Implement GXS group base64 public data export

Link to GXS group is a concept that is useful for almost all GXS based
  services, gen exchange now provides method to facilitate the
  implementation of group links at service layer.
Move waitToken in token service interface.

libretroshare/src/gxs/rsgenexchange.cc

@@ -21,6 +21,7 @@
  *                                                                             *
  *******************************************************************************/
 #include <unistd.h>
+#include <algorithm>
 
 #include "pqi/pqihash.h"
 #include "rsgenexchange.h"
@@ -38,8 +39,7 @@
 #include "rsgxsutil.h"
 #include "rsserver/p3face.h"
 #include "retroshare/rsevents.h"
-
-#include <algorithm>
+#include "util/radix64.h"
 
 #define PUB_GRP_MASK     0x000f
 #define RESTR_GRP_MASK   0x00f0
@@ -3445,6 +3445,71 @@ bool RsGenExchange::localSearch( const std::string& matchString,
 	return mNetService->search(matchString, results);
 }
 
+bool RsGenExchange::exportGroupBase64(
+        std::string& radix, const RsGxsGroupId& groupId, std::string& errMsg )
+{
+	constexpr auto fname = __PRETTY_FUNCTION__;
+	const auto failure = [&](const std::string& err)
+	{
+		errMsg = err;
+		RsErr() << fname << " " << err << std::endl;
+		return false;
+	};
+
+	if(groupId.isNull()) return failure("groupId cannot be null");
+
+	const std::list<RsGxsGroupId> groupIds({groupId});
+	RsTokReqOptions opts;
+	opts.mReqType = GXS_REQUEST_TYPE_GROUP_DATA;
+	uint32_t token;
+	mDataAccess->requestGroupInfo(
+	            token, RS_TOKREQ_ANSTYPE_DATA, opts, groupIds);
+	RsTokenService::GxsRequestStatus wtStatus = mDataAccess->waitToken(token);
+	if(wtStatus != RsTokenService::COMPLETE)
+		return failure( "waitToken(...) failed with: " +
+		                std::to_string(wtStatus) );
+
+	uint8_t* buf = nullptr;
+	uint32_t size;
+	RsGxsGroupId grpId;
+	if(!getSerializedGroupData(token, grpId, buf, size))
+		return failure("failed retrieving GXS data");
+
+	Radix64::encode(buf, static_cast<int>(size), radix);
+	free(buf);
+
+	return true;
+}
+
+bool RsGenExchange::importGroupBase64(
+        const std::string& radix, RsGxsGroupId& groupId,
+        std::string& errMsg )
+{
+	constexpr auto fname = __PRETTY_FUNCTION__;
+	const auto failure = [&](const std::string& err)
+	{
+		errMsg = err;
+		RsErr() << fname << " " << err << std::endl;
+		return false;
+	};
+
+	if(radix.empty()) return failure("radix is empty");
+
+	std::vector<uint8_t> mem = Radix64::decode(radix);
+	if(mem.empty()) return failure("radix seems corrupted");
+
+	// On success this also import the group as pending validation
+	if(!deserializeGroupData(
+	            mem.data(), static_cast<uint32_t>(mem.size()),
+	            reinterpret_cast<RsGxsGroupId*>(&groupId) ))
+		return failure("failed deserializing group");
+
+	return true;
+}
+
 RsGxsChanges::RsGxsChanges() :
     RsEvent(RsEventType::GXS_CHANGES), mServiceType(RsServiceType::NONE),
     mService(nullptr) {}
+
+RsGxsIface::~RsGxsIface() = default;
+RsGxsGroupSummary::~RsGxsGroupSummary() = default;

libretroshare/src/gxs/rsgenexchange.h

@@ -95,7 +95,8 @@ typedef std::map<RsGxsGrpMsgIdPair, std::vector<RsGxsMsgItem*> > GxsMsgRelatedDa
 
 class RsGixs;
 
-class RsGenExchange : public RsNxsObserver, public RsTickingThread, public RsGxsIface
+class RsGenExchange : public RsNxsObserver, public RsTickingThread,
+        public RsGxsIface
 {
 public:
 
@@ -325,6 +326,19 @@ public:
 	bool localSearch( const std::string& matchString,
 	                  std::list<RsGxsGroupSummary>& results );
 
+	/// @see RsGxsIface
+	bool exportGroupBase64(
+	        std::string& radix, const RsGxsGroupId& groupId,
+	        std::string& errMsg = RS_DEFAULT_STORAGE_PARAM(std::string)
+	        ) override;
+
+	/// @see RsGxsIface
+	bool importGroupBase64(
+	        const std::string& radix,
+	        RsGxsGroupId& groupId = RS_DEFAULT_STORAGE_PARAM(RsGxsGroupId),
+	        std::string& errMsg = RS_DEFAULT_STORAGE_PARAM(std::string)
+	        ) override;
+
 protected:
 
 	bool messagePublicationTest(const RsGxsMsgMetaData&) ;