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phab/src/applications/files/engine/base/PhabricatorFileStorageEngine.php
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PhabricatorFileStorageEngine.php
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<?php
/*
* Copyright 2011 Facebook, Inc.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
/**
* Defines a storage engine which can write file data somewhere (like a
* database, local disk, Amazon S3, the A:\ drive, or a custom filer) and
* retrieve it later.
*
* You can extend this class to provide new file storage backends.
*
* For more information, see @{article:File Storage Technical Documentation}.
*
* @task meta Engine Metadata
* @task file Managing File Data
* @group filestorage
*/
abstract class PhabricatorFileStorageEngine {
final public function __construct() {
// <empty>
}
/* -( Engine Metadata )---------------------------------------------------- */
/**
* Return a unique, nonempty string which identifies this storage engine.
* This is used to look up the storage engine when files needs to be read or
* deleted. For instance, if you store files by giving them to a duck for
* safe keeping in his nest down by the pond, you might return 'duck' from
* this method.
*
* @return string Unique string for this engine, max length 32.
* @task meta
*/
abstract public function getEngineIdentifier();
/* -( Managing File Data )------------------------------------------------- */
/**
* Write file data to the backing storage and return a handle which can later
* be used to read or delete it. For example, if the backing storage is local
* disk, the handle could be the path to the file.
*
* The caller will provide a $params array, which may be empty or may have
* some metadata keys (like "name" and "author") in it. You should be prepared
* to handle writes which specify no metadata, but might want to optionally
* use some keys in this array for debugging or logging purposes. This is
* the same dictionary passed to @{method:PhabricatorFile::NewFromFileData},
* so you could conceivably do custom things with it.
*
* If you are unable to write for whatever reason (e.g., the disk is full),
* throw an exception. If there are other satisfactory but less-preferred
* storage engines available, they will be tried.
*
* @param string The file data to write.
* @param array File metadata (name, author), if available.
* @return string Unique string which identifies the stored file, max length
* 255.
* @task file
*/
abstract public function writeFile($data, array $params);
/**
* Read the contents of a file previously written by @{method:writeFile}.
*
* @param string The handle returned from @{method:writeFile} when the
* file was written.
* @return string File contents.
* @task file
*/
abstract public function readFile($handle);
/**
* Delete the data for a file previously written by @{method:writeFile}.
*
* @param string The handle returned from @{method:writeFile} when the
* file was written.
* @return void
* @task file
*/
abstract public function deleteFile($handle);
}
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