opensim/OpenSim/Framework/IAssetCache.cs

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using OpenMetaverse;
using OpenMetaverse.Packets;

namespace OpenSim.Framework
{
    public delegate void AssetRequestCallback(UUID assetId, AssetBase asset);

    /// <summary>
    /// Interface to the local asset cache.  This is the mechanism through which assets can be added and requested.
    /// </summary>
    public interface IAssetCache :  IPlugin
    {
        /// <value>
        /// The 'server' from which assets can be requested and to which assets are persisted.
        /// </value>
       
        void Initialise(ConfigSettings cs);

        /// <summary>
        /// Report statistical data to the log.
        /// </summary>
        void ShowState();
        
        /// <summary>
        /// Clear the asset cache.
        /// </summary>
        void Clear();
        
        /// <summary>
        /// Get an asset only if it's already in the cache.
        /// </summary>
        /// <param name="assetId"></param>
        /// <param name="asset"></param>
        /// <returns>true if the asset was in the cache, false if it was not</returns>
        bool TryGetCachedAsset(UUID assetID, out AssetBase asset);
        
        /// <summary>
        /// Asynchronously retrieve an asset.
        /// </summary>
        /// <param name="assetId"></param>
        /// <param name="callback">
        /// <param name="isTexture"></param>
        /// A callback invoked when the asset has either been found or not found.
        /// If the asset was found this is called with the asset UUID and the asset data
        /// If the asset was not found this is still called with the asset UUID but with a null asset data reference</param>
        void GetAsset(UUID assetID, AssetRequestCallback callback, bool isTexture);
        
        /// <summary>
        /// Synchronously retreive an asset.  If the asset isn't in the cache, a request will be made to the persistent store to
        /// load it into the cache.
        /// </summary>
        ///
        /// XXX We'll keep polling the cache until we get the asset or we exceed
        /// the allowed number of polls.  This isn't a very good way of doing things since a single thread
        /// is processing inbound packets, so if the asset server is slow, we could block this for up to
        /// the timeout period.  Whereever possible we want to use the asynchronous callback GetAsset()
        ///
        /// <param name="assetID"></param>
        /// <param name="isTexture"></param>
        /// <returns>null if the asset could not be retrieved</returns>
        AssetBase GetAsset(UUID assetID, bool isTexture);
        
        /// <summary>
        /// Add an asset to both the persistent store and the cache.
        /// </summary>
        /// <param name="asset"></param>
        void AddAsset(AssetBase asset);
        
        /// <summary>
        /// Expire an asset from the cache
        /// </summary>
        /// Allows you to clear a specific asset by uuid out
        /// of the asset cache.  This is needed because the osdynamic
        /// texture code grows the asset cache without bounds.  The
        /// real solution here is a much better cache archicture, but
        /// this is a stop gap measure until we have such a thing.
        void ExpireAsset(UUID assetID);
        
        /// <summary>
        /// Handle an asset request from the client.  The result will be sent back asynchronously.
        /// </summary>
        /// <param name="userInfo"></param>
        /// <param name="transferRequest"></param>
        void AddAssetRequest(IClientAPI userInfo, TransferRequestPacket transferRequest);
    }

}