Add support for sending empty linkage sets to clear receiver databases

4 files changed, 89 insertions, 62 deletions

diff --git a/doc/servicelinking.mux b/doc/servicelinking.mux
index 5706351..d591f5c 100644
--- a/doc/servicelinking.mux
+++ b/doc/servicelinking.mux
@@ -42,10 +42,14 @@ linking {
         ; set this to true.
         international false
 
-        ; Every linkage set has to contain a service from the current ensemble (mandatory)
+        ; If the keyservice and list are absent, a FIG with an empty list will be transmitted for
+        ; this linkage set. This instructs receivers to delete their corresponding database entry
+        ; (Change Event Indicator for FIG0/6)
+
+        ; Every linkage set has to contain a service from the current ensemble. keyservice may be omitted.
         keyservice srv-fu
 
-        ; List of services to be included (mandatory)
+        ; List of services to be included (mandatory if keyservice given)
         list {
             ; Every service has a uid that can be used as a human-readable description
 
diff --git a/src/ConfigParser.cpp b/src/ConfigParser.cpp
index d484787..f51eb03 100644
--- a/src/ConfigParser.cpp
+++ b/src/ConfigParser.cpp
@@ -102,61 +102,65 @@ static void parse_linkage(ptree& pt,
             bool active = pt_set.get("active", true);
             bool hard = pt_set.get("hard", true);
             bool international = pt_set.get("international", false);
-
             string service_uid = pt_set.get("keyservice", "");
-            if (service_uid.empty()) {
-                etiLog.level(error) << "Key Service for linking set " <<
-                    setuid << " invalid or missing";
-                throw runtime_error("Invalid service linking definition");
-            }
 
             auto linkageset = make_shared<LinkageSet>(setuid, lsn, active, hard, international);
             linkageset->keyservice = service_uid; // TODO check if it exists
 
             auto pt_list = pt_set.get_child_optional("list");
-            if (not pt_list) {
-                etiLog.level(error) << "list missing in linking set " <<
-                    setuid;
-                throw runtime_error("Invalid service linking definition");
-            }
 
-            for (const auto& it : *pt_list) {
-                const string linkuid = it.first;
-                const ptree pt_link = it.second;
-
-                ServiceLink link;
-
-                string link_type = pt_link.get("type", "");
-                if (link_type == "dab") link.type = ServiceLinkType::DAB;
-                else if (link_type == "fm") link.type = ServiceLinkType::FM;
-                else if (link_type == "drm") link.type = ServiceLinkType::DRM;
-                else if (link_type == "amss") link.type = ServiceLinkType::AMSS;
-                else {
-                    etiLog.level(error) << "Invalid type " << link_type <<
-                        " for link " << linkuid;
+            if (service_uid.empty()) {
+                if (pt_list) {
+                    etiLog.level(error) << "list defined but no keyservice in linking set " <<
+                        setuid;
                     throw runtime_error("Invalid service linking definition");
                 }
-
-                link.id = hexparse(pt_link.get("id", "0"));
-                if (link.id == 0) {
-                    etiLog.level(error) << "id for link " <<
-                        linkuid << " invalid or missing";
+            }
+            else {
+                if (not pt_list) {
+                    etiLog.level(error) << "list missing in linking set " <<
+                        setuid;
                     throw runtime_error("Invalid service linking definition");
                 }
 
-                if (international) {
-                    link.ecc = hexparse(pt_link.get("ecc", "0"));
-                    if (link.ecc == 0) {
-                        etiLog.level(error) << "ecc for link " <<
+                for (const auto& it : *pt_list) {
+                    const string linkuid = it.first;
+                    const ptree pt_link = it.second;
+
+                    ServiceLink link;
+
+                    string link_type = pt_link.get("type", "");
+                    if (link_type == "dab") link.type = ServiceLinkType::DAB;
+                    else if (link_type == "fm") link.type = ServiceLinkType::FM;
+                    else if (link_type == "drm") link.type = ServiceLinkType::DRM;
+                    else if (link_type == "amss") link.type = ServiceLinkType::AMSS;
+                    else {
+                        etiLog.level(error) << "Invalid type " << link_type <<
+                            " for link " << linkuid;
+                        throw runtime_error("Invalid service linking definition");
+                    }
+
+                    link.id = hexparse(pt_link.get("id", "0"));
+                    if (link.id == 0) {
+                        etiLog.level(error) << "id for link " <<
                             linkuid << " invalid or missing";
                         throw runtime_error("Invalid service linking definition");
                     }
-                }
-                else {
-                    link.ecc = 0;
-                }
 
-                linkageset->id_list.push_back(link);
+                    if (international) {
+                        link.ecc = hexparse(pt_link.get("ecc", "0"));
+                        if (link.ecc == 0) {
+                            etiLog.level(error) << "ecc for link " <<
+                                linkuid << " invalid or missing";
+                            throw runtime_error("Invalid service linking definition");
+                        }
+                    }
+                    else {
+                        link.ecc = 0;
+                    }
+
+                    linkageset->id_list.push_back(link);
+                }
             }
             ensemble->linkagesets.push_back(linkageset);
         }
diff --git a/src/MuxElements.cpp b/src/MuxElements.cpp
index e19c93d..9c1fc7a 100644
--- a/src/MuxElements.cpp
+++ b/src/MuxElements.cpp
@@ -665,26 +665,35 @@ bool dabEnsemble::validate_linkage_sets()
 {
     for (const auto& ls : linkagesets) {
         const std::string keyserviceuid = ls->keyservice;
-        const auto& keyservice = std::find_if(
-                services.cbegin(),
-                services.cend(),
-                [&](const std::shared_ptr<DabService>& srv) {
+        if (keyserviceuid.empty()) {
+            if (not ls->id_list.empty()) {
+                etiLog.log(error, "Linkage set 0x%04x with empty key service "
+                        "should have an empty list.", ls->lsn);
+                return false;
+            }
+        }
+        else {
+            const auto& keyservice = std::find_if(
+                    services.cbegin(),
+                    services.cend(),
+                    [&](const std::shared_ptr<DabService>& srv) {
                     return srv->uid == keyserviceuid;
-                });
+                    });
 
-        if (keyservice == services.end()) {
-            etiLog.log(error, "Invalid key service %s in linkage set 0x%04x",
-                    keyserviceuid.c_str(), ls->lsn);
-            return false;
-        }
+            if (keyservice == services.end()) {
+                etiLog.log(error, "Invalid key service %s in linkage set 0x%04x",
+                        keyserviceuid.c_str(), ls->lsn);
+                return false;
+            }
 
-        // need to add key service to num_ids
-        const size_t num_ids = 1 + ls->id_list.size();
-        if (num_ids > 0x0F) {
-            etiLog.log(error,
-                    "Too many links for linkage set 0x%04x",
-                    ls->lsn);
-            return false;
+            // need to add key service to num_ids
+            const size_t num_ids = 1 + ls->id_list.size();
+            if (num_ids > 0x0F) {
+                etiLog.log(error,
+                        "Too many links for linkage set 0x%04x",
+                        ls->lsn);
+                return false;
+            }
         }
     }
 
diff --git a/src/fig/FIG0_6.cpp b/src/fig/FIG0_6.cpp
index b7776f4..8af8ded 100644
--- a/src/fig/FIG0_6.cpp
+++ b/src/fig/FIG0_6.cpp
@@ -80,8 +80,11 @@ FillStatus FIG0_6::fill(uint8_t *buf, size_t max_size)
         const bool PD = false;
         const bool ILS = linkageSetFIG0_6->international;
 
-        // need to add key service to num_ids
-        const size_t num_ids = 1 + linkageSetFIG0_6->id_list.size();
+        // need to add key service to num_ids, unless it is empty which means we
+        // send a CEI
+        const size_t num_ids = linkageSetFIG0_6->keyservice.empty() ?
+            // do not transmit list if keyservice empty, it should anyway be empty
+            0 : (1 + linkageSetFIG0_6->id_list.size());
 
         if (num_ids > 0x0F) {
             etiLog.log(error,
@@ -117,7 +120,7 @@ FillStatus FIG0_6::fill(uint8_t *buf, size_t max_size)
 
         FIGtype0_6 *fig0_6 = (FIGtype0_6*)buf;
 
-        fig0_6->IdListFlag = (num_ids > 0);
+        fig0_6->IdListFlag = (num_ids > 0); // C/N=0 and IdListFlag=0 is CEI
         fig0_6->LA = linkageSetFIG0_6->active;
         fig0_6->SH = linkageSetFIG0_6->hard;
         fig0_6->ILS = ILS;
@@ -127,6 +130,10 @@ FillStatus FIG0_6::fill(uint8_t *buf, size_t max_size)
         buf += sizeof(struct FIGtype0_6);
         remaining -= sizeof(struct FIGtype0_6);
 
+        etiLog.log(debug,
+                "Linkage set 0x%04x wrote %d",
+                linkageSetFIG0_6->lsn, fig0->Length);
+
         if (num_ids > 0) {
             FIGtype0_6_header *header = (FIGtype0_6_header*)buf;
             header->rfu = 0;
@@ -243,7 +250,10 @@ void FIG0_6::update()
     for (const auto& linkageset : m_rti->ensemble->linkagesets) {
         const auto lsn = linkageset->lsn;
 
-        for (const auto& link : linkageset->id_list) {
+        if (linkageset->keyservice.empty()) {
+            linkageSubsets.push_back(*linkageset);
+        }
+        else for (const auto& link : linkageset->id_list) {
             const auto type = link.type;
 
             const auto subset =