GitSharp.Core.DirectoryCache.DirCache.ReadFrom C# (CSharp) Method

		private void ReadFrom(Stream inStream)
		{
			var @in = new StreamReader(inStream);
			MessageDigest md = Constants.newMessageDigest();

			// Read the index header and verify we understand it.
			//
			var hdr = new byte[20];
			IO.ReadFully(inStream, hdr, 0, 12);
			md.Update(hdr, 0, 12);
			if (!IsDIRC(hdr))
			{
				throw new CorruptObjectException("Not a DIRC file.");
			}

			int ver = NB.DecodeInt32(hdr, 4);
			if (ver != 2)
			{
				throw new CorruptObjectException("Unknown DIRC version " + ver);
			}

			_entryCnt = NB.DecodeInt32(hdr, 8);
			if (_entryCnt < 0)
			{
				throw new CorruptObjectException("DIRC has too many entries.");
			}

			// Load the individual file entries.
			//
			var infos = new byte[InfoLen * _entryCnt];
			_sortedEntries = new DirCacheEntry[_entryCnt];
			for (int i = 0; i < _entryCnt; i++)
			{
				_sortedEntries[i] = new DirCacheEntry(infos, i * InfoLen, inStream, md);
			}
			_lastModified = _liveFile.LastWriteTime;

			// After the file entries are index extensions, and then a footer.
			//
			while (true)
			{
				var pos = inStream.Position;
				IO.ReadFully(inStream, hdr, 0, 20);

				int nextByte = @in.Read();
				if (nextByte < 0 || inStream.Position == inStream.Length)
				{
					// No extensions present; the file ended where we expected.
					//
					break;
				}
				inStream.Seek(pos, SeekOrigin.Begin);

				switch (NB.DecodeInt32(hdr, 0))
				{
					case ExtTree:
						var raw = new byte[NB.DecodeInt32(hdr, 4)];
						md.Update(hdr, 0, 8);
						IO.skipFully(inStream, 8);
						IO.ReadFully(inStream, raw, 0, raw.Length);
						md.Update(raw, 0, raw.Length);
						_cacheTree = new DirCacheTree(raw, new MutableInteger(), null);
						break;

					default:
						if (hdr[0] >= (byte)'A' && hdr[0] <= (byte)'Z')
						{
							// The extension is optional and is here only as
							// a performance optimization. Since we do not
							// understand it, we can safely skip past it.
							//
							IO.skipFully(inStream, NB.decodeUInt32(hdr, 4));
						}
						else
						{
							// The extension is not an optimization and is
							// _required_ to understand this index format.
							// Since we did not trap it above we must abort.
							//
							throw new CorruptObjectException("DIRC extension '"
									+ Constants.CHARSET.GetString(hdr.Take(4).ToArray())
									+ "' not supported by this version.");
						}

						break;
				}
			}

			byte[] exp = md.Digest();
			if (!exp.SequenceEqual(hdr))
			{
				throw new CorruptObjectException("DIRC checksum mismatch");
			}
		}