fix(MAM): Add MAM save

MAM API can be serialized and saved into files. This PR create a
temporarily file to save MSS after first time. Send MAM message can be
faster in second call and after in this way.

accelerator/apis.c

@@ -201,6 +201,7 @@ status_t api_mam_send_message(const iota_config_t* const tangle,
                               const iota_client_service_t* const service,
                               char const* const payload, char** json_result) {
   status_t ret = SC_OK;
+  retcode_t rc = RC_OK;
   mam_api_t mam;
   const bool last_packet = true;
   bundle_transactions_t* bundle = NULL;
@@ -210,8 +211,14 @@ status_t api_mam_send_message(const iota_config_t* const tangle,
   send_mam_req_t* req = send_mam_req_new();
   send_mam_res_t* res = send_mam_res_new();
 
-  // Creating MAM API
-  if (mam_api_init(&mam, (tryte_t*)SEED)) {
+  // Loading and creating MAM API
+  if ((rc = mam_api_load(tangle->mam_file, &mam)) ==
+      RC_UTILS_FAILED_TO_OPEN_FILE) {
+    if (mam_api_init(&mam, (tryte_t*)SEED)) {
+      ret = SC_MAM_FAILED_INIT;
+      goto done;
+    }
+  } else if (rc != RC_OK) {
     ret = SC_MAM_FAILED_INIT;
     goto done;
   }
@@ -255,9 +262,9 @@ status_t api_mam_send_message(const iota_config_t* const tangle,
   ret = send_mam_res_serialize(json_result, res);
 
 done:
-  // Destroying MAM API
+  // Save and destroying MAM API
   if (ret != SC_MAM_FAILED_INIT) {
-    if (mam_api_destroy(&mam) != RC_OK) {
+    if (mam_api_save(&mam, tangle->mam_file) || mam_api_destroy(&mam)) {
       ret = SC_MAM_FAILED_DESTROYED;
     }
   }

accelerator/config.c

@@ -72,6 +72,7 @@ status_t ta_config_default_init(ta_config_t* const info,
                                 ta_cache_t* const cache,
                                 iota_client_service_t* const service) {
   status_t ret = SC_OK;
+  char mss_tmp[] = "/tmp/XXXXXX";
   if (info == NULL || tangle == NULL || cache == NULL || service == NULL) {
     return SC_TA_NULL;
   }
@@ -92,6 +93,8 @@ status_t ta_config_default_init(ta_config_t* const info,
 
   log_info(logger_id, "Initializing IRI configuration\n");
   tangle->milestone_depth = MILESTONE_DEPTH;
+  mkstemp(mss_tmp);
+  strncpy(tangle->mam_file, mss_tmp, FSIZE);
   tangle->mss_depth = MSS_DEPTH;
   tangle->mwm = MWM;
   tangle->seed = SEED;

accelerator/config.h

@@ -27,6 +27,7 @@ extern "C" {
 #define IRI_HOST "localhost"
 #define IRI_PORT 14265
 #define MILESTONE_DEPTH 3
+#define FSIZE 11
 #define MSS_DEPTH 4
 #define MWM 14
 #define SEED                                                                   \
@@ -50,6 +51,7 @@ typedef struct ta_info_s {
 /** struct type of iota configuration */
 typedef struct ta_config_s {
   uint8_t milestone_depth; /**< Depth of API argument */
+  char mam_file[FSIZE];    /** Save file for mam struct like MSS, skn... */
   uint8_t mss_depth;       /**< Depth of MSS layer merkle tree */
   uint8_t mwm;             /**< Minimum weight magnitude of API argument */
   /** Seed to generate address. This does not do any signature yet. */