public IEnumerable <TapeRecord> ReadRecords(long afterVersion, int maxCount)
{
if (afterVersion < 0)
{
throw new ArgumentOutOfRangeException("afterVersion", "Must be zero or greater.");
}
if (maxCount <= 0)
{
throw new ArgumentOutOfRangeException("maxCount", "Must be more than zero.");
}
// afterVersion + maxCount > long.MaxValue, but transformed to avoid overflow
if (afterVersion > long.MaxValue - maxCount)
{
throw new ArgumentOutOfRangeException("maxCount", "Version will exceed long.MaxValue.");
}
var blob = _container.GetBlockBlobReference(_blobName);
var dataExists = blob.Exists();
// we return empty result if writer didn't even start writing to the storage.
if (!dataExists)
{
return(Enumerable.Empty <TapeRecord>());
}
var blockList = blob.DownloadBlockList();
var range = GetReadRange(blockList, afterVersion, maxCount);
if (range.Item4 == 0)
{
return(new TapeRecord[0]);
}
using (var s = blob.OpenRead())
{
s.ReadAheadSize = range.Item2;
s.Seek(range.Item1, SeekOrigin.Begin);
using (var reader = new BinaryReader(s))
{
var bytes = reader.ReadBytes(range.Item2);
using (var ms = new MemoryStream(bytes))
{
TapeStreamSerializer.SkipRecords(range.Item3, ms);
var records = Enumerable.Range(0, range.Item4)
.Select(i => TapeStreamSerializer.ReadRecord(ms))
.ToArray();
return(records);
}
}
}
}
public void WriteRecordTest()
{
byte[] expecteddata = Encoding.UTF8.GetBytes("TEST");
const long expectedversion = 3L;
var expectedrecord = new TapeRecord(expectedversion, expecteddata);
using (MemoryStream ms = new MemoryStream())
{
new TapeStreamSerializer().WriteRecord(ms, expecteddata, expectedversion);
ms.Seek(0, SeekOrigin.Begin);
var actual = new TapeStreamSerializer().ReadRecord(ms);
Assert.AreEqual(expectedrecord.Version, actual.Version);
Assert.AreEqual(expectedrecord.Data[0], actual.Data[0]);
}
}
public bool TryAppend(byte[] buffer, TapeAppendCondition appendCondition = new TapeAppendCondition())
{
if (buffer == null)
{
throw new ArgumentNullException("buffer");
}
if (buffer.Length == 0)
{
throw new ArgumentException("Buffer must contain at least one byte.");
}
long version;
int lastBlockSize;
long offset;
long firstVersion;
long count;
List <string> blockNames;
var blob = _container.GetBlockBlobReference(_blobName);
if (blob.Exists())
{
var blockList = blob.DownloadBlockList().ToArray();
blockNames = blockList.Select(bl => bl.Name).ToList();
var lastBlock = blockList.LastOrDefault();
if (default(ListBlockItem) == lastBlock)
{
version = 0;
lastBlockSize = int.MaxValue;
offset = 0;
firstVersion = 1;
count = 0;
}
else
{
var nameInfo = Naming.GetInfo(DecodeName(lastBlock.Name));
firstVersion = nameInfo.FirstVersion;
version = nameInfo.FirstVersion - 1 + nameInfo.Count;
count = nameInfo.Count;
if (lastBlock.Size > int.MaxValue)
{
throw new InvalidOperationException("last block size must be in 'int' range");
}
lastBlockSize = (int)lastBlock.Size;
offset = blockList.Reverse().Skip(1).Sum(l => l.Size);
}
}
else
{
version = 0;
lastBlockSize = int.MaxValue;
offset = 0;
firstVersion = 1;
count = 0;
blockNames = new List <string>();
}
if (!appendCondition.Satisfy(version))
{
return(false);
}
if (version > long.MaxValue - 1)
{
throw new IndexOutOfRangeException("Version is more than long.MaxValue.");
}
if (buffer.Length > FourMb)
{
throw new ArgumentException("buffer size must be less than or equal to 4 Mb", "buffer");
}
using (var outStream = new MemoryStream())
{
if (buffer.Length < MaxBlockSize && lastBlockSize <= MaxBlockSize - buffer.Length)
{
// read old block
using (var s = blob.OpenRead())
{
s.Seek(offset, SeekOrigin.Begin);
s.CopyTo(outStream);
TapeStreamSerializer.WriteRecord(outStream, buffer, version + 1);
count++;
blockNames.RemoveAt(blockNames.Count - 1);
}
}
else
{
TapeStreamSerializer.WriteRecord(outStream, buffer, version + 1);
firstVersion = version + 1;
count = 1;
}
var blockId = EncodeName(Naming.GetName(firstVersion, count));
string md5Hash;
outStream.Seek(0, SeekOrigin.Begin);
using (var md5 = MD5.Create()) {
md5Hash = Convert.ToBase64String(md5.ComputeHash(outStream));
}
outStream.Seek(0, SeekOrigin.Begin);
blob.PutBlock(blockId, outStream, md5Hash);
blockNames.Add(blockId);
blob.PutBlockList(blockNames);
return(true);
}
}
