Fixed line length calculations in BestEncodingFilter

Fixes issue #497

MimeKit/IO/Filters/BestEncodingFilter.cs

@@ -42,6 +42,7 @@ public class BestEncodingFilter : IMimeFilter
 		int markerLength;
 		bool hasMarker;
 		int total;
+		byte pc;
 
 		/// <summary>
 		/// Initializes a new instance of the <see cref="BestEncodingFilter"/> class.
@@ -153,9 +154,13 @@ unsafe void Scan (byte* inptr, byte* inend)
 						marker[markerLength++] = c;
 
 					linelen++;
+					pc = c;
 				}
 
 				if (c == (byte) '\n') {
+					if (pc == (byte) '\r')
+						linelen--;
+
 					maxline = Math.Max (maxline, linelen);
 					linelen = 0;
 
@@ -259,6 +264,7 @@ public void Reset ()
 			count0 = 0;
 			count8 = 0;
 			total = 0;
+			pc = 0;
 		}
 
 		#endregion

UnitTests/IO/Filters/FilterTests.cs

@@ -206,6 +206,30 @@ public void TestBestEncodingFilter ()
 					Assert.AreEqual (ContentEncoding.QuotedPrintable, encoding, "French (long lines) no constraint.");
 				}
 			}
+
+			filter.Reset ();
+
+			// Test 78 character line length with CRLF
+			using (var stream = new MemoryStream ()) {
+				using (var filtered = new FilteredStream (stream)) {
+					var buffer = Encoding.ASCII.GetBytes ("abcdefghijklmnopqrstuvwxyzabcdefghijklmnopqrstuvwxyzabcdefghijklmnopqrstuvwxyz\r\nabc\r\n");
+					ContentEncoding encoding;
+
+					filtered.Add (filter);
+
+					filtered.Write (buffer, 0, buffer.Length);
+					filtered.Flush ();
+
+					encoding = filter.GetBestEncoding (EncodingConstraint.SevenBit, 78);
+					Assert.AreEqual (ContentEncoding.SevenBit, encoding, "78-character line; 7bit constraint.");
+
+					encoding = filter.GetBestEncoding (EncodingConstraint.EightBit, 78);
+					Assert.AreEqual (ContentEncoding.SevenBit, encoding, "78-character line; 8bit constraint.");
+
+					encoding = filter.GetBestEncoding (EncodingConstraint.None, 78);
+					Assert.AreEqual (ContentEncoding.SevenBit, encoding, "78-character line; no constraint.");
+				}
+			}
 		}
 
 		[Test]