You are here: Foswiki>System Web>Category>DeveloperDocumentationCategory>PerlDoc (21 Nov 2014, ProjectContributor)Edit Attach
internal package Foswiki::Store
See PublishedAPI for packages intended to be used by Plugin and Contrib authors, or browse all packages.
See also Developing plugins, Developer's Bible, Technical Overview

internal package Foswiki::Store

This class is a pure virtual base class that specifies the interface between the actual store implementation and the rest of the Foswiki system.

Subclasses of this class (known as "store implementations") are responsible for checking for topic existance, access permissions, and all the other general admin tasks required of a store.

This class knows nothing about how the data is actually stored - that knowledge is entirely encapsulated in the implementation.

The general contract for methods in the class requires that errors are signalled using exceptions. Foswiki::AccessControlException is used for access control exceptions, and Error::Simple for all other types of error.

The reference implementations of this base class Foswiki::Store::PlainFileStore, which can be obtained from PlainFileStoreContrib.

Methods of this class and all subclasses should only be called from Foswiki and Foswiki::Meta. All other system components must delegate store interactions via Foswiki::Meta.

For readers who are familiar with Foswiki version 1.0.0, this class describes the interface to the old Foswiki::Store without actually implementing it.

Note that most methods are passed a Foswiki::Meta object. This pattern is employed to reinforce the encapsulation of a "path" in a meta object, and also to allow the store to modify META fields in the object, something it would be unable to do if passed $web, $topic.

Version numbers are required to be positive, non-zero integers. When passing in version numbers to the methods of a store implementation, 0, undef and '' are treated as referring to the latest (most recent) revision of the object. Version numbers are required to increase (later version numbers are greater than earlier) but are not required to be sequential.

IMPORTANT: the store must be able to handle unicode topic and attachment names, and unicode topic content. The store is expected to do any necessary encoding/decoding from/to unicode.

ClassMethod new()

Construct a Store module.

ObjectMethod finish()

Break circular references.

StaticMethod cleanUpRevID( $rev ) → $integer

Cleans up (maps) a user-supplied revision ID and converts it to an integer number that can be incremented to create a new revision number.

This method should be used to sanitise user-provided revision IDs.

Returns 0 if it was unable to determine a valid rev number from the string passed.

Works with RCS format (e.g. 1.2) rev IDs and plain integer numbers.

ObjectMethod getWorkArea( $key ) → $directorypath

Gets a private directory uniquely identified by $key. The directory is intended as a work area for plugins.

The standard is a directory named the same as "key" under $Foswiki::cfg{WorkingDir}/work_areas

ObjectMethod getAttachmentURL( $web, $topic, $attachment, %options ) → $url

Get a URL that points at an attachment. The URL may be absolute, or relative to the the page being rendered (if that makes sense for the store implementation).
  • =$session - the current Foswiki session
  • $web - name of the web for the URL
  • $topic - name of the topic
  • $attachment - name of the attachment, defaults to no attachment
  • %options - parameters to be attached to the URL

Supported %options are:
  • topic_version - version of topic to retrieve attachment from
  • attachment_version - version of attachment to retrieve
  • absolute - if the returned URL must be absolute, rather than relative

If $web is not given, $topic and $attachment are ignored/ If $topic is not given, $attachment is ignored.

If topic_version is not given, the most recent revision of the topic should be linked. Similarly if attachment_version= is not given, the most recent revision of the attachment will be assumed. If topic_version is specified but attachment_version is not (or the specified attachment_version is not present), then the most recent version of the attachment in that topic version will be linked. Stores may not support topic_version and attachment_version.

The default implementation is suitable for use with stores that put attachments in a web-visible directory, pointed at by $Foswiki::cfg{PubUrlPath}. As such it may also be used as a fallback for distributed topics (such as those in System) when content is not held in the store itself (e.g. if the store doesn't recognise the web it can call SUPER::getAttachmentURL)

As required by RFC3986, the returned URL may only contain the allowed characters -A-Za-z0-9_.~!*\'();:@&=+$,/?%#[]

StaticMethod decode($octets) → $unicode

Utility function to decode a binary string of octets read from the store and known known to be encoded using the currently selected {Store}{Encoding} (or UTF-8 if none is set) into perl characters (unicode). May die if $octets contains an invalid byte sequence for the encoding.

This utility function should not be used to decode topic text. For performance reasons, we don't need to NFC normalize file contents, only the filenames themselves.

StaticMethod encode($unicode, CROAK) → $octets

Utility function to encode a perl character string into a string of octets encoded using the currently selected {Store}{Encoding} (or UTF-8 if none is set).

If CROAK is true, it will die if $unicode cannot be represented in the {Store}{Encoding}. Set this for filename encoding. Leave false for content encoding.

If CROAK is false, then characters that cannot be represented will be converted to named entities if possible, otherwise numeric entities.

ObjectMethod readTopic($topicObject, $version) → ($rev, $isLatest)

  • $topicObject - Foswiki::Meta object
  • $version - revision identifier, or undef
Reads the given version of a topic, and populates the $topicObject. If the $version is undef, or there is no revision numbered $version, then reads the most recent version.

Returns the version identifier of the topic that was actually read. If the topic does not exist in the store, then $rev is undef. $isLatest will be set to true if the version loaded (or not loaded) is the latest available version.

Note: Implementations of this method must call Foswiki::Meta::setLoadStatus($rev, $isLatest) to set the load status of the meta object.

ObjectMethod moveAttachment( $oldTopicObject, $oldAttachment, $newTopicObject, $newAttachment )

  • $oldTopicObject, $oldAttachment - spec of attachment to move
  • $newTopicObject, $newAttachment= - where to move to
Move an attachment from one topic to another.

The caller to this routine should check that all topics are valid, and access is permitted. $oldAttachment and $newAttachment must be given and may not be perl false.

ObjectMethod copyAttachment( $oldTopicObject, $oldAttachment, $newTopicObject, $newAttachment )

  • $oldTopicObject, $oldAttachment - spec of attachment to copy
  • $newTopicObject, $newAttachment= - where to move to
Copy an attachment from one topic to another.

The caller to this routine should check that all topics are valid, and access is permitted. $oldAttachment and $newAttachment must be given and may not be perl false.

ObjectMethod attachmentExists( $topicObject, $att ) → $boolean

Determine if the attachment already exists on the given topic

ObjectMethod moveTopic( $oldTopicObject, $newTopicObject, $cUID )

All parameters must be defined and must be untainted.

Implementation must invoke 'update' on event listeners.

ObjectMethod moveWeb( $oldWebObject, $newWebObject, $cUID )

Move a web.

Implementation must invoke 'update' on event listeners.

ObjectMethod testAttachment( $topicObject, $attachment, $test ) → $value

Performs a type test on the given attachment file. * $attachment - name of the attachment to test e.g lolcat.gif * $test - the test to perform e.g. 'r'

The return value is the value that would be returned by the standard perl file operations, as indicated by $type

* r File is readable by current user * w File is writable by current user * e File exists. * z File has zero size. * s File has nonzero size (returns size). * T File is an ASCII text file (heuristic guess). * B File is a "binary" file (opposite of T). * M Last modification time (epoch seconds). * A Last access time (epoch seconds).

Note that all these types should behave as the equivalent standard perl operator behaves, except M and A which are independent of the script start time (see perldoc -f -X for more information)

Other standard Perl file tests may also be supported on some store implementations, but cannot be relied on.

Errors will be signalled by an Error::Simple exception.

ObjectMethod openAttachment( $topicObject, $attachment, $mode, %opts ) → $text

Opens a stream onto the attachment. This method is primarily to support virtual file systems, and as such access controls are not checked, plugin handlers are not called, and it does not update the meta-data in the topicObject.

$mode can be '<', '>' or '>>' for read, write, and append respectively. %

%opts can take different settings depending on $mode.
  • $mode='<'
    • version - revision of the object to open e.g. version => 6
  • $mode='>' or ='>>'
    • no options
Errors will be signalled by an Error exception.

ObjectMethod getRevisionHistory ( $topicObject [, $attachment] ) → $iterator

  • $topicObject - Foswiki::Meta for the topic
  • $attachment - name of an attachment (optional)
Get an iterator over the list of revisions of the object. The iterator returns the revision identifiers (which will usually be numbers) starting with the most recent revision.

MUST WORK FOR ATTACHMENTS AS WELL AS TOPICS

If the object does not exist, returns an empty iterator ($iterator->hasNext() will be false).

ObjectMethod getNextRevision ( $topicObject ) → $revision

Get the ientifier for the next revision of the topic. That is, the identifier for the revision that we will create when we next save.

ObjectMethod getRevisionDiff ( $topicObject, $rev2, $contextLines ) → \@diffArray

Get difference between two versions of the same topic. The differences are computed over the embedded store form.

Return reference to an array of differences
  • $topicObject - topic, first revision loaded
  • $rev2 - second revision
  • $contextLines - number of lines of context required

Each difference is of the form [ $type, $right, $left ] where
type Means
+ Added
- Deleted
c Changed
u Unchanged
l Line Number

ObjectMethod getVersionInfo($topicObject, $rev, $attachment) → \%info

Get revision info for a topic or attachment.
  • $topicObject Topic object, required
  • $rev revision number. If 0, undef, or out-of-range, will get info about the most recent revision.
  • $attachment (optional) attachment filename; undef for a topic
Return %info with at least:
date in epochSec
user user object
version the revision number
comment comment in the store system, may or may not be the same as the comment in embedded meta-data

If $attachment and $rev are both given, then $rev applies to the attachment, not the topic.

ObjectMethod saveAttachment( $topicObject, $attachment, $stream, $cUID, \%options ) → $revNum

Save a new revision of an attachment, the content of which will come from an input stream $stream.
  • $topicObject - Foswiki::Meta for the topic
  • $attachment - name of the attachment
  • $stream - input stream delivering attachment data
  • $cUID - user doing the save
  • \%options - Ref to hash of options
\%options may include:
  • forcedate - force the revision date to be this (epoch secs) X forcedate must be equal to or later than the date of the most recent revision already stored for the topic.
  • minor - True if this is a minor change (used in log)
  • comment - a comment associated with the save
Returns the number of the revision saved.

Note: \%options was added in Foswiki 2.0

ObjectMethod saveTopic( $topicObject, $cUID, $options ) → $integer

Save a topic or attachment without invoking plugin handlers.
  • $topicObject - Foswiki::Meta for the topic
  • $cUID - cUID of user doing the saving
  • $options - Ref to hash of options
$options may include:
  • forcenewrevision - force a new revision even if one isn't needed
  • forcedate - force the revision date to be this (epoch secs) X forcedate must be equal to or later than the date of the most recent revision already stored for the topic.
  • minor - True if this is a minor change (used in log)
  • comment - a comment associated with the save

Returns the new revision identifier.

Implementation must invoke 'update' on event listeners.

ObjectMethod repRev( $topicObject, $cUID, %options ) → $rev

Replace last (top) revision of a topic with different content. The different content is taken from the content currently loaded in $topicObject.

Parameters and return value as saveTopic, except
  • %options - as for saveTopic, with the extra options:
    • operation - set to the name of the operation performing the save. This is used only in the log, and is normally cmd or save. It defaults to save.

Used to try to avoid the deposition of 'unecessary' revisions, for example where a user quickly goes back and fixes a spelling error.

Also provided as a means for administrators to rewrite history (forcedate).

It is up to the store implementation if this is different to a normal save or not.

Returns the id of the latest revision.

Implementation must invoke 'update' on event listeners.

ObjectMethod delRev( $topicObject, $cUID ) → $rev

  • $topicObject - Foswiki::Meta topic object
  • $cUID - cUID of user doing the deleting

Parameters and return value as saveTopic.

Provided as a means for administrators to rewrite history.

Delete last entry in repository, restoring the previous revision.

It is up to the store implementation whether this actually does delete a revision or not; some implementations will simply promote the previous revision up to the head.

Implementation must invoke 'update' on event listeners.

ObjectMethod atomicLockInfo( $topicObject ) → ($cUID, $time)

If there is a lock on the topic, return it.

ObjectMethod atomicLock( $topicObject, $cUID )

  • $topicObject - Foswiki::Meta topic object
  • $cUID cUID of user doing the locking
Grab a topic lock on the given topic.

ObjectMethod atomicUnlock( $topicObject )

Release the topic lock on the given topic. A topic lock will cause other processes that also try to claim a lock to block. It is important to release a topic lock after a guard section is complete. This should normally be done in a 'finally' block. See man Error for more info.

Topic locks are used to make store operations atomic. They are note the locks used when a topic is edited; those are Leases (see getLease)

ObjectMethod webExists( $web ) → $boolean

Test if web exists
  • $web - Web name, required, e.g. 'Sandbox'

ObjectMethod topicExists( $web, $topic ) → $boolean

Test if topic exists
  • $web - Web name, optional, e.g. 'Main'
  • $topic - Topic name, required, e.g. 'TokyoOffice', or "Main.TokyoOffice"

ObjectMethod getApproxRevTime ( $web, $topic ) → $epochSecs

Get an approximate rev time for the latest rev of the topic. This method is used to optimise searching. Needs to be as fast as possible.

ObjectMethod eachChange( $meta, $time ) → $iterator

Get an iterator over the list of all the changes between $time and now. $time is a time in seconds since 1st Jan 1970, and is not guaranteed to return any changes that occurred before (now - {Store}{RememberChangesFor}). Changes are returned in most-recent-first order.

$meta may be a web or a topic. If it's a web, then all changes for all topics within that web will be iterated. If it's a topic, only changes for that topic (since the topic name was first used) will be iterated. Each change is returned as a reference to a hash containing the fields documented for recordChange().

Store implementors should note that if compatibility with Foswiki < 2 is required, the following additional fields must be returned:
  • topic - name of the topic the change occurred to
  • user - wikiname of the changing user
  • more - formatted string indicating if the change was minor or not

ObjectMethod recordChange(%args)

Record that the store item changed, and who changed it, and why

  • verb - the action - one of
    • update - a web, topic or attachment has been modified
    • insert - a web, topic or attachment is being inserted
    • remove - a topic or attachment is being removed
  • cuid - who is making the change
  • revision - the revision of the topic that the change appears in
  • path - canonical web.topic path for the affected object
  • attachment - attachment name (optional)
  • oldpath - canonical web.topic path for the origin of a move/rename
  • oldattachment - origin of move
  • minor - boolean true if this change is flagged as minor
  • comment - descriptive text

ObjectMethod eachAttachment( $topicObject ) → \$iterator

Return an iterator over the list of attachments stored for the given topic. This will get a list of the attachments actually stored for the topic, which may be a longer list than the list that comes from the topic meta-data, which only lists the attachments that are normally visible to the user.

The iterator iterates over attachment names.

ObjectMethod eachTopic( $webObject ) → $iterator

Get list of all topics in a web as an iterator

ObjectMethod eachWeb($webObject, $all ) → $iterator

Return an iterator over each subweb. If $all is set, will return a list of all web names under $web. The iterator returns web pathnames relative to $web.

The list of web names is sorted alphabetically by full path name e.g.
  • AWeb
  • AWeb/SubWeb
  • AWeb/XWeb
  • BWeb

ObjectMethod remove( $cUID, $om, $attachment )

  • $cUID who is doing the removing
  • $om - thing being removed (web or topic)
  • $attachment - optional attachment being removed

Destroy a thing, utterly.

Implementation must invoke 'remove' on event listeners.

ObjectMethod query($query, $inputTopicSet, $session, \%options) → $outputTopicSet

Search for data in the store (not web based).
  • $query either a Foswiki::Search::Node or a Foswiki::Query::Node.
  • $inputTopicSet is a reference to an iterator containing a list of topic paths. If set to undef, the search/query algo will create a new iterator using eachWeb()/eachTopic() and the topic and excludetopics options

Returns a Foswiki::Search::InfoCache iterator

ObjectMethod getRevisionAtTime( $topicObject, $time ) → $rev

  • $topicObject - topic
  • $time - time (in epoch secs) for the rev

Get the revision identifier of a topic at a specific time. Returns a single-digit rev number or undef if it couldn't be determined (either because the topic isn't that old, or there was a problem)

ObjectMethod getLease( $topicObject ) → $lease

  • $topicObject - topic

If there is an lease on the topic, return the lease, otherwise undef. A lease is a block of meta-information about a topic that can be recovered (this is a hash containing user, taken and expires). Leases are taken out when a topic is edited. Only one lease can be active on a topic at a time. Leases are used to warn if another user is already editing a topic.

ObjectMethod setLease( $topicObject, $length )

Take out an lease on the given topic for this user for $length seconds.

See getLease for more details about Leases.

ObjectMethod removeSpuriousLeases( $web )

Remove leases that are not related to a topic. These can get left behind in some store implementations when a topic is created, but never saved.

Edit  | Attach | Print version | History: r1 | Backlinks | View wiki text | Edit wiki text | More topic actions
Topic revision: r1 - 21 Nov 2014, ProjectContributor
This site is powered by FoswikiCopyright © by the contributing authors. All material on this site is the property of the contributing authors.
Ideas, requests, problems regarding Foswiki? Send feedback