private static BaseMetadata readMetadataFromDatabase(string location, ReadOptions options, CancellationToken token, int timeoutSeconds)
{
BaseMetadata metadata = null;
using (MetadataDbCommands metadataCommands = new MetadataDbCommands())
{
metadata = metadataCommands.findMetadataByLocation(location);
if (metadata != null)
{
metadata.IsImported = true;
if (options.HasFlag(ReadOptions.LEAVE_STREAM_OPENED_AFTER_READ))
{
Stream data = FileUtils.waitForFileAccess(location, FileAccess.Read,
FILE_OPEN_ASYNC_TIMEOUT_MS, token);
metadata.Data = data;
}
// check if metadata stored in the database is outdated
FileInfo info = new FileInfo(location);
info.Refresh();
if (info.Exists == false)
{
metadata.MetadataReadError = new FileNotFoundException("File not found", location);
return(metadata);
}
if ((info.LastWriteTime - metadata.LastModifiedDate) > TimeSpan.FromSeconds(10))
{
// metadata is outdated so update in database
Logger.Log.Info("Updated: " + location + " - Database timestamp: " + metadata.LastModifiedDate.ToString() + " Disk timestamp: " + info.LastWriteTime.ToString());
int id = metadata.Id;
metadata = MetadataFileFactory.read(location, options, token, timeoutSeconds);
if (metadata != null)
{
metadata.IsImported = true;
metadata.Id = id;
write(metadata, WriteOptions.WRITE_TO_DATABASE, null);
}
}
if (info.Attributes.HasFlag(FileAttributes.ReadOnly))
{
metadata.IsReadOnly = true;
}
}
}
return(metadata);
}
public static void write(BaseMetadata metadata, WriteOptions options, CancellableOperationProgressBase progress = null)
{
if (options.HasFlag(WriteOptions.AUTO) || options.HasFlag(WriteOptions.WRITE_TO_DISK))
{
MetadataFileFactory.write(metadata, progress);
}
if (metadata.IsImported && (options.HasFlag(WriteOptions.AUTO) || options.HasFlag(WriteOptions.WRITE_TO_DATABASE)))
{
using (MetadataDbCommands metadataCommands = new MetadataDbCommands())
{
metadata = metadataCommands.update(metadata);
}
}
metadata.IsModified = false;
}
/// <summary>
/// Returns null when metadata does not exist
/// UnknownMetadata when metadata is not recognized
/// </summary>
/// <param name="location"></param>
/// <param name="options"></param>
/// <param name="token"></param>
/// <returns></returns>
public static BaseMetadata read(string location, ReadOptions options, CancellationToken token, int timeoutSeconds = 60)
{
limitConcurrentReadsSemaphore.Wait(token);
try
{
// initialize metadata with a dummy in case of exceptions
BaseMetadata metadata = null;
if (string.IsNullOrEmpty(location) || token.IsCancellationRequested == true)
{
return(metadata);
}
else if (FileUtils.isUrl(location))
{
metadata = readMetadataFromWeb(location, options, token, timeoutSeconds);
}
else
{
if (options.HasFlag(ReadOptions.AUTO) || options.HasFlag(ReadOptions.READ_FROM_DATABASE))
{
metadata = readMetadataFromDatabase(location, options, token, timeoutSeconds);
}
if ((metadata == null && options.HasFlag(ReadOptions.AUTO)) ||
options.HasFlag(ReadOptions.READ_FROM_DISK))
{
metadata = MetadataFileFactory.read(location, options, token, timeoutSeconds);
}
}
metadata.IsModified = false;
return(metadata);
}
catch (OperationCanceledException)
{
// convert operationcanceled to taskcanceled when the token aborts waiting for the semaphore
throw new TaskCanceledException();
}
finally
{
limitConcurrentReadsSemaphore.Release();
}
}
