Make sure the closed slot is always freed (me-no-dev#68)

* Tidy up and fix some edge cases.

* Make sure we always release a closed_slot.

Author: matt123p

src/AsyncTCP.cpp

@@ -82,8 +82,8 @@ static TaskHandle_t _async_service_task_handle = NULL;
 
 SemaphoreHandle_t _slots_lock;
 const int _number_of_closed_slots = CONFIG_LWIP_MAX_ACTIVE_TCP;
-static int _closed_slots[_number_of_closed_slots];
-static int _closed_index = []() {
+static uint32_t _closed_slots[_number_of_closed_slots];
+static uint32_t _closed_index = []() {
     _slots_lock = xSemaphoreCreateBinary();
     xSemaphoreGive(_slots_lock);
     for (int i = 0; i < _number_of_closed_slots; ++ i) {
@@ -565,17 +565,7 @@ AsyncClient::AsyncClient(tcp_pcb* pcb)
     _pcb = pcb;
     _closed_slot = -1;
     if(_pcb){
-        xSemaphoreTake(_slots_lock, portMAX_DELAY);
-        int closed_slot_min_index = 0;
-        for (int i = 0; i < _number_of_closed_slots; ++ i) {
-            if ((_closed_slot == -1 || _closed_slots[i] <= closed_slot_min_index) && _closed_slots[i] != 0) {
-                closed_slot_min_index = _closed_slots[i];
-                _closed_slot = i;
-            }
-        }
-        _closed_slots[_closed_slot] = 0;
-        xSemaphoreGive(_slots_lock);
-
+        _allocate_closed_slot();
         _rx_last_packet = millis();
         tcp_arg(_pcb, this);
         tcp_recv(_pcb, &_tcp_recv);
@@ -589,6 +579,7 @@ AsyncClient::~AsyncClient(){
     if(_pcb) {
         _close();
     }
+    _free_closed_slot();
 }
 
 /*
@@ -714,7 +705,6 @@ bool AsyncClient::connect(const char* host, uint16_t port){
     ip_addr_t addr;
 
     if(!_start_async_task()){
-      Serial.println("failed to start task");
       log_e("failed to start task");
       return false;
     }
@@ -825,6 +815,29 @@ int8_t AsyncClient::_close(){
     return err;
 }
 
+void AsyncClient::_allocate_closed_slot(){
+    xSemaphoreTake(_slots_lock, portMAX_DELAY);
+    uint32_t closed_slot_min_index = 0;
+    for (int i = 0; i < _number_of_closed_slots; ++ i) {
+        if ((_closed_slot == -1 || _closed_slots[i] <= closed_slot_min_index) && _closed_slots[i] != 0) {
+            closed_slot_min_index = _closed_slots[i];
+            _closed_slot = i;
+        }
+    }
+    if (_closed_slot != -1) {
+        _closed_slots[_closed_slot] = 0;
+    }
+    xSemaphoreGive(_slots_lock);
+}
+
+void AsyncClient::_free_closed_slot(){
+    if (_closed_slot != -1) {
+        _closed_slots[_closed_slot] = _closed_index;
+        _closed_slot = -1;
+        ++ _closed_index;
+    }
+}
+
 /*
  * Private Callbacks
  * */
@@ -879,8 +892,7 @@ int8_t AsyncClient::_lwip_fin(tcp_pcb* pcb, int8_t err) {
     if(tcp_close(_pcb) != ERR_OK) {
         tcp_abort(_pcb);
     }
-    _closed_slots[_closed_slot] = _closed_index;
-    ++ _closed_index;
+    _free_closed_slot();
     _pcb = NULL;
     return ERR_OK;
 }

src/AsyncTCP.h

@@ -170,6 +170,8 @@ class AsyncClient {
     uint16_t _connect_port;
 
     int8_t _close();
+    void _free_closed_slot();
+    void _allocate_closed_slot();
     int8_t _connected(void* pcb, int8_t err);
     void _error(int8_t err);
     int8_t _poll(tcp_pcb* pcb);