[Config] Add in custom CRC function pointer

Requested such that a user can implement the crc stream function via configurable function pointer
parameter

Documentation update required explaining the config

inc/voyager.h

@@ -72,9 +72,18 @@ typedef union {
     voyager_bootloader_app_size_t app_size;
 } voyager_bootloader_nvm_data_t;
 
+/**
+ * @brief voyager_custom_crc_stream_F Function pointer signature for a custom CRC stream function
+ * @param byte The byte to process
+ * @param crc pointer to the current CRC value that is expected to be modified
+ */
+typedef void (*voyager_custom_crc_stream_F)(const uint8_t byte, voyager_bootloader_app_crc_t *const crc);
+
 typedef struct {
     bool jump_to_app_after_dfu_recv_complete;  // Controls whether the system jumps to application or to IDLE after completion of
                                                // DFU
+    voyager_custom_crc_stream_F
+        custom_crc_stream;  // Custom function pointer signature to allow an override of the base CRC method
 } voyager_bootloader_config_t;
 
 /** Primary Bootloader Functions **/

src/voyager.c

@@ -658,7 +658,11 @@ voyager_bootloader_app_crc_t voyager_private_calculate_crc(const void *buffer, c
 }
 
 void voyager_private_calculate_crc_stream(const uint8_t byte, voyager_bootloader_app_crc_t *const crc) {
-    *crc = (*crc << 8) ^ crc32_table[(((*crc) >> 24) ^ byte) & 255];
+    if (voyager_data.config->custom_crc_stream != NULL) {
+        voyager_data.config->custom_crc_stream(byte, crc);
+    } else {
+        *crc = (*crc << 8) ^ crc32_table[(((*crc) >> 24) ^ byte) & 255];
+    }
 }
 
 #ifdef VOYAGER_UNIT_TEST

test/main.cpp

@@ -4,5 +4,6 @@
 IMPORT_TEST_GROUP(dummy_test);
 IMPORT_TEST_GROUP(test_bootloader_state_machine);
 IMPORT_TEST_GROUP(test_dfu);
+IMPORT_TEST_GROUP(test_bootloader_api);
 
 int main(int ac, char **av) { return CommandLineTestRunner::RunAllTests(ac, av); }

test/test_api.cpp

@@ -0,0 +1,56 @@
+#include <CppUTestExt/MockSupport.h>
+
+#include "CppUTest/TestHarness.h"
+#include "test_defaults.hpp"
+
+extern "C" {
+#include "mock_dfu.h"
+#include "mock_nvm.h"
+#include "voyager.h"
+#include "voyager_private.h"
+}
+
+extern const voyager_bootloader_config_t default_test_config;
+
+// create a test group
+TEST_GROUP(test_bootloader_api){
+
+    void setup(){mock().clear();
+mock_nvm_data_t *nvm_data = mock_nvm_get_data();
+
+uint8_t *mock_app_start_address = mock_dfu_get_flash();
+nvm_data->app_start_address = (uintptr_t)mock_app_start_address;
+nvm_data->app_end_address = nvm_data->app_start_address + FAKE_FLASH_SIZE * 2;
+nvm_data->app_size = FAKE_FLASH_SIZE;
+mock_dfu_init();
+}
+
+void teardown() { mock().clear(); }
+}
+;
+
+// Test that a nullptr'ed config returns an error
+TEST(test_bootloader_api, test_init_nullptr_is_rejected) {
+    CHECK_EQUAL(VOYAGER_ERROR_INVALID_ARGUMENT, voyager_bootloader_init(NULL));
+}
+
+// The below is not implemented as a mock due to the function pointer implementation
+static const voyager_bootloader_app_crc_t test_crc_constant = 0xDEADBEEF;
+
+void custom_crc_implementation(const uint8_t byte, voyager_bootloader_app_crc_t *const crc) {
+    (void)byte;
+    *crc = test_crc_constant;
+}
+
+// Test that a custom CRC implementation can be overriden with the function pointer
+TEST(test_bootloader_api, test_custom_crc_implementation) {
+    // Make a struct with a custom CRC function pointer
+    voyager_bootloader_config_t config_custom_crc{.jump_to_app_after_dfu_recv_complete = true,
+                                                  .custom_crc_stream = custom_crc_implementation};
+
+    voyager_bootloader_init(&config_custom_crc);
+
+    voyager_bootloader_app_crc_t test_crc;
+    voyager_private_calculate_crc_stream(1, &test_crc);
+    CHECK_EQUAL(test_crc_constant, test_crc);
+}

test/test_bootloader.cpp

@@ -108,8 +108,3 @@ TEST(test_bootloader_state_machine, test_app_good_crc_verify) {
     // Ensure that the voyager data request is set to VOYAGER_REQUEST_KEEP_IDLE
     CHECK_EQUAL(VOYAGER_REQUEST_KEEP_IDLE, voyager_private_get_data()->request);
 }
-
-// Test that a nullptr'ed config returns an error
-TEST(test_bootloader_state_machine, test_init_nullptr_is_rejected) {
-    CHECK_EQUAL(VOYAGER_ERROR_INVALID_ARGUMENT, voyager_bootloader_init(NULL));
-}

test/test_defaults.cpp

@@ -2,4 +2,5 @@
 
 const voyager_bootloader_config_t default_test_config{
     .jump_to_app_after_dfu_recv_complete = true,
+    .custom_crc_stream = NULL,
 };