Feature/mstp extended frames cobs encoding (#183)

* added COBS encode and decode from BACnet standard

* Add unit tests for COBS encoding and decoding

* Improve COBS unit test and API.

Co-authored-by: Steve Karg <skarg@users.sourceforge.net>

test/bacnet/datalink/cobs/CMakeLists.txt

@@ -0,0 +1,41 @@
+# SPDX-License-Identifier: MIT
+
+cmake_minimum_required(VERSION 3.10 FATAL_ERROR)
+
+get_filename_component(basename ${CMAKE_CURRENT_SOURCE_DIR} NAME)
+project(test_${basename}
+	VERSION 1.0.0
+	LANGUAGES C)
+
+
+string(REGEX REPLACE
+    "/test/bacnet/[a-zA-Z_/-]*$"
+    "/src"
+    SRC_DIR
+    ${CMAKE_CURRENT_SOURCE_DIR})
+string(REGEX REPLACE
+    "/test/bacnet/[a-zA-Z_/-]*$"
+    "/test"
+    TST_DIR
+    ${CMAKE_CURRENT_SOURCE_DIR})
+set(ZTST_DIR "${TST_DIR}/ztest/src")
+
+add_compile_definitions(
+    MAX_APDU=1476
+	CONFIG_ZTEST=1
+	)
+
+include_directories(
+	${SRC_DIR}
+	${TST_DIR}/ztest/include
+	)
+
+add_executable(${PROJECT_NAME}
+    # File(s) under test
+	${SRC_DIR}/bacnet/datalink/cobs.c
+    # Support files and stubs (pathname alphabetical)
+    # Test and test library files
+	./src/main.c
+	${ZTST_DIR}/ztest_mock.c
+	${ZTST_DIR}/ztest.c
+	)

test/bacnet/datalink/cobs/src/main.c

@@ -0,0 +1,62 @@
+/*
+ * Copyright (c) 2020 Legrand North America, LLC.
+ *
+ * SPDX-License-Identifier: MIT
+ */
+
+/* @file
+ * @brief test BACnet COBS encode/decode APIs
+ */
+
+#include <ztest.h>
+#include <stdlib.h>
+#include <bacnet/datalink/cobs.h>
+#include <bacnet/bytes.h>
+
+/**
+ * @addtogroup bacnet_tests
+ * @{
+ */
+
+/**
+ * @brief Test CRC8 from Annex G 1.0 of BACnet Standard
+ */
+static void test_COBS_Encode_Decode(void)
+{
+    uint8_t buffer[MAX_APDU] = { 0x55, 0xff, 0 };
+    uint8_t encoded_buffer[COBS_ENCODED_SIZE(MAX_APDU)+
+        COBS_ENCODED_CRC_SIZE] = { 0 };
+    //uint8_t encoded_buffer[MAX_APDU*2] = { 0 };
+    uint8_t test_buffer[MAX_APDU] = { 0 };
+    unsigned i;
+    size_t encoded_buffer_length, test_buffer_length;
+
+    for (i = 2; i < sizeof(buffer); i++) {
+        buffer[i] = i%0xff;
+    }
+    encoded_buffer_length = cobs_frame_encode(encoded_buffer,
+        sizeof(encoded_buffer), buffer, sizeof(buffer));
+    zassert_true(encoded_buffer_length > 0,
+        "COBS encoded buffer empty!");
+    test_buffer_length = cobs_frame_decode(test_buffer, sizeof(test_buffer),
+        encoded_buffer, encoded_buffer_length);
+    for (i = 0; i < sizeof(buffer); i++) {
+        zassert_true(buffer[i] == test_buffer[i],
+            "COBS encode/decode fail");
+    }
+    zassert_true(test_buffer_length == sizeof(buffer),
+        "COBS encode/decode length fail");
+}
+/**
+ * @}
+ */
+
+
+void test_main(void)
+{
+    ztest_test_suite(cobs_tests,
+     ztest_unit_test(test_COBS_Encode_Decode)
+     );
+
+    ztest_run_test_suite(cobs_tests);
+}