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Prevent JSON buffer clear after failed lock attempt

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(alternative to #3743)
This commit is contained in:
Blaz Kristan 2024-02-07 18:58:56 +01:00
parent e165838e54
commit 6dcd9596a2
1 changed files with 13 additions and 11 deletions
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24
wled00/json.cpp
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@ -1030,17 +1030,18 @@ void serializeModeNames(JsonArray arr)
} }
} }
// Global buffer locking response helper class (to make sure lock is released when AsyncJsonResponse is destroyed)
// Global buffer locking response helper class class LockedJsonResponse: public AsyncJsonResponse {
class GlobalBufferAsyncJsonResponse: public JSONBufferGuard, public AsyncJsonResponse {
public: public:
inline GlobalBufferAsyncJsonResponse(bool isArray) : JSONBufferGuard(17), AsyncJsonResponse(pDoc, isArray) {}; // WARNING: constructor assumes requestJSONBufferLock() was successfully acquired externally/prior to constructing the instance
virtual ~GlobalBufferAsyncJsonResponse() {}; // Not a good practice with C++. Unfortunately AsyncJsonResponse only has 2 constructors - for dynamic buffer or existing buffer,
// with existing buffer it clears its content during construction
// Other members are inherited // if the lock was not acquired (using JSONBufferGuard class) previous implementation still cleared existing buffer
inline LockedJsonResponse(JsonDocument *doc, bool isArray) : AsyncJsonResponse(doc, isArray) {};
// destructor will remove JSON buffer lock when response is destroyed in AsyncWebServer
virtual ~LockedJsonResponse() { releaseJSONBufferLock(); };
}; };
void serveJson(AsyncWebServerRequest* request) void serveJson(AsyncWebServerRequest* request)
{ {
byte subJson = 0; byte subJson = 0;
@ -1071,12 +1072,13 @@ void serveJson(AsyncWebServerRequest* request)
return; return;
} }
GlobalBufferAsyncJsonResponse *response = new GlobalBufferAsyncJsonResponse(subJson==JSON_PATH_FXDATA || subJson==JSON_PATH_EFFECTS); // will clear and convert JsonDocument into JsonArray if necessary if (!requestJSONBufferLock(17)) {
if (!response->owns_lock()) {
serveJsonError(request, 503, ERR_NOBUF); serveJsonError(request, 503, ERR_NOBUF);
delete response;
return; return;
} }
// releaseJSONBufferLock() will be called when "response" is destroyed (from AsyncWebServer)
// make sure you delete "response" if no "request->send(response);" is made
LockedJsonResponse *response = new LockedJsonResponse(pDoc, subJson==JSON_PATH_FXDATA || subJson==JSON_PATH_EFFECTS); // will clear and convert JsonDocument into JsonArray if necessary
JsonVariant lDoc = response->getRoot(); JsonVariant lDoc = response->getRoot();