Refactor sleep tracing driver identifier to be pointer to the driver filepath.

The use of __FILE__ macro to get a usable identifier from the driver path
causes the path of the file to be stored in the .text region of the binary.
Given that this remains for the entire duration of the program, storing a
pointer to this string as an identifier is more efficient than copying the
contents of the string during lookup/insertion.

Author: Steven Cartmell

hal/mbed_sleep_manager.c

@@ -30,27 +30,20 @@ static uint16_t deep_sleep_lock = 0U;
 
 #ifdef MBED_SLEEP_TRACING_ENABLED
 
-// Length of the identifier extracted from the driver name to store for logging.
-#define IDENTIFIER_WIDTH 15
 // Number of drivers that can be stored in the structure
 #define STATISTIC_COUNT  10
 
 typedef struct sleep_statistic {
-    char identifier[IDENTIFIER_WIDTH];
+    const char* identifier;
     uint8_t count;
 } sleep_statistic_t;
 
 static sleep_statistic_t sleep_stats[STATISTIC_COUNT];
 
 static sleep_statistic_t* sleep_tracker_find(const char *const filename)
 {
-    char temp[IDENTIFIER_WIDTH];
-    strncpy(temp, filename, IDENTIFIER_WIDTH);
-    temp[IDENTIFIER_WIDTH - 1] = '\0';
-
-    // Search for the a driver matching the current name and return it's index
     for (int i = 0; i < STATISTIC_COUNT; ++i) {
-        if (strcmp(sleep_stats[i].identifier, temp) == 0) {
+        if (sleep_stats[i].identifier == filename) {
             return &sleep_stats[i];
         }
     }
@@ -60,15 +53,9 @@ static sleep_statistic_t* sleep_tracker_find(const char *const filename)
 
 static sleep_statistic_t* sleep_tracker_add(const char* const filename)
 {
-    char temp[IDENTIFIER_WIDTH];
-    strncpy(temp, filename, IDENTIFIER_WIDTH);
-    temp[IDENTIFIER_WIDTH - 1] = '\0';
-
     for (int i = 0; i < STATISTIC_COUNT; ++i) {
-        if (sleep_stats[i].identifier[0] == '\0') {
-            core_util_critical_section_enter();
-            strncpy(sleep_stats[i].identifier, temp, sizeof(temp));
-            core_util_critical_section_exit();
+        if (sleep_stats[i].identifier == NULL) {
+            sleep_stats[i].identifier = filename;
 
             return &sleep_stats[i];
         }
@@ -87,12 +74,12 @@ static void sleep_tracker_print_stats(void)
             continue;
         }
 
-        if (sleep_stats[i].identifier[0] == '\0') {
+        if (sleep_stats[i].identifier == NULL) {
             return;
         }
 
         debug("[id: %s, count: %u]\r\n", sleep_stats[i].identifier,
-                                          sleep_stats[i].count);
+                                         sleep_stats[i].count);
     }
 }