Fix infinite loop when reading truncated data; Add unit test for expected exception (#157)

Author: nirosys

Diff for: Amazon.IonDotnet.Tests/Internals/BinaryReaderTest.cs

@@ -335,6 +335,25 @@ public void MultipleBlobs()
             }
         }
 
+        [TestMethod]
+        public void ReadAll_FailOnTruncatedData()
+        {
+            IIonReader binReader;
+            using (var ms = new MemoryStream()) {
+                ReadOnlySpan<byte> fullString = new ReadOnlySpan<byte>(new byte[] {
+                        0xE0, 0x01, 0x00, 0xEA, 0x85, 0x31, 0x32, 0x33, 0x34, 0x35
+                });
+                ms.Write(fullString.Slice(0, 9));
+
+                ms.Seek(0, SeekOrigin.Begin);
+                binReader = IonReaderBuilder.Build(ms);
+
+                var type = binReader.MoveNext();
+                Assert.AreEqual(IonType.String, type);
+                Assert.ThrowsException<UnexpectedEofException>(() => binReader.StringValue());
+            }
+        }
+
         /// <summary>
         /// Aims to test the correctness of skipping with step in-out in the middle
         /// of container

Diff for: Amazon.IonDotnet/Internals/Binary/RawBinaryReader.cs

@@ -1167,6 +1167,13 @@ private void ReadAll(Span<byte> bufferSpan, int length)
             while (length > 0)
             {
                 var amount = this.input.Read(bufferSpan.Slice(0, length));
+
+                // length > 0 (because we didn't stop)
+                if (amount == 0)
+                {
+                   throw new UnexpectedEofException();
+                }
+
                 length -= amount;
                 bufferSpan = bufferSpan.Slice(amount);
                 this.localRemaining -= amount;