API:EPrints/Storage - Revision history

Tdb01r at 13:34, 25 July 2013

2013-07-25T13:34:21Z

← Older revision		Revision as of 13:34, 25 July 2013
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	<!-- Pod2Wiki=head_name -->		<!-- Pod2Wiki=head_name -->
	==NAME==		==NAME==
	EPrints::Storage - manage data streams in ~~the~~ storage devices		EPrints::Storage - manage data streams in storage devices (storage layer)

	<!-- Edit below this comment -->		<!-- Edit below this comment -->
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	<source lang="perl">my $store = $repository->storage();		<source lang="perl">my $store = $repository->storage();

			$str = "Hello, World!";
			open(my $fh, "<", \$str);
			$f = sub {
			read($fh, my $buffer, 6); # just to demonstrate!
			return $buffer;
			};
	$store->store(		$store->store(
	$fileobj, # file object		$fileobj, # file object
	~~"diddle.pdf"~~, # ~~filename~~		$f, # callback
	~~$fh~~ # ~~file handle~~		1024, # offset
	);</source>		);</source>

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	This module is the storage control layer which uses [[API:EPrints/Plugin/Storage\|EPrints::Plugin::Storage]] plugins to support various storage back-ends. It enables the storage, retrieval and deletion of data streams. The maximum size of a stream is dependent on the back-end storage mechanism.		This module is the storage control layer which uses [[API:EPrints/Plugin/Storage\|EPrints::Plugin::Storage]] plugins to support various storage back-ends. It enables the storage, retrieval and deletion of data streams. The maximum size of a stream is dependent on the back-end storage mechanism.

	Storage works on [[API:EPrints/DataObj/File\|EPrints::DataObj::File]] objects, which record the size of the data stream and where it has been stored. Unless a specific storage back-end is used where a file is stored depends on the storage policy~~, by default~~ located in ''lib/storage/default.xml'':		Storage works on [[API:EPrints/DataObj/File\|EPrints::DataObj::File]] objects, which record the size of the data stream and where it has been stored. Unless a specific storage back-end is used, where a file is stored depends on the storage policy which is located in ''lib/storage/default.xml'':

	<source lang="xml"><store xmlns="http://eprints.org/ep3/storage" xmlns:epc="http://eprints.org/ep3/control">		<source lang="xml"><store xmlns="http://eprints.org/ep3/storage" xmlns:epc="http://eprints.org/ep3/control">
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	</store></source>		</store></source>

	The storage policy is a EP-script file that resolves to a list of one or more "plugin" elements. When storing, all matching plugins will be given the data stream to store (i.e. multiple copies). When retrieving, the first plugin to be successfully opened for reading will be used. The item context used ~~within~~ the storage policy is the [[API:EPrints/DataObj/File\|EPrints::DataObj::File]]~~, which may only contain partial information~~.		The storage policy is a EP-script file that resolves to a list of one or more "plugin" elements. When storing, all matching plugins will be given the data stream to store (i.e. multiple copies). When retrieving, the first plugin to be successfully opened for reading will be used. The item context used when the storage policy is evaluated is the [[API:EPrints/DataObj/File\|EPrints::DataObj::File]].

			<!-- Edit below this comment -->


			<!-- Pod2Wiki= -->
			<!-- Pod2Wiki=head_callbacks -->
			===Callbacks===
			Writing to and retrieving from data streams makes use of callback functions. This allows data to be streamed (to avoid memory overheads) and for flexibility in where data is going.

			For details on the callback API see [[API:EPrints/DataObj/File#get_file\|EPrints::DataObj::File/get_file]] and [[API:EPrints/DataObj/File#set_file\|EPrints::DataObj::File/set_file]] for retrieving and writing respectively.

	<!-- Edit below this comment -->		<!-- Edit below this comment -->

Tdb01r at 09:51, 25 July 2013

2013-07-25T09:51:00Z

Show changes

Simon.mcleish@gmail.com: /* close_write */ Reminder that this is an alternative to store.

2013-02-20T12:41:34Z

close_write: Reminder that this is an alternative to store.

← Older revision		Revision as of 12:41, 20 February 2013
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	<!-- Edit below this comment -->		<!-- Edit below this comment -->
			This, along with open_write and write, is an alternative to the store method.

	<!-- Pod2Wiki= -->		<!-- Pod2Wiki= -->
	<!-- Pod2Wiki=head_copyright -->		<!-- Pod2Wiki=head_copyright -->

	==COPYRIGHT==		==COPYRIGHT==
	Copyright 2000-2011 University of Southampton.		Copyright 2000-2011 University of Southampton.

Simon.mcleish@gmail.com: /* open_write */ Reminder that this is an alternative to store.

2013-02-20T12:41:07Z

open_write: Reminder that this is an alternative to store.

← Older revision		Revision as of 12:41, 20 February 2013
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	<!-- Edit below this comment -->		<!-- Edit below this comment -->
			This, along with open_write and close_write, is an alternative to the store method.

	<!-- Pod2Wiki= -->		<!-- Pod2Wiki= -->
	<!-- Pod2Wiki=head_close_write -->		<!-- Pod2Wiki=head_close_write -->

	===close_write===		===close_write===

Simon.mcleish@gmail.com: /* open_write */ Reminder that this is an alternative to store.

2013-02-20T12:40:42Z

open_write: Reminder that this is an alternative to store.

← Older revision		Revision as of 12:40, 20 February 2013
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	<!-- Edit below this comment -->		<!-- Edit below this comment -->
			This, along with write and close_write, is an alternative to the store method.

	<!-- Pod2Wiki= -->		<!-- Pod2Wiki= -->
	<!-- Pod2Wiki=head_write -->		<!-- Pod2Wiki=head_write -->

	===write===		===write===

Simon.mcleish@gmail.com: /* get_local_copy */ Update of parameters to reflect current version usage

2013-02-20T12:38:52Z

get_local_copy: Update of parameters to reflect current version usage

← Older revision		Revision as of 12:38, 20 February 2013
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	===get_local_copy===		===get_local_copy===

	<source lang="perl">$fh = $store->get_local_copy( $fileobj )		<source lang="perl">$fh = $store->get_local_copy( $fileobj, $sourceid )

	</source>		</source>
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	<!-- Pod2Wiki= -->		<!-- Pod2Wiki= -->
	<!-- Pod2Wiki=head_get_remote_copy -->		<!-- Pod2Wiki=head_get_remote_copy -->

	===get_remote_copy===		===get_remote_copy===

Simon.mcleish@gmail.com: /* delete */ Update list of parameters to reflect usage in current release examples.

2013-02-20T11:45:26Z

delete: Update list of parameters to reflect usage in current release examples.

← Older revision		Revision as of 11:45, 20 February 2013
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	===delete===		===delete===

	<source lang="perl">$success = $store->delete( $fileobj )		<source lang="perl">$success = $store->delete( $fileobj, $sourceid )

	</source>		</source>
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	<!-- Pod2Wiki= -->		<!-- Pod2Wiki= -->
	<!-- Pod2Wiki=head_delete_copy -->		<!-- Pod2Wiki=head_delete_copy -->

	===delete_copy===		===delete_copy===

Simon.mcleish@gmail.com: /* retrieve */ Updated parameters to match existing code.

2013-02-20T11:06:42Z

retrieve: Updated parameters to match existing code.

← Older revision		Revision as of 11:06, 20 February 2013
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	===retrieve===		===retrieve===

	<source lang="perl">$success = $store->retrieve( $fileobj, $offset, $n, CALLBACK )		<source lang="perl">$success = $store->retrieve( $fileobj, $sourceid, $offset, $n, CALLBACK )

	</source>		</source>
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	<!-- Pod2Wiki= -->		<!-- Pod2Wiki= -->
	<!-- Pod2Wiki=head_delete -->		<!-- Pod2Wiki=head_delete -->

	===delete===		===delete===

Simon.mcleish@gmail.com: /* store */ Indicating that the new developer who hasn't encountered this before should check other methods to be sure that they choose the right ones for their circumstances.

2013-02-20T11:04:32Z

store: Indicating that the new developer who hasn't encountered this before should check other methods to be sure that they choose the right ones for their circumstances.

← Older revision		Revision as of 11:04, 20 February 2013
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	<!-- Edit below this comment -->		<!-- Edit below this comment -->
			The combination of methods open_write, write, and close_write can be used as an alternative to this method.

	<!-- Pod2Wiki= -->		<!-- Pod2Wiki= -->
	<!-- Pod2Wiki=head_retrieve -->		<!-- Pod2Wiki=head_retrieve -->

	===retrieve===		===retrieve===

Tdb01r at 09:56, 22 January 2013

2013-01-22T09:56:19Z

Show changes