Event handling refactoring

This change separates definitions in esp_event.h and functions in event.c into several parts:
- event structure definitions (esp_event.h)
- default implementations of event handlers (event_default_handlers.c)
- default implementation of event loop (event_loop.c, esp_event_loop.h)

Purpose of this change is to allow applications choose their own poison:
- full control of event loop at the expense of more bootstrap code
- pre-defined event task firing event callbacks, but less code in app_main.c

components/esp32/event_loop.c

@@ -0,0 +1,118 @@
+// Copyright 2015-2016 Espressif Systems (Shanghai) PTE LTD
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include <stddef.h>
+#include <stdlib.h>
+#include <string.h>
+
+#include "esp_err.h"
+#include "esp_wifi.h"
+#include "esp_event.h"
+#include "esp_event_loop.h"
+#include "esp_task.h"
+
+#include "freertos/FreeRTOS.h"
+#include "freertos/task.h"
+#include "freertos/queue.h"
+#include "freertos/semphr.h"
+
+#include "tcpip_adapter.h"
+#include "esp_log.h"
+#include "sdkconfig.h"
+
+
+static const char* TAG = "event";
+static bool s_event_init_flag = false;
+static QueueHandle_t s_event_queue = NULL;
+static system_event_cb_t s_event_handler_cb = NULL;
+static void *s_event_ctx = NULL;
+
+static esp_err_t esp_wifi_post_event_to_user(system_event_t *event)
+{
+    if (s_event_handler_cb) {
+        return (*s_event_handler_cb)(s_event_ctx, event);
+    }
+    return ESP_OK;
+}
+
+static void esp_system_event_task(void *pvParameters)
+{
+    system_event_t evt;
+    esp_err_t ret;
+
+    while (1) {
+        if (xQueueReceive(s_event_queue, &evt, portMAX_DELAY) == pdPASS) {
+            ret = esp_event_process_default(&evt);
+            if (ret != ESP_OK) {
+                ESP_LOGE(TAG, "default event handler failed!");
+            }
+            ret = esp_wifi_post_event_to_user(&evt);
+            if (ret != ESP_OK) {
+                ESP_LOGE(TAG, "post event to user fail!");
+            }
+        }
+    }
+}
+
+system_event_cb_t esp_event_set_cb(system_event_cb_t cb, void *ctx)
+{
+    system_event_cb_t old_cb = s_event_handler_cb;
+
+    s_event_handler_cb = cb;
+    s_event_ctx = ctx;
+
+    return old_cb;
+}
+
+esp_err_t esp_event_send(system_event_t *event)
+{
+    portBASE_TYPE ret;
+
+    ret = xQueueSendToBack(s_event_queue, event, 0);
+
+    if (pdPASS != ret) {
+        if (event) {
+            ESP_LOGE(TAG, "e=%d f", event->event_id);
+        } else {
+            ESP_LOGE(TAG, "e null");
+        }
+        return ESP_FAIL;
+    }
+
+    return ESP_OK;
+}
+
+QueueHandle_t esp_event_loop_get_queue(void)
+{
+    return s_event_queue;
+}
+
+esp_err_t esp_event_loop_init(system_event_cb_t cb, void *ctx)
+{
+    if (s_event_init_flag) {
+        return ESP_FAIL;
+    }
+
+    s_event_handler_cb = cb;
+    s_event_ctx = ctx;
+
+    s_event_queue = xQueueCreate(CONFIG_SYSTEM_EVENT_QUEUE_SIZE, sizeof(system_event_t));
+
+    xTaskCreatePinnedToCore(esp_system_event_task, "eventTask",
+            ESP_TASKD_EVENT_STACK, NULL, ESP_TASKD_EVENT_PRIO, NULL, 0);
+
+    s_event_init_flag = true;
+    return ESP_OK;
+}
+