Merge pull request #3648 from willmmiles/json-response-locking

Expand JSON buffer lock scope to entire web reply
wled · Jan 6, 2024 · 801d92b · 801d92b
2 parents 6ad4493 + 7711617
commit 801d92b
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Showing 2 changed files with 30 additions and 3 deletions.
diff --git a/wled00/fcn_declare.h b/wled00/fcn_declare.h
@@ -360,6 +360,22 @@ um_data_t* simulateSound(uint8_t simulationId);
 void enumerateLedmaps();
 uint8_t get_random_wheel_index(uint8_t pos);
 
+// RAII guard class for the JSON Buffer lock
+// Modeled after std::lock_guard
+class JSONBufferGuard {
+  bool holding_lock;
+  public:
+    inline JSONBufferGuard(uint8_t module=255) : holding_lock(requestJSONBufferLock(module)) {};
+    inline ~JSONBufferGuard() { if (holding_lock) releaseJSONBufferLock(); };
+    inline JSONBufferGuard(const JSONBufferGuard&) = delete; // Noncopyable
+    inline JSONBufferGuard& operator=(const JSONBufferGuard&) = delete;
+    inline JSONBufferGuard(JSONBufferGuard&& r) : holding_lock(r.holding_lock) { r.holding_lock = false; };  // but movable
+    inline JSONBufferGuard& operator=(JSONBufferGuard&& r) { holding_lock |= r.holding_lock; r.holding_lock = false; return *this; };
+    inline bool owns_lock() const { return holding_lock; }
+    explicit inline operator bool() const { return owns_lock(); };
+    inline void release() { if (holding_lock) releaseJSONBufferLock(); holding_lock = false; }
+};
+
 #ifdef WLED_ADD_EEPROM_SUPPORT
 //wled_eeprom.cpp
 void applyMacro(byte index);

diff --git a/wled00/json.cpp b/wled00/json.cpp
@@ -1009,6 +1009,17 @@ void serializeModeNames(JsonArray arr)
   }
 }
 
+
+// Global buffer locking response helper class
+class GlobalBufferAsyncJsonResponse: public JSONBufferGuard, public AsyncJsonResponse {
+  public:
+  inline GlobalBufferAsyncJsonResponse(bool isArray) : JSONBufferGuard(17), AsyncJsonResponse(pDoc, isArray) {};
+  virtual ~GlobalBufferAsyncJsonResponse() {};
+
+  // Other members are inherited
+};
+
+
 static volatile bool servingClient = false;
 void serveJson(AsyncWebServerRequest* request)
 {
@@ -1050,12 +1061,13 @@ void serveJson(AsyncWebServerRequest* request)
     return;
   }
 
-  if (!requestJSONBufferLock(17)) {
+  GlobalBufferAsyncJsonResponse *response = new GlobalBufferAsyncJsonResponse(subJson==JSON_PATH_FXDATA || subJson==JSON_PATH_EFFECTS); // will clear and convert JsonDocument into JsonArray if necessary
+  if (!response->owns_lock()) {
     serveJsonError(request, 503, ERR_NOBUF);
     servingClient = false;
+    delete response;
     return;
   }
-  AsyncJsonResponse *response = new AsyncJsonResponse(pDoc, subJson==JSON_PATH_FXDATA || subJson==JSON_PATH_EFFECTS); // will clear and convert JsonDocument into JsonArray if necessary
 
   JsonVariant lDoc = response->getRoot();
 
@@ -1098,7 +1110,6 @@ void serveJson(AsyncWebServerRequest* request)
   DEBUG_PRINT(F("JSON content length: ")); DEBUG_PRINTLN(len);
 
   request->send(response);
-  releaseJSONBufferLock();
   servingClient = false;
 }