rtk: encode RTCM data in base64

This makes it possible to use this in language wrappers such as Python.

src/mavsdk/plugins/rtk/include/plugins/rtk/rtk.h

@@ -62,7 +62,7 @@ class Rtk : public PluginBase {
      * @brief RTCM data type
      */
     struct RtcmData {
-        std::string data{}; /**< @brief The data encoded as a string */
+        std::string data_base64{}; /**< @brief The data encoded as a base64 string */
     };
 
     /**

src/mavsdk/plugins/rtk/rtk.cpp

@@ -24,14 +24,14 @@ Rtk::Result Rtk::send_rtcm_data(RtcmData rtcm_data) const
 
 bool operator==(const Rtk::RtcmData& lhs, const Rtk::RtcmData& rhs)
 {
-    return (rhs.data == lhs.data);
+    return (rhs.data_base64 == lhs.data_base64);
 }
 
 std::ostream& operator<<(std::ostream& str, Rtk::RtcmData const& rtcm_data)
 {
     str << std::setprecision(15);
     str << "rtcm_data:" << '\n' << "{\n";
-    str << "    data: " << rtcm_data.data << '\n';
+    str << "    data_base64: " << rtcm_data.data_base64 << '\n';
     str << '}';
     return str;
 }

src/mavsdk/plugins/rtk/rtk_impl.cpp

@@ -1,5 +1,5 @@
 #include "rtk_impl.h"
-#include "unused.h"
+#include "base64.h"
 
 namespace mavsdk {
 
@@ -30,8 +30,10 @@ Rtk::Result RtkImpl::send_rtcm_data(Rtk::RtcmData rtcm_data)
 {
     constexpr size_t field_len = MAVLINK_MSG_GPS_RTCM_DATA_FIELD_DATA_LEN;
 
+    std::vector<uint8_t> decoded = base64_decode(rtcm_data.data_base64);
+
     const size_t num_packets_required =
-        rtcm_data.data.size() / field_len + (rtcm_data.data.size() % field_len == 0 ? 0 : 1);
+        decoded.size() / field_len + (decoded.size() % field_len == 0 ? 0 : 1);
 
     // The maximum is 4 times the 180 bytes because we only have two bits to
     // denote the fragment ID.
@@ -40,11 +42,11 @@ Rtk::Result RtkImpl::send_rtcm_data(Rtk::RtcmData rtcm_data)
     }
 
     // Copy length before we change it.
-    size_t bytes_to_send = rtcm_data.data.size();
+    size_t bytes_to_send = decoded.size();
 
     // The mavlink helpers memcpy, so we need to make sure we're not
     // copying from where we shouldn't.
-    rtcm_data.data.resize(num_packets_required * field_len);
+    decoded.resize(num_packets_required * field_len);
 
     for (size_t i = 0; i < num_packets_required; ++i) {
         const uint8_t flags =
@@ -59,7 +61,7 @@ Rtk::Result RtkImpl::send_rtcm_data(Rtk::RtcmData rtcm_data)
                     &message,
                     flags,
                     static_cast<uint8_t>(std::min(field_len, bytes_to_send)),
-                    reinterpret_cast<const uint8_t*>(rtcm_data.data.c_str() + (i * field_len)));
+                    (decoded.data() + (i * field_len)));
                 return message;
             })) {
             ++_sequence;