Feature: Implement fstring topics

src/PubSubClient.cpp

@@ -525,6 +525,10 @@ bool PubSubClient::publish(const char* topic, const char* payload, bool retained
     return publish(topic, payload, MQTT_QOS0, retained);
 }
 
+bool PubSubClient::publish(const __FlashStringHelper* topic, const char* payload, uint8_t qos, bool retained) {
+    return publish(topic, (const uint8_t*)payload, payload ? strnlen(payload, MQTT_MAX_POSSIBLE_PACKET_SIZE) : 0, qos, retained);
+}
+
 bool PubSubClient::publish(const char* topic, const char* payload, uint8_t qos, bool retained) {
     return publish(topic, (const uint8_t*)payload, payload ? strnlen(payload, MQTT_MAX_POSSIBLE_PACKET_SIZE) : 0, qos, retained);
 }
@@ -545,11 +549,23 @@ bool PubSubClient::publish(const char* topic, const uint8_t* payload, size_t ple
     return false;
 }
 
-bool PubSubClient::publish_P(const char* topic, const char* payload, bool retained) {
+bool PubSubClient::publish(const __FlashStringHelper* topic, const uint8_t* payload, size_t plength, uint8_t qos, bool retained) {
+    if (beginPublish(topic, plength, qos, retained)) {
+        size_t rc = write(payload, plength);
+        return endPublish() && (rc == plength);
+    }
+    return false;
+}
+
+bool PubSubClient::publish_P(const char* topic, PGM_P payload, bool retained) {
     return publish_P(topic, payload, MQTT_QOS0, retained);
 }
 
-bool PubSubClient::publish_P(const char* topic, const char* payload, uint8_t qos, bool retained) {
+bool PubSubClient::publish_P(const __FlashStringHelper* topic, PGM_P payload, uint8_t qos, bool retained) {
+    return publish_P(topic, (const uint8_t*)payload, payload ? strnlen_P(payload, MQTT_MAX_POSSIBLE_PACKET_SIZE) : 0, qos, retained);
+}
+
+bool PubSubClient::publish_P(const char* topic, PGM_P payload, uint8_t qos, bool retained) {
     return publish_P(topic, (const uint8_t*)payload, payload ? strnlen_P(payload, MQTT_MAX_POSSIBLE_PACKET_SIZE) : 0, qos, retained);
 }
 
@@ -565,27 +581,50 @@ bool PubSubClient::publish_P(const char* topic, const uint8_t* payload, size_t p
     return false;
 }
 
+bool PubSubClient::publish_P(const __FlashStringHelper* topic, const uint8_t* payload, size_t plength, uint8_t qos, bool retained) {
+    if (beginPublish(topic, plength, qos, retained)) {
+        size_t rc = write_P(payload, plength);
+        return endPublish() && (rc == plength);
+    }
+    return false;
+}
+
 bool PubSubClient::beginPublish(const char* topic, size_t plength, bool retained) {
     return beginPublish(topic, plength, MQTT_QOS0, retained);
 }
 
-bool PubSubClient::beginPublish(const char* topic, size_t plength, uint8_t qos, bool retained) {
+template <bool PROGMEM_TOPIC, typename TopicT>
+bool PubSubClient::beginPublishImpl(TopicT topic, size_t plength, uint8_t qos, bool retained) {
     if (!topic) return false;
-    if (strlen(topic) == 0) return false;  // empty topic is not allowed
-    if (qos > MQTT_QOS2) {                 // only valid QoS supported
+
+    // get topic length depending on storage (RAM vs PROGMEM)
+    size_t topicLen;
+    if (PROGMEM_TOPIC) {
+        topicLen = strlen_P(topic);
+    } else {
+        topicLen = strlen(topic);
+    }
+    if (topicLen == 0) return false;  // empty topic is not allowed
+
+    if (qos > MQTT_QOS2) {  // only valid QoS supported
         ERROR_PSC_PRINTF_P("beginPublish() called with invalid QoS %u\n", qos);
         return false;
     }
+
     const size_t nextMsgLen = (qos > MQTT_QOS0) ? 2 : 0;  // add 2 bytes for nextMsgId if QoS > 0
     // check if the header, the topic (including 2 length bytes) and nextMsgId fit into the _buffer
-    if (connected() && (MQTT_MAX_HEADER_SIZE + strlen(topic) + 2 + nextMsgLen <= _bufferSize)) {
+    if (connected() && (MQTT_MAX_HEADER_SIZE + topicLen + 2 + nextMsgLen <= _bufferSize)) {
         // first write the topic at the end of the maximal variable header (MQTT_MAX_HEADER_SIZE) to the _buffer
-        size_t topicLen = writeString(topic, MQTT_MAX_HEADER_SIZE) - MQTT_MAX_HEADER_SIZE;
+        if (PROGMEM_TOPIC) {
+            topicLen = writeString_P(topic, MQTT_MAX_HEADER_SIZE) - MQTT_MAX_HEADER_SIZE;
+        } else {
+            topicLen = writeString(topic, MQTT_MAX_HEADER_SIZE) - MQTT_MAX_HEADER_SIZE;
+        }
         if (qos > MQTT_QOS0) {
             // if QoS 1 or 2, we need to send the nextMsgId (packet identifier) after topic
             writeNextMsgId(MQTT_MAX_HEADER_SIZE + topicLen);
         }
-        // we now know the length of the topic string (lenght + 2 bytes signalling the length) and can build the variable header information
+        // we now know the length of the topic string (length + 2 bytes signalling the length) and can build the variable header information
         const uint8_t header = MQTTPUBLISH | MQTT_QOS_GET_HDR(qos) | (retained ? MQTTRETAINED : 0);
         uint8_t hdrLen = buildHeader(header, topicLen + nextMsgLen + plength);
         if (hdrLen == 0) return false;  // exit here in case of header generation failure
@@ -597,6 +636,19 @@ bool PubSubClient::beginPublish(const char* topic, size_t plength, uint8_t qos,
     return false;
 }
 
+bool PubSubClient::beginPublish(const char* topic, size_t plength, uint8_t qos, bool retained) {
+    return beginPublishImpl<false, const char*>(topic, plength, qos, retained);
+}
+
+bool PubSubClient::beginPublish(const __FlashStringHelper* topic, size_t plength, uint8_t qos, bool retained) {
+    // convert FlashStringHelper in PROGMEM-pointer
+    return beginPublishImpl<true, PGM_P>(reinterpret_cast<const char*>(topic), plength, qos, retained);
+}
+
+bool PubSubClient::beginPublish_P(PGM_P topic, size_t plength, uint8_t qos, bool retained) {
+    return beginPublishImpl<true, PGM_P>(topic, plength, qos, retained);
+}
+
 bool PubSubClient::endPublish() {
     if (connected()) {
         if (_bufferWritePos > 0) {
@@ -632,7 +684,7 @@ uint8_t PubSubClient::buildHeader(uint8_t header, size_t length) {
     } while ((len > 0) && (hdrLen < MQTT_MAX_HEADER_SIZE - 1));
 
     if (len > 0) {
-        ERROR_PSC_PRINTF_P("buildHeader() length too big %zu, left %zu\n", length, len);
+        ERROR_PSC_PRINTF_P("buildHeader: header=0x%02X, length too big %zu, left %zu\n", header, length, len);
         return 0;
     }
 
@@ -665,7 +717,7 @@ size_t PubSubClient::write_P(const uint8_t* buf, size_t size) {
  *
  * @param  header Header byte, e.g. MQTTCONNECT, MQTTPUBLISH, MQTTSUBSCRIBE, MQTTUNSUBSCRIBE.
  * @param  length Length of _buffer to write.
- * @return True if successfully sent, otherwise false if buildHeader() failed or buffer could not be written.
+ * @return True if successfully sent, otherwise false if build header failed or buffer could not be written.
  */
 bool PubSubClient::writeControlPacket(uint8_t header, size_t length) {
     uint8_t hdrLen = buildHeader(header, length);
@@ -712,6 +764,31 @@ size_t PubSubClient::writeBuffer(size_t pos, size_t size) {
     return rc;
 }
 
+template <bool PROGMEM_STRING, typename StringT>
+size_t PubSubClient::writeStringImpl(StringT string, size_t pos) {
+    if (!string) return pos;
+
+    size_t sLen;
+    if (PROGMEM_STRING) {
+        sLen = strlen_P(string);
+    } else {
+        sLen = strlen(string);
+    }
+    if ((pos + 2 + sLen <= _bufferSize) && (sLen <= 0xFFFF)) {
+        _buffer[pos++] = (uint8_t)(sLen >> 8);
+        _buffer[pos++] = (uint8_t)(sLen & 0xFF);
+        if (PROGMEM_STRING) {
+            memcpy_P(_buffer + pos, string, sLen);
+        } else {
+            memcpy(_buffer + pos, string, sLen);
+        }
+        pos += sLen;
+    } else {
+        ERROR_PSC_PRINTF_P("writeStringImpl(): string (%zu) does not fit into buf (%zu)\n", pos + 2 + sLen, _bufferSize);
+    }
+    return pos;
+}
+
 /**
  * @brief  Write an UTF-8 encoded string to the internal buffer at a given position. The string can have a length of 0 to 65535 bytes (depending on size of
  * internal buffer). The buffer is prefixed with two bytes representing the length of the string. See section 1.5.3 of MQTT v3.1.1 protocol specification.
@@ -723,18 +800,22 @@ size_t PubSubClient::writeBuffer(size_t pos, size_t size) {
  * @return New position in the internal buffer (pos + 2 + string length), or pos if a buffer overrun would occur or the string is a nullptr.
  */
 size_t PubSubClient::writeString(const char* string, size_t pos) {
-    if (!string) return pos;
+    return writeStringImpl<false, const char*>(string, pos);
+}
 
-    size_t sLen = strlen(string);
-    if ((pos + 2 + sLen <= _bufferSize) && (sLen <= 0xFFFF)) {
-        _buffer[pos++] = (uint8_t)(sLen >> 8);
-        _buffer[pos++] = (uint8_t)(sLen & 0xFF);
-        memcpy(_buffer + pos, string, sLen);
-        pos += sLen;
-    } else {
-        ERROR_PSC_PRINTF_P("writeString(): string (%zu) does not fit into buf (%zu)\n", pos + 2 + sLen, _bufferSize);
-    }
-    return pos;
+/**
+ * @brief  Write an UTF-8 encoded PROGMEM string to the internal buffer at a given position. The string can have a length of 0 to 65535 bytes (depending on
+ * size of internal buffer). The buffer is prefixed with two bytes representing the length of the string. See section 1.5.3 of MQTT v3.1.1 protocol
+ * specification.
+ * @note   If the string does not fit in the buffer or is longer than 65535 bytes nothing is written to the buffer and the returned position is
+ * unchanged.
+ *
+ * @param  string PROGMEM 'C' string of the data that shall be written in the buffer.
+ * @param  pos Position in the internal buffer to write the string.
+ * @return New position in the internal buffer (pos + 2 + string length), or pos if a buffer overrun would occur or the string is a nullptr.
+ */
+size_t PubSubClient::writeString_P(PGM_P string, size_t pos) {
+    return writeStringImpl<true, PGM_P>(string, pos);
 }
 
 /**

src/PubSubClient.h

@@ -199,9 +199,15 @@ class PubSubClient : public Print {
     uint8_t buildHeader(uint8_t header, size_t length);
     bool writeControlPacket(uint8_t header, size_t length);
     size_t writeBuffer(size_t pos, size_t size);
+    template <bool PROGMEM_STRING, typename StringT>
+    size_t writeStringImpl(StringT string, size_t pos);
     size_t writeString(const char* string, size_t pos);
+    size_t writeString_P(PGM_P string, size_t pos);
     size_t writeNextMsgId(size_t pos);
 
+    template <bool PROGMEM_TOPIC, typename TopicT>
+    bool beginPublishImpl(TopicT topic, size_t plength, uint8_t qos, bool retained);
+
     // Add to buffer and flush if full (only to be used with beginPublish/endPublish)
     size_t appendBuffer(uint8_t data);
     size_t flushBuffer();
@@ -524,6 +530,17 @@ class PubSubClient : public Print {
      */
     bool publish(const char* topic, const char* payload, uint8_t qos, bool retained);
 
+    /**
+     * @brief Publishes a message to the specified topic.
+     * @param topic The topic from __FlashStringHelper to publish to.
+     * @param payload The message to publish.
+     * @param qos The quality of service (\ref group_qos) to publish at. [0, 1, 2].
+     * @param retained Publish the message with the retain flag.
+     * @return true If the publish succeeded.
+     * false If the publish failed, either connection lost or message too large.
+     */
+    bool publish(const __FlashStringHelper* topic, const char* payload, uint8_t qos, bool retained);
+
     /**
      * @brief Publishes a non retained message to the specified topic using QoS 0.
      * @param topic The topic to publish to.
@@ -557,6 +574,18 @@ class PubSubClient : public Print {
      */
     bool publish(const char* topic, const uint8_t* payload, size_t plength, uint8_t qos, bool retained);
 
+    /**
+     * @brief Publishes a message to the specified topic.
+     * @param topic The topic from __FlashStringHelper to publish to.
+     * @param payload The message to publish.
+     * @param plength The length of the payload.
+     * @param qos The quality of service (\ref group_qos) to publish at. [0, 1, 2].
+     * @param retained Publish the message with the retain flag.
+     * @return true If the publish succeeded.
+     * false If the publish failed, either connection lost or message too large.
+     */
+    bool publish(const __FlashStringHelper* topic, const uint8_t* payload, size_t plength, uint8_t qos, bool retained);
+
     /**
      * @brief Publishes a message stored in PROGMEM to the specified topic using QoS 0.
      * @param topic The topic to publish to.
@@ -565,7 +594,7 @@ class PubSubClient : public Print {
      * @return true If the publish succeeded.
      * false If the publish failed, either connection lost or message too large.
      */
-    bool publish_P(const char* topic, const char* payload, bool retained);
+    bool publish_P(const char* topic, PGM_P payload, bool retained);
 
     /**
      * @brief Publishes a message stored in PROGMEM to the specified topic.
@@ -576,7 +605,18 @@ class PubSubClient : public Print {
      * @return true If the publish succeeded.
      * false If the publish failed, either connection lost or message too large.
      */
-    bool publish_P(const char* topic, const char* payload, uint8_t qos, bool retained);
+    bool publish_P(const char* topic, PGM_P payload, uint8_t qos, bool retained);
+
+    /**
+     * @brief Publishes a message stored in PROGMEM to the specified topic.
+     * @param topic The topic from __FlashStringHelper to publish to.
+     * @param payload The message to publish.
+     * @param qos The quality of service (\ref group_qos) to publish at. [0, 1, 2].
+     * @param retained Publish the message with the retain flag.
+     * @return true If the publish succeeded.
+     * false If the publish failed, either connection lost or message too large.
+     */
+    bool publish_P(const __FlashStringHelper* topic, PGM_P payload, uint8_t qos, bool retained);
 
     /**
      * @brief Publishes a message stored in PROGMEM to the specified topic using QoS 0.
@@ -601,6 +641,18 @@ class PubSubClient : public Print {
      */
     bool publish_P(const char* topic, const uint8_t* payload, size_t plength, uint8_t qos, bool retained);
 
+    /**
+     * @brief Publishes a message stored in PROGMEM to the specified topic.
+     * @param topic The topic from __FlashStringHelper to publish to.
+     * @param payload The message from PROGMEM to publish.
+     * @param plength The length of the payload.
+     * @param qos The quality of service (\ref group_qos) to publish at. [0, 1, 2].
+     * @param retained Publish the message with the retain flag.
+     * @return true If the publish succeeded.
+     * false If the publish failed, either connection lost or message too large.
+     */
+    bool publish_P(const __FlashStringHelper* topic, const uint8_t* payload, size_t plength, uint8_t qos, bool retained);
+
     /**
      * @brief Start to publish a message using QoS 0.
      * This API:
@@ -634,6 +686,40 @@ class PubSubClient : public Print {
      */
     bool beginPublish(const char* topic, size_t plength, uint8_t qos, bool retained);
 
+    /**
+     * @brief Start to publish a message using a topic from __FlashStringHelper F().
+     * This API:
+     *   beginPublish(...)
+     *   one or more calls to write(...)
+     *   endPublish()
+     * Allows for arbitrarily large payloads to be sent without them having to be copied into
+     * a new buffer and held in memory at one time.
+     * @param topic The topic from __FlashStringHelper to publish to.
+     * @param plength The length of the payload.
+     * @param qos The quality of service (\ref group_qos) to publish at. [0, 1, 2].
+     * @param retained Publish the message with the retain flag.
+     * @return true If the publish succeeded.
+     * false If the publish failed, either connection lost or message too large.
+     */
+    bool beginPublish(const __FlashStringHelper* topic, size_t plength, uint8_t qos, bool retained);
+
+    /**
+     * @brief Start to publish a message using a topic in PROGMEM.
+     * This API:
+     *   beginPublish_P(...)
+     *   one or more calls to write(...)
+     *   endPublish()
+     * Allows for arbitrarily large payloads to be sent without them having to be copied into
+     * a new buffer and held in memory at one time.
+     * @param topic The topic in PROGMEM to publish to.
+     * @param plength The length of the payload.
+     * @param qos The quality of service (\ref group_qos) to publish at. [0, 1, 2].
+     * @param retained Publish the message with the retain flag.
+     * @return true If the publish succeeded.
+     * false If the publish failed, either connection lost or message too large.
+     */
+    bool beginPublish_P(PGM_P topic, size_t plength, uint8_t qos, bool retained);
+
     /**
      * @brief Finish sending a message that was started with a call to beginPublish.
      * @return true If the publish succeeded.

tests/src/lib/Arduino.h

@@ -20,9 +20,14 @@ extern void loop(void);
 unsigned long millis(void);
 }
 
+class __FlashStringHelper;
 #define PROGMEM
+#define PGM_P  const char*
+#define memcpy_P memcpy
+#define strlen_P strlen
 #define strnlen_P strnlen
 #define pgm_read_byte_near(x) *(x)
+#define F(x) (reinterpret_cast<const __FlashStringHelper*>(x))
 
 #define yield(x) {}