/// <summary> /// Returns true if the remote storage ETag and user file system ETags are equal. False - otherwise. /// </summary> /// <param name="userFileSystemPath">User file system item.</param> /// <param name="remoteStorageItem">Remote storage item info.</param> /// <remarks> /// ETag is updated on the server during every document update and is sent to client with a file. /// During client->server update it is sent back to the remote storage together with a modified content. /// This ensures the changes on the server are not overwritten if the document on the server is modified. /// </remarks> internal static async Task <bool> ETagEqualsAsync(string userFileSystemPath, FileSystemItemBasicInfo remoteStorageItem) { string remoteStorageETag = remoteStorageItem.ETag; string userFileSystemETag = await ETag.GetETagAsync(userFileSystemPath); if (string.IsNullOrEmpty(remoteStorageETag) && string.IsNullOrEmpty(userFileSystemETag)) { // We assume the remote storage is not using ETags or no ETag is ssociated with this file/folder. return(true); } return(remoteStorageETag == userFileSystemETag); }
/// <summary> /// Creates or updates folder in the remote storage. /// </summary> /// <param name="remoteStoragePath">Path of the folder to be created or updated in the remote storage.</param> /// <param name="newInfo">New information about the folder, such as modification date, attributes, custom data, etc.</param> /// <param name="mode">Specifies if a new folder should be created or existing folder should be updated.</param> /// <returns>New ETag returned from the remote storage.</returns> protected async Task <string> CreateOrUpdateFolderAsync(string remoteStoragePath, IFolderBasicInfo newInfo, FileMode mode) { // Get ETag and lock-token here and send it to the remote storage with the new item content/info if needed. if (mode == FileMode.Open) { // Get ETag. string eTag = await ETag.GetETagAsync(UserFileSystemPath); // Get lock-token. string lockToken = Lock?.LockToken; } DirectoryInfo remoteStorageItem = new DirectoryInfo(remoteStoragePath); try { Program.RemoteStorageMonitorInstance.Enabled = false; // Disable RemoteStorageMonitor to avoid circular calls. remoteStorageItem.Create(); string userFileSystemPath = Mapping.ReverseMapPath(remoteStoragePath); if (mode == FileMode.Open) { // Verify that the item in the remote storage is not modified since it was downloaded to the user file system. // In your real-life application you will send the ETag to the server as part of the update request. FileSystemItemBasicInfo itemInfo = Mapping.GetUserFileSysteItemBasicInfo(remoteStorageItem); if (!(await ETag.ETagEqualsAsync(userFileSystemPath, itemInfo))) { throw new ConflictException(Modified.Server, "Item is modified in the remote storage, ETags not equal."); } } // Update ETag/LastWriteTime in user file system, so the synchronyzation or remote storage monitor would not start the new update. // This is only required to avoid circular updates because of the simplicity of this sample. // In your real-life application you will receive a new ETag from server in the update response. string eTag = newInfo.LastWriteTime.ToBinary().ToString(); await ETag.SetETagAsync(userFileSystemPath, eTag); remoteStorageItem.Attributes = newInfo.Attributes; remoteStorageItem.CreationTimeUtc = newInfo.CreationTime; remoteStorageItem.LastWriteTimeUtc = newInfo.LastWriteTime; remoteStorageItem.LastAccessTimeUtc = newInfo.LastAccessTime; remoteStorageItem.LastWriteTimeUtc = newInfo.LastWriteTime; return(eTag); } finally { Program.RemoteStorageMonitorInstance.Enabled = true; } }
/// <summary> /// Returns true if the remote storage ETag and user file system ETags are equal. False - otherwise. /// </summary> /// <param name="userFileSystemPath">User file system item.</param> /// <param name="remoteStorageItem">Remote storage item info.</param> /// <remarks> /// ETag is updated on the server during every document update and is sent to client with a file. /// During client->server update it is sent back to the remote storage together with a modified content. /// This ensures the changes on the server are not overwritten if the document on the server is modified. /// </remarks> internal static async Task <bool> ETagEqualsAsync(string userFileSystemPath, FileSystemItemBasicInfo remoteStorageItem) { string remoteStorageETag = remoteStorageItem.ETag; // Intstead of the real ETag we store remote storage LastWriteTime when // creating and updating files/folders. string userFileSystemETag = await ETag.GetETagAsync(userFileSystemPath); if (string.IsNullOrEmpty(userFileSystemETag)) { // No ETag associated with the file. This is a new file created in user file system. return(false); } return(remoteStorageETag == userFileSystemETag); }
/// <summary> /// Creates or updates file in the remote storage. /// </summary> /// <param name="remoteStoragePath">Path of the file to be created or updated in the remote storage.</param> /// <param name="newInfo">New information about the file, such as modification date, attributes, custom data, etc.</param> /// <param name="mode">Specifies if a new file should be created or existing file should be updated.</param> /// <param name="newContentStream">New file content or null if the file content is not modified.</param> /// <returns>New ETag returned from the remote storage.</returns> protected async Task <string> CreateOrUpdateFileAsync(string remoteStoragePath, IFileBasicInfo newInfo, FileMode mode, Stream newContentStream = null) { // Get ETag and lock-token here and send it to the remote storage with the new item content/info if needed. if (mode == FileMode.Open) { // Get ETag. string eTag = await ETag.GetETagAsync(UserFileSystemPath); // Get lock-token. string lockToken = Lock?.LockToken; } FileInfo remoteStorageItem = new FileInfo(remoteStoragePath); try { Program.RemoteStorageMonitorInstance.Enabled = false; // Disable RemoteStorageMonitor to avoid circular calls. // If another thread is trying to sync the same file, this call will fail in other threads. // In your implementation you must lock your remote storage file, or block it for reading and writing by other means. await using (FileStream remoteStorageStream = remoteStorageItem.Open(mode, FileAccess.Write, FileShare.None)) { string userFileSystemPath = Mapping.ReverseMapPath(remoteStoragePath); if (mode == FileMode.Open) { // Verify that the item in the remote storage is not modified since it was downloaded to the user file system. // In your real-life application you will send the ETag to the server as part of the update request. FileSystemItemBasicInfo itemInfo = Mapping.GetUserFileSysteItemBasicInfo(remoteStorageItem); if (!(await ETag.ETagEqualsAsync(userFileSystemPath, itemInfo))) { throw new ConflictException(Modified.Server, "Item is modified in the remote storage, ETags not equal."); } } // Update ETag/LastWriteTime in user file system, so the synchronyzation or remote storage monitor would not start the new update. // This is only required to avoid circular updates because of the simplicity of this sample. // In your real-life application you will receive a new ETag from the server in the update response // and return it from this method. string eTag = newInfo.LastWriteTime.ToBinary().ToString(); await ETag.SetETagAsync(userFileSystemPath, eTag); // Update remote storage file content. if (newContentStream != null) { await newContentStream.CopyToAsync(remoteStorageStream); remoteStorageStream.SetLength(newContentStream.Length); } // Update remote storage file basic info. WindowsFileSystemItem.SetFileInformation( remoteStorageStream.SafeFileHandle, newInfo.Attributes, newInfo.CreationTime, newInfo.LastWriteTime, newInfo.LastAccessTime, newInfo.LastWriteTime); return(eTag); } } finally { Program.RemoteStorageMonitorInstance.Enabled = true; } }