/main/contrib/NGit/NGit.Storage.File/UnpackedObject.cs

/*
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using System.IO;
using ICSharpCode.SharpZipLib;
using ICSharpCode.SharpZipLib.Zip.Compression;
using NGit;
using NGit.Errors;
using NGit.Storage.File;
using NGit.Util;
using Sharpen;

namespace NGit.Storage.File
{
	/// <summary>Loose object loader.</summary>
	/// <remarks>Loose object loader. This class loads an object not stored in a pack.</remarks>
	public class UnpackedObject
	{
		private const int BUFFER_SIZE = 8192;

		/// <summary>Parse an object from the unpacked object format.</summary>
		/// <remarks>Parse an object from the unpacked object format.</remarks>
		/// <param name="raw">complete contents of the compressed object.</param>
		/// <param name="id">
		/// expected ObjectId of the object, used only for error reporting
		/// in exceptions.
		/// </param>
		/// <returns>loader to read the inflated contents.</returns>
		/// <exception cref="System.IO.IOException">the object cannot be parsed.</exception>
		public static ObjectLoader Parse(byte[] raw, AnyObjectId id)
		{
			WindowCursor wc = new WindowCursor(null);
			try
			{
				return Open(new ByteArrayInputStream(raw), null, id, wc);
			}
			finally
			{
				wc.Release();
			}
		}

		/// <exception cref="System.IO.IOException"></exception>
		internal static ObjectLoader Open(InputStream @in, FilePath path, AnyObjectId id, 
			WindowCursor wc)
		{
			try
			{
				@in = Buffer(@in);
				@in.Mark(20);
				byte[] hdr = new byte[64];
				IOUtil.ReadFully(@in, hdr, 0, 2);
				if (IsStandardFormat(hdr))
				{
					@in.Reset();
					Inflater inf = wc.Inflater();
					InputStream zIn = Inflate(@in, inf);
					int avail = ReadSome(zIn, hdr, 0, 64);
					if (avail < 5)
					{
						throw new CorruptObjectException(id, JGitText.Get().corruptObjectNoHeader);
					}
					MutableInteger p = new MutableInteger();
					int type = Constants.DecodeTypeString(id, hdr, unchecked((byte)' '), p);
					long size = RawParseUtils.ParseLongBase10(hdr, p.value, p);
					if (size < 0)
					{
						throw new CorruptObjectException(id, JGitText.Get().corruptObjectNegativeSize);
					}
					if (hdr[p.value++] != 0)
					{
						throw new CorruptObjectException(id, JGitText.Get().corruptObjectGarbageAfterSize
							);
					}
					if (path == null && int.MaxValue < size)
					{
						LargeObjectException.ExceedsByteArrayLimit e;
						e = new LargeObjectException.ExceedsByteArrayLimit();
						e.SetObjectId(id);
						throw e;
					}
					if (size < wc.GetStreamFileThreshold() || path == null)
					{
						byte[] data = new byte[(int)size];
						int n = avail - p.value;
						if (n > 0)
						{
							System.Array.Copy(hdr, p.value, data, 0, n);
						}
						IOUtil.ReadFully(zIn, data, n, data.Length - n);
						CheckValidEndOfStream(@in, inf, id, hdr);
						return new ObjectLoader.SmallObject(type, data);
					}
					return new UnpackedObject.LargeObject(type, size, path, id, wc.db);
				}
				else
				{
					ReadSome(@in, hdr, 2, 18);
					int c = hdr[0] & unchecked((int)(0xff));
					int type = (c >> 4) & 7;
					long size = c & 15;
					int shift = 4;
					int p = 1;
					while ((c & unchecked((int)(0x80))) != 0)
					{
						c = hdr[p++] & unchecked((int)(0xff));
						size += (c & unchecked((int)(0x7f))) << shift;
						shift += 7;
					}
					switch (type)
					{
						case Constants.OBJ_COMMIT:
						case Constants.OBJ_TREE:
						case Constants.OBJ_BLOB:
						case Constants.OBJ_TAG:
						{
							// Acceptable types for a loose object.
							break;
						}

						default:
						{
							throw new CorruptObjectException(id, JGitText.Get().corruptObjectInvalidType);
						}
					}
					if (path == null && int.MaxValue < size)
					{
						LargeObjectException.ExceedsByteArrayLimit e;
						e = new LargeObjectException.ExceedsByteArrayLimit();
						e.SetObjectId(id);
						throw e;
					}
					if (size < wc.GetStreamFileThreshold() || path == null)
					{
						@in.Reset();
						IOUtil.SkipFully(@in, p);
						Inflater inf = wc.Inflater();
						InputStream zIn = Inflate(@in, inf);
						byte[] data = new byte[(int)size];
						IOUtil.ReadFully(zIn, data, 0, data.Length);
						CheckValidEndOfStream(@in, inf, id, hdr);
						return new ObjectLoader.SmallObject(type, data);
					}
					return new UnpackedObject.LargeObject(type, size, path, id, wc.db);
				}
			}
			catch (SharpZipBaseException)
			{
				throw new CorruptObjectException(id, JGitText.Get().corruptObjectBadStream);
			}
		}

		/// <exception cref="System.IO.IOException"></exception>
		internal static long GetSize(InputStream @in, AnyObjectId id, WindowCursor wc)
		{
			try
			{
				@in = Buffer(@in);
				@in.Mark(20);
				byte[] hdr = new byte[64];
				IOUtil.ReadFully(@in, hdr, 0, 2);
				if (IsStandardFormat(hdr))
				{
					@in.Reset();
					Inflater inf = wc.Inflater();
					InputStream zIn = Inflate(@in, inf);
					int avail = ReadSome(zIn, hdr, 0, 64);
					if (avail < 5)
					{
						throw new CorruptObjectException(id, JGitText.Get().corruptObjectNoHeader);
					}
					MutableInteger p = new MutableInteger();
					Constants.DecodeTypeString(id, hdr, unchecked((byte)' '), p);
					long size = RawParseUtils.ParseLongBase10(hdr, p.value, p);
					if (size < 0)
					{
						throw new CorruptObjectException(id, JGitText.Get().corruptObjectNegativeSize);
					}
					return size;
				}
				else
				{
					ReadSome(@in, hdr, 2, 18);
					int c = hdr[0] & unchecked((int)(0xff));
					long size = c & 15;
					int shift = 4;
					int p = 1;
					while ((c & unchecked((int)(0x80))) != 0)
					{
						c = hdr[p++] & unchecked((int)(0xff));
						size += (c & unchecked((int)(0x7f))) << shift;
						shift += 7;
					}
					return size;
				}
			}
			catch (SharpZipBaseException)
			{
				throw new CorruptObjectException(id, JGitText.Get().corruptObjectBadStream);
			}
		}

		/// <exception cref="System.IO.IOException"></exception>
		/// <exception cref="NGit.Errors.CorruptObjectException"></exception>
		private static void CheckValidEndOfStream(InputStream @in, Inflater inf, AnyObjectId
			 id, byte[] buf)
		{
			for (; ; )
			{
				int r;
				try
				{
					r = inf.Inflate(buf);
				}
				catch (SharpZipBaseException)
				{
					throw new CorruptObjectException(id, JGitText.Get().corruptObjectBadStream);
				}
				if (r != 0)
				{
					throw new CorruptObjectException(id, JGitText.Get().corruptObjectIncorrectLength);
				}
				if (inf.IsFinished)
				{
					if (inf.RemainingInput != 0 || @in.Read() != -1)
					{
						throw new CorruptObjectException(id, JGitText.Get().corruptObjectBadStream);
					}
					break;
				}
				if (!inf.IsNeedingInput)
				{
					throw new CorruptObjectException(id, JGitText.Get().corruptObjectBadStream);
				}
				r = @in.Read(buf);
				if (r <= 0)
				{
					throw new CorruptObjectException(id, JGitText.Get().corruptObjectBadStream);
				}
				inf.SetInput(buf, 0, r);
			}
		}

		private static bool IsStandardFormat(byte[] hdr)
		{
			// Try to determine if this is a standard format loose object or
			// a pack style loose object. The standard format is completely
			// compressed with zlib so the first byte must be 0x78 (15-bit
			// window size, deflated) and the first 16 bit word must be
			// evenly divisible by 31. Otherwise its a pack style object.
			//
			int fb = hdr[0] & unchecked((int)(0xff));
			return fb == unchecked((int)(0x78)) && (((fb << 8) | hdr[1] & unchecked((int)(0xff
				))) % 31) == 0;
		}

		private static InputStream Inflate(InputStream @in, long size, ObjectId id)
		{
			Inflater inf = InflaterCache.Get();
			return new _InflaterInputStream_286(size, id, @in, inf);
		}

		private sealed class _InflaterInputStream_286 : InflaterInputStream
		{
			public _InflaterInputStream_286(long size, ObjectId id, InputStream baseArg1, Inflater
				 baseArg2) : base(baseArg1, baseArg2)
			{
				this.size = size;
				this.id = id;
				this.remaining = size;
			}

			private long remaining;

			/// <exception cref="System.IO.IOException"></exception>
			public override int Read(byte[] b, int off, int cnt)
			{
				try
				{
					int r = base.Read(b, off, cnt);
					if (r > 0)
					{
						this.remaining -= r;
					}
					return r;
				}
				catch (SharpZipBaseException)
				{
					throw new CorruptObjectException(id, JGitText.Get().corruptObjectBadStream);
				}
			}

			/// <exception cref="System.IO.IOException"></exception>
			public override void Close()
			{
				try
				{
					if (this.remaining <= 0)
					{
						UnpackedObject.CheckValidEndOfStream(this.@in, this.inf, id, new byte[64]);
					}
				}
				finally
				{
					InflaterCache.Release(this.inf);
					base.Close();
				}
			}

			private readonly long size;

			private readonly ObjectId id;
		}

		private static InflaterInputStream Inflate(InputStream @in, Inflater inf)
		{
			return new InflaterInputStream(@in, inf, BUFFER_SIZE);
		}

		private static BufferedInputStream Buffer(InputStream @in)
		{
			return new BufferedInputStream(@in, BUFFER_SIZE);
		}

		/// <exception cref="System.IO.IOException"></exception>
		private static int ReadSome(InputStream @in, byte[] hdr, int off, int cnt)
		{
			int avail = 0;
			while (0 < cnt)
			{
				int n = @in.Read(hdr, off, cnt);
				if (n < 0)
				{
					break;
				}
				avail += n;
				off += n;
				cnt -= n;
			}
			return avail;
		}

		internal sealed class LargeObject : ObjectLoader
		{
			private readonly int type;

			private readonly long size;

			private readonly FilePath path;

			private readonly ObjectId id;

			private readonly FileObjectDatabase source;

			internal LargeObject(int type, long size, FilePath path, AnyObjectId id, FileObjectDatabase
				 db)
			{
				this.type = type;
				this.size = size;
				this.path = path;
				this.id = id.Copy();
				this.source = db;
			}

			public override int GetType()
			{
				return type;
			}

			public override long GetSize()
			{
				return size;
			}

			public override bool IsLarge()
			{
				return true;
			}

			/// <exception cref="NGit.Errors.LargeObjectException"></exception>
			public override byte[] GetCachedBytes()
			{
				throw new LargeObjectException(id);
			}

			/// <exception cref="NGit.Errors.MissingObjectException"></exception>
			/// <exception cref="System.IO.IOException"></exception>
			public override ObjectStream OpenStream()
			{
				InputStream @in;
				try
				{
					@in = Buffer(new FileInputStream(path));
				}
				catch (FileNotFoundException)
				{
					// If the loose file no longer exists, it may have been
					// moved into a pack file in the mean time. Try again
					// to locate the object.
					//
					return source.Open(id, type).OpenStream();
				}
				bool ok = false;
				try
				{
					byte[] hdr = new byte[64];
					@in.Mark(20);
					IOUtil.ReadFully(@in, hdr, 0, 2);
					if (IsStandardFormat(hdr))
					{
						@in.Reset();
						@in = Buffer(Inflate(@in, size, id));
						while (0 < @in.Read())
						{
							continue;
						}
					}
					else
					{
						ReadSome(@in, hdr, 2, 18);
						int c = hdr[0] & unchecked((int)(0xff));
						int p = 1;
						while ((c & unchecked((int)(0x80))) != 0)
						{
							c = hdr[p++] & unchecked((int)(0xff));
						}
						@in.Reset();
						IOUtil.SkipFully(@in, p);
						@in = Buffer(Inflate(@in, size, id));
					}
					ok = true;
					return new ObjectStream.Filter(type, size, @in);
				}
				finally
				{
					if (!ok)
					{
						@in.Close();
					}
				}
			}
		}
	}
}