file.module in Drupal 10

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

File

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\Environment;
use Drupal\Component\Utility\NestedArray;
use Drupal\Core\Datetime\Entity\DateFormat;
use Drupal\Core\Entity\EntityStorageInterface;
use Drupal\Core\Field\FieldDefinitionInterface;
use Drupal\Core\File\Exception\FileException;
use Drupal\Core\File\Exception\FileExistsException;
use Drupal\Core\File\Exception\FileWriteException;
use Drupal\Core\File\Exception\InvalidStreamWrapperException;
use Drupal\Core\File\FileSystemInterface;
use Drupal\Core\Form\FormStateInterface;
use Drupal\Core\Link;
use Drupal\Core\Messenger\MessengerInterface;
use Drupal\Core\Render\BubbleableMetadata;
use Drupal\Core\Render\Element;
use Drupal\Core\Routing\RouteMatchInterface;
use Drupal\Core\Template\Attribute;
use Drupal\Core\Url;
use Drupal\file\Entity\File;
use Drupal\file\FileInterface;
use Drupal\file\Upload\FileValidationException;
use Drupal\file\Upload\FormUploadedFile;
use Symfony\Component\HttpFoundation\File\Exception\FileException as SymfonyFileException;
use Symfony\Component\HttpFoundation\File\Exception\FormSizeFileException;
use Symfony\Component\HttpFoundation\File\Exception\IniSizeFileException;
use Symfony\Component\HttpFoundation\File\Exception\NoFileException;
use Symfony\Component\HttpFoundation\File\Exception\PartialFileException;

// cspell:ignore abiword
// 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>.', [
        ':field' => Url::fromRoute('help.page', [
          'name' => 'field',
        ])
          ->toString(),
        ':field_ui' => \Drupal::moduleHandler()
          ->moduleExists('field_ui') ? Url::fromRoute('help.page', [
          'name' => 'field_ui',
        ])
          ->toString() : '#',
        ':file_documentation' => 'https://www.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.', [
        ':field_ui' => \Drupal::moduleHandler()
          ->moduleExists('field_ui') ? Url::fromRoute('help.page', [
          'name' => 'field_ui',
        ])
          ->toString() : '#',
      ]) . '</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>.', [
        ':file-system' => Url::fromRoute('system.file_system_settings')
          ->toString(),
        ':system-help' => Url::fromRoute('help.page', [
          'name' => 'system',
        ])
          ->toString(),
      ]) . '</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_field_widget_info_alter().
 */
function file_field_widget_info_alter(array &$info) {

  // Allows using the 'uri' widget for the 'file_uri' field type, which uses it
  // as the default widget.
  // @see \Drupal\file\Plugin\Field\FieldType\FileUriItem
  $info['uri']['field_types'][] = 'file_uri';
}

/**
 * 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 array $validators
 *   (optional) An 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 callback functions will be called in the
 *   order specified in the array, then the hook hook_file_validate()
 *   will be invoked so other modules can validate the new file.
 *
 * @return array
 *   An array containing validation error messages.
 *
 * @see hook_file_validate()
 */
function file_validate(FileInterface $file, $validators = []) {

  // Call the validation functions specified by this function's caller.
  $errors = [];
  foreach ($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.
  $errors = array_merge($errors, \Drupal::moduleHandler()
    ->invokeAll('file_validate', [
    $file,
  ]));

  // Ensure the file does not contain a malicious extension. At this point
  // \Drupal\file\Upload\FileUploadHandler::handleFileUpload() will have munged
  // the file so it does not contain a malicious extension. Contributed and
  // custom code that calls this method needs to take similar steps if they need
  // to permit files with malicious extensions to be uploaded.
  if (empty($errors) && !\Drupal::config('system.file')
    ->get('allow_insecure_uploads') && preg_match(FileSystemInterface::INSECURE_EXTENSION_REGEX, $file
    ->getFilename())) {
    $errors[] = t('For security reasons, your upload has been rejected.');
  }
  return $errors;
}

/**
 * Checks for files with names longer than can be stored in the database.
 *
 * @param \Drupal\file\FileInterface $file
 *   A file entity.
 *
 * @return array
 *   An empty array if the file name length is smaller than the limit or an
 *   array containing an error message if it's not or is empty.
 */
function file_validate_name_length(FileInterface $file) {
  $errors = [];
  if (!$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 string $extensions
 *   A string with a space separated list of allowed extensions.
 *
 * @return array
 *   An empty array if the file extension is allowed or an array containing an
 *   error message if it's not.
 *
 * @see hook_file_validate()
 */
function file_validate_extensions(FileInterface $file, $extensions) {
  $errors = [];
  $regex = '/\\.(' . preg_replace('/ +/', '|', preg_quote($extensions)) . ')$/i';

  // Filename may differ from the basename, for instance in case files migrated
  // from D7 file entities. Because of that new files are saved temporarily with
  // a generated file name, without the original extension, we will use the
  // generated filename property for extension validation only in case of
  // temporary files; and use the file system file name in case of permanent
  // files.
  $subject = $file
    ->isTemporary() ? $file
    ->getFilename() : $file
    ->getFileUri();
  if (!preg_match($regex, $subject)) {
    $errors[] = t('Only files with the following extensions are allowed: %files-allowed.', [
      '%files-allowed' => $extensions,
    ]);
  }
  return $errors;
}

/**
 * Checks that the file's size is below certain limits.
 *
 * @param \Drupal\file\FileInterface $file
 *   A file entity.
 * @param int $file_limit
 *   (optional) The maximum file size in bytes. Zero (the default) indicates
 *   that no limit should be enforced.
 * @param int $user_limit
 *   (optional) The maximum number of bytes the user is allowed. Zero (the
 *   default) indicates that no limit should be enforced.
 *
 * @return array
 *   An empty array if the file size is below limits or an array containing an
 *   error message if it's not.
 *
 * @see hook_file_validate()
 */
function file_validate_size(FileInterface $file, $file_limit = 0, $user_limit = 0) {
  $user = \Drupal::currentUser();
  $errors = [];
  if ($file_limit && $file
    ->getSize() > $file_limit) {
    $errors[] = t('The file is %filesize exceeding the maximum file size of %maxsize.', [
      '%filesize' => format_size($file
        ->getSize()),
      '%maxsize' => format_size($file_limit),
    ]);
  }

  // Save a query by only calling spaceUsed() when a limit is provided.
  if ($user_limit && \Drupal::entityTypeManager()
    ->getStorage('file')
    ->spaceUsed($user
    ->id()) + $file
    ->getSize() > $user_limit) {
    $errors[] = t('The file is %filesize which would exceed your disk quota of %quota.', [
      '%filesize' => format_size($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 array
 *   An empty array if the file is a valid image or an array containing an error
 *   message if it's not.
 *
 * @see hook_file_validate()
 */
function file_validate_is_image(FileInterface $file) {
  $errors = [];
  $image_factory = \Drupal::service('image.factory');
  $image = $image_factory
    ->get($file
    ->getFileUri());
  if (!$image
    ->isValid()) {
    $supported_extensions = $image_factory
      ->getSupportedExtensions();
    $errors[] = t('The image file is invalid or the image type is not allowed. Allowed types: %types', [
      '%types' => implode(', ', $supported_extensions),
    ]);
  }
  return $errors;
}

/**
 * Verifies that image dimensions are within the specified maximum and minimum.
 *
 * Non-image files will be ignored. If an 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 string|int $maximum_dimensions
 *   (optional) A string in the form WIDTHxHEIGHT; for example, '640x480' or
 *   '85x85'. If an image toolkit is installed, the image will be resized down
 *   to these dimensions. A value of zero (the default) indicates no restriction
 *   on size, so no resizing will be attempted.
 * @param string|int $minimum_dimensions
 *   (optional) A string in the form WIDTHxHEIGHT. This will check that the
 *   image meets a minimum size. A value of zero (the default) indicates that
 *   there is no restriction on size.
 *
 * @return array
 *   An empty array if the file meets the specified dimensions, was resized
 *   successfully to meet those requirements or is not an image. If the image
 *   does not meet the requirements or an attempt to resize it fails, an array
 *   containing the error message will be returned.
 *
 * @see hook_file_validate()
 */
function file_validate_image_resolution(FileInterface $file, $maximum_dimensions = 0, $minimum_dimensions = 0) {
  $errors = [];

  // Check first that the file is an image.
  $image_factory = \Drupal::service('image.factory');
  $image = $image_factory
    ->get($file
    ->getFileUri());
  if ($image
    ->isValid()) {
    $scaling = FALSE;
    if ($maximum_dimensions) {

      // Check that it is smaller than the given dimensions.
      [
        $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)) {
          $scaling = TRUE;
          $image
            ->save();
          if (!empty($width) && !empty($height)) {
            $message = t('The image was resized to fit within the maximum allowed dimensions of %dimensions pixels. The new dimensions of the resized image are %new_widthx%new_height pixels.', [
              '%dimensions' => $maximum_dimensions,
              '%new_width' => $image
                ->getWidth(),
              '%new_height' => $image
                ->getHeight(),
            ]);
          }
          elseif (empty($width)) {
            $message = t('The image was resized to fit within the maximum allowed height of %height pixels. The new dimensions of the resized image are %new_widthx%new_height pixels.', [
              '%height' => $height,
              '%new_width' => $image
                ->getWidth(),
              '%new_height' => $image
                ->getHeight(),
            ]);
          }
          elseif (empty($height)) {
            $message = t('The image was resized to fit within the maximum allowed width of %width pixels. The new dimensions of the resized image are %new_widthx%new_height pixels.', [
              '%width' => $width,
              '%new_width' => $image
                ->getWidth(),
              '%new_height' => $image
                ->getHeight(),
            ]);
          }
          \Drupal::messenger()
            ->addStatus($message);
        }
        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.
      [
        $width,
        $height,
      ] = explode('x', $minimum_dimensions);
      if ($image
        ->getWidth() < $width || $image
        ->getHeight() < $height) {
        if ($scaling) {
          $errors[] = t('The resized image is too small. The minimum dimensions are %dimensions pixels and after resizing, the image size will be %widthx%height pixels.', [
            '%dimensions' => $minimum_dimensions,
            '%width' => $image
              ->getWidth(),
            '%height' => $image
              ->getHeight(),
          ]);
        }
        else {
          $errors[] = t('The image is too small. The minimum dimensions are %dimensions pixels and the image size is %widthx%height pixels.', [
            '%dimensions' => $minimum_dimensions,
            '%width' => $image
              ->getWidth(),
            '%height' => $image
              ->getHeight(),
          ]);
        }
      }
    }
  }
  return $errors;
}

/**
 * Examines a file entity and returns appropriate content headers for download.
 *
 * @param \Drupal\file\FileInterface $file
 *   A file entity.
 *
 * @return array
 *   An associative array of headers, as expected by
 *   \Symfony\Component\HttpFoundation\StreamedResponse.
 */
function file_get_content_headers(FileInterface $file) {
  return [
    'Content-Type' => $file
      ->getMimeType(),
    'Content-Length' => $file
      ->getSize(),
    'Cache-Control' => 'private',
  ];
}

/**
 * Implements hook_theme().
 */
function file_theme() {
  return [
    // From file.module.
    'file_link' => [
      'variables' => [
        'file' => NULL,
        'description' => NULL,
        'attributes' => [],
      ],
    ],
    'file_managed_file' => [
      'render element' => 'element',
    ],
    'file_audio' => [
      'variables' => [
        'files' => [],
        'attributes' => NULL,
      ],
    ],
    'file_video' => [
      'variables' => [
        'files' => [],
        'attributes' => NULL,
      ],
    ],
    // From file.field.inc.
    'file_widget_multiple' => [
      'render element' => 'element',
      'file' => 'file.field.inc',
    ],
    'file_upload_help' => [
      'variables' => [
        'description' => NULL,
        'upload_validators' => NULL,
        'cardinality' => NULL,
      ],
      '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\FileRepositoryInterface $file_repository */
  $file_repository = \Drupal::service('file.repository');
  $file = $file_repository
    ->loadByUri($uri);
  if (!$file) {
    return;
  }

  // Find out if a temporary file is still used in the system.
  if ($file
    ->isTemporary()) {
    $usage = \Drupal::service('file.usage')
      ->listUsage($file);
    if (empty($usage) && $file
      ->getOwnerId() != \Drupal::currentUser()
      ->id()) {

      // Deny access to temporary files without usage that are not owned by the
      // same user. This prevents the security issue that a private file that
      // was protected by field permissions becomes available after its usage
      // was removed and before it is actually deleted from the file system.
      // Modules that depend on this behavior should make the file permanent
      // instead.
      return -1;
    }
  }

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

  /** @var \Drupal\Core\StreamWrapper\StreamWrapperManagerInterface $stream_wrapper_manager */
  $stream_wrapper_manager = \Drupal::service('stream_wrapper_manager');

  // 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')
      ->accessCheck(FALSE)
      ->condition('status', FileInterface::STATUS_PERMANENT, '<>')
      ->condition('changed', \Drupal::time()
      ->getRequestTime() - $age, '<')
      ->range(0, 100)
      ->execute();
    $files = $file_storage
      ->loadMultiple($fids);
    foreach ($files as $file) {
      $references = \Drupal::service('file.usage')
        ->listUsage($file);
      if (empty($references)) {
        if (!file_exists($file
          ->getFileUri())) {
          if (!$stream_wrapper_manager
            ->isValidUri($file
            ->getFileUri())) {
            \Drupal::logger('file system')
              ->warning('Temporary file "%path" that was deleted during garbage collection did not exist on the filesystem. This could be caused by a missing stream wrapper.', [
              '%path' => $file
                ->getFileUri(),
            ]);
          }
          else {
            \Drupal::logger('file system')
              ->warning('Temporary file "%path" that was deleted during garbage collection did not exist on the filesystem.', [
              '%path' => $file
                ->getFileUri(),
            ]);
          }
        }

        // Delete the file entity. If the file does not exist, this will
        // generate a second notice in the watchdog.
        $file
          ->delete();
      }
      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.', [
          '%path' => $file
            ->getFileUri(),
          '%modules' => implode(', ', array_keys($references)),
        ]);
      }
    }
  }
}

/**
 * Saves form file uploads.
 *
 * 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 array $element
 *   The FAPI element whose values are being saved.
 * @param \Drupal\Core\Form\FormStateInterface $form_state
 *   The current state of the form.
 * @param null|int $delta
 *   (optional) The delta of the file to return the file entity.
 *   Defaults to NULL.
 * @param int $replace
 *   (optional) The replace behavior when the destination file already exists.
 *   Possible values include:
 *   - FileSystemInterface::EXISTS_REPLACE: Replace the existing file.
 *   - FileSystemInterface::EXISTS_RENAME: (default) Append
 *     _{incrementing number} until the filename is unique.
 *   - FileSystemInterface::EXISTS_ERROR: Do nothing and return FALSE.
 *
 * @return array|\Drupal\file\FileInterface|null|false
 *   An array of file entities or a single file entity if $delta != NULL. Each
 *   array element contains the file entity if the upload succeeded or FALSE if
 *   there was an error. Function returns NULL if no file was uploaded.
 *
 * @internal
 *   This function is internal, and may be removed in a minor version release.
 *   It wraps file_save_upload() to allow correct error handling in forms.
 *   Contrib and custom code should not call this function, they should use the
 *   managed file upload widgets in core.
 *
 * @see https://www.drupal.org/project/drupal/issues/3069020
 * @see https://www.drupal.org/project/drupal/issues/2482783
 */
function _file_save_upload_from_form(array $element, FormStateInterface $form_state, $delta = NULL, $replace = FileSystemInterface::EXISTS_RENAME) {

  // Get all errors set before calling this method. This will also clear them
  // from the messenger service.
  $errors_before = \Drupal::messenger()
    ->deleteByType(MessengerInterface::TYPE_ERROR);
  $upload_location = $element['#upload_location'] ?? FALSE;
  $upload_name = implode('_', $element['#parents']);
  $upload_validators = $element['#upload_validators'] ?? [];
  $result = file_save_upload($upload_name, $upload_validators, $upload_location, $delta, $replace);

  // Get new errors that are generated while trying to save the upload. This
  // will also clear them from the messenger service.
  $errors_new = \Drupal::messenger()
    ->deleteByType(MessengerInterface::TYPE_ERROR);
  if (!empty($errors_new)) {
    if (count($errors_new) > 1) {

      // Render multiple errors into a single message.
      // This is needed because only one error per element is supported.
      $render_array = [
        'error' => [
          '#markup' => t('One or more files could not be uploaded.'),
        ],
        'item_list' => [
          '#theme' => 'item_list',
          '#items' => $errors_new,
        ],
      ];
      $error_message = \Drupal::service('renderer')
        ->renderPlain($render_array);
    }
    else {
      $error_message = reset($errors_new);
    }
    $form_state
      ->setError($element, $error_message);
  }

  // Ensure that errors set prior to calling this method are still shown to the
  // user.
  if (!empty($errors_before)) {
    foreach ($errors_before as $error) {
      \Drupal::messenger()
        ->addError($error);
    }
  }
  return $result;
}

/**
 * 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.
 *
 * Note that this function does not support correct form error handling. The
 * file upload widgets in core do support this. It is advised to use these in
 * any custom form, instead of calling this function.
 *
 * @param string $form_field_name
 *   A string that is the associative array key of the upload form element in
 *   the form array.
 * @param array $validators
 *   (optional) An associative array of callback functions used to validate the
 *   file. See file_validate() for a full discussion of the array format.
 *   If the array is empty, it will be set up to call file_validate_extensions()
 *   with a safe list of extensions, as follows: "jpg jpeg gif png txt doc
 *   xls pdf ppt pps odt ods odp". To allow all extensions, you must explicitly
 *   set this array to ['file_validate_extensions' => '']. (Beware: this is not
 *   safe and should only be allowed for trusted users, if at all.)
 * @param string|false $destination
 *   (optional) A string containing the URI that the file should be copied to.
 *   This must be a stream wrapper URI. If this value is omitted or set to
 *   FALSE, Drupal's temporary files scheme will be used ("temporary://").
 * @param null|int $delta
 *   (optional) The delta of the file to return the file entity.
 *   Defaults to NULL.
 * @param int $replace
 *   (optional) The replace behavior when the destination file already exists.
 *   Possible values include:
 *   - FileSystemInterface::EXISTS_REPLACE: Replace the existing file.
 *   - FileSystemInterface::EXISTS_RENAME: (default) Append
 *     _{incrementing number} until the filename is unique.
 *   - FileSystemInterface::EXISTS_ERROR: Do nothing and return FALSE.
 *
 * @return array|\Drupal\file\FileInterface|null|false
 *   An array of file entities or a single file entity if $delta != NULL. Each
 *   array element contains the file entity if the upload succeeded or FALSE if
 *   there was an error. Function returns NULL if no file was uploaded.
 *
 * @see _file_save_upload_from_form()
 *
 * @todo: move this logic to a service in https://www.drupal.org/node/2244513.
 */
function file_save_upload($form_field_name, $validators = [], $destination = FALSE, $delta = NULL, $replace = FileSystemInterface::EXISTS_RENAME) {
  static $upload_cache;
  $all_files = \Drupal::request()->files
    ->get('files', []);

  // Make sure there's an upload to process.
  if (empty($all_files[$form_field_name])) {
    return NULL;
  }
  $file_upload = $all_files[$form_field_name];

  // 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 = [
      $file_upload,
    ];
  }
  if ($destination === FALSE || $destination === NULL) {
    $destination = 'temporary://';
  }

  /** @var \Drupal\file\Upload\FileUploadHandler $file_upload_handler */
  $file_upload_handler = \Drupal::service('file.upload_handler');

  /** @var \Drupal\Core\Render\RendererInterface $renderer */
  $renderer = \Drupal::service('renderer');
  $files = [];

  /** @var \Symfony\Component\HttpFoundation\File\UploadedFile $uploaded_file */
  foreach ($uploaded_files as $i => $uploaded_file) {
    try {
      $form_uploaded_file = new FormUploadedFile($uploaded_file);
      $result = $file_upload_handler
        ->handleFileUpload($form_uploaded_file, $validators, $destination, $replace);
      $file = $result
        ->getFile();

      // If the filename has been modified, let the user know.
      if ($result
        ->isRenamed()) {
        if ($result
          ->isSecurityRename()) {
          $message = t('For security reasons, your upload has been renamed to %filename.', [
            '%filename' => $file
              ->getFilename(),
          ]);
        }
        else {
          $message = t('Your upload has been renamed to %filename.', [
            '%filename' => $file
              ->getFilename(),
          ]);
        }
        \Drupal::messenger()
          ->addStatus($message);
      }
      $files[$i] = $file;
    } catch (FileExistsException $e) {
      \Drupal::messenger()
        ->addError(t('Destination file "%file" exists', [
        '%file' => $destination . $uploaded_file
          ->getFilename(),
      ]));
      $files[$i] = FALSE;
    } catch (InvalidStreamWrapperException $e) {
      \Drupal::messenger()
        ->addError(t('The file could not be uploaded because the destination "%destination" is invalid.', [
        '%destination' => $destination,
      ]));
      $files[$i] = FALSE;
    } catch (IniSizeFileException|FormSizeFileException $e) {
      \Drupal::messenger()
        ->addError(t('The file %file could not be saved because it exceeds %maxsize, the maximum allowed size for uploads.', [
        '%file' => $uploaded_file
          ->getFilename(),
        '%maxsize' => format_size(Environment::getUploadMaxSize()),
      ]));
      $files[$i] = FALSE;
    } catch (PartialFileException|NoFileException $e) {
      \Drupal::messenger()
        ->addError(t('The file %file could not be saved because the upload did not complete.', [
        '%file' => $uploaded_file
          ->getFilename(),
      ]));
      $files[$i] = FALSE;
    } catch (SymfonyFileException $e) {
      \Drupal::messenger()
        ->addError(t('The file %file could not be saved. An unknown error has occurred.', [
        '%file' => $uploaded_file
          ->getFilename(),
      ]));
      $files[$i] = FALSE;
    } catch (FileValidationException $e) {
      $message = [
        'error' => [
          '#markup' => t('The specified file %name could not be uploaded.', [
            '%name' => $e
              ->getFilename(),
          ]),
        ],
        'item_list' => [
          '#theme' => 'item_list',
          '#items' => $e
            ->getErrors(),
        ],
      ];

      // @todo Add support for render arrays in
      // \Drupal\Core\Messenger\MessengerInterface::addMessage()?
      // @see https://www.drupal.org/node/2505497.
      \Drupal::messenger()
        ->addError($renderer
        ->renderPlain($message));
      $files[$i] = FALSE;
    } catch (FileWriteException $e) {
      \Drupal::messenger()
        ->addError(t('File upload error. Could not move uploaded file.'));
      \Drupal::logger('file')
        ->notice('Upload error. Could not move uploaded file %file to destination %destination.', [
        '%file' => $uploaded_file
          ->getClientOriginalName(),
        '%destination' => $destination . '/' . $uploaded_file
          ->getClientOriginalName(),
      ]);
      $files[$i] = FALSE;
    } catch (FileException $e) {
      \Drupal::messenger()
        ->addError(t('The file %filename could not be uploaded because the name is invalid.', [
        '%filename' => $uploaded_file
          ->getClientOriginalName(),
      ]));
      $files[$i] = FALSE;
    }
  }

  // Add files to the cache.
  $upload_cache[$form_field_name] = $files;
  return isset($delta) ? $files[$delta] : $files;
}

/**
 * Determines the preferred upload progress implementation.
 *
 * @return string|false
 *   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. APCu only supports one at a time.
    if (extension_loaded('uploadprogress')) {
      $implementation = 'uploadprogress';
    }
  }
  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 $options, BubbleableMetadata $bubbleable_metadata) {
  $token_service = \Drupal::token();
  $url_options = [
    'absolute' => TRUE,
  ];
  if (isset($options['langcode'])) {
    $url_options['language'] = \Drupal::languageManager()
      ->getLanguage($options['langcode']);
    $langcode = $options['langcode'];
  }
  else {
    $langcode = NULL;
  }
  $replacements = [];
  if ($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] = $file
            ->getFilename();
          break;
        case 'path':
          $replacements[$original] = $file
            ->getFileUri();
          break;
        case 'mime':
          $replacements[$original] = $file
            ->getMimeType();
          break;
        case 'size':
          $replacements[$original] = format_size($file
            ->getSize());
          break;
        case 'url':

          // Ideally, this would use return a relative URL, but because tokens
          // are also often used in e-mails, it's better to keep absolute file
          // URLs. The 'url.site' cache context is associated to ensure the
          // correct absolute URL is used in case of a multisite setup.
          $replacements[$original] = $file
            ->createFileUrl(FALSE);
          $bubbleable_metadata
            ->addCacheContexts([
            'url.site',
          ]);
          break;

        // These tokens are default variations on the chained tokens handled below.
        case 'created':
          $date_format = DateFormat::load('medium');
          $bubbleable_metadata
            ->addCacheableDependency($date_format);
          $replacements[$original] = \Drupal::service('date.formatter')
            ->format($file
            ->getCreatedTime(), 'medium', '', NULL, $langcode);
          break;
        case 'changed':
          $date_format = DateFormat::load('medium');
          $bubbleable_metadata = $bubbleable_metadata
            ->addCacheableDependency($date_format);
          $replacements[$original] = \Drupal::service('date.formatter')
            ->format($file
            ->getChangedTime(), 'medium', '', NULL, $langcode);
          break;
        case 'owner':
          $owner = $file
            ->getOwner();
          $bubbleable_metadata
            ->addCacheableDependency($owner);
          $name = $owner
            ->label();
          $replacements[$original] = $name;
          break;
      }
    }
    if ($date_tokens = $token_service
      ->findWithPrefix($tokens, 'created')) {
      $replacements += $token_service
        ->generate('date', $date_tokens, [
        'date' => $file
          ->getCreatedTime(),
      ], $options, $bubbleable_metadata);
    }
    if ($date_tokens = $token_service
      ->findWithPrefix($tokens, 'changed')) {
      $replacements += $token_service
        ->generate('date', $date_tokens, [
        'date' => $file
          ->getChangedTime(),
      ], $options, $bubbleable_metadata);
    }
    if (($owner_tokens = $token_service
      ->findWithPrefix($tokens, 'owner')) && $file
      ->getOwner()) {
      $replacements += $token_service
        ->generate('user', $owner_tokens, [
        'user' => $file
          ->getOwner(),
      ], $options, $bubbleable_metadata);
    }
  }
  return $replacements;
}

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

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

/**
 * Form submission handler for upload / remove buttons of managed_file elements.
 *
 * @see \Drupal\file\Element\ManagedFile::processManagedFile()
 */
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
    ->getTriggeringElement()['#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 \Drupal\file\Element\ManagedFile::valueCallback()
  // 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']) {
      $remove_fids = [];
      foreach (Element::children($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;
      $fids = [];
    }
    foreach ($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 $form_state->getValues() and FormState::$input to reflect
    // that the file has been removed, so that the form is rebuilt correctly.
    // $form_state->getValues() must be updated in case additional submit
    // handlers run, and for form building functions that run during the
    // rebuild, such as when the managed_file element is part of a field widget.
    // FormState::$input must be updated so that
    // \Drupal\file\Element\ManagedFile::valueCallback() has correct information
    // during the rebuild.
    $form_state
      ->setValueForElement($element['fids'], implode(' ', $fids));
    NestedArray::setValue($form_state
      ->getUserInput(), $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 calling $form_state->disableRedirect() would suffice.
  // However, we choose to always rebuild, to keep the form processing workflow
  // consistent between the two buttons.
  $form_state
    ->setRebuild();
}

/**
 * Saves any files that have been uploaded into a managed_file element.
 *
 * @param array $element
 *   The FAPI element whose values are being saved.
 * @param \Drupal\Core\Form\FormStateInterface $form_state
 *   The current state of the form.
 *
 * @return array|false
 *   An array of file entities for each file that was saved, keyed by its file
 *   ID. Each array element contains a file entity. Function returns FALSE if
 *   upload directory could not be created or no files were uploaded.
 */
function file_managed_file_save_upload($element, FormStateInterface $form_state) {
  $upload_name = implode('_', $element['#parents']);
  $all_files = \Drupal::request()->files
    ->get('files', []);
  if (empty($all_files[$upload_name])) {
    return FALSE;
  }
  $file_upload = $all_files[$upload_name];
  $destination = $element['#upload_location'] ?? NULL;
  if (isset($destination) && !\Drupal::service('file_system')
    ->prepareDirectory($destination, FileSystemInterface::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.', [
      '%directory' => $destination,
      '%name' => $element['#field_name'],
    ]);
    $form_state
      ->setError($element, 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 (!($files = _file_save_upload_from_form($element, $form_state))) {
      \Drupal::logger('file')
        ->notice('The file upload failed. %upload', [
        '%upload' => $upload_name,
      ]);
      return [];
    }

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

/**
 * 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'];
  $variables['attributes'] = [];
  if (isset($element['#id'])) {
    $variables['attributes']['id'] = $element['#id'];
  }
  if (!empty($element['#attributes']['class'])) {
    $variables['attributes']['class'] = (array) $element['#attributes']['class'];
  }
}

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

  /** @var \Drupal\Core\File\FileUrlGeneratorInterface $file_url_generator */
  $file_url_generator = \Drupal::service('file_url_generator');
  $url = $file_url_generator
    ->generate($file
    ->getFileUri());
  $mime_type = $file
    ->getMimeType();
  $options['attributes']['type'] = $mime_type;

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

  // Classes to add to the file field for icons.
  $classes = [
    'file',
    // Add a specific class for each and every mime type.
    'file--mime-' . strtr($mime_type, [
      '/' => '-',
      '.' => '-',
    ]),
    // Add a more general class for groups of well known MIME types.
    'file--' . file_icon_class($mime_type),
  ];

  // Set file classes to the options array.
  $variables['attributes'] = new Attribute($variables['attributes']);
  $variables['attributes']
    ->addClass($classes);
  $variables['file_size'] = format_size($file
    ->getSize() ?? 0);
  $variables['link'] = Link::fromTextAndUrl($link_text, $url
    ->mergeOptions($options))
    ->toRenderable();
}

/**
 * Gets a class for the icon for a MIME type.
 *
 * @param string $mime_type
 *   A MIME type.
 *
 * @return string
 *   A class associated with the file.
 */
function file_icon_class($mime_type) {

  // Search for a group with the files MIME type.
  $generic_mime = (string) file_icon_map($mime_type);
  if (!empty($generic_mime)) {
    return $generic_mime;
  }

  // Use generic icons for each category that provides such icons.
  foreach ([
    'audio',
    'image',
    'text',
    'video',
  ] as $category) {
    if (strpos($mime_type, $category) === 0) {
      return $category;
    }
  }

  // If there's no generic icon for the type the general class.
  return 'general';
}

/**
 * Determines the generic icon MIME package based on a file's MIME type.
 *
 * @param string $mime_type
 *   A MIME type.
 *
 * @return string|false
 *   The generic icon MIME package expected for this file.
 */
function file_icon_map($mime_type) {
  switch ($mime_type) {

    // 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';

    // Acrobat types
    case 'application/pdf':
    case 'application/x-pdf':
    case 'applications/vnd.pdf':
    case 'text/pdf':
    case 'text/x-pdf':
      return 'application-pdf';
    default:
      return FALSE;
  }
}

/**
 * Retrieves a list of references to a file.
 *
 * @param \Drupal\file\FileInterface $file
 *   A file entity.
 * @param \Drupal\Core\Field\FieldDefinitionInterface|null $field
 *   (optional) A field definition to be used for this check. If given,
 *   limits the reference check to the given field. Defaults to NULL.
 * @param int $age
 *   (optional) A constant that specifies which references to count. Use
 *   EntityStorageInterface::FIELD_LOAD_REVISION (the default) to retrieve all
 *   references within all revisions or
 *   EntityStorageInterface::FIELD_LOAD_CURRENT to retrieve references only in
 *   the current revisions of all entities that have references to this file.
 * @param string $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 are given but
 *   $field is not the same type as $field_type, an empty array will be
 *   returned. Defaults to 'file'.
 *
 * @return array
 *   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__, []);
  $field_columns =& drupal_static(__FUNCTION__ . ':field_columns', []);

  // Fill the static cache, disregard $field and $field_type for now.
  if (!isset($references[$file
    ->id()][$age])) {
    $references[$file
      ->id()][$age] = [];
    $usage_list = \Drupal::service('file.usage')
      ->listUsage($file);
    $file_usage_list = $usage_list['file'] ?? [];
    foreach ($file_usage_list as $entity_type_id => $entity_ids) {
      $entities = \Drupal::entityTypeManager()
        ->getStorage($entity_type_id)
        ->loadMultiple(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] = [];

          // 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) {

          // Iterate over the field items to find the referenced file and field
          // name. This will fail if the usage checked is in a non-current
          // revision because field items are from the current
          // revision.
          // We also iterate over all translations because a file can be linked
          // to a language other than the default.
          foreach ($entity
            ->getTranslationLanguages() as $langcode => $language) {
            foreach ($entity
              ->getTranslation($langcode)
              ->get($field_name) as $item) {
              if ($file
                ->id() == $item->{$field_column}) {
                $references[$file
                  ->id()][$age][$field_name][$entity_type_id][$entity
                  ->id()] = $entity;
                break;
              }
            }
          }
        }
      }
    }
  }
  $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.
  $entity_field_manager = \Drupal::service('entity_field.manager');
  if ($field || $field_type) {
    foreach ($return as $field_name => $data) {
      foreach (array_keys($data) as $entity_type_id) {
        $field_storage_definitions = $entity_field_manager
          ->getFieldStorageDefinitions($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;
}

Functions

Name	Description
file_cron	Implements hook_cron().
file_field_widget_info_alter	Implements hook_field_widget_info_alter().
file_file_download	Implements hook_file_download().
file_file_predelete	Implements hook_ENTITY_TYPE_predelete() for file entities.
file_get_content_headers	Examines a file entity and returns appropriate content headers for download.
file_get_file_references	Retrieves a list of references to a file.
file_help	Implements hook_help().
file_icon_class	Gets a class for the icon for a MIME type.
file_icon_map	Determines the generic icon MIME package based on a file's MIME type.
file_managed_file_save_upload	Saves any files that have been uploaded into a managed_file element.
file_managed_file_submit	Form submission handler for upload / remove buttons of managed_file elements.
file_progress_implementation	Determines the preferred upload progress implementation.
file_save_upload	Saves file uploads to a new location.
file_theme	Implements hook_theme().
file_tokens	Implements hook_tokens().
file_token_info	Implements hook_token_info().
file_validate	Checks that a file meets the criteria specified by the validators.
file_validate_extensions	Checks that the filename ends with an allowed extension.
file_validate_image_resolution	Verifies that image dimensions are within the specified maximum and minimum.
file_validate_is_image	Checks that the file is recognized as a valid image.
file_validate_name_length	Checks for files with names longer than can be stored in the database.
file_validate_size	Checks that the file's size is below certain limits.
template_preprocess_file_link	Prepares variables for file link templates.
template_preprocess_file_managed_file	Prepares variables for file form widget templates.
_file_save_upload_from_form	Saves form file uploads.