source: downloads/ogre/OgreMain/include/OgreResource.h @ 45

/*
-----------------------------------------------------------------------------
This source file is part of OGRE
    (Object-oriented Graphics Rendering Engine)
For the latest info, see http://www.ogre3d.org/

Copyright (c) 2000-2006 Torus Knot Software Ltd
Also see acknowledgements in Readme.html

This program is free software; you can redistribute it and/or modify it under
the terms of the GNU Lesser General Public License as published by the Free Software
Foundation; either version 2 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 Lesser General Public License for more details.

You should have received a copy of the GNU Lesser General Public License along with
this program; if not, write to the Free Software Foundation, Inc., 59 Temple
Place - Suite 330, Boston, MA 02111-1307, USA, or go to
http://www.gnu.org/copyleft/lesser.txt.

You may alternatively use this source under the terms of a specific version of
the OGRE Unrestricted License provided you have obtained such a license from
Torus Knot Software Ltd.
-----------------------------------------------------------------------------
*/
#ifndef _Resource_H__
#define _Resource_H__

#include "OgrePrerequisites.h"
#include "OgreString.h"
#include "OgreSharedPtr.h"
#include "OgreStringInterface.h"

namespace Ogre {

    typedef unsigned long ResourceHandle;


        // Forward declaration
        class ManualResourceLoader;

        /** Abstract class reprensenting a loadable resource (e.g. textures, sounds etc)
        @remarks
            Resources are data objects that must be loaded and managed throughout
                        an application. A resource might be a mesh, a texture, or any other
                        piece of data - the key thing is that they must be identified by 
                        a name which is unique, must be loaded only once,
                        must be managed efficiently in terms of retrieval, and they may
                        also be unloadable to free memory up when they have not been used for
                        a while and the memory budget is under stress.
                @par
                        All Resource instances must be a member of a resource group; see
                        ResourceGroupManager for full details.
        @par
            Subclasses must implement:
                        <ol>
                        <li>A constructor, overriding the same parameters as the constructor
                            defined by this class. Subclasses are not allowed to define
                                constructors with other parameters; other settings must be
                                settable through accessor methods before loading.</li>
            <li>The loadImpl() and unloadImpl() methods - mSize must be set 
                                after loadImpl()</li>
                        <li>StringInterface ParamCommand and ParamDictionary setups
                            in order to allow setting of core parameters (prior to load)
                                through a generic interface.</li>
                        </ol>
    */
        class _OgreExport Resource : public StringInterface
    {
        public:
                OGRE_AUTO_MUTEX // public to allow external locking
                class Listener
                {
                public:
                        Listener() {}
                        virtual ~Listener() {}

                        /** Callback to indicate that background loading has completed.
                        @remarks
                                This callback is only relevant when a Resource has been
                                marked as background loaded (@see Resource::setBackgroundLoaded)
                                , and occurs when that loading has completed. The call itself
                                does not itself occur in the thread which is doing the loading;
                                when loading is complete a response indicator is placed with the
                                ResourceGroupManager, which will then be sent back to the 
                                listener as part of the application's primary frame loop thread.
                        */
                        virtual void backgroundLoadingComplete(Resource*) {}
                        
                };
                
                /// Enum identifying the loading state of the resource
                enum LoadingState
                {
                        /// Not loaded
                        LOADSTATE_UNLOADED,
                        /// Loading is in progress
                        LOADSTATE_LOADING,
                        /// Fully loaded
                        LOADSTATE_LOADED,
                        /// Currently unloading
                        LOADSTATE_UNLOADING
                };
    protected:
                /// Creator
                ResourceManager* mCreator;
                /// Unique name of the resource
        String mName;
                /// The name of the resource group
                String mGroup;
                /// Numeric handle for more efficient look up than name
        ResourceHandle mHandle;
                /// Is the resource currently loaded?
        volatile LoadingState mLoadingState;
                /// Is this resource going to be background loaded? Only applicable for multithreaded
                volatile bool mIsBackgroundLoaded;
                /// Mutex to cover the status of loading
                OGRE_MUTEX(mLoadingStatusMutex)
                /// The size of the resource in bytes
        size_t mSize;
                /// Is this file manually loaded?
                bool mIsManual;
                /// Origin of this resource (e.g. script name) - optional
                String mOrigin;
                /// Optional manual loader; if provided, data is loaded from here instead of a file
                ManualResourceLoader* mLoader;

                typedef std::list<Listener*> ListenerList;
                ListenerList mListenerList;

                /** Protected unnamed constructor to prevent default construction. 
                */
                Resource() 
                        : mCreator(0), mHandle(0), mLoadingState(LOADSTATE_UNLOADED), 
                        mIsBackgroundLoaded(false),     mSize(0), mIsManual(0), mLoader(0)
                { 
                }

                /** Internal hook to perform actions before the load process, but
                        after the resource has been marked as 'loading'.
                @note Mutex will have already been acquired by the loading thread.
                        Also, this call will occur even when using a ManualResourceLoader 
                        (when loadImpl is not actually called)
                */
                virtual void preLoadImpl(void) {}
                /** Internal hook to perform actions after the load process, but
                        before the resource has been marked as fully loaded.
                @note Mutex will have already been acquired by the loading thread.
                        Also, this call will occur even when using a ManualResourceLoader 
                        (when loadImpl is not actually called)
                */
                virtual void postLoadImpl(void) {}

                /** Internal hook to perform actions before the unload process.
                @note Mutex will have already been acquired by the unloading thread.
                */
                virtual void preUnloadImpl(void) {}
                /** Internal hook to perform actions after the unload process, but
                before the resource has been marked as fully unloaded.
                @note Mutex will have already been acquired by the unloading thread.
                */
                virtual void postUnloadImpl(void) {}

                /** Internal implementation of the meat of the 'load' action, only called if this 
                        resource is not being loaded from a ManualResourceLoader. 
                */
                virtual void loadImpl(void) = 0;
                /** Internal implementation of the 'unload' action; called regardless of
                        whether this resource is being loaded from a ManualResourceLoader. 
                */
                virtual void unloadImpl(void) = 0;
                /** Calculate the size of a resource; this will only be called after 'load' */
                virtual size_t calculateSize(void) const = 0;

                /// Queue the firing of background loading complete event
                virtual void queueFireBackgroundLoadingComplete(void);

    public:
                /** Standard constructor.
                @param creator Pointer to the ResourceManager that is creating this resource
                @param name The unique name of the resource
                @param group The name of the resource group to which this resource belongs
                @param isManual Is this resource manually loaded? If so, you should really
                        populate the loader parameter in order that the load process
                        can call the loader back when loading is required. 
                @param loader Pointer to a ManualResourceLoader implementation which will be called
                        when the Resource wishes to load (should be supplied if you set
                        isManual to true). You can in fact leave this parameter null 
                        if you wish, but the Resource will never be able to reload if 
                        anything ever causes it to unload. Therefore provision of a proper
                        ManualResourceLoader instance is strongly recommended.
                */
                Resource(ResourceManager* creator, const String& name, ResourceHandle handle,
                        const String& group, bool isManual = false, ManualResourceLoader* loader = 0);

        /** Virtual destructor. Shouldn't need to be overloaded, as the resource
            deallocation code should reside in unload()
            @see
                Resource::unload()
        */
        virtual ~Resource();

        /** Loads the resource, if it is not already.
                @remarks
                        If the resource is loaded from a file, loading is automatic. If not,
                        if for example this resource gained it's data from procedural calls
                        rather than loading from a file, then this resource will not reload 
                        on it's own.
                @param backgroundThread Indicates whether the caller of this method is
                        the background resource loading thread. 
                        
        */
        virtual void load(bool backgroundThread = false);

                /** Reloads the resource, if it is already loaded.
                @remarks
                        Calls unload() and then load() again, if the resource is already
                        loaded. If it is not loaded already, then nothing happens.
                */
                virtual void reload(void);

        /** Returns true if the Resource is reloadable, false otherwise.
        */
        bool isReloadable(void) const
        {
            return !mIsManual || mLoader;
        }

        /** Is this resource manually loaded?
                */
                bool isManuallyLoaded(void) const
                {
                        return mIsManual;
                }

                /** Unloads the resource; this is not permanent, the resource can be
                        reloaded later if required.
        */
                virtual void unload(void);

        /** Retrieves info about the size of the resource.
        */
        size_t getSize(void) const
        { 
            return mSize; 
        }

        /** 'Touches' the resource to indicate it has been used.
        */
        virtual void touch(void);

        /** Gets resource name.
        */
        const String& getName(void) const 
        { 
            return mName; 
        }

        ResourceHandle getHandle(void) const
        {
            return mHandle;
        }

        /** Returns true if the Resource has been loaded, false otherwise.
        */
        bool isLoaded(void) const 
        { 
                        // No lock required to read this state since no modify
            return (mLoadingState == LOADSTATE_LOADED); 
        }

                /** Returns whether the resource is currently in the process of
                        background loading.
                */
                LoadingState isLoading() const
                {
                        return mLoadingState;
                }

                /** Returns the current loading state.
                */
                LoadingState getLoadingState() const
                {
                        return mLoadingState;
                }



                /** Returns whether this Resource has been earmarked for background loading.
                @remarks
                        This option only makes sense when you have built Ogre with 
                        thread support (OGRE_THREAD_SUPPORT). If a resource has been marked
                        for background loading, then it won't load on demand like normal
                        when load() is called. Instead, it will ignore request to load()
                        except if the caller indicates it is the background loader. Any
                        other users of this resource should check isLoaded(), and if that
                        returns false, don't use the resource and come back later.
                */
                bool isBackgroundLoaded(void) const { return mIsBackgroundLoaded; }

                /** Tells the resource whether it is background loaded or not.
                @remarks
                        @see Resource::isBackgroundLoaded . Note that calling this only
                        defers the normal on-demand loading behaviour of a resource, it
                        does not actually set up a thread to make sure the resource gets
                        loaded in the background. You should use ResourceBackgroundLoadingQueue
                        to manage the actual loading (which will call this method itself).
                */
                void setBackgroundLoaded(bool bl) { mIsBackgroundLoaded = bl; }

                /** Escalates the loading of a background loaded resource. 
                @remarks
                        If a resource is set to load in the background, but something needs
                        it before it's been loaded, there could be a problem. If the user
                        of this resource really can't wait, they can escalate the loading
                        which basically pulls the loading into the current thread immediately.
                        If the resource is already being loaded but just hasn't quite finished
                        then this method will simply wait until the background load is complete.
                */
                void escalateLoading();

                /** Register a listener on this resource.
                        @see Resource::Listener
                */
                void addListener(Listener* lis);

                /** Remove a listener on this resource.
                        @see Resource::Listener
                */
                void removeListener(Listener* lis);

                /// Gets the group which this resource is a member of
                const String& getGroup(void) { return mGroup; }

                /** Change the resource group ownership of a Resource.
                @remarks
                        This method is generally reserved for internal use, although
                        if you really know what you're doing you can use it to move
                        this resource from one group to another.
                @param newGroup Name of the new group
                */
                void changeGroupOwnership(const String& newGroup);

                /// Gets the manager which created this resource
                ResourceManager* getCreator(void) { return mCreator; }
                /** Get the origin of this resource, e.g. a script file name.
                @remarks
                        This property will only contain something if the creator of
                        this resource chose to populate it. Script loaders are advised
                        to populate it.
                */
                const String& getOrigin(void) const { return mOrigin; }
                /// Notify this resource of it's origin
                void _notifyOrigin(const String& origin) { mOrigin = origin; }

    };

        /** Shared pointer to a Resource.
        @remarks
                This shared pointer allows many references to a resource to be held, and
                when the final reference is removed, the resource will be destroyed. 
                Note that the ResourceManager which created this Resource will be holding
                at least one reference, so this resource will not get destroyed until 
                someone removes the resource from the manager - this at least gives you
                strong control over when resources are freed. But the nature of the 
                shared pointer means that if anyone refers to the removed resource in the
                meantime, the resource will remain valid.
        @par
                You may well see references to ResourcePtr (i.e. ResourcePtr&) being passed 
                around internally within Ogre. These are 'weak references' ie they do 
                not increment the reference count on the Resource. This is done for 
                efficiency in temporary operations that shouldn't need to incur the 
                overhead of maintaining the reference count; however we don't recommend 
                you do it yourself since these references are not guaranteed to remain valid.
        */
        typedef SharedPtr<Resource> ResourcePtr;

        /** Interface describing a manual resource loader.
        @remarks
                Resources are usually loaded from files; however in some cases you
                want to be able to set the data up manually instead. This provides
                some problems, such as how to reload a Resource if it becomes
                unloaded for some reason, either because of memory constraints, or
                because a device fails and some or all of the data is lost.
        @par
                This interface should be implemented by all classes which wish to
                provide manual data to a resource. They provide a pointer to themselves
                when defining the resource (via the appropriate ResourceManager), 
                and will be called when the Resource tries to load. 
                They should implement the loadResource method such that the Resource 
                is in the end set up exactly as if it had loaded from a file, 
                although the implementations will likely differ between subclasses 
                of Resource, which is why no generic algorithm can be stated here. 
        @note
                The loader must remain valid for the entire life of the resource,
                so that if need be it can be called upon to re-load the resource
                at any time.
        */
        class _OgreExport ManualResourceLoader
        {
        public:
                ManualResourceLoader() {}
                virtual ~ManualResourceLoader() {}

                /** Called when a resource wishes to load.
                @param resource The resource which wishes to load
                */
                virtual void loadResource(Resource* resource) = 0;
        };
}

#endif