Implementing the concurrent access. Supports well more than 5 devices, enough for the house

Provider/main/http_server.cpp

@@ -28,11 +28,53 @@ constexpr uint8 kGZ_Extension_Length = sizeof(".gz") - 1;
 
 #define FILE_PATH_MAX (ESP_VFS_PATH_MAX + 128)
 #define SCRATCH_BUFSIZE 4096
+#define MAX_SCRATCH_BUFFERS 10
 
 typedef struct
 {
-  char scratch[SCRATCH_BUFSIZE];
-} http_server_data_t;
+  char *buffers[MAX_SCRATCH_BUFFERS];
+  bool in_use[MAX_SCRATCH_BUFFERS];
+} scratch_pool_t;
+
+static scratch_pool_t global_scratch_pool = {};
+
+char *get_scratch_buffer()
+{
+  for (int i = 0; i < MAX_SCRATCH_BUFFERS; i++)
+  {
+    if (!global_scratch_pool.in_use[i])
+    {
+      if (global_scratch_pool.buffers[i] == NULL)
+      {
+        global_scratch_pool.buffers[i] = (char *)malloc(SCRATCH_BUFSIZE);
+        if (global_scratch_pool.buffers[i] == NULL)
+        {
+          ESP_LOGE(TAG, "Failed to allocate scratch buffer from heap!");
+          return NULL;
+        }
+      }
+      global_scratch_pool.in_use[i] = true;
+      return global_scratch_pool.buffers[i];
+    }
+  }
+  ESP_LOGE(TAG, "All scratch buffers in use! Increase MAX_SCRATCH_BUFFERS");
+  return NULL;
+}
+
+void free_scratch_buffer(char *buffer)
+{
+  if (buffer == NULL)
+    return;
+  for (int i = 0; i < MAX_SCRATCH_BUFFERS; i++)
+  {
+    if (global_scratch_pool.buffers[i] == buffer)
+    {
+      global_scratch_pool.in_use[i] = false;
+      return;
+    }
+  }
+  ESP_LOGE(TAG, "Attempted to free unknown scratch buffer!");
+}
 
 #ifdef CONFIG_CALENDINK_DEPLOY_WEB_PAGES
 // Set HTTP response content type according to file extension
@@ -138,8 +180,14 @@ internal esp_err_t static_file_handler(httpd_req_t *req)
 
   set_content_type_from_file(req, filepath);
 
-  http_server_data_t *rest_context = (http_server_data_t *)req->user_ctx;
-  char *chunk = rest_context->scratch;
+  char *chunk = get_scratch_buffer();
+  if (chunk == NULL)
+  {
+    close(fd);
+    httpd_resp_send_err(req, HTTPD_500_INTERNAL_SERVER_ERROR, "Server busy");
+    return ESP_FAIL;
+  }
+
   ssize_t read_bytes;
 
   do
@@ -155,6 +203,7 @@ internal esp_err_t static_file_handler(httpd_req_t *req)
       {
         close(fd);
         ESP_LOGE(TAG, "File sending failed!");
+        free_scratch_buffer(chunk);
         httpd_resp_sendstr_chunk(req, NULL); // Abort sending
         return ESP_FAIL;
       }
@@ -162,6 +211,7 @@ internal esp_err_t static_file_handler(httpd_req_t *req)
   } while (read_bytes > 0);
 
   close(fd);
+  free_scratch_buffer(chunk);
   httpd_resp_send_chunk(req, NULL, 0); // End response
 
   return ESP_OK;
@@ -210,17 +260,12 @@ internal httpd_handle_t start_webserver(void)
     ESP_LOGI(TAG, "LittleFS mounted on /www");
   }
 #endif
-  http_server_data_t *rest_context =
-      (http_server_data_t *)calloc(1, sizeof(http_server_data_t));
-  if (rest_context == NULL)
-  {
-    ESP_LOGE(TAG, "No memory for rest context");
-    return NULL;
-  }
 
   httpd_config_t config = HTTPD_DEFAULT_CONFIG();
   config.uri_match_fn = httpd_uri_match_wildcard;
   config.max_uri_handlers = 20;
+  config.max_open_sockets = 24;
+  config.lru_purge_enable = true;
 
   httpd_handle_t server = NULL;
   ESP_LOGI(TAG, "Starting HTTP Server on port: '%d'", config.server_port);
@@ -262,7 +307,7 @@ internal httpd_handle_t start_webserver(void)
     httpd_uri_t static_get_uri = {.uri = "/*",
                                   .method = HTTP_GET,
                                   .handler = static_file_handler,
-                                  .user_ctx = rest_context};
+                                  .user_ctx = NULL};
     httpd_register_uri_handler(server, &static_get_uri);
 #endif
 
@@ -270,7 +315,6 @@ internal httpd_handle_t start_webserver(void)
   }
 
   ESP_LOGE(TAG, "Error starting server!");
-  free(rest_context);
   return NULL;
 }