Update //third_party/protobuf to version 3.

third_party/protobuf/csharp/src/Google.Protobuf/CodedInputStream.cs

+#region Copyright notice and license
+// Protocol Buffers - Google's data interchange format
+// Copyright 2008 Google Inc.  All rights reserved.
+// https://developers.google.com/protocol-buffers/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+#endregion
+
+using Google.Protobuf.Collections;
+using System;
+using System.Collections.Generic;
+using System.IO;
+
+namespace Google.Protobuf
+{
+    /// <summary>
+    /// Reads and decodes protocol message fields.
+    /// </summary>
+    /// <remarks>
+    /// <para>
+    /// This class is generally used by generated code to read appropriate
+    /// primitives from the stream. It effectively encapsulates the lowest
+    /// levels of protocol buffer format.
+    /// </para>
+    /// <para>
+    /// Repeated fields and map fields are not handled by this class; use <see cref="RepeatedField{T}"/>
+    /// and <see cref="MapField{TKey, TValue}"/> to serialize such fields.
+    /// </para>
+    /// </remarks>
+    public sealed class CodedInputStream
+    {
+        /// <summary>
+        /// Buffer of data read from the stream or provided at construction time.
+        /// </summary>
+        private readonly byte[] buffer;
+
+        /// <summary>
+        /// The index of the buffer at which we need to refill from the stream (if there is one).
+        /// </summary>
+        private int bufferSize;
+
+        private int bufferSizeAfterLimit = 0;
+        /// <summary>
+        /// The position within the current buffer (i.e. the next byte to read)
+        /// </summary>
+        private int bufferPos = 0;
+
+        /// <summary>
+        /// The stream to read further input from, or null if the byte array buffer was provided
+        /// directly on construction, with no further data available.
+        /// </summary>
+        private readonly Stream input;
+
+        /// <summary>
+        /// The last tag we read. 0 indicates we've read to the end of the stream
+        /// (or haven't read anything yet).
+        /// </summary>
+        private uint lastTag = 0;
+
+        /// <summary>
+        /// The next tag, used to store the value read by PeekTag.
+        /// </summary>
+        private uint nextTag = 0;
+        private bool hasNextTag = false;
+
+        internal const int DefaultRecursionLimit = 64;
+        internal const int DefaultSizeLimit = 64 << 20; // 64MB
+        internal const int BufferSize = 4096;
+
+        /// <summary>
+        /// The total number of bytes read before the current buffer. The
+        /// total bytes read up to the current position can be computed as
+        /// totalBytesRetired + bufferPos.
+        /// </summary>
+        private int totalBytesRetired = 0;
+
+        /// <summary>
+        /// The absolute position of the end of the current message.
+        /// </summary> 
+        private int currentLimit = int.MaxValue;
+
+        private int recursionDepth = 0;
+
+        private readonly int recursionLimit;
+        private readonly int sizeLimit;
+
+        #region Construction
+        // Note that the checks are performed such that we don't end up checking obviously-valid things
+        // like non-null references for arrays we've just created.
+
+        /// <summary>
+        /// Creates a new CodedInputStream reading data from the given byte array.
+        /// </summary>
+        public CodedInputStream(byte[] buffer) : this(null, Preconditions.CheckNotNull(buffer, "buffer"), 0, buffer.Length)
+        {            
+        }
+
+        /// <summary>
+        /// Creates a new CodedInputStream that reads from the given byte array slice.
+        /// </summary>
+        public CodedInputStream(byte[] buffer, int offset, int length)
+            : this(null, Preconditions.CheckNotNull(buffer, "buffer"), offset, offset + length)
+        {            
+            if (offset < 0 || offset > buffer.Length)
+            {
+                throw new ArgumentOutOfRangeException("offset", "Offset must be within the buffer");
+            }
+            if (length < 0 || offset + length > buffer.Length)
+            {
+                throw new ArgumentOutOfRangeException("length", "Length must be non-negative and within the buffer");
+            }
+        }
+
+        /// <summary>
+        /// Creates a new CodedInputStream reading data from the given stream.
+        /// </summary>
+        public CodedInputStream(Stream input) : this(input, new byte[BufferSize], 0, 0)
+        {
+            Preconditions.CheckNotNull(input, "input");
+        }
+
+        /// <summary>
+        /// Creates a new CodedInputStream reading data from the given
+        /// stream and buffer, using the default limits.
+        /// </summary>
+        internal CodedInputStream(Stream input, byte[] buffer, int bufferPos, int bufferSize)
+        {
+            this.input = input;
+            this.buffer = buffer;
+            this.bufferPos = bufferPos;
+            this.bufferSize = bufferSize;
+            this.sizeLimit = DefaultSizeLimit;
+            this.recursionLimit = DefaultRecursionLimit;
+        }
+
+        /// <summary>
+        /// Creates a new CodedInputStream reading data from the given
+        /// stream and buffer, using the specified limits.
+        /// </summary>
+        /// <remarks>
+        /// This chains to the version with the default limits instead of vice versa to avoid
+        /// having to check that the default values are valid every time.
+        /// </remarks>
+        internal CodedInputStream(Stream input, byte[] buffer, int bufferPos, int bufferSize, int sizeLimit, int recursionLimit)
+            : this(input, buffer, bufferPos, bufferSize)
+        {
+            if (sizeLimit <= 0)
+            {
+                throw new ArgumentOutOfRangeException("sizeLimit", "Size limit must be positive");
+            }
+            if (recursionLimit <= 0)
+            {
+                throw new ArgumentOutOfRangeException("recursionLimit!", "Recursion limit must be positive");
+            }
+            this.sizeLimit = sizeLimit;
+            this.recursionLimit = recursionLimit;
+        }
+        #endregion
+
+        /// <summary>
+        /// Creates a <see cref="CodedInputStream"/> with the specified size and recursion limits, reading
+        /// from an input stream.
+        /// </summary>
+        /// <remarks>
+        /// This method exists separately from the constructor to reduce the number of constructor overloads.
+        /// It is likely to be used considerably less frequently than the constructors, as the default limits
+        /// are suitable for most use cases.
+        /// </remarks>
+        /// <param name="input">The input stream to read from</param>
+        /// <param name="sizeLimit">The total limit of data to read from the stream.</param>
+        /// <param name="recursionLimit">The maximum recursion depth to allow while reading.</param>
+        /// <returns>A <c>CodedInputStream</c> reading from <paramref name="input"/> with the specified size
+        /// and recursion limits.</returns>
+        public static CodedInputStream CreateWithLimits(Stream input, int sizeLimit, int recursionLimit)
+        {
+            return new CodedInputStream(input, new byte[BufferSize], 0, 0, sizeLimit, recursionLimit);
+        }
+
+        /// <summary>
+        /// Returns the current position in the input stream, or the position in the input buffer
+        /// </summary>
+        public long Position 
+        {
+            get
+            {
+                if (input != null)
+                {
+                    return input.Position - ((bufferSize + bufferSizeAfterLimit) - bufferPos);
+                }
+                return bufferPos;
+            }
+        }
+
+        /// <summary>
+        /// Returns the last tag read, or 0 if no tags have been read or we've read beyond
+        /// the end of the stream.
+        /// </summary>
+        internal uint LastTag { get { return lastTag; } }
+
+        /// <summary>
+        /// Returns the size limit for this stream.
+        /// </summary>
+        /// <remarks>
+        /// This limit is applied when reading from the underlying stream, as a sanity check. It is
+        /// not applied when reading from a byte array data source without an underlying stream.
+        /// The default value is 64MB.
+        /// </remarks>
+        /// <value>
+        /// The size limit.
+        /// </value>
+        public int SizeLimit { get { return sizeLimit; } }
+
+        /// <summary>
+        /// Returns the recursion limit for this stream. This limit is applied whilst reading messages,
+        /// to avoid maliciously-recursive data.
+        /// </summary>
+        /// <remarks>
+        /// The default limit is 64.
+        /// </remarks>
+        /// <value>
+        /// The recursion limit for this stream.
+        /// </value>
+        public int RecursionLimit { get { return recursionLimit; } }
+
+        #region Validation
+        /// <summary>
+        /// Verifies that the last call to ReadTag() returned tag 0 - in other words,
+        /// we've reached the end of the stream when we expected to.
+        /// </summary>
+        /// <exception cref="InvalidProtocolBufferException">The 
+        /// tag read was not the one specified</exception>
+        internal void CheckReadEndOfStreamTag()
+        {
+            if (lastTag != 0)
+            {
+                throw InvalidProtocolBufferException.MoreDataAvailable();
+            }
+        }
+        #endregion
+
+        #region Reading of tags etc
+
+        /// <summary>
+        /// Peeks at the next field tag. This is like calling <see cref="ReadTag"/>, but the
+        /// tag is not consumed. (So a subsequent call to <see cref="ReadTag"/> will return the
+        /// same value.)
+        /// </summary>
+        public uint PeekTag()
+        {
+            if (hasNextTag)
+            {
+                return nextTag;
+            }
+
+            uint savedLast = lastTag;
+            nextTag = ReadTag();
+            hasNextTag = true;
+            lastTag = savedLast; // Undo the side effect of ReadTag
+            return nextTag;
+        }
+
+        /// <summary>
+        /// Reads a field tag, returning the tag of 0 for "end of stream".
+        /// </summary>
+        /// <remarks>
+        /// If this method returns 0, it doesn't necessarily mean the end of all
+        /// the data in this CodedInputStream; it may be the end of the logical stream
+        /// for an embedded message, for example.
+        /// </remarks>
+        /// <returns>The next field tag, or 0 for end of stream. (0 is never a valid tag.)</returns>
+        public uint ReadTag()
+        {
+            if (hasNextTag)
+            {
+                lastTag = nextTag;
+                hasNextTag = false;
+                return lastTag;
+            }
+
+            // Optimize for the incredibly common case of having at least two bytes left in the buffer,
+            // and those two bytes being enough to get the tag. This will be true for fields up to 4095.
+            if (bufferPos + 2 <= bufferSize)
+            {
+                int tmp = buffer[bufferPos++];
+                if (tmp < 128)
+                {
+                    lastTag = (uint)tmp;
+                }
+                else
+                {
+                    int result = tmp & 0x7f;
+                    if ((tmp = buffer[bufferPos++]) < 128)
+                    {
+                        result |= tmp << 7;
+                        lastTag = (uint) result;
+                    }
+                    else
+                    {
+                        // Nope, rewind and go the potentially slow route.
+                        bufferPos -= 2;
+                        lastTag = ReadRawVarint32();
+                    }
+                }
+            }
+            else
+            {
+                if (IsAtEnd)
+                {
+                    lastTag = 0;
+                    return 0; // This is the only case in which we return 0.
+                }
+
+                lastTag = ReadRawVarint32();
+            }
+            if (lastTag == 0)
+            {
+                // If we actually read zero, that's not a valid tag.
+                throw InvalidProtocolBufferException.InvalidTag();
+            }
+            return lastTag;
+        }
+
+        /// <summary>
+        /// Skips the data for the field with the tag we've just read.
+        /// This should be called directly after <see cref="ReadTag"/>, when
+        /// the caller wishes to skip an unknown field.
+        /// </summary>
+        public void SkipLastField()
+        {
+            if (lastTag == 0)
+            {
+                throw new InvalidOperationException("SkipLastField cannot be called at the end of a stream");
+            }
+            switch (WireFormat.GetTagWireType(lastTag))
+            {
+                case WireFormat.WireType.StartGroup:
+                    SkipGroup();
+                    break;
+                case WireFormat.WireType.EndGroup:
+                    // Just ignore; there's no data following the tag.
+                    break;
+                case WireFormat.WireType.Fixed32:
+                    ReadFixed32();
+                    break;
+                case WireFormat.WireType.Fixed64:
+                    ReadFixed64();
+                    break;
+                case WireFormat.WireType.LengthDelimited:
+                    var length = ReadLength();
+                    SkipRawBytes(length);
+                    break;
+                case WireFormat.WireType.Varint:
+                    ReadRawVarint32();
+                    break;
+            }
+        }
+
+        private void SkipGroup()
+        {
+            // Note: Currently we expect this to be the way that groups are read. We could put the recursion
+            // depth changes into the ReadTag method instead, potentially...
+            recursionDepth++;
+            if (recursionDepth >= recursionLimit)
+            {
+                throw InvalidProtocolBufferException.RecursionLimitExceeded();
+            }
+            uint tag;
+            do
+            {
+                tag = ReadTag();
+                if (tag == 0)
+                {
+                    throw InvalidProtocolBufferException.TruncatedMessage();
+                }
+                // This recursion will allow us to handle nested groups.
+                SkipLastField();
+            } while (WireFormat.GetTagWireType(tag) != WireFormat.WireType.EndGroup);
+            recursionDepth--;
+        }
+
+        /// <summary>
+        /// Reads a double field from the stream.
+        /// </summary>
+        public double ReadDouble()
+        {
+            return BitConverter.Int64BitsToDouble((long) ReadRawLittleEndian64());
+        }
+
+        /// <summary>
+        /// Reads a float field from the stream.
+        /// </summary>
+        public float ReadFloat()
+        {
+            if (BitConverter.IsLittleEndian && 4 <= bufferSize - bufferPos)
+            {
+                float ret = BitConverter.ToSingle(buffer, bufferPos);
+                bufferPos += 4;
+                return ret;
+            }
+            else
+            {
+                byte[] rawBytes = ReadRawBytes(4);
+                if (!BitConverter.IsLittleEndian)
+                {
+                    ByteArray.Reverse(rawBytes);
+                }
+                return BitConverter.ToSingle(rawBytes, 0);
+            }
+        }
+
+        /// <summary>
+        /// Reads a uint64 field from the stream.
+        /// </summary>
+        public ulong ReadUInt64()
+        {
+            return ReadRawVarint64();
+        }
+
+        /// <summary>
+        /// Reads an int64 field from the stream.
+        /// </summary>
+        public long ReadInt64()
+        {
+            return (long) ReadRawVarint64();
+        }
+
+        /// <summary>
+        /// Reads an int32 field from the stream.
+        /// </summary>
+        public int ReadInt32()
+        {
+            return (int) ReadRawVarint32();
+        }
+
+        /// <summary>
+        /// Reads a fixed64 field from the stream.
+        /// </summary>
+        public ulong ReadFixed64()
+        {
+            return ReadRawLittleEndian64();
+        }
+
+        /// <summary>
+        /// Reads a fixed32 field from the stream.
+        /// </summary>
+        public uint ReadFixed32()
+        {
+            return ReadRawLittleEndian32();
+        }
+
+        /// <summary>
+        /// Reads a bool field from the stream.
+        /// </summary>
+        public bool ReadBool()
+        {
+            return ReadRawVarint32() != 0;
+        }
+
+        /// <summary>
+        /// Reads a string field from the stream.
+        /// </summary>
+        public string ReadString()
+        {
+            int length = ReadLength();
+            // No need to read any data for an empty string.
+            if (length == 0)
+            {
+                return "";
+            }
+            if (length <= bufferSize - bufferPos)
+            {
+                // Fast path:  We already have the bytes in a contiguous buffer, so
+                //   just copy directly from it.
+                String result = CodedOutputStream.Utf8Encoding.GetString(buffer, bufferPos, length);
+                bufferPos += length;
+                return result;
+            }
+            // Slow path: Build a byte array first then copy it.
+            return CodedOutputStream.Utf8Encoding.GetString(ReadRawBytes(length), 0, length);
+        }
+
+        /// <summary>
+        /// Reads an embedded message field value from the stream.
+        /// </summary>   
+        public void ReadMessage(IMessage builder)
+        {
+            int length = ReadLength();
+            if (recursionDepth >= recursionLimit)
+            {
+                throw InvalidProtocolBufferException.RecursionLimitExceeded();
+            }
+            int oldLimit = PushLimit(length);
+            ++recursionDepth;
+            builder.MergeFrom(this);
+            CheckReadEndOfStreamTag();
+            // Check that we've read exactly as much data as expected.
+            if (!ReachedLimit)
+            {
+                throw InvalidProtocolBufferException.TruncatedMessage();
+            }
+            --recursionDepth;
+            PopLimit(oldLimit);
+        }
+
+        /// <summary>
+        /// Reads a bytes field value from the stream.
+        /// </summary>   
+        public ByteString ReadBytes()
+        {
+            int length = ReadLength();
+            if (length <= bufferSize - bufferPos && length > 0)
+            {
+                // Fast path:  We already have the bytes in a contiguous buffer, so
+                //   just copy directly from it.
+                ByteString result = ByteString.CopyFrom(buffer, bufferPos, length);
+                bufferPos += length;
+                return result;
+            }
+            else
+            {
+                // Slow path:  Build a byte array and attach it to a new ByteString.
+                return ByteString.AttachBytes(ReadRawBytes(length));
+            }
+        }
+
+        /// <summary>
+        /// Reads a uint32 field value from the stream.
+        /// </summary>   
+        public uint ReadUInt32()
+        {
+            return ReadRawVarint32();
+        }
+
+        /// <summary>
+        /// Reads an enum field value from the stream. If the enum is valid for type T,
+        /// then the ref value is set and it returns true.  Otherwise the unknown output
+        /// value is set and this method returns false.
+        /// </summary>   
+        public int ReadEnum()
+        {
+            // Currently just a pass-through, but it's nice to separate it logically from WriteInt32.
+            return (int) ReadRawVarint32();
+        }
+
+        /// <summary>
+        /// Reads an sfixed32 field value from the stream.
+        /// </summary>   
+        public int ReadSFixed32()
+        {
+            return (int) ReadRawLittleEndian32();
+        }
+
+        /// <summary>
+        /// Reads an sfixed64 field value from the stream.
+        /// </summary>   
+        public long ReadSFixed64()
+        {
+            return (long) ReadRawLittleEndian64();
+        }
+
+        /// <summary>
+        /// Reads an sint32 field value from the stream.
+        /// </summary>   
+        public int ReadSInt32()
+        {
+            return DecodeZigZag32(ReadRawVarint32());
+        }
+
+        /// <summary>
+        /// Reads an sint64 field value from the stream.
+        /// </summary>   
+        public long ReadSInt64()
+        {
+            return DecodeZigZag64(ReadRawVarint64());
+        }
+
+        /// <summary>
+        /// Reads a length for length-delimited data.
+        /// </summary>
+        /// <remarks>
+        /// This is internally just reading a varint, but this method exists
+        /// to make the calling code clearer.
+        /// </remarks>
+        public int ReadLength()
+        {
+            return (int) ReadRawVarint32();
+        }
+
+        /// <summary>
+        /// Peeks at the next tag in the stream. If it matches <paramref name="tag"/>,
+        /// the tag is consumed and the method returns <c>true</c>; otherwise, the
+        /// stream is left in the original position and the method returns <c>false</c>.
+        /// </summary>
+        public bool MaybeConsumeTag(uint tag)
+        {
+            if (PeekTag() == tag)
+            {
+                hasNextTag = false;
+                return true;
+            }
+            return false;
+        }
+
+        #endregion
+
+        #region Underlying reading primitives
+
+        /// <summary>
+        /// Same code as ReadRawVarint32, but read each byte individually, checking for
+        /// buffer overflow.
+        /// </summary>
+        private uint SlowReadRawVarint32()
+        {
+            int tmp = ReadRawByte();
+            if (tmp < 128)
+            {
+                return (uint) tmp;
+            }
+            int result = tmp & 0x7f;
+            if ((tmp = ReadRawByte()) < 128)
+            {
+                result |= tmp << 7;
+            }
+            else
+            {
+                result |= (tmp & 0x7f) << 7;
+                if ((tmp = ReadRawByte()) < 128)
+                {
+                    result |= tmp << 14;
+                }
+                else
+                {
+                    result |= (tmp & 0x7f) << 14;
+                    if ((tmp = ReadRawByte()) < 128)
+                    {
+                        result |= tmp << 21;
+                    }
+                    else
+                    {
+                        result |= (tmp & 0x7f) << 21;
+                        result |= (tmp = ReadRawByte()) << 28;
+                        if (tmp >= 128)
+                        {
+                            // Discard upper 32 bits.
+                            for (int i = 0; i < 5; i++)
+                            {
+                                if (ReadRawByte() < 128)
+                                {
+                                    return (uint) result;
+                                }
+                            }
+                            throw InvalidProtocolBufferException.MalformedVarint();
+                        }
+                    }
+                }
+            }
+            return (uint) result;
+        }
+
+        /// <summary>
+        /// Reads a raw Varint from the stream.  If larger than 32 bits, discard the upper bits.
+        /// This method is optimised for the case where we've got lots of data in the buffer.
+        /// That means we can check the size just once, then just read directly from the buffer
+        /// without constant rechecking of the buffer length.
+        /// </summary>
+        internal uint ReadRawVarint32()
+        {
+            if (bufferPos + 5 > bufferSize)
+            {
+                return SlowReadRawVarint32();
+            }
+
+            int tmp = buffer[bufferPos++];
+            if (tmp < 128)
+            {
+                return (uint) tmp;
+            }
+            int result = tmp & 0x7f;
+            if ((tmp = buffer[bufferPos++]) < 128)
+            {
+                result |= tmp << 7;
+            }
+            else
+            {
+                result |= (tmp & 0x7f) << 7;
+                if ((tmp = buffer[bufferPos++]) < 128)
+                {
+                    result |= tmp << 14;
+                }
+                else
+                {
+                    result |= (tmp & 0x7f) << 14;
+                    if ((tmp = buffer[bufferPos++]) < 128)
+                    {
+                        result |= tmp << 21;
+                    }
+                    else
+                    {
+                        result |= (tmp & 0x7f) << 21;
+                        result |= (tmp = buffer[bufferPos++]) << 28;
+                        if (tmp >= 128)
+                        {
+                            // Discard upper 32 bits.
+                            // Note that this has to use ReadRawByte() as we only ensure we've
+                            // got at least 5 bytes at the start of the method. This lets us
+                            // use the fast path in more cases, and we rarely hit this section of code.
+                            for (int i = 0; i < 5; i++)
+                            {
+                                if (ReadRawByte() < 128)
+                                {
+                                    return (uint) result;
+                                }
+                            }
+                            throw InvalidProtocolBufferException.MalformedVarint();
+                        }
+                    }
+                }
+            }
+            return (uint) result;
+        }
+
+        /// <summary>
+        /// Reads a varint from the input one byte at a time, so that it does not
+        /// read any bytes after the end of the varint. If you simply wrapped the
+        /// stream in a CodedInputStream and used ReadRawVarint32(Stream)
+        /// then you would probably end up reading past the end of the varint since
+        /// CodedInputStream buffers its input.
+        /// </summary>
+        /// <param name="input"></param>
+        /// <returns></returns>
+        internal static uint ReadRawVarint32(Stream input)
+        {
+            int result = 0;
+            int offset = 0;
+            for (; offset < 32; offset += 7)
+            {
+                int b = input.ReadByte();
+                if (b == -1)
+                {
+                    throw InvalidProtocolBufferException.TruncatedMessage();
+                }
+                result |= (b & 0x7f) << offset;
+                if ((b & 0x80) == 0)
+                {
+                    return (uint) result;
+                }
+            }
+            // Keep reading up to 64 bits.
+            for (; offset < 64; offset += 7)
+            {
+                int b = input.ReadByte();
+                if (b == -1)
+                {
+                    throw InvalidProtocolBufferException.TruncatedMessage();
+                }
+                if ((b & 0x80) == 0)
+                {
+                    return (uint) result;
+                }
+            }
+            throw InvalidProtocolBufferException.MalformedVarint();
+        }
+
+        /// <summary>
+        /// Reads a raw varint from the stream.
+        /// </summary>
+        internal ulong ReadRawVarint64()
+        {
+            int shift = 0;
+            ulong result = 0;
+            while (shift < 64)
+            {
+                byte b = ReadRawByte();
+                result |= (ulong) (b & 0x7F) << shift;
+                if ((b & 0x80) == 0)
+                {
+                    return result;
+                }
+                shift += 7;
+            }
+            throw InvalidProtocolBufferException.MalformedVarint();
+        }
+
+        /// <summary>
+        /// Reads a 32-bit little-endian integer from the stream.
+        /// </summary>
+        internal uint ReadRawLittleEndian32()
+        {
+            uint b1 = ReadRawByte();
+            uint b2 = ReadRawByte();
+            uint b3 = ReadRawByte();
+            uint b4 = ReadRawByte();
+            return b1 | (b2 << 8) | (b3 << 16) | (b4 << 24);
+        }
+
+        /// <summary>
+        /// Reads a 64-bit little-endian integer from the stream.
+        /// </summary>
+        internal ulong ReadRawLittleEndian64()
+        {
+            ulong b1 = ReadRawByte();
+            ulong b2 = ReadRawByte();
+            ulong b3 = ReadRawByte();
+            ulong b4 = ReadRawByte();
+            ulong b5 = ReadRawByte();
+            ulong b6 = ReadRawByte();
+            ulong b7 = ReadRawByte();
+            ulong b8 = ReadRawByte();
+            return b1 | (b2 << 8) | (b3 << 16) | (b4 << 24)
+                   | (b5 << 32) | (b6 << 40) | (b7 << 48) | (b8 << 56);
+        }
+
+        /// <summary>
+        /// Decode a 32-bit value with ZigZag encoding.
+        /// </summary>
+        /// <remarks>
+        /// ZigZag encodes signed integers into values that can be efficiently
+        /// encoded with varint.  (Otherwise, negative values must be 
+        /// sign-extended to 64 bits to be varint encoded, thus always taking
+        /// 10 bytes on the wire.)
+        /// </remarks>
+        internal static int DecodeZigZag32(uint n)
+        {
+            return (int)(n >> 1) ^ -(int)(n & 1);
+        }
+
+        /// <summary>
+        /// Decode a 32-bit value with ZigZag encoding.
+        /// </summary>
+        /// <remarks>
+        /// ZigZag encodes signed integers into values that can be efficiently
+        /// encoded with varint.  (Otherwise, negative values must be 
+        /// sign-extended to 64 bits to be varint encoded, thus always taking
+        /// 10 bytes on the wire.)
+        /// </remarks>
+        internal static long DecodeZigZag64(ulong n)
+        {
+            return (long)(n >> 1) ^ -(long)(n & 1);
+        }
+        #endregion
+
+        #region Internal reading and buffer management
+
+        /// <summary>
+        /// Sets currentLimit to (current position) + byteLimit. This is called
+        /// when descending into a length-delimited embedded message. The previous
+        /// limit is returned.
+        /// </summary>
+        /// <returns>The old limit.</returns>
+        internal int PushLimit(int byteLimit)
+        {
+            if (byteLimit < 0)
+            {
+                throw InvalidProtocolBufferException.NegativeSize();
+            }
+            byteLimit += totalBytesRetired + bufferPos;
+            int oldLimit = currentLimit;
+            if (byteLimit > oldLimit)
+            {
+                throw InvalidProtocolBufferException.TruncatedMessage();
+            }
+            currentLimit = byteLimit;
+
+            RecomputeBufferSizeAfterLimit();
+
+            return oldLimit;
+        }
+
+        private void RecomputeBufferSizeAfterLimit()
+        {
+            bufferSize += bufferSizeAfterLimit;
+            int bufferEnd = totalBytesRetired + bufferSize;
+            if (bufferEnd > currentLimit)
+            {
+                // Limit is in current buffer.
+                bufferSizeAfterLimit = bufferEnd - currentLimit;
+                bufferSize -= bufferSizeAfterLimit;
+            }
+            else
+            {
+                bufferSizeAfterLimit = 0;
+            }
+        }
+
+        /// <summary>
+        /// Discards the current limit, returning the previous limit.
+        /// </summary>
+        internal void PopLimit(int oldLimit)
+        {
+            currentLimit = oldLimit;
+            RecomputeBufferSizeAfterLimit();
+        }
+
+        /// <summary>
+        /// Returns whether or not all the data before the limit has been read.
+        /// </summary>
+        /// <returns></returns>
+        internal bool ReachedLimit
+        {
+            get
+            {
+                if (currentLimit == int.MaxValue)
+                {
+                    return false;
+                }
+                int currentAbsolutePosition = totalBytesRetired + bufferPos;
+                return currentAbsolutePosition >= currentLimit;
+            }
+        }
+
+        /// <summary>
+        /// Returns true if the stream has reached the end of the input. This is the
+        /// case if either the end of the underlying input source has been reached or
+        /// the stream has reached a limit created using PushLimit.
+        /// </summary>
+        public bool IsAtEnd
+        {
+            get { return bufferPos == bufferSize && !RefillBuffer(false); }
+        }
+
+        /// <summary>
+        /// Called when buffer is empty to read more bytes from the
+        /// input.  If <paramref name="mustSucceed"/> is true, RefillBuffer() gurantees that
+        /// either there will be at least one byte in the buffer when it returns
+        /// or it will throw an exception.  If <paramref name="mustSucceed"/> is false,
+        /// RefillBuffer() returns false if no more bytes were available.
+        /// </summary>
+        /// <param name="mustSucceed"></param>
+        /// <returns></returns>
+        private bool RefillBuffer(bool mustSucceed)
+        {
+            if (bufferPos < bufferSize)
+            {
+                throw new InvalidOperationException("RefillBuffer() called when buffer wasn't empty.");
+            }
+
+            if (totalBytesRetired + bufferSize == currentLimit)
+            {
+                // Oops, we hit a limit.
+                if (mustSucceed)
+                {
+                    throw InvalidProtocolBufferException.TruncatedMessage();
+                }
+                else
+                {
+                    return false;
+                }
+            }
+
+            totalBytesRetired += bufferSize;
+
+            bufferPos = 0;
+            bufferSize = (input == null) ? 0 : input.Read(buffer, 0, buffer.Length);
+            if (bufferSize < 0)
+            {
+                throw new InvalidOperationException("Stream.Read returned a negative count");
+            }
+            if (bufferSize == 0)
+            {
+                if (mustSucceed)
+                {
+                    throw InvalidProtocolBufferException.TruncatedMessage();
+                }
+                else
+                {
+                    return false;
+                }
+            }
+            else
+            {
+                RecomputeBufferSizeAfterLimit();
+                int totalBytesRead =
+                    totalBytesRetired + bufferSize + bufferSizeAfterLimit;
+                if (totalBytesRead > sizeLimit || totalBytesRead < 0)
+                {
+                    throw InvalidProtocolBufferException.SizeLimitExceeded();
+                }
+                return true;
+            }
+        }
+
+        /// <summary>
+        /// Read one byte from the input.
+        /// </summary>
+        /// <exception cref="InvalidProtocolBufferException">
+        /// the end of the stream or the current limit was reached
+        /// </exception>
+        internal byte ReadRawByte()
+        {
+            if (bufferPos == bufferSize)
+            {
+                RefillBuffer(true);
+            }
+            return buffer[bufferPos++];
+        }
+
+        /// <summary>
+        /// Reads a fixed size of bytes from the input.
+        /// </summary>
+        /// <exception cref="InvalidProtocolBufferException">
+        /// the end of the stream or the current limit was reached
+        /// </exception>
+        internal byte[] ReadRawBytes(int size)
+        {
+            if (size < 0)
+            {
+                throw InvalidProtocolBufferException.NegativeSize();
+            }
+
+            if (totalBytesRetired + bufferPos + size > currentLimit)
+            {
+                // Read to the end of the stream (up to the current limit) anyway.
+                SkipRawBytes(currentLimit - totalBytesRetired - bufferPos);
+                // Then fail.
+                throw InvalidProtocolBufferException.TruncatedMessage();
+            }
+
+            if (size <= bufferSize - bufferPos)
+            {
+                // We have all the bytes we need already.
+                byte[] bytes = new byte[size];
+                ByteArray.Copy(buffer, bufferPos, bytes, 0, size);
+                bufferPos += size;
+                return bytes;
+            }
+            else if (size < buffer.Length)
+            {
+                // Reading more bytes than are in the buffer, but not an excessive number
+                // of bytes.  We can safely allocate the resulting array ahead of time.
+
+                // First copy what we have.
+                byte[] bytes = new byte[size];
+                int pos = bufferSize - bufferPos;
+                ByteArray.Copy(buffer, bufferPos, bytes, 0, pos);
+                bufferPos = bufferSize;
+
+                // We want to use RefillBuffer() and then copy from the buffer into our
+                // byte array rather than reading directly into our byte array because
+                // the input may be unbuffered.
+                RefillBuffer(true);
+
+                while (size - pos > bufferSize)
+                {
+                    Buffer.BlockCopy(buffer, 0, bytes, pos, bufferSize);
+                    pos += bufferSize;
+                    bufferPos = bufferSize;
+                    RefillBuffer(true);
+                }
+
+                ByteArray.Copy(buffer, 0, bytes, pos, size - pos);
+                bufferPos = size - pos;
+
+                return bytes;
+            }
+            else
+            {
+                // The size is very large.  For security reasons, we can't allocate the
+                // entire byte array yet.  The size comes directly from the input, so a
+                // maliciously-crafted message could provide a bogus very large size in
+                // order to trick the app into allocating a lot of memory.  We avoid this
+                // by allocating and reading only a small chunk at a time, so that the
+                // malicious message must actually *be* extremely large to cause
+                // problems.  Meanwhile, we limit the allowed size of a message elsewhere.
+
+                // Remember the buffer markers since we'll have to copy the bytes out of
+                // it later.
+                int originalBufferPos = bufferPos;
+                int originalBufferSize = bufferSize;
+
+                // Mark the current buffer consumed.
+                totalBytesRetired += bufferSize;
+                bufferPos = 0;
+                bufferSize = 0;
+
+                // Read all the rest of the bytes we need.
+                int sizeLeft = size - (originalBufferSize - originalBufferPos);
+                List<byte[]> chunks = new List<byte[]>();
+
+                while (sizeLeft > 0)
+                {
+                    byte[] chunk = new byte[Math.Min(sizeLeft, buffer.Length)];
+                    int pos = 0;
+                    while (pos < chunk.Length)
+                    {
+                        int n = (input == null) ? -1 : input.Read(chunk, pos, chunk.Length - pos);
+                        if (n <= 0)
+                        {
+                            throw InvalidProtocolBufferException.TruncatedMessage();
+                        }
+                        totalBytesRetired += n;
+                        pos += n;
+                    }
+                    sizeLeft -= chunk.Length;
+                    chunks.Add(chunk);
+                }
+
+                // OK, got everything.  Now concatenate it all into one buffer.
+                byte[] bytes = new byte[size];
+
+                // Start by copying the leftover bytes from this.buffer.
+                int newPos = originalBufferSize - originalBufferPos;
+                ByteArray.Copy(buffer, originalBufferPos, bytes, 0, newPos);
+
+                // And now all the chunks.
+                foreach (byte[] chunk in chunks)
+                {
+                    Buffer.BlockCopy(chunk, 0, bytes, newPos, chunk.Length);
+                    newPos += chunk.Length;
+                }
+
+                // Done.
+                return bytes;
+            }
+        }
+
+        /// <summary>
+        /// Reads and discards <paramref name="size"/> bytes.
+        /// </summary>
+        /// <exception cref="InvalidProtocolBufferException">the end of the stream
+        /// or the current limit was reached</exception>
+        private void SkipRawBytes(int size)
+        {
+            if (size < 0)
+            {
+                throw InvalidProtocolBufferException.NegativeSize();
+            }
+
+            if (totalBytesRetired + bufferPos + size > currentLimit)
+            {
+                // Read to the end of the stream anyway.
+                SkipRawBytes(currentLimit - totalBytesRetired - bufferPos);
+                // Then fail.
+                throw InvalidProtocolBufferException.TruncatedMessage();
+            }
+
+            if (size <= bufferSize - bufferPos)
+            {
+                // We have all the bytes we need already.
+                bufferPos += size;
+            }
+            else
+            {
+                // Skipping more bytes than are in the buffer.  First skip what we have.
+                int pos = bufferSize - bufferPos;
+
+                // ROK 5/7/2013 Issue #54: should retire all bytes in buffer (bufferSize)
+                // totalBytesRetired += pos;
+                totalBytesRetired += bufferSize;
+                
+                bufferPos = 0;
+                bufferSize = 0;
+
+                // Then skip directly from the InputStream for the rest.
+                if (pos < size)
+                {
+                    if (input == null)
+                    {
+                        throw InvalidProtocolBufferException.TruncatedMessage();
+                    }
+                    SkipImpl(size - pos);
+                    totalBytesRetired += size - pos;
+                }
+            }
+        }
+
+        /// <summary>
+        /// Abstraction of skipping to cope with streams which can't really skip.
+        /// </summary>
+        private void SkipImpl(int amountToSkip)
+        {
+            if (input.CanSeek)
+            {
+                long previousPosition = input.Position;
+                input.Position += amountToSkip;
+                if (input.Position != previousPosition + amountToSkip)
+                {
+                    throw InvalidProtocolBufferException.TruncatedMessage();
+                }
+            }
+            else
+            {
+                byte[] skipBuffer = new byte[Math.Min(1024, amountToSkip)];
+                while (amountToSkip > 0)
+                {
+                    int bytesRead = input.Read(skipBuffer, 0, Math.Min(skipBuffer.Length, amountToSkip));
+                    if (bytesRead <= 0)
+                    {
+                        throw InvalidProtocolBufferException.TruncatedMessage();
+                    }
+                    amountToSkip -= bytesRead;
+                }
+            }
+        }
+
+        #endregion
+    }
+}