SavedStruct: Introduce saved_struct_get_metadata (#3392)

* SavedStruct: Replace saved_struct_get_payload_size with saved_struct_get_metadata
  This new function can obtain the magic value, version and payload size
  all at once. This makes the function useful e.g.
  for backwards compatibility.
* SavedStruct: const-qualify saved_struct_save
* Toolbox: add saved struct documentation

Co-authored-by: あく <alleteam@gmail.com>

applications/services/bt/bt_service/bt_keys_storage.c

@@ -72,16 +72,19 @@ bool bt_keys_storage_load(BtKeysStorage* instance) {
     bool loaded = false;
     do {
         // Get payload size
+        uint8_t magic = 0, version = 0;
         size_t payload_size = 0;
-        if(!saved_struct_get_payload_size(
-               furi_string_get_cstr(instance->file_path),
-               BT_KEYS_STORAGE_MAGIC,
-               BT_KEYS_STORAGE_VERSION,
-               &payload_size)) {
+        if(!saved_struct_get_metadata(
+               furi_string_get_cstr(instance->file_path), &magic, &version, &payload_size)) {
             FURI_LOG_E(TAG, "Failed to read payload size");
             break;
         }
 
+        if(magic != BT_KEYS_STORAGE_MAGIC || version != BT_KEYS_STORAGE_VERSION) {
+            FURI_LOG_E(TAG, "Saved data version is mismatched");
+            break;
+        }
+
         if(payload_size > instance->nvm_sram_buff_size) {
             FURI_LOG_E(TAG, "Saved data doesn't fit ram buffer");
             break;

applications/services/bt/bt_settings.c

@@ -15,7 +15,7 @@ bool bt_settings_load(BtSettings* bt_settings) {
         BT_SETTINGS_PATH, bt_settings, sizeof(BtSettings), BT_SETTINGS_MAGIC, BT_SETTINGS_VERSION);
 }
 
-bool bt_settings_save(BtSettings* bt_settings) {
+bool bt_settings_save(const BtSettings* bt_settings) {
     furi_assert(bt_settings);
 
     return saved_struct_save(

applications/services/bt/bt_settings.h

@@ -15,7 +15,7 @@ typedef struct {
 
 bool bt_settings_load(BtSettings* bt_settings);
 
-bool bt_settings_save(BtSettings* bt_settings);
+bool bt_settings_save(const BtSettings* bt_settings);
 
 #ifdef __cplusplus
 }

applications/services/expansion/expansion_settings.c

@@ -19,7 +19,7 @@ bool expansion_settings_load(ExpansionSettings* settings) {
         EXPANSION_SETTINGS_VERSION);
 }
 
-bool expansion_settings_save(ExpansionSettings* settings) {
+bool expansion_settings_save(const ExpansionSettings* settings) {
     furi_assert(settings);
     return saved_struct_save(
         EXPANSION_SETTINGS_PATH,

applications/services/expansion/expansion_settings.h

@@ -36,7 +36,7 @@ bool expansion_settings_load(ExpansionSettings* settings);
  * @param[in] settings pointer to an ExpansionSettings instance to save settings from.
  * @returns true if the settings were successfully saved, false otherwise.
  */
-bool expansion_settings_save(ExpansionSettings* settings);
+bool expansion_settings_save(const ExpansionSettings* settings);
 
 #ifdef __cplusplus
 }

lib/toolbox/saved_struct.c

@@ -13,7 +13,12 @@ typedef struct {
     uint32_t timestamp;
 } SavedStructHeader;
 
-bool saved_struct_save(const char* path, void* data, size_t size, uint8_t magic, uint8_t version) {
+bool saved_struct_save(
+    const char* path,
+    const void* data,
+    size_t size,
+    uint8_t magic,
+    uint8_t version) {
     furi_check(path);
     furi_check(data);
     furi_check(size);
@@ -35,7 +40,7 @@ bool saved_struct_save(const char* path, void* data, size_t size, uint8_t magic,
     if(result) {
         // Calculate checksum
         uint8_t checksum = 0;
-        uint8_t* source = data;
+        const uint8_t* source = data;
         for(size_t i = 0; i < size; i++) {
             checksum += source[i];
         }
@@ -63,6 +68,10 @@ bool saved_struct_save(const char* path, void* data, size_t size, uint8_t magic,
 }
 
 bool saved_struct_load(const char* path, void* data, size_t size, uint8_t magic, uint8_t version) {
+    furi_check(path);
+    furi_check(data);
+    furi_check(size);
+
     FURI_LOG_I(TAG, "Loading \"%s\"", path);
 
     SavedStructHeader header;
@@ -126,13 +135,12 @@ bool saved_struct_load(const char* path, void* data, size_t size, uint8_t magic,
     return result;
 }
 
-bool saved_struct_get_payload_size(
+bool saved_struct_get_metadata(
     const char* path,
-    uint8_t magic,
-    uint8_t version,
+    uint8_t* magic,
+    uint8_t* version,
     size_t* payload_size) {
     furi_check(path);
-    furi_check(payload_size);
 
     SavedStructHeader header;
     Storage* storage = furi_record_open(RECORD_STORAGE);
@@ -146,26 +154,22 @@ bool saved_struct_get_payload_size(
             break;
         }
 
-        size_t bytes_count = storage_file_read(file, &header, sizeof(SavedStructHeader));
-        if(bytes_count != sizeof(SavedStructHeader)) {
+        if(storage_file_read(file, &header, sizeof(SavedStructHeader)) !=
+           sizeof(SavedStructHeader)) {
             FURI_LOG_E(TAG, "Failed to read header");
             break;
         }
 
-        if((header.magic != magic) || (header.version != version)) {
-            FURI_LOG_E(
-                TAG,
-                "Magic(%d != %d) or Version(%d != %d) mismatch of file \"%s\"",
-                header.magic,
-                magic,
-                header.version,
-                version,
-                path);
-            break;
+        if(magic) {
+            *magic = header.magic;
         }
-
+        if(version) {
+            *version = header.version;
+        }
+        if(payload_size) {
             uint64_t file_size = storage_file_size(file);
             *payload_size = file_size - sizeof(SavedStructHeader);
+        }
 
         result = true;
     } while(false);

lib/toolbox/saved_struct.h

@@ -1,3 +1,8 @@
+/**
+ * @file saved_struct.h
+ * @brief SavedStruct - data serialization/de-serialization
+ * 
+ */
 #pragma once
 
 #include <stdint.h>
@@ -8,14 +13,50 @@
 extern "C" {
 #endif
 
+/** Load data from the file in saved structure format
+ *
+ * @param[in]  path     The path to the file
+ * @param[out] data     Pointer to the memory where to load data
+ * @param[in]  size     The size of the data
+ * @param[in]  magic    The magic to embed into metadata
+ * @param[in]  version  The version to embed into metadata
+ *
+ * @return     true on success, false otherwise
+ */
 bool saved_struct_load(const char* path, void* data, size_t size, uint8_t magic, uint8_t version);
 
-bool saved_struct_save(const char* path, void* data, size_t size, uint8_t magic, uint8_t version);
-
-bool saved_struct_get_payload_size(
+/** Save data in saved structure format
+ *
+ * @param[in]  path     The path to the file
+ * @param[in]  data     Pointer to the memory where data
+ * @param[in]  size     The size of the data
+ * @param[in]  magic    The magic to embed into metadata
+ * @param[in]  version  The version to embed into metadata
+ *
+ * @return     true on success, false otherwise
+ */
+bool saved_struct_save(
     const char* path,
+    const void* data,
+    size_t size,
     uint8_t magic,
-    uint8_t version,
+    uint8_t version);
+
+/** Get SavedStructure file metadata
+ *
+ * @param[in]  path          The path to the file
+ * @param[out] magic         Pointer to store magic or NULL if you don't need it
+ * @param[out] version       Pointer to store version or NULL if you don't need
+ *                           it
+ * @param[out] payload_size  Pointer to store payload size or NULL if you don't
+ *                           need it
+ *
+ * @return     true on success, false otherwise
+ */
+bool saved_struct_get_metadata(
+    const char* path,
+    uint8_t* magic,
+    uint8_t* version,
     size_t* payload_size);
 
 #ifdef __cplusplus

targets/f18/api_symbols.csv

@@ -2303,9 +2303,9 @@ Function,+,rpc_system_app_set_callback,void,"RpcAppSystem*, RpcAppSystemCallback
 Function,+,rpc_system_app_set_error_code,void,"RpcAppSystem*, uint32_t"
 Function,+,rpc_system_app_set_error_text,void,"RpcAppSystem*, const char*"
 Function,-,rpmatch,int,const char*
-Function,+,saved_struct_get_payload_size,_Bool,"const char*, uint8_t, uint8_t, size_t*"
+Function,+,saved_struct_get_metadata,_Bool,"const char*, uint8_t*, uint8_t*, size_t*"
 Function,+,saved_struct_load,_Bool,"const char*, void*, size_t, uint8_t, uint8_t"
-Function,+,saved_struct_save,_Bool,"const char*, void*, size_t, uint8_t, uint8_t"
+Function,+,saved_struct_save,_Bool,"const char*, const void*, size_t, uint8_t, uint8_t"
 Function,-,scalbln,double,"double, long int"
 Function,-,scalblnf,float,"float, long int"
 Function,-,scalblnl,long double,"long double, long"

targets/f7/api_symbols.csv

@@ -2866,9 +2866,9 @@ Function,+,rpc_system_app_set_callback,void,"RpcAppSystem*, RpcAppSystemCallback
 Function,+,rpc_system_app_set_error_code,void,"RpcAppSystem*, uint32_t"
 Function,+,rpc_system_app_set_error_text,void,"RpcAppSystem*, const char*"
 Function,-,rpmatch,int,const char*
-Function,+,saved_struct_get_payload_size,_Bool,"const char*, uint8_t, uint8_t, size_t*"
+Function,+,saved_struct_get_metadata,_Bool,"const char*, uint8_t*, uint8_t*, size_t*"
 Function,+,saved_struct_load,_Bool,"const char*, void*, size_t, uint8_t, uint8_t"
-Function,+,saved_struct_save,_Bool,"const char*, void*, size_t, uint8_t, uint8_t"
+Function,+,saved_struct_save,_Bool,"const char*, const void*, size_t, uint8_t, uint8_t"
 Function,-,scalbln,double,"double, long int"
 Function,-,scalblnf,float,"float, long int"
 Function,-,scalblnl,long double,"long double, long"