AP_Logger: add option allocate scripting format strings in msg_fmt_for_name

libraries/AP_Logger/AP_Logger.cpp

@@ -1076,7 +1076,7 @@ bool AP_Logger::assert_same_fmt_for_name(const AP_Logger::log_write_fmt *f,
 }
 #endif
 
-AP_Logger::log_write_fmt *AP_Logger::msg_fmt_for_name(const char *name, const char *labels, const char *units, const char *mults, const char *fmt, const bool direct_comp)
+AP_Logger::log_write_fmt *AP_Logger::msg_fmt_for_name(const char *name, const char *labels, const char *units, const char *mults, const char *fmt, const bool direct_comp, const bool copy_strings)
 {
     WITH_SEMAPHORE(log_write_fmts_sem);
     struct log_write_fmt *f;
@@ -1117,11 +1117,40 @@ AP_Logger::log_write_fmt *AP_Logger::msg_fmt_for_name(const char *name, const ch
         return nullptr;
     }
     f->msg_type = msg_type;
-    f->name = name;
-    f->fmt = fmt;
-    f->labels = labels;
-    f->units = units;
-    f->mults = mults;
+
+    if (copy_strings) {
+        // cannot use pointers to memory that might move, must allocate and copy
+        struct log_write_fmt_strings *ls_copy = (struct log_write_fmt_strings*)malloc(sizeof(log_write_fmt_strings));
+        if (ls_copy == nullptr) {
+            free(f);
+            return nullptr;
+        }
+
+        strncpy_noterm(ls_copy->name, name, sizeof(ls_copy->name));
+        strncpy_noterm(ls_copy->format, fmt, sizeof(ls_copy->format));
+        strncpy_noterm(ls_copy->labels, labels, sizeof(ls_copy->labels));
+
+        f->name = ls_copy->name;
+        f->fmt = ls_copy->format;
+        f->labels = ls_copy->labels;
+
+        if (units != nullptr) {
+            strncpy_noterm(ls_copy->units, units, sizeof(ls_copy->units));
+            f->units = ls_copy->units;
+        }
+
+        if (mults != nullptr) {
+            strncpy_noterm(ls_copy->multipliers, mults, sizeof(ls_copy->multipliers));
+            f->mults = ls_copy->multipliers;
+        }
+
+    } else {
+        f->name = name;
+        f->fmt = fmt;
+        f->labels = labels;
+        f->units = units;
+        f->mults = mults;
+    }
 
     int16_t tmp = Write_calc_msg_len(fmt);
     if (tmp == -1) {
@@ -1131,37 +1160,41 @@ AP_Logger::log_write_fmt *AP_Logger::msg_fmt_for_name(const char *name, const ch
 
     f->msg_len = tmp;
 
-    // add to front of list
-    f->next = log_write_fmts;
-    log_write_fmts = f;
+    // add direct_comp formats to start of list, otherwise add to the end, this minimises the number of string comparisons when walking the list in future calls
+    if (direct_comp || (log_write_fmts == nullptr)) {
+        f->next = log_write_fmts;
+        log_write_fmts = f;
+    } else {
+        struct log_write_fmt *list_end = log_write_fmts;
+        while (list_end->next) {
+            list_end=list_end->next;
+        }
+        list_end->next = f;
+    }
 
 #if CONFIG_HAL_BOARD == HAL_BOARD_SITL
-    char ls_name[LS_NAME_SIZE] = {};
-    char ls_format[LS_FORMAT_SIZE] = {};
-    char ls_labels[LS_LABELS_SIZE] = {};
-    char ls_units[LS_UNITS_SIZE] = {};
-    char ls_multipliers[LS_MULTIPLIERS_SIZE] = {};
+    struct log_write_fmt_strings ls_strings = {};
     struct LogStructure ls = {
         f->msg_type,
         f->msg_len,
-        ls_name,
-        ls_format,
-        ls_labels,
-        ls_units,
-        ls_multipliers
+        ls_strings.name,
+        ls_strings.format,
+        ls_strings.labels,
+        ls_strings.units,
+        ls_strings.multipliers
     };
-    memcpy((char*)ls_name, f->name, MIN(sizeof(ls_name), strlen(f->name)));
-    memcpy((char*)ls_format, f->fmt, MIN(sizeof(ls_format), strlen(f->fmt)));
-    memcpy((char*)ls_labels, f->labels, MIN(sizeof(ls_labels), strlen(f->labels)));
+    memcpy((char*)ls_strings.name, f->name, MIN(sizeof(ls_strings.name), strlen(f->name)));
+    memcpy((char*)ls_strings.format, f->fmt, MIN(sizeof(ls_strings.format), strlen(f->fmt)));
+    memcpy((char*)ls_strings.labels, f->labels, MIN(sizeof(ls_strings.labels), strlen(f->labels)));
     if (f->units != nullptr) {
-        memcpy((char*)ls_units, f->units, MIN(sizeof(ls_units), strlen(f->units)));
+        memcpy((char*)ls_strings.units, f->units, MIN(sizeof(ls.units), strlen(f->units)));
     } else {
-        memset((char*)ls_units, '?', MIN(sizeof(ls_format), strlen(f->fmt)));
+        memset((char*)ls_strings.units, '?', MIN(sizeof(ls.format), strlen(f->fmt)));
     }
     if (f->mults != nullptr) {
-        memcpy((char*)ls_multipliers, f->mults, MIN(sizeof(ls_multipliers), strlen(f->mults)));
+        memcpy((char*)ls_strings.multipliers, f->mults, MIN(sizeof(ls_strings.multipliers), strlen(f->mults)));
     } else {
-        memset((char*)ls_multipliers, '?', MIN(sizeof(ls_format), strlen(f->fmt)));
+        memset((char*)ls_strings.multipliers, '?', MIN(sizeof(ls_strings.format), strlen(f->fmt)));
     }
     if (!validate_structure(&ls, (int16_t)-1)) {
         AP_BoardConfig::config_error("See console: Log structure invalid");

libraries/AP_Logger/AP_Logger.h

@@ -435,7 +435,7 @@ public:
     } *log_write_fmts;
 
     // return (possibly allocating) a log_write_fmt for a name
-    struct log_write_fmt *msg_fmt_for_name(const char *name, const char *labels, const char *units, const char *mults, const char *fmt, const bool direct_comp = false);
+    struct log_write_fmt *msg_fmt_for_name(const char *name, const char *labels, const char *units, const char *mults, const char *fmt, const bool direct_comp = false, const bool copy_strings = false);
 
     // output a FMT message for each backend if not already done so
     void Safe_Write_Emit_FMT(log_write_fmt *f);
@@ -525,6 +525,14 @@ private:
     bool _force_log_disarmed:1;
     bool _force_long_log_persist:1;
 
+    struct log_write_fmt_strings {
+        char name[LS_NAME_SIZE];
+        char format[LS_FORMAT_SIZE];
+        char labels[LS_LABELS_SIZE];
+        char units[LS_UNITS_SIZE];
+        char multipliers[LS_MULTIPLIERS_SIZE];
+    };
+
     // remember formats for replay
     void save_format_Replay(const void *pBuffer);
 

libraries/AP_Logger/AP_Logger_Backend.cpp

@@ -181,20 +181,16 @@ bool AP_Logger_Backend::Write_Emit_FMT(uint8_t msg_type)
 #endif
 
     // get log structure from front end:
-    char ls_name[LS_NAME_SIZE] = {};
-    char ls_format[LS_FORMAT_SIZE] = {};
-    char ls_labels[LS_LABELS_SIZE] = {};
-    char ls_units[LS_UNITS_SIZE] = {};
-    char ls_multipliers[LS_MULTIPLIERS_SIZE] = {};
+    struct AP_Logger::log_write_fmt_strings ls = {};
     struct LogStructure logstruct = {
         // these will be overwritten, but need to keep the compiler happy:
         0,
         0,
-        ls_name,
-        ls_format,
-        ls_labels,
-        ls_units,
-        ls_multipliers
+        ls.name,
+        ls.format,
+        ls.labels,
+        ls.units,
+        ls.multipliers
     };
     if (!_front.fill_log_write_logstructure(logstruct, msg_type)) {
         // this is a bug; we've been asked to write out the FMT