Fix TokenWriter::WriteString not escaping properly special characters

src/UglyToad.PdfPig.Tests/Writer/TokenWriterTests.cs

@@ -0,0 +1,30 @@
+namespace UglyToad.PdfPig.Tests.Writer
+{
+    using Integration;
+    using PdfPig.Writer;
+    using System.IO;
+    using UglyToad.PdfPig.Tokens;
+    using Xunit;
+
+    public class TokenWriterTests
+    {
+
+        [Fact]
+        public void EscapeSpecialCharacter()
+        {
+            using (var memStream = new MemoryStream())
+            {
+                TokenWriter.WriteToken(new StringToken("\\"), memStream);
+                TokenWriter.WriteToken(new StringToken("(Hello)"), memStream);
+
+                // Read Test
+                memStream.Position = 0;
+                using (var streamReader = new StreamReader(memStream))
+                {
+                    var line = streamReader.ReadToEnd();
+                    Assert.Equal("(\\\\) (\\(Hello\\)) ", line);
+                }
+            }
+        }
+    }
+}

src/UglyToad.PdfPig/Writer/TokenWriter.cs

@@ -16,6 +16,8 @@
     /// </summary>
     public class TokenWriter
     {
+        private static readonly byte Backslash = GetByte("\\");
+
         private static readonly byte ArrayStart = GetByte("[");
         private static readonly byte ArrayEnd = GetByte("]");
 
@@ -374,6 +376,12 @@
                 for (var i = 0; i < stringToken.Data.Length; i++)
                 {
                     var c = stringToken.Data[i];
+
+                    if (c == (char) StringStart || c == (char)StringEnd || c == (char) Backslash)
+                    {
+                        stringToken = new StringToken(stringToken.Data.Insert(i++, "\\"), stringToken.EncodedWith);
+                    }
+
                     // Close enough.
                     if (c > 250)
                     {