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EPrints::DataObj::File - a stored file


This class contains the technical metadata associated with a file. A file is a sequence of bytes stored in the storage layer (a "stored object"). Utility methods for storing and retrieving the stored object from the storage layer are made available.

Revision numbers on File work slightly differently to other objects. A File is only revised when it's stored object is changed and not when changes to it's metadata are made.

This class is a subclass of EPrints::DataObj::SubObject.


  • fileid
Unique identifier for this file.
  • rev_number (int)
The number of the current revision of this file.
  • datasetid
Id of the dataset of the parent object.
  • objectid
Id of the parent object.
  • filename
Name of the file (may contain directory separators).
  • mime_type
MIME type of the file (e.g. "image/png").
  • hash
Check sum of the file.
  • hash_type
Name of check sum algorithm used (e.g. "MD5").
  • filesize
Size of the file in bytes.
  • mtime
Last modification time of the file.
  • url
Virtual field for storing the file's URL.
  • data
Virtual field for storing the file's content.


Constructor Methods


$dataobj = EPrints::DataObj::File->new_from_filename( $session, $dataobj, $filename )

Convenience method to get an existing File object for $filename stored in $dataobj.

Returns undef if no such record exists.


$dataobj = EPrints::DataObj::File->create_from_data( $session, $data [, $dataset ] )

Create a new File record using $data.

Private data elements:

  _content - content to pass to [[API:EPrints/DataObj/File#set_file|set_file]].
  _filepath - path to source file used for improved mime-type detection

Class Methods


$thing = EPrints::DataObj::File->get_system_field_info

Core fields.


$dataset = EPrints::DataObj::File->get_dataset_id

Returns the id of the EPrints::DataSet object to which this record belongs.

Object Methods


$new_file = $file->clone( $parent )

Clone the $file object (including contained files) and return the new object.


$success = $file->remove

Delete the stored file.


$file->update( $epdata )


$filename = $file->get_local_copy()

Return the name of a local copy of the file (may be a File::Temp object).

Will retrieve and cache the remote object if necessary.


$success = $file->add_file( $filepath, $filename [, $preserve_path ] )

Read and store the contents of $filepath at $filename.

If $preserve_path is untrue will strip any leading path in $filename.


$bytes = $file->upload( $filehandle, $filename, $filesize [, $preserve_path ] )

Read and store the data from $filehandle at $filename at the next revision number.


Returns the number of bytes read from $filehandle or undef on failure.


$success = $stored->write_copy( $filename )

Write a copy of this file to $filename.

Returns true if the written file contains the same number of bytes as the stored file.


$success = $stored->write_copy_fh( $filehandle )

Write a copy of this file to $filehandle.


$md5 = $stored->generate_md5

Calculates and returns the MD5 for this file.


$digest = $file->generate_sha( [ ALGORITHM ] )

Generate a SHA for this file, see Digest::SHA for a list of supported algorithms. Defaults to "256" (SHA-256).

Returns the hex-encoded digest.


$stored->add_plugin_copy( $plugin, $sourceid )

Add a copy of this file stored using $plugin identified by $sourceid.


$stored->remove_plugin_copy( $plugin )

Remove the copy of this file stored using $plugin.


$success = $stored->get_file( CALLBACK [, $offset, $n ] )

Get the contents of the stored file.

$offset is the position in bytes to start reading from, defaults to 0.

$n is the number of bytes to read, defaults to filesize.


sub {
	my( $buffer ) = @_;

	print $buffer;

	return 1;

Returning 0 from the callback will cause the read to abort.


$content_length = $stored->set_file( CONTENT, $content_length )

Write $content_length bytes from CONTENT to the file object. Updates filesize and hash (you must call commit).

Returns $content_length or undef on failure.

If CONTENT has fewer bytes than $content_length the result is undetermined and a warning will be printed.

CONTENT may be any one of:

Will be called until it returns empty string ("").
sub {
	sysread($fh, my $buffer, 1024);
	return $buffer;
A scalar reference to a string of octets that will be written as-is.
  • GLOB
Will be treated as a file handle and read with sysread() until the eof.


$content_length = $file->set_file_chunk( CONTENT, $content_length, $offset, $total )

Write a chunk of data to the content, overwriting or appending to the existing content. See set_file for CONTENT and $content_length. filesize is updated if $offset + $content_length is greater than the current filesize.

$offset is the starting point (in bytes) to write. $total is the total file size, used to determine where to store the content.

Returns the number of bytes written or undef on failure.



EPrints::DataObj and EPrints::DataSet.


Copyright 2000-2013 University of Southampton.



