diff options
author | vnugent <public@vaughnnugent.com> | 2023-01-08 14:44:01 -0500 |
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committer | vnugent <public@vaughnnugent.com> | 2023-01-08 14:44:01 -0500 |
commit | be6dc557a3b819248b014992eb96c1cb21f8112b (patch) | |
tree | 5361530552856ba8154bfcfbfac8377549117c9e /Utils/src/Async/AsyncUpdatableResource.cs | |
parent | 072a1294646542a73007784d08a35ffcad557b1b (diff) |
Initial commit
Diffstat (limited to 'Utils/src/Async/AsyncUpdatableResource.cs')
-rw-r--r-- | Utils/src/Async/AsyncUpdatableResource.cs | 111 |
1 files changed, 111 insertions, 0 deletions
diff --git a/Utils/src/Async/AsyncUpdatableResource.cs b/Utils/src/Async/AsyncUpdatableResource.cs new file mode 100644 index 0000000..b4ce519 --- /dev/null +++ b/Utils/src/Async/AsyncUpdatableResource.cs @@ -0,0 +1,111 @@ +/* +* Copyright (c) 2022 Vaughn Nugent +* +* Library: VNLib +* Package: VNLib.Utils +* File: AsyncUpdatableResource.cs +* +* AsyncUpdatableResource.cs is part of VNLib.Utils which is part of the larger +* VNLib collection of libraries and utilities. +* +* VNLib.Utils 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 2 of the License, +* or (at your option) any later version. +* +* VNLib.Utils 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 VNLib.Utils. If not, see http://www.gnu.org/licenses/. +*/ + +using System; +using System.IO; +using System.Text.Json; +using System.Threading.Tasks; + +using VNLib.Utils.IO; +using VNLib.Utils.Resources; + +namespace VNLib.Utils.Async +{ + /// <summary> + /// A callback delegate used for updating a <see cref="AsyncUpdatableResource"/> + /// </summary> + /// <param name="source">The <see cref="AsyncUpdatableResource"/> to be updated</param> + /// <param name="data">The serialized data to be stored/updated</param> + /// <exception cref="ResourceUpdateFailedException"></exception> + public delegate Task AsyncUpdateCallback(object source, Stream data); + /// <summary> + /// A callback delegate invoked when a <see cref="AsyncUpdatableResource"/> delete is requested + /// </summary> + /// <param name="source">The <see cref="AsyncUpdatableResource"/> to be deleted</param> + /// <exception cref="ResourceDeleteFailedException"></exception> + public delegate Task AsyncDeleteCallback(object source); + + /// <summary> + /// Implemented by a resource that is backed by an external data store, that when modified or deleted will + /// be reflected to the backing store. + /// </summary> + public abstract class AsyncUpdatableResource : BackedResourceBase, IAsyncExclusiveResource + { + protected abstract AsyncUpdateCallback UpdateCb { get; } + protected abstract AsyncDeleteCallback DeleteCb { get; } + + /// <summary> + /// Releases the resource and flushes pending changes to its backing store. + /// </summary> + /// <returns>A task that represents the async operation</returns> + /// <exception cref="InvalidOperationException"></exception> + /// <exception cref="ResourceDeleteFailedException"></exception> + /// <exception cref="ResourceUpdateFailedException"></exception> + public virtual async ValueTask ReleaseAsync() + { + //If resource has already been realeased, return + if (IsReleased) + { + return; + } + //If deleted flag is set, invoke the delete callback + if (Deleted) + { + await DeleteCb(this).ConfigureAwait(true); + } + //If the state has been modifed, flush changes to the store + else if (Modified) + { + await FlushPendingChangesAsync().ConfigureAwait(true); + } + //Set the released value + IsReleased = true; + } + + /// <summary> + /// <para> + /// Writes the current state of the the resource to the backing store + /// immediatly by invoking the specified callback. + /// </para> + /// <para> + /// Only call this method if your store supports multiple state updates + /// </para> + /// </summary> + protected virtual async Task FlushPendingChangesAsync() + { + //Get the resource + object resource = GetResource(); + //Open a memory stream to store data in + using VnMemoryStream data = new(); + //Serialize and write to stream + VnEncoding.JSONSerializeToBinary(resource, data, resource.GetType(), base.JSO); + //Reset stream to begining + _ = data.Seek(0, SeekOrigin.Begin); + //Invoke update callback + await UpdateCb(this, data).ConfigureAwait(true); + //Clear modified flag + Modified = false; + } + } +} |