Allow padding to be enabled / disabled via cmake, and value set

CMakeLists.txt

@@ -7,6 +7,8 @@ project(isotp LANGUAGES C VERSION 1.0.1 DESCRIPTION "A platform-agnostic ISOTP i
 
 option(isotpc_USE_INCLUDE_DIR "Copy header files to separate include directory in current binary dir for better separation of header files to combat potential naming conflicts." OFF)
 option(isotpc_STATIC_LIBRARY "Compile libisotpc as a static library, instead of a shared library." OFF)
+option(isotpc_PAD_CAN_FRAMES "Pad CAN frames to their full size." ON)
+set(isotpc_CAN_FRAME_PAD_VALUE "0xAA" CACHE STRING "Padding byte value to be used in CAN frames if enabled")
 
 if (isotpc_STATIC_LIBRARY)
     add_library(isotp STATIC ${CMAKE_CURRENT_SOURCE_DIR}/isotp.c)
@@ -25,6 +27,13 @@ target_compile_options(
     -Wno-unknown-pragmas # ignore unknown pragmas, such as #pragma region
 )
 
+###
+# Provide padding configuration
+###
+if (isotpc_PAD_CAN_FRAMES)
+    target_compile_definitions(isotp PRIVATE -DISO_TP_FRAME_PADDING -DISO_TP_FRAME_PADDING_VALUE=${isotpc_CAN_FRAME_PAD_VALUE})
+endif()
+
 ###
 # Check for debug builds
 ###

Makefile

@@ -53,7 +53,7 @@ $(BIN)/$(LIB_NAME).$(MAJOR_VER).$(MINOR_VER).$(REVISION): libisotp.o
 # Compiles the isotp.c TU to an object file. 
 ###
 libisotp.o: isotp.c
-	${COMP} -c $^ -o $@ ${CFLAGS}
+	${COMP} -c $^ -o $@ ${CFLAGS} -DISO_TP_FRAME_PADDING
 
 install: all
 	@printf "Installing $(LIB_NAME) to $(INSTALL_DIR)...\n"

isotp.c

@@ -39,7 +39,7 @@ static int isotp_send_flow_control(IsoTpLink* link, uint8_t flow_status, uint8_t
 
     /* send message */
 #ifdef ISO_TP_FRAME_PADDING
-    (void) memset(message.as.flow_control.reserve, ISO_TP_FRAME_PADDING, sizeof(message.as.flow_control.reserve));
+    (void) memset(message.as.flow_control.reserve, ISO_TP_FRAME_PADDING_VALUE, sizeof(message.as.flow_control.reserve));
     ret = isotp_user_send_can(link->send_arbitration_id, message.as.data_array.ptr, sizeof(message));
 #else
     ret = isotp_user_send_can(link->send_arbitration_id,
@@ -65,7 +65,7 @@ static int isotp_send_single_frame(IsoTpLink* link, uint32_t id) {
 
     /* send message */
 #ifdef ISO_TP_FRAME_PADDING
-    (void) memset(message.as.single_frame.data + link->send_size, ISO_TP_FRAME_PADDING, sizeof(message.as.single_frame.data) - link->send_size);
+    (void) memset(message.as.single_frame.data + link->send_size, ISO_TP_FRAME_PADDING_VALUE, sizeof(message.as.single_frame.data) - link->send_size);
     ret = isotp_user_send_can(id, message.as.data_array.ptr, sizeof(message));
 #else
     ret = isotp_user_send_can(id,
@@ -120,7 +120,7 @@ static int isotp_send_consecutive_frame(IsoTpLink* link) {
 
     /* send message */
 #ifdef ISO_TP_FRAME_PADDING
-    (void) memset(message.as.consecutive_frame.data + data_length, ISO_TP_FRAME_PADDING, sizeof(message.as.consecutive_frame.data) - data_length);
+    (void) memset(message.as.consecutive_frame.data + data_length, ISO_TP_FRAME_PADDING_VALUE, sizeof(message.as.consecutive_frame.data) - data_length);
     ret = isotp_user_send_can(link->send_arbitration_id, message.as.data_array.ptr, sizeof(message));
 #else
     ret = isotp_user_send_can(link->send_arbitration_id,

isotp_config.h

@@ -23,7 +23,13 @@
 
 /* Private: Determines if by default, padding is added to ISO-TP message frames.
  */
-#define ISO_TP_FRAME_PADDING 0xAA
+//#define ISO_TP_FRAME_PADDING 0xAA
+
+/* Private: Value to use when padding frames if enabled by ISO_TP_FRAME_PADDING
+ */
+#ifndef ISO_TP_FRAME_PADDING_VALUE
+#define ISO_TP_FRAME_PADDING_VALUE 0xAA
+#endif
 
 #endif