public GenerateFilePreview(
IOptions <StorageConfiguration> storageConfig,
FileStorageService fileStorageService)
{
StorageConfig = storageConfig.Value;
FileStorageService = fileStorageService;
PreviewFileExtensions = new HashSet <string>(
PreviewFileTypes.List,
StringComparer.InvariantCultureIgnoreCase);
}
public async Task <string> GeneratePreview(Guid datasetId, Guid fileId, CancellationToken cancellationToken)
{
cancellationToken.ThrowIfCancellationRequested();
var details = await FileStorageService.GetDatasetFileStorageDetails(datasetId, fileId, cancellationToken);
var blob = details as DatasetFileBlobStorageDetails;
if (blob == null)
{
return(null);
}
var fileExt = Path.GetExtension(blob.Name).TrimStart('.');
if (!PreviewFileExtensions.Contains(fileExt))
{
return(null);
}
var credentials = new StorageCredentials(blob.Account, StorageConfig.Accounts[blob.Account]);
var storageAcct = new CloudStorageAccount(credentials, true);
var blobClient = storageAcct.CreateCloudBlobClient();
var blobContainer = blobClient.GetContainerReference(blob.Container);
var blobReference = blobContainer.GetBlockBlobReference(blob.FullName);
int readLen;
var readBytes = new byte[MaxPreviewSize];
using (var readStream = await blobReference.OpenReadAsync(null, null, null, cancellationToken))
{
readLen = await readStream.ReadAsync(readBytes, 0, readBytes.Length, cancellationToken);
}
int previewLen = readLen;
while (previewLen > 0)
{
byte ch = readBytes[previewLen - 1];
if (ch == '\n')
{
break;
}
--previewLen;
}
if (previewLen == 0)
{
previewLen = readLen;
}
return(Encoding.UTF8.GetString(readBytes, 0, previewLen));
}