ImageMetadataLoader.h

/*
    Scan Tailor - Interactive post-processing tool for scanned pages.
    Copyright (C) 2007-2008  Joseph Artsimovich <joseph_a@mail.ru>

    This program is free software: you can redistribute it and/or modify
    it under the terms of the GNU General Public License as published by
    the Free Software Foundation, either version 3 of the License, or
    (at your option) any later version.

    This program is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    GNU General Public License for more details.

    You should have received a copy of the GNU General Public License
    along with this program.  If not, see <http://www.gnu.org/licenses/>.
*/

#ifndef IMAGEMETADATALOADER_H_
#define IMAGEMETADATALOADER_H_

#include "VirtualFunction.h"
#include "RefCountable.h"
#include "IntrusivePtr.h"
#include <vector>

class QString;
class QIODevice;
class ImageMetadata;

class ImageMetadataLoader : public RefCountable
{
public:
	enum Status {
		LOADED, /**< Loaded successfully */
		NO_IMAGES, /**< File contained no images. */
		FORMAT_NOT_RECOGNIZED, /**< File format not recognized. */
		GENERIC_ERROR /**< Some other error has occurred. */
	};
	
	/**
	 * \brief Registers a loader for a particular image format.
	 *
	 * This function may not be called before main() or after additional
	 * threads have been created.
	 */
	static void registerLoader(IntrusivePtr<ImageMetadataLoader> const& loader);
	
	template<typename OutFunc>
	static Status load(QIODevice& io_device, OutFunc out);
	
	template<typename OutFunc>
	static Status load(QString const& file_path, OutFunc out);
protected:
	virtual ~ImageMetadataLoader() {}
	
	/**
	 * \brief Loads metadata from a particular image format.
	 *
	 * This function must be reentrant, as it may be called from multiple
	 * threads at the same time.
	 *
	 * \param io_device The I/O device to read from.  Usually a QFile.
	 *        In case FORMAT_NO_RECOGNIZED is returned, the implementation
	 *        must leave \p io_device in its original state.
	 * \param out A callback functional object that will be called to handle
	 *        the image metadata.  If there are multiple images (pages) in
	 *        the file, this object will be called multiple times.
	 */
	virtual Status loadMetadata(
		QIODevice& io_device,
		VirtualFunction1<void, ImageMetadata const&>& out) = 0;
private:
	static Status loadImpl(
		QIODevice& io_device,
		VirtualFunction1<void, ImageMetadata const&>& out);
	
	static Status loadImpl(
		QString const& file_path,
		VirtualFunction1<void, ImageMetadata const&>& out);
	
	typedef std::vector<IntrusivePtr<ImageMetadataLoader> > LoaderList;
	static LoaderList m_sLoaders;
};


template<typename OutFunc>
ImageMetadataLoader::Status
ImageMetadataLoader::load(QIODevice& io_device, OutFunc out)
{
	ProxyFunction1<OutFunc, void, ImageMetadata const&> proxy(out);
	return loadImpl(io_device, proxy);
}

template<typename OutFunc>
ImageMetadataLoader::Status
ImageMetadataLoader::load(QString const& file_path, OutFunc out)
{
	ProxyFunction1<OutFunc, void, ImageMetadata const&> proxy(out);
	return loadImpl(file_path, proxy);
}

#endif