Static allocation of statistics buffer

[terratec]

For issue #1242

[github-actions]

Test Results

20 tests  ±0   20 ✅ ±0   0s ⏱️ ±0s
 1 suites ±0    0 💤 ±0 
 1 files   ±0    0 ❌ ±0 

Results for commit 032a3c9. ± Comparison against base commit ac7e70f.

♻️ This comment has been updated with latest results.

[mutatrum]

I don't think this needs to be a linked list now, it can just be an array.

[terratec]

Should we instead use a virtual index (0-720) for data retrieval and convert it to the current index (e.g. 359-719-0-358)?
Or should we return all the copied and reordered data at once with newly allocated memory?

[mutatrum]

Not sure if I understand the question. I would keep stack of the size and the start of the data in the array (head), then you can convert any position to the array position by modulo 720.

[mutatrum]

Use heap_caps_malloc with MALLOC_CAP_DEFAULT | MALLOC_CAP_SPIRAM to force it into PSRAM?

[WantClue]

There is a current potential for a memory leak with duplicate staticbuffer creating.

my suggested change would be

if (NULL == statisticsBuffer) {
-        createStatisticsBuffer();
+        pthread_mutex_lock(&statisticsDataLock);
+        if (NULL == statisticsBuffer) {
+            pthread_mutex_unlock(&statisticsDataLock);
+            createStatisticsBuffer();
+        } else {
+            pthread_mutex_unlock(&statisticsDataLock);
+        }
     }

Also please make sure to simplify it and I agree with @mutatrum that there is no need for a linked list