added two value constructor to specify buffer sizes separately

Author: 256dpi

README.md

@@ -28,7 +28,7 @@ Other shields and boards should also work if they provide a [Client](https://www
 
 ## Notes
 
-- The maximum size for packets being published and received is set by default to 128 bytes. To change the buffer sizes, you need to use `MQTTClient client(256)` instead of just `MQTTClient client` on the top of your sketch. The passed value denotes the read and write buffer size. **Beginning with version 2.6, the message payload is sent separately during publishing. Therefore, the write buffer is only needed to encode the packet header and topic, for which the default 128 bytes should be enough. However, the receiving of messages is still fully constrained by the read buffer.**
+- The maximum size for packets being published and received is set by default to 128 bytes. To change the buffer sizes, you need to use `MQTTClient client(256)` or `MQTTClient client(256, 512)` instead of just `MQTTClient client` at the top of your sketch. A single value denotes both the read and write buffer size, two values specify them separately. **Beginning with version 2.6, the message payload is sent directly during publishing. Therefore, the write buffer is only needed to encode the packet header and topic, for which the default 128 bytes should be enough. However, the receiving of messages is still fully constrained by the read buffer, which may be increased if necessary.**
 
 - On the ESP8266 it has been reported that an additional `delay(10);` after `client.loop();` fixes many stability issues with WiFi connections.
 

src/MQTTClient.cpp

@@ -158,11 +158,12 @@ static void MQTTClientHandler(lwmqtt_client_t * /*client*/, void *ref, lwmqtt_st
 #endif
 }
 
-MQTTClient::MQTTClient(int bufSize) {
+MQTTClient::MQTTClient(int readBufSize, int writeBufSize) {
   // allocate buffers
-  this->bufSize = (size_t)bufSize;
-  this->readBuf = (uint8_t *)malloc((size_t)bufSize + 1);
-  this->writeBuf = (uint8_t *)malloc((size_t)bufSize);
+  this->readBufSize = (size_t)readBufSize;
+  this->writeBufSize = (size_t)writeBufSize;
+  this->readBuf = (uint8_t *)malloc((size_t)readBufSize + 1);
+  this->writeBuf = (uint8_t *)malloc((size_t)writeBufSize);
 }
 
 MQTTClient::~MQTTClient() {
@@ -184,7 +185,7 @@ void MQTTClient::begin(Client &_client) {
   this->netClient = &_client;
 
   // initialize client
-  lwmqtt_init(&this->client, this->writeBuf, this->bufSize, this->readBuf, this->bufSize);
+  lwmqtt_init(&this->client, this->writeBuf, this->writeBufSize, this->readBuf, this->readBufSize);
 
   // set timers
   lwmqtt_set_timers(&this->client, &this->timer1, &this->timer2, lwmqtt_arduino_timer_set, lwmqtt_arduino_timer_get);

src/MQTTClient.h

@@ -65,7 +65,8 @@ typedef struct {
 
 class MQTTClient {
  private:
-  size_t bufSize = 0;
+  size_t readBufSize = 0;
+  size_t writeBufSize = 0;
   uint8_t *readBuf = nullptr;
   uint8_t *writeBuf = nullptr;
 
@@ -94,7 +95,8 @@ class MQTTClient {
  public:
   void *ref = nullptr;
 
-  explicit MQTTClient(int bufSize = 128);
+  explicit MQTTClient(int bufSize = 128) : MQTTClient(bufSize, bufSize) {}
+  MQTTClient(int readSize, int writeBufSize);
 
   ~MQTTClient();