NFC: Add payload builder into ndef::MessageBuilder

features/nfc/nfc/ndef/MessageBuilder.h

@@ -38,6 +38,31 @@ namespace ndef {
 class MessageBuilder {
 
 public:
+    /**
+     * Build a record payload.
+     */
+    struct PayloadBuilder {
+        /**
+         * Return the size of the payload built by this object.
+         *
+         * @return The size of the payload.
+         */
+        virtual size_t size() const = 0;
+
+        /**
+         * Build the payload in a buffer that has the required size.
+         *
+         * @param buffer The buffer used to construct the payload.
+         */
+        virtual void build(const Span<uint8_t>& buffer) const = 0;
+
+    protected:
+        /**
+         * Non virtual destructor.
+         */
+        ~PayloadBuilder() { }
+    };
+
     /**
      * Create a new MessageBuilder that can be used to construct valid NDEF
      * messages.
@@ -67,6 +92,27 @@ public:
         bool is_last_record = false
     );
 
+    /**
+     * Append a new record to the message being built.
+     *
+     * @param type The type of the record to insert.
+     * @param builder The builder of the payload.
+     * @param is_last_record true if the record to insert is the last record of
+     * the payload or false otherwise.
+     *
+     * @return true if the record has been successfully inserted or false
+     * otherwise.
+     *
+     * @note insertion can fail if the message is already complete or if the
+     * size remaining in the message buffer is not large enough to makes the
+     * record inserted fit.
+     */
+    bool append_record(
+        const RecordType &type,
+        const PayloadBuilder &builder,
+        bool is_last_record = false
+    );
+
     /**
      * Append a new record to the message being built.
      *
@@ -78,7 +124,23 @@ public:
      * size remaining in the message buffer is not large enough to makes the
      * record inserted fit.
      */
-    bool append_record(const Record &record);
+    bool append_record(
+        const Record &record,
+        const PayloadBuilder *builder = NULL
+    );
+
+    /**
+     * Compute the size of a record.
+     *
+     * @param record The record used to compute the size.
+     * @param builder The payload builder if any.
+     *
+     * @return The size of the payload for the record in input.
+     */
+    static size_t compute_record_size(
+        const Record &record,
+        const PayloadBuilder* builder = NULL
+    );
 
     /**
      * Reset the builder state.
@@ -107,17 +169,17 @@ public:
 
 private:
     // append fields
-    void append_header(const Record &record);
+    void append_header(const Record &record, const PayloadBuilder*);
     void append_type_length(const Record &record);
-    void append_payload_length(const Record &);
+    void append_payload_length(const Record &, const PayloadBuilder*);
     void append_id_length(const Record &);
     void append_type(const Record &);
     void append_id(const Record &);
-    void append_payload(const Record &);
+    void append_payload(const Record &, const PayloadBuilder*);
 
     // helpers
-    static size_t compute_record_size(const Record &record);
+    static bool is_short_payload(const Record &record, const PayloadBuilder*);
-    static bool is_short_payload(const Record &record);
+    static size_t get_payload_size(const Record &, const PayloadBuilder*);
 
     // builder state.
     Span<uint8_t> _message_buffer;

features/nfc/source/nfc/ndef/MessageBuilder.cpp

@@ -47,7 +47,24 @@ bool MessageBuilder::append_record(
     return append_record(record);
 }
 
-bool MessageBuilder::append_record(const Record &record)
+bool MessageBuilder::append_record(
+    const RecordType &type,
+    const PayloadBuilder &builder,
+    bool is_last_record
+) {
+    Record record(
+        type,
+        RecordPayload(),
+        RecordID(),
+        /* chunk */ false,
+        is_last_record
+    );
+
+    return append_record(record, &builder);
+}
+
+
+bool MessageBuilder::append_record(const Record &record, const PayloadBuilder *builder)
 {
     if (_message_ended) {
         return false;
@@ -88,7 +105,7 @@ bool MessageBuilder::append_record(const Record &record)
             return false;
         }
 
-        if (!record.payload.empty()) {
+        if (get_payload_size(record, builder)) {
             return false;
         }
     }
@@ -107,18 +124,18 @@ bool MessageBuilder::append_record(const Record &record)
         return false;
     }
 
-    size_t record_size = compute_record_size(record);
+    size_t record_size = compute_record_size(record, builder);
     if (record_size > (_message_buffer.size() - _position)) {
         return false;
     }
 
-    append_header(record);
+    append_header(record, builder);
     append_type_length(record);
-    append_payload_length(record);
+    append_payload_length(record, builder);
     append_id_length(record);
     append_type(record);
     append_id(record);
-    append_payload(record);
+    append_payload(record, builder);
 
     if (record.chunk) {
         _in_chunk = true;
@@ -161,12 +178,12 @@ Span<const uint8_t> MessageBuilder::get_message() const
     }
 }
 
-size_t MessageBuilder::compute_record_size(const Record &record)
+size_t MessageBuilder::compute_record_size(const Record &record, const PayloadBuilder *builder)
 {
     size_t record_size = 0;
     record_size = 1; /* header */
     record_size += 1; /* type length */
-    record_size += is_short_payload(record) ? 1 : 4;
+    record_size += is_short_payload(record, builder) ? 1 : 4;
 
     if (!record.id.empty()) {
         record_size += 1;
@@ -174,12 +191,12 @@ size_t MessageBuilder::compute_record_size(const Record &record)
 
     record_size += record.type.value.size();
     record_size += record.id.size();
-    record_size += record.payload.size();
+    record_size += get_payload_size(record, builder);
 
     return record_size;
 }
 
-void MessageBuilder::append_header(const Record &record)
+void MessageBuilder::append_header(const Record &record, const PayloadBuilder *builder)
 {
     uint8_t header = 0;
     if (!_message_started) {
@@ -196,7 +213,7 @@ void MessageBuilder::append_header(const Record &record)
         header |= Header::chunk_flag_bit;
     }
 
-    if (is_short_payload(record)) {
+    if (is_short_payload(record, builder)) {
         header |= Header::short_record_bit;
     }
 
@@ -213,18 +230,13 @@ void MessageBuilder::append_type_length(const Record &record)
     _message_buffer[_position++] = record.type.value.size();
 }
 
-void MessageBuilder::append_payload_length(const Record &record)
+void MessageBuilder::append_payload_length(const Record &record, const PayloadBuilder *builder)
 {
-    if (record.payload.empty()) {
+    size_t size = get_payload_size(record, builder);
-        _message_buffer[_position++] = 0;
-        return;
-    }
 
-    if (is_short_payload(record)) {
+    if (is_short_payload(record, builder)) {
-        _message_buffer[_position++] = record.payload.size();
+        _message_buffer[_position++] = size;
     } else {
-        // TODO: proper host to network
-        uint32_t size = record.payload.size();
         _message_buffer[_position++] = (size >> 24) & 0xFF;
         _message_buffer[_position++] = (size >> 16) & 0xFF;
         _message_buffer[_position++] = (size >> 8) & 0xFF;
@@ -269,29 +281,40 @@ void MessageBuilder::append_id(const Record &record)
     _position += record.id.size();
 }
 
-void MessageBuilder::append_payload(const Record &record)
+void MessageBuilder::append_payload(const Record &record, const PayloadBuilder *builder)
 {
-    if (record.payload.empty()) {
+    size_t size = get_payload_size(record, builder);
+    if (!size) {
         return;
     }
 
+    if (builder) {
+        builder->build(_message_buffer.subspan(_position, size));
+    } else {
         memcpy(
             _message_buffer.data() + _position,
             record.payload.data(),
-        record.payload.size()
+            size
         );
-    _position += record.payload.size();
     }
 
-bool MessageBuilder::is_short_payload(const Record &record)
+    _position += size;
+}
+
+bool MessageBuilder::is_short_payload(const Record &record, const PayloadBuilder *builder)
 {
-    if (record.payload.size() <= 255) {
+    if (get_payload_size(record, builder) <= 255) {
         return true;
     } else {
         return false;
     }
 }
 
+size_t MessageBuilder::get_payload_size(const Record &record, const PayloadBuilder *builder)
+{
+    return builder ? builder->size() : record.payload.size();
+}
+
 } // namespace ndef
 } // namespace nfc
 } // namespace mbed