_files)) {
        $existing = reset($existing_files);
        $file->fid = $existing->id();
        $file->setOriginalId($existing->id());
        $file->setFilename($existing->getFilename());
      }
    }
    // If we are renaming around an existing file (rather than a directory),
    // use its basename for the filename.
    elseif ($replace == FILE_EXISTS_RENAME && is_file($destination)) {
      $file->setFilename(drupal_basename($destination));
    }

    $file->save();

    // Inform modules that the file has been copied.
    \Drupal::moduleHandler()->invokeAll('file_copy', array($file, $source));

    return $file;
  }
  return FALSE;
}

/**
 * Moves a file to a new location and update the file's database entry.
 *
 * Moving a file is performed by copying the file to the new location and then
 * deleting the original.
 * - Checks if $source and $destination are valid and readable/writable.
 * - Performs a file move if $source is not equal to $destination.
 * - If file already exists in $destination either the call will error out,
 *   replace the file or rename the file based on the $replace parameter.
 * - Adds the new file to the files database.
 *
 * @param \Drupal\file\FileInterface $source
 *   A file entity.
 * @param $destination
 *   A string containing the destination that $source should be moved to.
 *   This must be a stream wrapper URI.
 * @param $replace
 *   Replace behavior when the destination file already exists:
 *   - FILE_EXISTS_REPLACE - Replace the existing file. If a managed file with
 *       the destination name exists then its database entry will be updated and
 *       $source->delete() called after invoking hook_file_move().
 *       If no database entry is found then the source files record will be
 *       updated.
 *   - FILE_EXISTS_RENAME - Append _{incrementing number} until the filename is
 *       unique.
 *   - FILE_EXISTS_ERROR - Do nothing and return FALSE.
 *
 * @return \Drupal\file\FileInterface
 *   Resulting file entity for success, or FALSE in the event of an error.
 *
 * @see file_unmanaged_move()
 * @see hook_file_move()
 */
function file_move(FileInterface $source, $destination = NULL, $replace = FILE_EXISTS_RENAME) {
  if (!file_valid_uri($destination)) {
    if (($realpath = drupal_realpath($source->getFileUri())) !== FALSE) {
      \Drupal::logger('file')->notice('File %file (%realpath) could not be moved because the destination %destination is invalid. This may be caused by improper use of file_move() or a missing stream wrapper.', array('%file' => $source->getFileUri(), '%realpath' => $realpath, '%destination' => $destination));
    }
    else {
      \Drupal::logger('file')->notice('File %file could not be moved because the destination %destination is invalid. This may be caused by improper use of file_move() or a missing stream wrapper.', array('%file' => $source->getFileUri(), '%destination' => $destination));
    }
    drupal_set_message(t('The specified file %file could not be moved because the destination is invalid. More information is available in the system log.', array('%file' => $source->getFileUri())), 'error');
    return FALSE;
  }

  if ($uri = file_unmanaged_move($source->getFileUri(), $destination, $replace)) {
    $delete_source = FALSE;

    $file = clone $source;
    $file->setFileUri($uri);
    // If we are replacing an existing file re-use its database record.
    if ($replace == FILE_EXISTS_REPLACE) {
      $existing_files = entity_load_multiple_by_properties('file', array('uri' => $uri));
      if (count($existing_files)) {
        $existing = reset($existing_files);
        $delete_source = TRUE;
        $file->fid = $existing->id();
        $file->uuid = $existing->uuid();
      }
    }
    // If we are renaming around an existing file (rather than a directory),
    // use its basename for the filename.
    elseif ($replace == FILE_EXISTS_RENAME && is_file($destination)) {
      $file->setFilename(drupal_basename($destination));
    }

    $file->save();

    // Inform modules that the file has been moved.
    \Drupal::moduleHandler()->invokeAll('file_move', array($file, $source));

    // Delete the original if it's not in use elsewhere.
    if ($delete_source && !\Drupal::service('file.usage')->listUsage($source)) {
      $source->delete();
    }

    return $file;
  }
  return FALSE;
}

/**
 * Checks that a file meets the criteria specified by the validators.
 *
 * After executing the validator callbacks specified hook_file_validate() will
 * also be called to allow other modules to report errors about the file.
 *
 * @param \Drupal\file\FileInterface $file
 *   A file entity.
 * @param $validators
 *   An optional, associative array of callback functions used to validate the
 *   file. The keys are function names and the values arrays of callback
 *   parameters which will be passed in after the file entity. The
 *   functions should return an array of error messages; an empty array
 *   indicates that the file passed validation. The functions will be called in
 *   the order specified.
 *
 * @return
 *   An array containing validation error messages.
 *
 * @see hook_file_validate()
 */
function file_validate(FileInterface $file, $validators = array()) {
  // Call the validation functions specified by this function's caller.
  $errors = array();
  foreach ($validators as $function => $args) {
    if (function_exists($function)) {
      array_unshift($args, $file);
      $errors = array_merge($errors, call_user_func_array($function, $args));
    }
  }

  // Let other modules perform validation on the new file.
  return array_merge($errors, \Drupal::moduleHandler()->invokeAll('file_validate', array($file)));
}

/**
 * Checks for files with names longer than can be stored in the database.
 *
 * @param \Drupal\file\FileInterface $file
 *   A file entity.
 *
 * @return
 *   An array. If the file name is too long, it will contain an error message.
 */
function file_validate_name_length(FileInterface $file) {
  $errors = array();

  if (!$file->getFilename()) {
    $errors[] = t("The file's name is empty. Please give a name to the file.");
  }
  if (strlen($file->getFilename()) > 240) {
    $errors[] = t("The file's name exceeds the 240 characters limit. Please rename the file and try again.");
  }
  return $errors;
}

/**
 * Checks that the filename ends with an allowed extension.
 *
 * @param \Drupal\file\FileInterface $file
 *   A file entity.
 * @param $extensions
 *   A string with a space separated list of allowed extensions.
 *
 * @return
 *   An array. If the file extension is not allowed, it will contain an error
 *   message.
 *
 * @see hook_file_validate()
 */
function file_validate_extensions(FileInterface $file, $extensions) {
  $errors = array();

  $regex = '/\.(' . preg_replace('/ +/', '|', preg_quote($extensions)) . ')$/i';
  if (!preg_match($regex, $file->getFilename())) {
    $errors[] = t('Only files with the following extensions are allowed: %files-allowed.', array('%files-allowed' => $extensions));
  }
  return $errors;
}

/**
 * Checks that the file's size is below certain limits.
 *
 * @param \Drupal\file\FileInterface $file
 *   A file entity.
 * @param $file_limit
 *   An integer specifying the maximum file size in bytes. Zero indicates that
 *   no limit should be enforced.
 * @param $user_limit
 *   An integer specifying the maximum number of bytes the user is allowed.
 *   Zero indicates that no limit should be enforced.
 *
 * @return
 *   An array. If the file size exceeds limits, it will contain an error
 *   message.
 *
 * @see hook_file_validate()
 */
function file_validate_size(FileInterface $file, $file_limit = 0, $user_limit = 0) {
  $user = \Drupal::currentUser();
  $errors = array();

  if ($file_limit && $file->getSize() > $file_limit) {
    $errors[] = t('The file is %filesize exceeding the maximum file size of %maxsize.', array('%filesize' => format_size($file->getSize()), '%maxsize' => format_size($file_limit)));
  }

  // Save a query by only calling spaceUsed() when a limit is provided.
  if ($user_limit && (\Drupal::entityManager()->getStorage('file')->spaceUsed($user->id()) + $file->getSize()) > $user_limit) {
    $errors[] = t('The file is %filesize which would exceed your disk quota of %quota.', array('%filesize' => format_size($file->getSize()), '%quota' => format_size($user_limit)));
  }

  return $errors;
}

/**
 * Checks that the file is recognized as a valid image.
 *
 * @param \Drupal\file\FileInterface $file
 *   A file entity.
 *
 * @return
 *   An array. If the file is not an image, it will contain an error message.
 *
 * @see hook_file_validate()
 */
function file_validate_is_image(FileInterface $file) {
  $errors = array();

  $image_factory = \Drupal::service('image.factory');
  $image = $image_factory->get($file->getFileUri());
  if (!$image->isValid()) {
    $supported_extensions = $image_factory->getSupportedExtensions();
    $errors[] = t('Image type not supported. Allowed types: %types', array('%types' => implode(' ', $supported_extensions)));
  }

  return $errors;
}

/**
 * Verifies that image dimensions are within the specified maximum and minimum.
 *
 * Non-image files will be ignored. If a image toolkit is available the image
 * will be scaled to fit within the desired maximum dimensions.
 *
 * @param \Drupal\file\FileInterface $file
 *   A file entity. This function may resize the file affecting its size.
 * @param $maximum_dimensions
 *   An optional string in the form WIDTHxHEIGHT e.g. '640x480' or '85x85'. If
 *   an image toolkit is installed the image will be resized down to these
 *   dimensions. A value of 0 indicates no restriction on size, so resizing
 *   will be attempted.
 * @param $minimum_dimensions
 *   An optional string in the form WIDTHxHEIGHT. This will check that the
 *   image meets a minimum size. A value of 0 indicates no restriction.
 *
 * @return
 *   An array. If the file is an image and did not meet the requirements, it
 *   will contain an error message.
 *
 * @see hook_file_validate()
 */
function file_validate_image_resolution(FileInterface $file, $maximum_dimensions = 0, $minimum_dimensions = 0) {
  $errors = array();

  // Check first that the file is an image.
  $image_factory = \Drupal::service('image.factory');
  $image = $image_factory->get($file->getFileUri());
  if ($image->isValid()) {
    if ($maximum_dimensions) {
      // Check that it is smaller than the given dimensions.
      list($width, $height) = explode('x', $maximum_dimensions);
      if ($image->getWidth() > $width || $image->getHeight() > $height) {
        // Try to resize the image to fit the dimensions.
        if ($image->scale($width, $height)) {
          $image->save();
          $file->filesize = $image->getFileSize();
          drupal_set_message(t('The image was resized to fit within the maximum allowed dimensions of %dimensions pixels.', array('%dimensions' => $maximum_dimensions)));
        }
        else {
          $errors[] = t('The image exceeds the maximum allowed dimensions and an attempt to resize it failed.');
        }
      }
    }

    if ($minimum_dimensions) {
      // Check that it is larger than the given dimensions.
      list($width, $height) = explode('x', $minimum_dimensions);
      if ($image->getWidth() < $width || $image->getHeight() < $height) {
        $errors[] = t('The image is too small; the minimum dimensions are %dimensions pixels.', array('%dimensions' => $minimum_dimensions));
      }
    }
  }

  return $errors;
}

/**
 * Saves a file to the specified destination and creates a database entry.
 *
 * @param $data
 *   A string containing the contents of the file.
 * @param $destination
 *   A string containing the destination URI. This must be a stream wrapper URI.
 *   If no value is provided, a randomized name will be generated and the file
 *   will be saved using Drupal's default files scheme, usually "public://".
 * @param $replace
 *   Replace behavior when the destination file already exists:
 *   - FILE_EXISTS_REPLACE - Replace the existing file. If a managed file with
 *       the destination name exists then its database entry will be updated. If
 *       no database entry is found then a new one will be created.
 *   - FILE_EXISTS_RENAME - Append _{incrementing number} until the filename is
 *       unique.
 *   - FILE_EXISTS_ERROR - Do nothing and return FALSE.
 *
 * @return \Drupal\file\FileInterface
 *   A file entity, or FALSE on error.
 *
 * @see file_unmanaged_save_data()
 */
function file_save_data($data, $destination = NULL, $replace = FILE_EXISTS_RENAME) {
  $user = \Drupal::currentUser();

  if (empty($destination)) {
    $destination = file_default_scheme() . '://';
  }
  if (!file_valid_uri($destination)) {
    \Drupal::logger('file')->notice('The data could not be saved because the destination %destination is invalid. This may be caused by improper use of file_save_data() or a missing stream wrapper.', array('%destination' => $destination));
    drupal_set_message(t('The data could not be saved because the destination is invalid. More information is available in the system log.'), 'error');
    return FALSE;
  }

  if ($uri = file_unmanaged_save_data($data, $destination, $replace)) {
    // Create a file entity.
    $file = entity_create('file', array(
      'uri' => $uri,
      'uid' => $user->id(),
      'status' => FILE_STATUS_PERMANENT,
    ));
    // If we are replacing an existing file re-use its database record.
    // @todo Do not create a new entity in order to update it, see
    //   https://drupal.org/node/2241865
    if ($replace == FILE_EXISTS_REPLACE) {
      $existing_files = entity_load_multiple_by_properties('file', array('uri' => $uri));
      if (count($existing_files)) {
        $existing = reset($existing_files);
        $file->fid = $existing->id();
        $file->setOriginalId($existing->id());
        $file->setFilename($existing->getFilename());
      }
    }
    // If we are renaming around an existing file (rather than a directory),
    // use its basename for the filename.
    elseif ($replace == FILE_EXISTS_RENAME && is_file($destination)) {
      $file->setFilename(drupal_basename($destination));
    }

    $file->save();
    return $file;
  }
  return FALSE;
}

/**
 * Examines a file entity and returns appropriate content headers for download.
 *
 * @param \Drupal\file\FileInterface $file
 *   A file entity.
 *
 * @return
 *   An associative array of headers, as expected by
 *   \Symfony\Component\HttpFoundation\StreamedResponse.
 */
function file_get_content_headers(FileInterface $file) {
  $type = mime_header_encode($file->getMimeType());

  return array(
    'Content-Type' => $type,
    'Content-Length' => $file->getSize(),
    'Cache-Control' => 'private',
  );
}

/**
 * Implements hook_theme().
 */
function file_theme() {
  return array(
    // From file.module.
    'file_link' => array(
      'variables' => array('file' => NULL, 'icon_directory' => NULL, 'description' => NULL, 'attributes' => array()),
      'template' => 'file-link',
    ),
    'file_managed_file' => array(
      'render element' => 'element',
      'template' => 'file-managed-file',
    ),

    // From file.field.inc.
    'file_widget' => array(
      'render element' => 'element',
      'template' => 'file-widget',
      'file' => 'file.field.inc',
    ),
    'file_widget_multiple' => array(
      'render element' => 'element',
      'template' => 'file-widget-multiple',
      'file' => 'file.field.inc',
    ),
    'file_upload_help' => array(
      'variables' => array('description' => NULL, 'upload_validators' => NULL, 'cardinality' => NULL),
      'template' => 'file-upload-help',
      'file' => 'file.field.inc',
    ),
  );
}

/**
 * Implements hook_file_download().
 */
function file_file_download($uri) {
  // Get the file record based on the URI. If not in the database just return.
  /** @var \Drupal\file\FileInterface[] $files */
  $files = entity_load_multiple_by_properties('file', array('uri' => $uri));
  if (count($files)) {
    foreach ($files as $item) {
      // Since some database servers sometimes use a case-insensitive comparison
      // by default, double check that the filename is an exact match.
      if ($item->getFileUri() === $uri) {
        $file = $item;
        break;
      }
    }
  }
  if (!isset($file)) {
    return;
  }

  // Find out which (if any) fields of this type contain the file.
  $references = file_get_file_references($file, NULL, EntityStorageInterface::FIELD_LOAD_CURRENT, NULL);

  // Stop processing if there are no references in order to avoid returning
  // headers for files controlled by other modules. Make an exception for
  // temporary files where the host entity has not yet been saved (for example,
  // an image preview on a node/add form) in which case, allow download by the
  // file's owner.
  if (empty($references) && ($file->isPermanent() || $file->getOwnerId() != \Drupal::currentUser()->id())) {
    return;
  }

  if (!$file->access('download')) {
    return -1;
  }

  // Access is granted.
  $headers = file_get_content_headers($file);
  return $headers;
}

/**
 * Implements file_cron()
 */
function file_cron() {
  $age = \Drupal::config('system.file')->get('temporary_maximum_age');

  // Only delete temporary files if older than $age. Note that automatic cleanup
  // is disabled if $age set to 0.
  if ($age) {
    $fids = Drupal::entityQuery('file')
      ->condition('status', FILE_STATUS_PERMANENT, '<>')
      ->condition('changed', REQUEST_TIME - $age, '<')
      ->range(0, 100)
      ->execute();
    $files = file_load_multiple($fids);
    foreach ($files as $file) {
      $references = \Drupal::service('file.usage')->listUsage($file);
      if (empty($references)) {
        if (file_exists($file->getFileUri())) {
          $file->delete();
        }
        else {
          \Drupal::logger('file system')->error('Could not delete temporary file "%path" during garbage collection', array('%path' => $file->getFileUri()));
        }
      }
      else {
        \Drupal::logger('file system')->info('Did not delete temporary file "%path" during garbage collection because it is in use by the following modules: %modules.', array('%path' => $file->getFileUri(), '%modules' => implode(', ', array_keys($references))));
      }
    }
  }
}

/**
 * Saves file uploads to a new location.
 *
 * The files will be added to the {file_managed} table as temporary files.
 * Temporary files are periodically cleaned. Use the 'file.usage' service to
 * register the usage of the file which will automatically mark it as permanent.
 *
 * @param $form_field_name
 *   A string that is the associative array key of the upload form element in
 *   the form array.
 * @param \Drupal\Core\Form\FormStateInterface $form_state
 *   The current state of the form.
 * @param $validators
 *   An optional, associative array of callback functions used to validate the
 *   file. See file_validate() for a full discussion of the array format.
 *   If no extension validator is provided it will default to a limited safe
 *   list of extensions which is as follows: "jpg jpeg gif png txt
 *   doc xls pdf ppt pps odt ods odp". To allow all extensions you must
 *   explicitly set the 'file_validate_extensions' validator to an empty array
 *   (Beware: this is not safe and should only be allowed for trusted users, if
 *   at all).
 * @param $destination
 *   A string containing the URI that the file should be copied to. This must
 *   be a stream wrapper URI. If this value is omitted, Drupal's temporary
 *   files scheme will be used ("temporary://").
 * @param $delta
 *   Delta of the file to save or NULL to save all files. Defaults to NULL.
 * @param $replace
 *   Replace behavior when the destination file already exists:
 *   - FILE_EXISTS_REPLACE: Replace the existing file.
 *   - FILE_EXISTS_RENAME: Append _{incrementing number} until the filename is
 *     unique.
 *   - FILE_EXISTS_ERROR: Do nothing and return FALSE.
 *
 * @return
 *   Function returns array of files or a single file object if $delta
 *   != NULL. Each file object contains the file information if the
 *   upload succeeded or FALSE in the event of an error. Function
 *   returns NULL if no file was uploaded.
 *
 *   The documentation for the "File interface" group, which you can find under
 *   Related topics, or the header at the top of this file, documents the
 *   components of a file entity. In addition to the standard components,
 *   this function adds:
 *   - source: Path to the file before it is moved.
 *   - destination: Path to the file after it is moved (same as 'uri').
 */
function file_save_upload($form_field_name, $validators = array(), $destination = FALSE, $delta = NULL, $replace = FILE_EXISTS_RENAME) {
  $user = \Drupal::currentUser();
  static $upload_cache;

  $file_upload = \Drupal::request()->files->get("files[$form_field_name]", NULL, TRUE);
  // Make sure there's an upload to process.
  if (empty($file_upload)) {
    return NULL;
  }

  // Return cached objects without processing since the file will have
  // already been processed and the paths in $_FILES will be invalid.
  if (isset($upload_cache[$form_field_name])) {
    if (isset($delta)) {
      return $upload_cache[$form_field_name][$delta];
    }
    return $upload_cache[$form_field_name];
  }

  // Prepare uploaded files info. Representation is slightly different
  // for multiple uploads and we fix that here.
  $uploaded_files = $file_upload;
  if (!is_array($file_upload)) {
    $uploaded_files = array($file_upload);
  }

  $files = array();
  foreach ($uploaded_files as $i => $file_info) {
    // Check for file upload errors and return FALSE for this file if a lower
    // level system error occurred. For a complete list of errors:
    // See http://php.net/manual/features.file-upload.errors.php.
    switch ($file_info->getError()) {
      case UPLOAD_ERR_INI_SIZE:
      case UPLOAD_ERR_FORM_SIZE:
        drupal_set_message(t('The file %file could not be saved because it exceeds %maxsize, the maximum allowed size for uploads.', array('%file' => $file_info->getFilename(), '%maxsize' => format_size(file_upload_max_size()))), 'error');
        $files[$i] = FALSE;
        continue;

      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' => $file_info->getFilename())), 'error');
        $files[$i] = FALSE;
        continue;

      case UPLOAD_ERR_OK:
        // Final check that this is a valid upload, if it isn't, use the
        // default error handler.
        if (is_uploaded_file($file_info->getRealPath())) {
          break;
        }

        // Unknown error
      default:
        drupal_set_message(t('The file %file could not be saved. An unknown error has occurred.', array('%file' => $file_info->getFilename())), 'error');
        $files[$i] = FALSE;
        continue;

    }
    // Begin building file entity.
    $values = array(
      'uid' => $user->id(),
      'status' => 0,
      'filename' => $file_info->getClientOriginalName(),
      'uri' => $file_info->getRealPath(),
      'filesize' => $file_info->getSize(),
    );
    $values['filemime'] = file_get_mimetype($values['filename']);
    $file = entity_create('file', $values);

    $extensions = '';
    if (isset($validators['file_validate_extensions'])) {
      if (isset($validators['file_validate_extensions'][0])) {
        // Build the list of non-munged extensions if the caller provided them.
        $extensions = $validators['file_validate_extensions'][0];
      }
      else {
        // If 'file_validate_extensions' is set and the list is empty then the
        // caller wants to allow any extension. In this case we have to remove the
        // validator or else it will reject all extensions.
        unset($validators['file_validate_extensions']);
      }
    }
    else {
      // No validator was provided, so add one using the default list.
      // Build a default non-munged safe list for file_munge_filename().
      $extensions = 'jpg jpeg gif png txt doc xls pdf ppt pps odt ods odp';
      $validators['file_validate_extensions'] = array();
      $validators['file_validate_extensions'][0] = $extensions;
    }

    if (!empty($extensions)) {
      // Munge the filename to protect against possible malicious extension
      // hiding within an unknown file type (ie: filename.html.foo).
      $file->setFilename(file_munge_filename($file->getFilename(), $extensions));
    }

    // Rename potentially executable files, to help prevent exploits (i.e. will
    // rename filename.php.foo and filename.php to filename.php.foo.txt and
    // filename.php.txt, respectively). Don't rename if 'allow_insecure_uploads'
    // evaluates to TRUE.
    if (!\Drupal::config('system.file')->get('allow_insecure_uploads') && preg_match('/\.(php|pl|py|cgi|asp|js)(\.|$)/i', $file->getFilename()) && (substr($file->getFilename(), -4) != '.txt')) {
      $file->setMimeType('text/plain');
      // The destination filename will also later be used to create the URI.
      $file->setFilename($file->getFilename() . '.txt');
      // The .txt extension may not be in the allowed list of extensions. We have
      // to add it here or else the file upload will fail.
      if (!empty($extensions)) {
        $validators['file_validate_extensions'][0] .= ' txt';
        drupal_set_message(t('For security reasons, your upload has been renamed to %filename.', array('%filename' => $file->getFilename())));
      }
    }

    // If the destination is not provided, use the temporary directory.
    if (empty($destination)) {
      $destination = 'temporary://';
    }

    // Assert that the destination contains a valid stream.
    $destination_scheme = file_uri_scheme($destination);
    if (!file_stream_wrapper_valid_scheme($destination_scheme)) {
      drupal_set_message(t('The file could not be uploaded because the destination %destination is invalid.', array('%destination' => $destination)), 'error');
      $files[$i] = FALSE;
      continue;
    }

    $file->source = $form_field_name;
    // A file URI may already have a trailing slash or look like "public://".
    if (substr($destination, -1) != '/') {
      $destination .= '/';
    }
    $file->destination = file_destination($destination . $file->getFilename(), $replace);
    // If file_destination() returns FALSE then $replace === FILE_EXISTS_ERROR and
    // there's an existing file so we need to bail.
    if ($file->destination === FALSE) {
      drupal_set_message(t('The file %source could not be uploaded because a file by that name already exists in the destination %directory.', array('%source' => $form_field_name, '%directory' => $destination)), 'error');
      $files[$i] = FALSE;
      continue;
    }

    // Add in our check of the the file name length.
    $validators['file_validate_name_length'] = array();

    // Call the validation functions specified by this function's caller.
    $errors = file_validate($file, $validators);

    // Check for errors.
    if (!empty($errors)) {
      $message = t('The specified file %name could not be uploaded.', array('%name' => $file->getFilename()));
      if (count($errors) > 1) {
        $item_list = array(
          '#theme' => 'item_list',
          '#items' => $errors,
        );
        $message = SafeMarkup::set($message . drupal_render($item_list));
      }
      else {
        $message = SafeMarkup::set($message . ' ' . SafeMarkup::escape(array_pop($errors)));
      }
      drupal_set_message($message, 'error');
      $files[$i] = FALSE;
      continue;
    }

    // Move uploaded files from PHP's upload_tmp_dir to Drupal's temporary
    // directory. This overcomes open_basedir restrictions for future file
    // operations.
    $file->uri = $file->destination;
    if (!drupal_move_uploaded_file($file_info->getRealPath(), $file->getFileUri())) {
      drupal_set_message(t('File upload error. Could not move uploaded file.'), 'error');
      \Drupal::logger('file')->notice('Upload error. Could not move uploaded file %file to destination %destination.', array('%file' => $file->filename, '%destination' => $file->uri));
      $files[$i] = FALSE;
      continue;
    }

    // Set the permissions on the new file.
    drupal_chmod($file->getFileUri());

    // If we are replacing an existing file re-use its database record.
    // @todo Do not create a new entity in order to update it, see
    //   https://drupal.org/node/2241865
    if ($replace == FILE_EXISTS_REPLACE) {
      $existing_files = entity_load_multiple_by_properties('file', array('uri' => $file->getFileUri()));
      if (count($existing_files)) {
        $existing = reset($existing_files);
        $file->fid = $existing->id();
        $file->setOriginalId($existing->id());
      }
    }

    // If we made it this far it's safe to record this file in the database.
    $file->save();
    $files[$i] = $file;
  }

  // Add files to the cache.
  $upload_cache[$form_field_name] = $files;

  return isset($delta) ? $files[$delta] : $files;
}

/**
 * Determines the preferred upload progress implementation.
 *
 * @return
 *   A string indicating which upload progress system is available. Either "apc"
 *   or "uploadprogress". If neither are available, returns FALSE.
 */
function file_progress_implementation() {
  static $implementation;
  if (!isset($implementation)) {
    $implementation = FALSE;

    // We prefer the PECL extension uploadprogress because it supports multiple
    // simultaneous uploads. APC only supports one at a time.
    if (extension_loaded('uploadprogress')) {
      $implementation = 'uploadprogress';
    }
    elseif (extension_loaded('apc') && ini_get('apc.rfc1867')) {
      $implementation = 'apc';
    }
  }
  return $implementation;
}

/**
 * Implements hook_ENTITY_TYPE_predelete() for file entities.
 */
function file_file_predelete(File $file) {
  // TODO: Remove references to a file that is in-use.
}

/**
 * Implements hook_tokens().
 */
function file_tokens($type, $tokens, array $data = array(), array $options = array()) {
  $token_service = \Drupal::token();

  $url_options = array('absolute' => TRUE);
  if (isset($options['langcode'])) {
    $url_options['language'] = language_load($options['langcode']);
    $langcode = $options['langcode'];
  }
  else {
    $langcode = NULL;
  }
  $sanitize = !empty($options['sanitize']);

  $replacements = array();

  if ($type == 'file' && !empty($data['file'])) {
    /** @var \Drupal\file\FileInterface $file */
    $file = $data['file'];

    foreach ($tokens as $name => $original) {
      switch ($name) {
        // Basic keys and values.
        case 'fid':
          $replacements[$original] = $file->id();
          break;

        // Essential file data
        case 'name':
          $replacements[$original] = $sanitize ? String::checkPlain($file->getFilename()) : $file->getFilename();
          break;

        case 'path':
          $replacements[$original] = $sanitize ? String::checkPlain($file->getFileUri()) : $file->getFileUri();
          break;

        case 'mime':
          $replacements[$original] = $sanitize ? String::checkPlain($file->getMimeType()) : $file->getMimeType();
          break;

        case 'size':
          $replacements[$original] = format_size($file->getSize());
          break;

        case 'url':
          $replacements[$original] = $sanitize ? String::checkPlain(file_create_url($file->getFileUri())) : file_create_url($file->getFileUri());
          break;

        // These tokens are default variations on the chained tokens handled below.
        case 'created':
          $replacements[$original] = format_date($file->getCreatedTime(), 'medium', '', NULL, $langcode);
          break;

        case 'changed':
          $replacements[$original] = format_date($file->getChangedTime(), 'medium', '', NULL, $langcode);
          break;

        case 'owner':
          $name = $file->getOwner()->label();
          $replacements[$original] = $sanitize ? String::checkPlain($name) : $name;
          break;
      }
    }

    if ($date_tokens = $token_service->findWithPrefix($tokens, 'created')) {
      $replacements += $token_service->generate('date', $date_tokens, array('date' => $file->getCreatedTime()), $options);
    }

    if ($date_tokens = $token_service->findWithPrefix($tokens, 'changed')) {
      $replacements += $token_service->generate('date', $date_tokens, array('date' => $file->getChangedTime()), $options);
    }

    if (($owner_tokens = $token_service->findWithPrefix($tokens, 'owner')) && $file->getOwner()) {
      $replacements += $token_service->generate('user', $owner_tokens, array('user' => $file->getOwner()), $options);
    }
  }

  return $replacements;
}

/**
 * Implements hook_token_info().
 */
function file_token_info() {
  $types['file'] = array(
    'name' => t("Files"),
    'description' => t("Tokens related to uploaded files."),
    'needs-data' => 'file',
  );

  // File related tokens.
  $file['fid'] = array(
    'name' => t("File ID"),
    'description' => t("The unique ID of the uploaded file."),
  );
  $file['name'] = array(
    'name' => t("File name"),
    'description' => t("The name of the file on disk."),
  );
  $file['path'] = array(
    'name' => t("Path"),
    'description' => t("The location of the file relative to Drupal root."),
  );
  $file['mime'] = array(
    'name' => t("MIME type"),
    'description' => t("The MIME type of the file."),
  );
  $file['size'] = array(
    'name' => t("File size"),
    'description' => t("The size of the file."),
  );
  $file['url'] = array(
    'name' => t("URL"),
    'description' => t("The web-accessible URL for the file."),
  );
  $file['created'] = array(
    'name' => t("Created"),
    'description' => t("The date the file created."),
    'type' => 'date',
  );
  $file['changed'] = array(
    'name' => t("Changed"),
    'description' => t("The date the file was most recently changed."),
    'type' => 'date',
  );
  $file['owner'] = array(
    'name' => t("Owner"),
    'description' => t("The user who originally uploaded the file."),
    'type' => 'user',
  );

  return array(
    'types' => $types,
    'tokens' => array(
      'file' => $file,
    ),
  );
}

/**
 * Render API callback: Expands the managed_file element type.
 *
 * Expands the file type to include Upload and Remove buttons, as well as
 * support for a default value.
 *
 * This function is assigned as a #process callback in file_element_info().
 */
function file_managed_file_process($element, FormStateInterface $form_state, $form) {
  // Append the '-upload' to the #id so the field label's 'for' attribute
  // corresponds with the file element.
  $element['#id'] .= '-upload';

  // This is used sometimes so let's implode it just once.
  $parents_prefix = implode('_', $element['#parents']);

  $fids = isset($element['#value']['fids']) ? $element['#value']['fids'] : array();

  // Set some default element properties.
  $element['#progress_indicator'] = empty($element['#progress_indicator']) ? 'none' : $element['#progress_indicator'];
  $element['#files'] = !empty($fids) ? file_load_multiple($fids) : FALSE;
  $element['#tree'] = TRUE;

  $ajax_settings = array(
    'path' => 'file/ajax',
    'options' => array(
      'query' => array(
        'element_parents' => implode('/', $element['#array_parents']),
        'form_build_id' => $form['form_build_id']['#value'],
      ),
    ),
    'wrapper' => $element['#id'] . '-ajax-wrapper',
    'effect' => 'fade',
    'progress' => array(
      'type' => $element['#progress_indicator'],
      'message' => $element['#progress_message'],
    ),
  );

  // Set up the buttons first since we need to check if they were clicked.
  $element['upload_button'] = array(
    '#name' => $parents_prefix . '_upload_button',
    '#type' => 'submit',
    '#value' => t('Upload'),
    '#attributes' => array('class' => array('js-hide')),
    '#validate' => array(),
    '#submit' => array('file_managed_file_submit'),
    '#limit_validation_errors' => array($element['#parents']),
    '#ajax' => $ajax_settings,
    '#weight' => -5,
  );

  // Force the progress indicator for the remove button to be either 'none' or
  // 'throbber', even if the upload button is using something else.
  $ajax_settings['progress']['type'] = ($element['#progress_indicator'] == 'none') ? 'none' : 'throbber';
  $ajax_settings['progress']['message'] = NULL;
  $ajax_settings['effect'] = 'none';
  $element['remove_button'] = array(
    '#name' => $parents_prefix . '_remove_button',
    '#type' => 'submit',
    '#value' => $element['#multiple'] ? t('Remove selected') : t('Remove'),
    '#validate' => array(),
    '#submit' => array('file_managed_file_submit'),
    '#limit_validation_errors' => array($element['#parents']),
    '#ajax' => $ajax_settings,
    '#weight' => 1,
  );

  $element['fids'] = array(
    '#type' => 'hidden',
    '#value' => $fids,
  );

  // Add progress bar support to the upload if possible.
  if ($element['#progress_indicator'] == 'bar' && $implementation = file_progress_implementation()) {
    $upload_progress_key = mt_rand();

    if ($implementation == 'uploadprogress') {
      $element['UPLOAD_IDENTIFIER'] = array(
        '#type' => 'hidden',
        '#value' => $upload_progress_key,
        '#attributes' => array('class' => array('file-progress')),
        // Uploadprogress extension requires this field to be at the top of the
        // form.
        '#weight' => -20,
      );
    }
    elseif ($implementation == 'apc') {
      $element['APC_UPLOAD_PROGRESS'] = array(
        '#type' => 'hidden',
        '#value' => $upload_progress_key,
        '#attributes' => array('class' => array('file-progress')),
        // Uploadprogress extension requires this field to be at the top of the
        // form.
        '#weight' => -20,
      );
    }

    // Add the upload progress callback.
    $element['upload_button']['#ajax']['progress']['path'] = 'file/progress/' . $upload_progress_key;
  }

  // The file upload field itself.
  $element['upload'] = array(
    '#name' => 'files[' . $parents_prefix . ']',
    '#type' => 'file',
    '#title' => t('Choose a file'),
    '#title_display' => 'invisible',
    '#size' => $element['#size'],
    '#multiple' => $element['#multiple'],
    '#theme_wrappers' => array(),
    '#weight' => -10,
  );

  if (!empty($fids) && $element['#files']) {
    foreach ($element['#files'] as $delta => $file) {
      $file_link = array(
        '#theme' => 'file_link',
        '#file' => $file,
      );
      if ($element['#multiple']) {
        $element['file_' . $delta]['selected'] = array(
          '#type' => 'checkbox',
          '#title' => drupal_render($file_link),
        );
      }
      else {
        $element['file_' . $delta]['filename'] = $file_link += array('#weight' => -10);
      }
    }
  }

  // Add the extension list to the page as JavaScript settings.
  if (isset($element['#upload_validators']['file_validate_extensions'][0])) {
    $extension_list = implode(',', array_filter(explode(' ', $element['#upload_validators']['file_validate_extensions'][0])));
    $element['upload']['#attached']['js'] = array(
      array(
        'type' => 'setting',
        'data' => array('file' => array('elements' => array('#' . $element['#id'] => $extension_list)))
      )
    );
  }

  // Prefix and suffix used for Ajax replacement.
  $element['#prefix'] = '<div id="' . $element['#id'] . '-ajax-wrapper">';
  $element['#suffix'] = '</div>';

  return $element;
}

/**
 * Render API callback: Determines the value for a managed_file type element.
 *
 * This function is assigned as a #value_callback in file_element_info().
 */
function file_managed_file_value(&$element, $input, FormStateInterface $form_state) {
  // Find the current value of this field.
  $fids = !empty($input['fids']) ? explode(' ', $input['fids']) : array();
  foreach ($fids as $key => $fid) {
    $fids[$key] = (int) $fid;
  }

  // Process any input and save new uploads.
  if ($input !== FALSE) {
    $input['fids'] = $fids;
    $return = $input;

    // Uploads take priority over all other values.
    if ($files = file_managed_file_save_upload($element, $form_state)) {
      if ($element['#multiple']) {
        $fids = array_merge($fids, array_keys($files));
      }
      else {
        $fids = array_keys($files);
      }
    }
    else {
      // Check for #filefield_value_callback values.
      // Because FAPI does not allow multiple #value_callback values like it
      // does for #element_validate and #process, this fills the missing
      // functionality to allow File fields to be extended through FAPI.
      if (isset($element['#file_value_callbacks'])) {
        foreach ($element['#file_value_callbacks'] as $callback) {
          $callback($element, $input, $form_state);
        }
      }

      // Load files if the FIDs have changed to confirm they exist.
      if (!empty($input['fids'])) {
        $fids = array();
        foreach ($input['fids'] as $fid) {
          if ($file = file_load($fid)) {
            $fids[] = $file->id();
          }
        }
      }
    }
  }

  // If there is no input, set the default value.
  else {
    if ($element['#extended']) {
      $default_fids = isset($element['#default_value']['fids']) ? $element['#default_value']['fids'] : array();
      $return = isset($element['#default_value']) ? $element['#default_value'] : array('fids' => array());
    }
    else {
      $default_fids = isset($element['#default_value']) ? $element['#default_value'] : array();
      $return = array('fids' => array());
    }

    // Confirm that the file exists when used as a default value.
    if (!empty($default_fids)) {
      $fids = array();
      foreach ($default_fids as $fid) {
        if ($file = file_load($fid)) {
          $fids[] = $file->id();
        }
      }
    }
  }

  $return['fids'] = $fids;
  return $return;
}

/**
 * Render API callback: Validates the managed_file element.
 *
 * This function is assigned as a #element_validate callback in
 * file_element_info().
 */
function file_managed_file_validate(&$element, FormStateInterface $form_state) {
  // If referencing an existing file, only allow if there are existing
  // references. This prevents unmanaged files from being deleted if this
  // item were to be deleted.
  $clicked_button = end($form_state['triggering_element']['#parents']);
  if ($clicked_button != 'remove_button' && !empty($element['fids']['#value'])) {
    $fids = $element['fids']['#value'];
    foreach ($fids as $fid) {
      if ($file = file_load($fid)) {
        if ($file->isPermanent()) {
          $references = \Drupal::service('file.usage')->listUsage($file);
          if (empty($references)) {
            form_error($element, $form_state, t('The file used in the !name field may not be referenced.', array('!name' => $element['#title'])));
          }
        }
      }
      else {
        form_error($element, $form_state, t('The file referenced by the !name field does not exist.', array('!name' => $element['#title'])));
      }
    }
  }

  // Check required property based on the FID.
  if ($element['#required'] && empty($element['fids']['#value']) && !in_array($clicked_button, array('upload_button', 'remove_button'))) {
    form_error($element['upload'], $form_state, t('!name field is required.', array('!name' => $element['#title'])));
  }

  // Consolidate the array value of this field to array of FIDs.
  if (!$element['#extended']) {
    form_set_value($element, $element['fids']['#value'], $form_state);
  }
}

/**
 * Form submission handler for upload / remove buttons of managed_file elements.
 *
 * @see file_managed_file_process()
 */
function file_managed_file_submit($form, FormStateInterface $form_state) {
  // Determine whether it was the upload or the remove button that was clicked,
  // and set $element to the managed_file element that contains that button.
  $parents = $form_state['triggering_element']['#array_parents'];
  $button_key = array_pop($parents);
  $element = NestedArray::getValue($form, $parents);

  // No action is needed here for the upload button, because all file uploads on
  // the form are processed by file_managed_file_value() regardless of which
  // button was clicked. Action is needed here for the remove button, because we
  // only remove a file in response to its remove button being clicked.
  if ($button_key == 'remove_button') {
    $fids = array_keys($element['#files']);
    // Get files that will be removed.
    if ($element['#multiple']) {
      $remove_fids = array();
      foreach (Element::children($element) as $name) {
        if (strpos($name, 'file_') === 0 && $element[$name]['selected']['#value']) {
          $remove_fids[] = (int) substr($name, 5);
        }
      }
      $fids = array_diff($fids, $remove_fids);
    }
    else {
      // If we deal with single upload element remove the file and set
      // element's value to empty array (file could not be removed from
      // element if we don't do that).
      $remove_fids = $fids;
      $fids = array();
    }

    foreach ($remove_fids as $fid) {
      // If it's a temporary file we can safely remove it immediately, otherwise
      // it's up to the implementing module to remove usages of files to have them
      // removed.
      if ($element['#files'][$fid] && $element['#files'][$fid]->isTemporary()) {
        $element['#files'][$fid]->delete();
      }
    }
    // Update both $form_state['values'] and $form_state['input'] to reflect
    // that the file has been removed, so that the form is rebuilt correctly.
    // $form_state['values'] must be updated in case additional submit handlers
    // run, and for form building functions that run during the rebuild, such as
    // when the managed_file element is part of a field widget.
    // $form_state['input'] must be updated so that file_managed_file_value()
    // has correct information during the rebuild.
    form_set_value($element['fids'], implode(' ', $fids), $form_state);
    NestedArray::setValue($form_state['input'], $element['fids']['#parents'], implode(' ', $fids));
  }

  // Set the form to rebuild so that $form is correctly updated in response to
  // processing the file removal. Since this function did not change $form_state
  // if the upload button was clicked, a rebuild isn't necessary in that
  // situation and setting $form_state['no_redirect'] to TRUE would suffice.
  // However, we choose to always rebuild, to keep the form processing workflow
  // consistent between the two buttons.
  $form_state['rebuild'] = TRUE;
}

/**
 * Saves any files that have been uploaded into a managed_file element.
 *
 * @param $element
 *   The FAPI element whose values are being saved.
 * @param \Drupal\Core\Form\FormStateInterface $form_state
 *   The current state of the form.
 *
 * @return
 *   An array of file entities for each file that was saved, keyed by its file
 *   ID, or FALSE if no files were saved.
 */
function file_managed_file_save_upload($element, FormStateInterface $form_state) {
  $upload_name = implode('_', $element['#parents']);
  $file_upload = \Drupal::request()->files->get("files[$upload_name]", NULL, TRUE);
  if (empty($file_upload)) {
    return FALSE;
  }

  $destination = isset($element['#upload_location']) ? $element['#upload_location'] : NULL;
  if (isset($destination) && !file_prepare_directory($destination, FILE_CREATE_DIRECTORY)) {
    \Drupal::logger('file')->notice('The upload directory %directory for the file field !name could not be created or is not accessible. A newly uploaded file could not be saved in this directory as a consequence, and the upload was canceled.', array('%directory' => $destination, '!name' => $element['#field_name']));
    form_set_error($upload_name, $form_state, t('The file could not be uploaded.'));
    return FALSE;
  }

  // Save attached files to the database.
  $files_uploaded = $element['#multiple'] && count(array_filter($file_upload)) > 0;
  $files_uploaded |= !$element['#multiple'] && !empty($file_upload);
  if ($files_uploaded) {
    if (!$files = file_save_upload($upload_name, $element['#upload_validators'], $destination)) {
      \Drupal::logger('file')->notice('The file upload failed. %upload', array('%upload' => $upload_name));
      form_set_error($upload_name, $form_state, t('Files in the !name field were unable to be uploaded.', array('!name' => $element['#title'])));
      return array();
    }

    // Value callback expects FIDs to be keys.
    $files = array_filter($files);
    $fids = array_map(function($file) { return $file->id(); }, $files);

    return empty($files) ? array() : array_combine($fids, $files);
  }

  return array();
}

/**
 * Prepares variables for file form widget templates.
 *
 * Default template: file-managed-file.html.twig.
 *
 * @param array $variables
 *   An associative array containing:
 *   - element: A render element representing the file.
 */
function template_preprocess_file_managed_file(&$variables) {
  $element = $variables['element'];

  $variables['attributes'] = array();
  if (isset($element['#id'])) {
    $variables['attributes']['id'] = $element['#id'];
  }
  if (!empty($element['#attributes']['class'])) {
    $variables['attributes']['class'] = (array) $element['#attributes']['class'];
  }
  $variables['attributes']['class'][] = 'form-managed-file';
}

/**
 * Render API callback: Hides display of the upload or remove controls.
 *
 * Upload controls are hidden when a file is already uploaded. Remove controls
 * are hidden when there is no file attached. Controls are hidden here instead
 * of in file_managed_file_process(), because #access for these buttons depends
 * on the managed_file element's #value. See the documentation of form_builder()
 * for more detailed information about the relationship between #process,
 * #value, and #access.
 *
 * Because #access is set here, it affects display only and does not prevent
 * JavaScript or other untrusted code from submitting the form as though access
 * were enabled. The form processing functions for these elements should not
 * assume that the buttons can't be "clicked" just because they are not
 * displayed.
 *
 * This function is assigned as a #pre_render callback in file_element_info().
 *
 * @see file_managed_file_process()
 */
function file_managed_file_pre_render($element) {
  // If we already have a file, we don't want to show the upload controls.
  if (!empty($element['#value']['fids'])) {
    if (!$element['#multiple']) {
      $element['upload']['#access'] = FALSE;
      $element['upload_button']['#access'] = FALSE;
    }
  }
  // If we don't already have a file, there is nothing to remove.
  else {
    $element['remove_button']['#access'] = FALSE;
  }
  return $element;
}

/**
 * Prepares variables for file link templates.
 *
 * Default template: file-link.html.twig.
 *
 * @param array $variables
 *   An associative array containing:
 *   - file: A file object to which the link will be created.
 *   - icon_directory: (optional) A path to a directory of icons to be used for
 *     files. Defaults to the value of the "icon.directory" variable.
 *   - description: A description to be displayed instead of the filename.
 *   - attributes: An associative array of attributes to be placed in the a tag.
 */
function template_preprocess_file_link(&$variables) {
  $file = $variables['file'];
  $options = array(
    'attributes' => $variables['attributes'],
  );
  $icon_directory = $variables['icon_directory'];

  $url = file_create_url($file->getFileUri());
  $file_entity = ($file instanceof File) ? $file : file_load($file->fid);

  // Human-readable names, for use as text-alternatives to icons.
  $mime_name = array(
    'application/msword' => t('Microsoft Office document icon'),
    'application/vnd.ms-excel' => t('Office spreadsheet icon'),
    'application/vnd.ms-powerpoint' => t('Office presentation icon'),
    'application/pdf' => t('PDF icon'),
    'video/quicktime' => t('Movie icon'),
    'audio/mpeg' => t('Audio icon'),
    'audio/wav' => t('Audio icon'),
    'image/jpeg' => t('Image icon'),
    'image/png' => t('Image icon'),
    'image/gif' => t('Image icon'),
    'application/zip' => t('Package icon'),
    'text/html' => t('HTML icon'),
    'text/plain' => t('Plain text icon'),
    'application/octet-stream' => t('Binary Data'),
  );

  $variables['icon'] = array(
    '#theme' => 'image__file_icon',
    '#uri' => file_icon_url($file_entity, $icon_directory),
    '#alt' => (!empty($mime_name[$file->getMimeType()])) ? $mime_name[$file->getMimeType()] : t('File'),
    '#title' => String::checkPlain($file_entity->getFilename()),
    '#attributes' => array('class' => array('file-icon')),
  );

  // Set options as per anchor format described at
  // http://microformats.org/wiki/file-format-examples
  $options['attributes']['type'] = $file->getMimeType() . '; length=' . $file->getSize();

  // Use the description as the link text if available.
  if (empty($variables['description'])) {
    $link_text = $file_entity->getFilename();
  }
  else {
    $link_text = $variables['description'];
    $options['attributes']['title'] = String::checkPlain($file_entity->getFilename());
  }

  $variables['link'] = l($link_text, $url, $options);
  $variables['attributes'] = array('class' => array('file'));
}

/**
 * Creates a URL to the icon for a file entity.
 *
 * @param \Drupal\file\FileInterface $file
 *   A file entity.
 * @param $icon_directory
 *   (optional) A path to a directory of icons to be used for files. Defaults to
 *   the value of the "icon.directory" variable.
 *
 * @return
 *   A URL string to the icon, or FALSE if an appropriate icon cannot be found.
 */
function file_icon_url(FileInterface $file, $icon_directory = NULL) {
  if ($icon_path = file_icon_path($file, $icon_directory)) {
    return base_path() . $icon_path;
  }
  return FALSE;
}

/**
 * Creates a path to the icon for a file entity.
 *
 * @param \Drupal\file\FileInterface $file
 *   A file entity.
 * @param $icon_directory
 *   (optional) A path to a directory of icons to be used for files. Defaults to
 *   the value of the "icon.directory" variable.
 *
 * @return
 *   A string to the icon as a local path, or FALSE if an appropriate icon could
 *   not be found.
 */
function file_icon_path(FileInterface $file, $icon_directory = NULL) {
  // Use the default set of icons if none specified.
  if (!isset($icon_directory)) {
    $icon_directory = \Drupal::config('file.settings')->get('icon.directory');
  }

  // If there's an icon matching the exact mimetype, go for it.
  $dashed_mime = strtr($file->getMimeType(), array('/' => '-'));
  $icon_path = $icon_directory . '/' . $dashed_mime . '.png';
  if (file_exists($icon_path)) {
    return $icon_path;
  }

  // For a few mimetypes, we can "manually" map to a generic icon.
  $generic_mime = (string) file_icon_map($file);
  $icon_path = $icon_directory . '/' . $generic_mime . '.png';
  if ($generic_mime && file_exists($icon_path)) {
    return $icon_path;
  }

  // Use generic icons for each category that provides such icons.
  foreach (array('audio', 'image', 'text', 'video') as $category) {
    if (strpos($file->getMimeType(), $category . '/') === 0) {
      $icon_path = $icon_directory . '/' . $category . '-x-generic.png';
      if (file_exists($icon_path)) {
        return $icon_path;
      }
    }
  }

  // Try application-octet-stream as last fallback.
  $icon_path = $icon_directory . '/application-octet-stream.png';
  if (file_exists($icon_path)) {
    return $icon_path;
  }

  // No icon can be found.
  return FALSE;
}

/**
 * Determines the generic icon MIME package based on a file's MIME type.
 *
 * @param \Drupal\file\FileInterface $file
 *   A file entity.
 *
 * @return
 *   The generic icon MIME package expected for this file.
 */
function file_icon_map(FileInterface $file) {
  switch ($file->getMimeType()) {
    // Word document types.
    case 'application/msword':
    case 'application/vnd.ms-word.document.macroEnabled.12':
    case 'application/vnd.oasis.opendocument.text':
    case 'application/vnd.oasis.opendocument.text-template':
    case 'application/vnd.oasis.opendocument.text-master':
    case 'application/vnd.oasis.opendocument.text-web':
    case 'application/vnd.openxmlformats-officedocument.wordprocessingml.document':
    case 'application/vnd.stardivision.writer':
    case 'application/vnd.sun.xml.writer':
    case 'application/vnd.sun.xml.writer.template':
    case 'application/vnd.sun.xml.writer.global':
    case 'application/vnd.wordperfect':
    case 'application/x-abiword':
    case 'application/x-applix-word':
    case 'application/x-kword':
    case 'application/x-kword-crypt':
      return 'x-office-document';

    // Spreadsheet document types.
    case 'application/vnd.ms-excel':
    case 'application/vnd.ms-excel.sheet.macroEnabled.12':
    case 'application/vnd.oasis.opendocument.spreadsheet':
    case 'application/vnd.oasis.opendocument.spreadsheet-template':
    case 'application/vnd.openxmlformats-officedocument.spreadsheetml.sheet':
    case 'application/vnd.stardivision.calc':
    case 'application/vnd.sun.xml.calc':
    case 'application/vnd.sun.xml.calc.template':
    case 'application/vnd.lotus-1-2-3':
    case 'application/x-applix-spreadsheet':
    case 'application/x-gnumeric':
    case 'application/x-kspread':
    case 'application/x-kspread-crypt':
      return 'x-office-spreadsheet';

    // Presentation document types.
    case 'application/vnd.ms-powerpoint':
    case 'application/vnd.ms-powerpoint.presentation.macroEnabled.12':
    case 'application/vnd.oasis.opendocument.presentation':
    case 'application/vnd.oasis.opendocument.presentation-template':
    case 'application/vnd.openxmlformats-officedocument.presentationml.presentation':
    case 'application/vnd.stardivision.impress':
    case 'application/vnd.sun.xml.impress':
    case 'application/vnd.sun.xml.impress.template':
    case 'application/x-kpresenter':
      return 'x-office-presentation';

    // Compressed archive types.
    case 'application/zip':
    case 'application/x-zip':
    case 'application/stuffit':
    case 'application/x-stuffit':
    case 'application/x-7z-compressed':
    case 'application/x-ace':
    case 'application/x-arj':
    case 'application/x-bzip':
    case 'application/x-bzip-compressed-tar':
    case 'application/x-compress':
    case 'application/x-compressed-tar':
    case 'application/x-cpio-compressed':
    case 'application/x-deb':
    case 'application/x-gzip':
    case 'application/x-java-archive':
    case 'application/x-lha':
    case 'application/x-lhz':
    case 'application/x-lzop':
    case 'application/x-rar':
    case 'application/x-rpm':
    case 'application/x-tzo':
    case 'application/x-tar':
    case 'application/x-tarz':
    case 'application/x-tgz':
      return 'package-x-generic';

    // Script file types.
    case 'application/ecmascript':
    case 'application/javascript':
    case 'application/mathematica':
    case 'application/vnd.mozilla.xul+xml':
    case 'application/x-asp':
    case 'application/x-awk':
    case 'application/x-cgi':
    case 'application/x-csh':
    case 'application/x-m4':
    case 'application/x-perl':
    case 'application/x-php':
    case 'application/x-ruby':
    case 'application/x-shellscript':
    case 'text/vnd.wap.wmlscript':
    case 'text/x-emacs-lisp':
    case 'text/x-haskell':
    case 'text/x-literate-haskell':
    case 'text/x-lua':
    case 'text/x-makefile':
    case 'text/x-matlab':
    case 'text/x-python':
    case 'text/x-sql':
    case 'text/x-tcl':
      return 'text-x-script';

    // HTML aliases.
    case 'application/xhtml+xml':
      return 'text-html';

    // Executable types.
    case 'application/x-macbinary':
    case 'application/x-ms-dos-executable':
    case 'application/x-pef-executable':
      return 'application-x-executable';

    default:
      return FALSE;
  }
}

/**
 * Retrieves a list of references to a file.
 *
 * @param \Drupal\file\FileInterface $file
 *   A file entity.
 * @param \Drupal\Core\Field\FieldDefinitionInterface $field
 *   (optional) A field definition to be used for this check. If given, limits the
 *   reference check to the given field.
 * @param $age
 *   (optional) A constant that specifies which references to count. Use
 *   EntityStorageInterface::FIELD_LOAD_REVISION to retrieve all
 *   references within all revisions or
 *   EntityStorageInterface::FIELD_LOAD_CURRENT to retrieve references
 *   only in the current revisions.
 * @param $field_type
 *   (optional) The name of a field type. If given, limits the reference check
 *   to fields of the given type. If both $field and $field_type is given but
 *   $field is not the same type as $field_type, an empty array will be
 *   returned.
 *
 * @return
 *   A multidimensional array. The keys are field_name, entity_type,
 *   entity_id and the value is an entity referencing this file.
 *
 * @ingroup file
 */
function file_get_file_references(FileInterface $file, FieldDefinitionInterface $field = NULL, $age = EntityStorageInterface::FIELD_LOAD_REVISION, $field_type = 'file') {
  $references = &drupal_static(__FUNCTION__, array());
  $field_columns = &drupal_static(__FUNCTION__ . ':field_columns', array());

  // Fill the static cache, disregard $field and $field_type for now.
  if (!isset($references[$file->id()][$age])) {
    $references[$file->id()][$age] = array();
    $usage_list = \Drupal::service('file.usage')->listUsage($file);
    $file_usage_list = isset($usage_list['file']) ? $usage_list['file'] : array();
    foreach ($file_usage_list as $entity_type_id => $entity_ids) {
      $entity_type = \Drupal::entityManager()->getDefinition($entity_type_id);
      // The usage table contains usage of every revision. If we are looking
      // for every revision or the entity does not support revisions then
      // every usage is already a match.
      $match_entity_type = $age == EntityStorageInterface::FIELD_LOAD_REVISION || !$entity_type->hasKey('revision');
      $entities = entity_load_multiple($entity_type_id, array_keys($entity_ids));
      foreach ($entities as $entity) {
        $bundle = $entity->bundle();
        // We need to find file fields for this entity type and bundle.
        if (!isset($file_fields[$entity_type_id][$bundle])) {
          $file_fields[$entity_type_id][$bundle] = array();
          // This contains the possible field names.
          foreach ($entity->getFieldDefinitions() as $field_name => $field_definition) {
            // If this is the first time this field type is seen, check
            // whether it references files.
            if (!isset($field_columns[$field_definition->getType()])) {
              $field_columns[$field_definition->getType()] = file_field_find_file_reference_column($field_definition);
            }
            // If the field type does reference files then record it.
            if ($field_columns[$field_definition->getType()]) {
              $file_fields[$entity_type_id][$bundle][$field_name] = $field_columns[$field_definition->getType()];
            }
          }
        }
        foreach ($file_fields[$entity_type_id][$bundle] as $field_name => $field_column) {
          $match = $match_entity_type;
          // If we didn't match yet then iterate over the field items to find
          // the referenced file. This will fail if the usage checked is in a
          // non-current revision because field items are from the current
          // revision.
          if (!$match && ($items = $entity->get($field_name))) {
            foreach ($items as $item) {
              if ($file->id() == $item->{$field_column}) {
                $match = TRUE;
                break;
              }
            }
          }
          if ($match) {
            $references[$file->id()][$age][$field_name][$entity_type_id][$entity->id()] = $entity;
          }
        }
      }
    }
  }
  $return = $references[$file->id()][$age];
  // Filter the static cache down to the requested entries. The usual static
  // cache is very small so this will be very fast.
  if ($field || $field_type) {
    foreach ($return as $field_name => $data) {
      foreach (array_keys($data) as $entity_type_id) {
        $field_storage_definitions = \Drupal::entityManager()->getFieldStorageDefinitions($entity_type_id);
        $current_field = $field_storage_definitions[$field_name];
        if (($field_type && $current_field->getType() != $field_type) || ($field && $field->uuid() != $current_field->uuid())) {
          unset($return[$field_name][$entity_type_id]);
        }
      }
    }
  }
  return $return;
}

/**
 * Implements hook_permission().
 */
function file_permission() {
  $perms = array(
    'access files overview' => array(
      'title' => t('Access the Files overview page'),
      'description' => t('Get an overview of <a href="!url">all files</a>.', array('!url' => url('admin/content/files'))),
    ),
  );

  return $perms;
}

/**
 * Formats human-readable version of file status.
 *
 * @param int $choice
 *   integer Status code.
 * @return string
 *   string Text-represented file status.
 */
function _views_file_status($choice = NULL) {
  $status = array(
    0 => t('Temporary'),
    FILE_STATUS_PERMANENT => t('Permanent'),
  );

  if (isset($choice)) {
    return isset($status[$choice]) ? $status[$choice] : t('Unknown');
  }

  return $status;
}