DjVuSimplePort Class Reference

Simple port. More...

#include <DjVuPort.h>

Inheritance diagram for DjVuSimplePort:

[legend]

List of all members.

Public Member Functions
virtual bool	notify_error (const DjVuPort *source, const GUTF8String &msg)
virtual bool	notify_status (const DjVuPort *source, const GUTF8String &msg)
virtual GP< DataPool >	request_data (const DjVuPort *source, const GURL &url)
DjVuPort.h
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. Author: Andrei Erofeev <eaf@geocities.com>\ L\'eon Bottou <leonb@research.att.com> Version: $Id: DjVuPort.h,v 1.8 2003/11/07 22:08:21 leonb Exp $#
virtual bool	inherits (const GUTF8String &class_name) const

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Detailed Description

Simple port.

An instance of DjVuSimplePort# is automatically created when you create a {DjVuFile} or a {DjVuDocument} without specifying a port. This simple port can retrieve data for local urls (i.e. urls referring to local files) and display error messages on stderr#. All other notifications are ignored.

Definition at line 276 of file DjVuPort.h.

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Member Function Documentation

bool DjVuSimplePort::inherits

(

const GUTF8String &

class_name

)

const [inline, virtual]

Returns 1 if class_name# is #"DjVuPort"# or #"DjVuSimplePort"#.

Reimplemented from DjVuPort.

Definition at line 496 of file DjVuPort.h.

bool DjVuSimplePort::notify_error	(	const DjVuPort *	source,
		const GUTF8String &	msg
	)			[virtual]

Displays error on stderr#. Always returns 1.

Reimplemented from DjVuPort.

Reimplemented in DjVuErrorList.

Definition at line 662 of file DjVuPort.cpp.

bool DjVuSimplePort::notify_status	(	const DjVuPort *	source,
		const GUTF8String &	msg
	)			[virtual]

Displays status on stderr#. Always returns 1.

Reimplemented from DjVuPort.

Reimplemented in DjVuErrorList.

Definition at line 669 of file DjVuPort.cpp.

GP< DataPool > DjVuSimplePort::request_data	(	const DjVuPort *	source,
		const GURL &	url
	)			[virtual]

If url# is local, it created a {DataPool}, connects it to the file with the given name and returns.

Otherwise returns #0#.

Reimplemented from DjVuPort.

Reimplemented in DjVuErrorList.

Definition at line 648 of file DjVuPort.cpp.

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

• DjVuPort.h
• DjVuPort.cpp