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DjVuPort Class Reference

#include <DjVuPort.h>

Inheritance diagram for DjVuPort:

GPEnabled DjVuDocument DjVuFile DjVuImage DjVuMemoryPort DjVuSimplePort DjVuDocEditor DjVuErrorList

List of all members.

Detailed Description

Base class for notification targets. DjVuPort# provides base functionality for classes willing to take part in sending and receiving messages generated during decoding process. You need to derive your class from DjVuPort# if you want it to be able to send or receive requests. In addition, for receiving requests you should override one or more virtual function.

{ Important remark} --- All ports should be allocated on the heap using operator new# and immediately secured using a {GP} smart pointer. Ports which are not secured by a smart-pointer are not considered ``alive'' and never receive notifications!

Definition at line 141 of file DjVuPort.h.


These virtual functions may be overridden by the subclasses of DjVuPort#. They are called by the {DjVuPortcaster} when the port is alive and when there is a route between the source of the notification and this port.

enum  ErrorRecoveryAction { ABORT = 0, SKIP_PAGES = 1, SKIP_CHUNKS = 2, KEEP_ALL = 3 }
virtual GP< DjVuFileid_to_file (const DjVuPort *source, const GUTF8String &id)
virtual GURL id_to_url (const DjVuPort *source, const GUTF8String &id)
virtual void notify_chunk_done (const DjVuPort *source, const GUTF8String &name)
virtual void notify_decode_progress (const DjVuPort *source, float done)
virtual void notify_doc_flags_changed (const class DjVuDocument *source, long set_mask, long clr_mask)
virtual bool notify_error (const DjVuPort *source, const GUTF8String &msg)
virtual void notify_file_flags_changed (const class DjVuFile *source, long set_mask, long clr_mask)
virtual void notify_redisplay (const class DjVuImage *source)
virtual void notify_relayout (const class DjVuImage *source)
virtual bool notify_status (const DjVuPort *source, const GUTF8String &msg)
virtual GP< DataPoolrequest_data (const DjVuPort *source, const GURL &url)

Public Member Functions

 DjVuPort (const DjVuPort &port)
int get_count (void) const
DjVuPortoperator= (const DjVuPort &port)
Files #"DjVuPort.h"# and #"DjVuPort.cpp"# implement a communication mechanism between different parties involved in decoding DjVu files. It should be pretty clear that the creator of {DjVuDocument} and {DjVuFile} would like to receive some information about the progress of decoding, errors occurred, etc. It may also want to provide source data for decoders (like it's done in the plugin where the real data is downloaded from the net and is fed into DjVu decoders).

Normally this functionality is implemented by means of callbacks which are run when a given condition comes true. Unfortunately it's not quite easy to implement this strategy in our case. The reason is that there may be more than one "client" working with the same document, and the document should send the information to each of the clients. This could be done by means of callback {lists}, of course, but we want to achieve more bulletproof results: we want to be sure that the client that we're about to contact is still alive, and is not being destroyed by another thread. Besides, we are going to call these "callbacks" from many places, from many different classes. Maintaining multi-thread safe callback lists is very difficult.

Finally, we want to provide some default implementation of these "callbacks" in the library, which should attempt to process the requests themselves if they can, and contact the client only if they're unable to do it (like in the case of {DjVuPort::request_data}() with local URL where {DjVuDocument} can get the data from the hard drive itself not disturbing the document's creator.

Two classes implement a general communication mechanism: {DjVuPort} and {DjVuPortcaster}. Any sender and recipient of requests should be a subclass of {DjVuPort}. {DjVuPortcaster} maintains a map of routes between {DjVuPort}s, which should be configured by somebody else. Whenever a port wants to send a request, it calls the corresponding function of {DjVuPortcaster}, and the portcaster relays the request to all the destinations that it sees in the internal map.

The {DjVuPortcaster} is responsible for keeping the map up to date by getting rid of destinations that have been destroyed. Map updates are performed from a single place and are serialized by a global monitor.

DjVu decoder communication mechanism.

Andrei Erofeev <eaf@geocities.com>\ L\'eon Bottou <leonb@research.att.com>
DjVuPort.h,v 1.8 2003/11/07 22:08:21 leonb Exp

virtual bool inherits (const GUTF8String &class_name) const

Static Public Member Functions

static DjVuPortcasterget_portcaster (void)
static void operator delete (void *addr)
static void * operator new (size_t sz)

Protected Attributes

volatile int count
 The reference counter.

Static Private Attributes

static DjVuPortCorpse * corpse_head
static GCriticalSection * corpse_lock
static int corpse_num
static DjVuPortCorpse * corpse_tail


class  DjVuPortCorpse

The documentation for this class was generated from the following files:

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