diff --git a/Adafruit_MQTT.cpp b/Adafruit_MQTT.cpp index 84e4ad1..4c4dd96 100644 --- a/Adafruit_MQTT.cpp +++ b/Adafruit_MQTT.cpp @@ -323,7 +323,8 @@ bool Adafruit_MQTT::publish(const char *topic, const char *data, uint8_t qos) { bool Adafruit_MQTT::publish(const char *topic, uint8_t *data, uint16_t bLen, uint8_t qos) { // Construct and send publish packet. - uint16_t len = publishPacket(buffer, topic, data, bLen, qos); + uint16_t len = + publishPacket(buffer, topic, data, bLen, qos, (uint16_t)sizeof(buffer)); if (!sendPacket(buffer, len)) return false; @@ -686,11 +687,26 @@ uint8_t Adafruit_MQTT::connectPacket(uint8_t *packet) { return len; } +// packetAdditionalLen is a helper function used to figure out +// how bigger the payload needs to be in order to account for +// its variable length field. As per +// http://docs.oasis-open.org/mqtt/mqtt/v3.1.1/os/mqtt-v3.1.1-os.html#_Table_2.4_Size +static uint16_t packetAdditionalLen(uint16_t currLen) { + /* Increase length field based on current length */ + if (currLen < 128) + return 0; + if (currLen < 16384) + return 1; + if (currLen < 2097151) + return 2; + return 3; +} + // as per // http://docs.oasis-open.org/mqtt/mqtt/v3.1.1/os/mqtt-v3.1.1-os.html#_Toc398718040 uint16_t Adafruit_MQTT::publishPacket(uint8_t *packet, const char *topic, - uint8_t *data, uint16_t bLen, - uint8_t qos) { + uint8_t *data, uint16_t bLen, uint8_t qos, + uint16_t maxPacketLen) { uint8_t *p = packet; uint16_t len = 0; @@ -700,7 +716,22 @@ uint16_t Adafruit_MQTT::publishPacket(uint8_t *packet, const char *topic, if (qos > 0) { len += 2; // qos packet id } - len += bLen; // payload length + // Calculate additional bytes for length field (if any) + uint16_t additionalLen = packetAdditionalLen(len + bLen); + + // Payload length. When maxPacketLen provided is 0, let's + // assume buffer is big enough. Fingers crossed. + if (maxPacketLen == 0 || (len + bLen + 2 + additionalLen <= maxPacketLen)) { + len += bLen + additionalLen; + } else { + // If we make it here, we got a pickle: the payload is not going + // to fit in the packet buffer. Instead of corrupting memory, let's + // do something less damaging by reducing the bLen to what we are + // able to accomodate. Alternatively, consider using a bigger + // maxPacketLen. + bLen = maxPacketLen - (len + 2 + packetAdditionalLen(maxPacketLen)); + len = maxPacketLen - 4; + } // Now you can start generating the packet! p[0] = MQTT_CTRL_PUBLISH << 4 | qos << 1; diff --git a/Adafruit_MQTT.h b/Adafruit_MQTT.h index 089d0d4..495e043 100644 --- a/Adafruit_MQTT.h +++ b/Adafruit_MQTT.h @@ -262,7 +262,7 @@ private: uint8_t connectPacket(uint8_t *packet); uint8_t disconnectPacket(uint8_t *packet); uint16_t publishPacket(uint8_t *packet, const char *topic, uint8_t *payload, - uint16_t bLen, uint8_t qos); + uint16_t bLen, uint8_t qos, uint16_t maxPacketLen = 0); uint8_t subscribePacket(uint8_t *packet, const char *topic, uint8_t qos); uint8_t unsubscribePacket(uint8_t *packet, const char *topic); uint8_t pingPacket(uint8_t *packet); diff --git a/library.properties b/library.properties index 3b57b38..230e502 100644 --- a/library.properties +++ b/library.properties @@ -1,5 +1,5 @@ name=Adafruit MQTT Library -version=2.1.1 +version=2.2.0 author=Adafruit maintainer=Adafruit sentence=MQTT library that supports the FONA, ESP8266, Yun, and generic Arduino Client hardware.