private void SetupObjectContainerHeader()
{
// This method needs to set up the writer to do it's thing.
// There are two use cases for this writer.
// 1. This is a brand new, "in-memory" representation of the writer.
// 2. This is an existing blob, so we need to get the object container from blob storage.
// First, we need to check if the blob exists.
if (!this.blockBlob.Exists())
{
// The blob does not exist, we just create a new header and we are good
this.syncMarker = new byte[16];
new Random().NextBytes(syncMarker);
this.header = new ObjectContainerHeader(syncMarker)
{
CodecName = this.codec.Name,
Schema = this.serializer.WriterSchema.ToString()
};
// Since we are treating everything as in memory, we're going to fake the block list since we know there are none as of now.
this.blockNames = new List <string>();
}
else
{
// If the blob exists, we need to fetch our stuff so we can read
this.ReadObjectContainerHeaderFromBlob();
}
}
private void ReadObjectContainerHeaderFromBlob()
{
this.blockBlob.FetchAttributes();
// Deserialize the header from blob storage. We will only download the size of the header from blob storage.
using (var stream = this.blockBlob.OpenRead())
{
using (var decoder = new BinaryDecoder(stream, true))
{
this.header = ObjectContainerHeader.Read(decoder);
}
}
// We also need to set up the block list for appending. Since we already have it, let's use it.
// Get the existing block list.
var blockList = this.blockBlob.DownloadBlockList(BlockListingFilter.Committed);
this.blockNames = blockList
.Select(lbi => lbi.Name)
.ToList();
// Set this so the writer doesn't try to write the header again.
this.isHeaderWritten = true;
}