Validate that after reading a message, we've consumed as many bytes as we expected to.

We should now have no conformance failures.

conformance/failure_list_csharp.txt

-ProtobufInput.PrematureEofBeforeUnknownValue.BOOL
-ProtobufInput.PrematureEofBeforeUnknownValue.BYTES
-ProtobufInput.PrematureEofBeforeUnknownValue.DOUBLE
-ProtobufInput.PrematureEofBeforeUnknownValue.ENUM
-ProtobufInput.PrematureEofBeforeUnknownValue.FIXED32
-ProtobufInput.PrematureEofBeforeUnknownValue.FIXED64
-ProtobufInput.PrematureEofBeforeUnknownValue.FLOAT
-ProtobufInput.PrematureEofBeforeUnknownValue.INT32
-ProtobufInput.PrematureEofBeforeUnknownValue.INT64
-ProtobufInput.PrematureEofBeforeUnknownValue.MESSAGE
-ProtobufInput.PrematureEofBeforeUnknownValue.SFIXED32
-ProtobufInput.PrematureEofBeforeUnknownValue.SFIXED64
-ProtobufInput.PrematureEofBeforeUnknownValue.SINT32
-ProtobufInput.PrematureEofBeforeUnknownValue.SINT64
-ProtobufInput.PrematureEofBeforeUnknownValue.STRING
-ProtobufInput.PrematureEofBeforeUnknownValue.UINT32
-ProtobufInput.PrematureEofBeforeUnknownValue.UINT64
-ProtobufInput.PrematureEofInDelimitedDataForKnownNonRepeatedValue.MESSAGE
-ProtobufInput.PrematureEofInDelimitedDataForKnownRepeatedValue.MESSAGE
-ProtobufInput.PrematureEofInDelimitedDataForUnknownValue.BYTES
-ProtobufInput.PrematureEofInDelimitedDataForUnknownValue.MESSAGE
-ProtobufInput.PrematureEofInDelimitedDataForUnknownValue.STRING

csharp/src/Google.Protobuf.Test/GeneratedMessageTest.cs

@@ -259,7 +259,7 @@ namespace Google.Protobuf
             output.WriteTag(TestMap.MapInt32ForeignMessageFieldNumber, WireFormat.WireType.LengthDelimited);
             var nestedMessage = new ForeignMessage { C = 20 };
             // Size of the entry (tag, size written by WriteMessage, data written by WriteMessage)
-            output.WriteRawVarint32((uint)(nestedMessage.CalculateSize() + 3));
+            output.WriteLength(2 + nestedMessage.CalculateSize());
             output.WriteTag(2, WireFormat.WireType.LengthDelimited);
             output.WriteMessage(nestedMessage);
             output.Flush();
@@ -283,7 +283,7 @@ namespace Google.Protobuf
 
             // Each field can be represented in a single byte, with a single byte tag.
             // Total message size: 6 bytes.
-            output.WriteRawVarint32(6);
+            output.WriteLength(6);
             output.WriteTag(1, WireFormat.WireType.Varint);
             output.WriteInt32(key);
             output.WriteTag(2, WireFormat.WireType.Varint);
@@ -309,7 +309,7 @@ namespace Google.Protobuf
 
             // Each field can be represented in a single byte, with a single byte tag.
             // Total message size: 4 bytes.
-            output.WriteRawVarint32(4);
+            output.WriteLength(4);
             output.WriteTag(2, WireFormat.WireType.Varint);
             output.WriteInt32(value);
             output.WriteTag(1, WireFormat.WireType.Varint);
@@ -335,7 +335,7 @@ namespace Google.Protobuf
             var key1 = 10;
             var value1 = 20;
             output.WriteTag(TestMap.MapInt32Int32FieldNumber, WireFormat.WireType.LengthDelimited);
-            output.WriteRawVarint32(4);
+            output.WriteLength(4);
             output.WriteTag(1, WireFormat.WireType.Varint);
             output.WriteInt32(key1);
             output.WriteTag(2, WireFormat.WireType.Varint);
@@ -345,7 +345,7 @@ namespace Google.Protobuf
             var key2 = "a";
             var value2 = "b";
             output.WriteTag(TestMap.MapStringStringFieldNumber, WireFormat.WireType.LengthDelimited);
-            output.WriteRawVarint32(6); // 3 bytes per entry: tag, size, character
+            output.WriteLength(6); // 3 bytes per entry: tag, size, character
             output.WriteTag(1, WireFormat.WireType.LengthDelimited);
             output.WriteString(key2);
             output.WriteTag(2, WireFormat.WireType.LengthDelimited);
@@ -355,7 +355,7 @@ namespace Google.Protobuf
             var key3 = 15;
             var value3 = 25;
             output.WriteTag(TestMap.MapInt32Int32FieldNumber, WireFormat.WireType.LengthDelimited);
-            output.WriteRawVarint32(4);
+            output.WriteLength(4);
             output.WriteTag(1, WireFormat.WireType.Varint);
             output.WriteInt32(key3);
             output.WriteTag(2, WireFormat.WireType.Varint);
@@ -383,7 +383,7 @@ namespace Google.Protobuf
 
             // First entry
             output.WriteTag(TestMap.MapInt32Int32FieldNumber, WireFormat.WireType.LengthDelimited);
-            output.WriteRawVarint32(4);
+            output.WriteLength(4);
             output.WriteTag(1, WireFormat.WireType.Varint);
             output.WriteInt32(key);
             output.WriteTag(2, WireFormat.WireType.Varint);
@@ -391,7 +391,7 @@ namespace Google.Protobuf
 
             // Second entry - same key, different value
             output.WriteTag(TestMap.MapInt32Int32FieldNumber, WireFormat.WireType.LengthDelimited);
-            output.WriteRawVarint32(4);
+            output.WriteLength(4);
             output.WriteTag(1, WireFormat.WireType.Varint);
             output.WriteInt32(key);
             output.WriteTag(2, WireFormat.WireType.Varint);
@@ -619,5 +619,15 @@ namespace Google.Protobuf
             var empty = Empty.Parser.ParseFrom(data);
             Assert.AreEqual(new Empty(), empty);
         }
+
+        // This was originally seen as a conformance test failure.
+        [Test]
+        public void TruncatedMessageFieldThrows()
+        {
+            // 130, 3 is the message tag
+            // 1 is the data length - but there's no data.
+            var data = new byte[] { 130, 3, 1 };            
+            Assert.Throws<InvalidProtocolBufferException>(() => TestAllTypes.Parser.ParseFrom(data));
+        }
     }
 }

csharp/src/Google.Protobuf/CodedInputStream.cs

@@ -54,13 +54,37 @@ namespace Google.Protobuf
     /// </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 number of valid bytes in the buffer.
+        /// </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;
 
@@ -456,6 +480,11 @@ namespace Google.Protobuf
             ++recursionDepth;
             builder.MergeFrom(this);
             CheckLastTagWas(0);
+            // Check that we've read exactly as much data as expected.
+            if (!ReachedLimit)
+            {
+                throw InvalidProtocolBufferException.TruncatedMessage();
+            }
             --recursionDepth;
             PopLimit(oldLimit);
         }