From 76bf421a10abf2ca3cdd4e0c986764ccc522a4a8 Mon Sep 17 00:00:00 2001
From: Jeppe Frandsen <jeppe@algrens.dk>
Date: Thu, 12 Sep 2019 09:40:46 +0200
Subject: [PATCH] Added fix for duplication scenario (#16)

* Added fix for duplication scenario

* Minor whitespace fix
---
 .gitignore              |  2 +-
 include/Hdlcpp.hpp      |  3 ++-
 test/src/TestHdlcpp.cpp | 18 ++++++++++++++++++
 3 files changed, 21 insertions(+), 2 deletions(-)

diff --git a/.gitignore b/.gitignore
index a92c5f0..8e8e0ca 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1,2 +1,2 @@
 .vscode/settings.json
-.build-*
+.build*
diff --git a/include/Hdlcpp.hpp b/include/Hdlcpp.hpp
index 858c696..e171202 100644
--- a/include/Hdlcpp.hpp
+++ b/include/Hdlcpp.hpp
@@ -290,7 +290,8 @@ class Hdlcpp {
                 result = -EIO;
             }
 
-            discardBytes = i;
+            // Be sure to discard bytes (could be that destinationIndex > i in some cases)
+            discardBytes = destinationIndex > i ? destinationIndex : i;
             resetValues();
         }
 
diff --git a/test/src/TestHdlcpp.cpp b/test/src/TestHdlcpp.cpp
index a7c0f56..ff77ddf 100644
--- a/test/src/TestHdlcpp.cpp
+++ b/test/src/TestHdlcpp.cpp
@@ -228,4 +228,22 @@ TEST_CASE_METHOD(HdlcppFixture, "hdlcpp test", "[single-file]")
         readBuffer.assign(frame1, frame1 + sizeof(frame1));
         CHECK(hdlcpp->read(buffer, sizeof(buffer)) == 2);
     }
+
+    SECTION("Test duplication scenario")
+    {
+        // Frames captured from duplication scenario
+        const uint8_t frame1[] = { 0x7e, 0xff };
+        const uint8_t frame2[] = { 0x12, 0x4a, 0x07, 0x0a, 0x01, 0x03, 0x18, 0x07, 0x20, 0x64, 0xd5, 0x97 };
+        const uint8_t frame3[] = { 0x7e };
+        const uint8_t frame4[] = { 0x7e, 0xff, 0x61, 0x08, 0x82 };
+
+        readBuffer.assign(frame1, frame1 + sizeof(frame1));
+        CHECK(hdlcpp->read(buffer, sizeof(buffer)) == -ENOMSG);
+        readBuffer.assign(frame2, frame2 + sizeof(frame2));
+        CHECK(hdlcpp->read(buffer, sizeof(buffer)) == -ENOMSG);
+        readBuffer.assign(frame3, frame3 + sizeof(frame3));
+        CHECK(hdlcpp->read(buffer, sizeof(buffer)) == 9);
+        readBuffer.assign(frame4, frame4 + sizeof(frame4));
+        CHECK(hdlcpp->read(buffer, sizeof(buffer)) == -ENOMSG);
+    }
 }