Added VBITeletextDescriptorTag, TeletextDescriptorTag, LocalTimeOffsetDescriptorTag and PremiereContentTransmissionDescriptor to 'libsi'

7 files changed, 389 insertions, 16 deletions

diff --git a/libsi/descriptor.c b/libsi/descriptor.c
index b84e2c44..dc3b71aa 100644
--- a/libsi/descriptor.c
+++ b/libsi/descriptor.c
@@ -6,7 +6,7 @@
  *   the Free Software Foundation; either version 2 of the License, or     *
  *   (at your option) any later version.                                   *
  *                                                                         *
- *   $Id: descriptor.c 1.18 2006/02/25 10:06:05 kls Exp $
+ *   $Id: descriptor.c 1.19 2006/04/14 10:53:44 kls Exp $
  *                                                                         *
  ***************************************************************************/
 
@@ -318,6 +318,31 @@ void ParentalRatingDescriptor::Rating::Parse() {
    languageCode[3]=0;
 }
 
+void TeletextDescriptor::Parse() {
+   //this descriptor is only a header and a loop
+   teletextLoop.setData(data+sizeof(descr_teletext), getLength()-sizeof(descr_teletext));
+}
+
+void TeletextDescriptor::Teletext::Parse() {
+   s=data.getData<const item_teletext>();
+   languageCode[0]=s->lang_code1;
+   languageCode[1]=s->lang_code2;
+   languageCode[2]=s->lang_code3;
+   languageCode[3]=0;
+}
+
+int TeletextDescriptor::Teletext::getTeletextType() const {
+   return s->type;
+}
+
+int TeletextDescriptor::Teletext::getTeletextMagazineNumber() const {
+   return s->magazine_number;
+}
+
+int TeletextDescriptor::Teletext::getTeletextPageNumber() const {
+   return s->page_number;
+}
+
 int CaDescriptor::getCaType() const {
    return HILO(s->CA_type);
 }
@@ -536,6 +561,14 @@ void ComponentDescriptor::Parse() {
    description.setData(data+offset, getLength()-offset);
 }
 
+void PrivateDataSpecifierDescriptor::Parse() {
+   s=data.getData<const descr_private_data_specifier>();
+}
+
+int PrivateDataSpecifierDescriptor::getPrivateDataSpecifier() const {
+   return (HILO(s->private_data_specifier_hi) << 16) | HILO(s->private_data_specifier_lo);
+}
+
 void SubtitlingDescriptor::Parse() {
    subtitlingLoop.setData(data+sizeof(descr_subtitling), getLength()-sizeof(descr_subtitling));
 }
@@ -633,11 +666,47 @@ void MultilingualServiceNameDescriptor::Name::Parse() {
    name.setData(data+offset, mid->service_name_length);
 }
 
+void LocalTimeOffsetDescriptor::Parse() {
+   localTimeOffsetLoop.setData(data+sizeof(descr_local_time_offset), getLength()-sizeof(descr_local_time_offset));
+}
+
+int LocalTimeOffsetDescriptor::LocalTimeOffset::getCountryId() const {
+   return s->country_region_id;
+}
+
+int LocalTimeOffsetDescriptor::LocalTimeOffset::getLocalTimeOffsetPolarity() const {
+   return s->local_time_offset_polarity;
+}
+
+int LocalTimeOffsetDescriptor::LocalTimeOffset::getLocalTimeOffset() const {
+   return (s->local_time_offset_h << 8) | s->local_time_offset_m;
+}
+
+time_t LocalTimeOffsetDescriptor::LocalTimeOffset::getTimeOfChange() const {
+   return DVBTime::getTime(s->time_of_change_mjd_hi, s->time_of_change_mjd_lo, s->time_of_change_time_h, s->time_of_change_time_m, s->time_of_change_time_s);
+}
+
+int LocalTimeOffsetDescriptor::LocalTimeOffset::getNextTimeOffset() const {
+   return (s->next_time_offset_h << 8) | s->next_time_offset_m;
+}
+
+void LocalTimeOffsetDescriptor::LocalTimeOffset::Parse() {
+   s=data.getData<const local_time_offset_entry>();
+   countryCode[0]=s->country_code1;
+   countryCode[1]=s->country_code2;
+   countryCode[2]=s->country_code3;
+   countryCode[3]=0;
+}
+
 void LinkageDescriptor::Parse() {
    int offset=0;
+   s1 = NULL;
    data.setPointerAndOffset<const descr_linkage>(s, offset);
-   if (checkSize(getLength()-offset))
+   if (checkSize(getLength()-offset)) {
+      if (getLinkageType() == LinkageTypeMobileHandover)
+         data.setPointerAndOffset<const descr_linkage_8>(s1, offset);
       privateData.assign(data.getData(offset), getLength()-offset);
+      }
 }
 
 int LinkageDescriptor::getTransportStreamId() const {
@@ -656,6 +725,18 @@ LinkageType LinkageDescriptor::getLinkageType() const {
    return (LinkageType)s->linkage_type;
 }
 
+int LinkageDescriptor::getHandOverType() const {
+   return s1 == NULL ? 0 : s1->hand_over_type;
+}
+
+int LinkageDescriptor::getOriginType() const {
+   return s1 == NULL ? 0 : s1->origin_type;
+}
+
+int LinkageDescriptor::getId() const {
+   return s1 == NULL ? 0 : HILO(s1->id);
+}
+
 void ISO639LanguageDescriptor::Parse() {
    languageLoop.setData(data+sizeof(descr_iso_639_language), getLength()-sizeof(descr_iso_639_language));
    
@@ -704,6 +785,44 @@ int PDCDescriptor::getMinute() const {
    return s->pil2 & 0x3F;
 }
 
+void AncillaryDataDescriptor::Parse() {
+   int offset=0;
+   data.setPointerAndOffset<const descr_ancillary_data>(s, offset);
+}
+
+int AncillaryDataDescriptor::getAncillaryDataIdentifier() const {
+   return s->ancillary_data_identifier;
+}
+
+int PremiereContentTransmissionDescriptor::getOriginalNetworkId() const {
+   return HILO(s->original_network_id);
+}
+
+int PremiereContentTransmissionDescriptor::getTransportStreamId() const {
+   return HILO(s->transport_stream_id);
+}
+
+int PremiereContentTransmissionDescriptor::getServiceId() const {
+   return HILO(s->service_id);
+}
+
+int PremiereContentTransmissionDescriptor::getMJD() const {
+   return HILO(s->mjd);
+}
+
+void PremiereContentTransmissionDescriptor::Parse() {
+   s=data.getData<const descr_premiere_content_transmission>();
+   startTimeLoop.setData(data+sizeof(descr_premiere_content_transmission), getLength()-sizeof(descr_premiere_content_transmission));
+}
+
+time_t PremiereContentTransmissionDescriptor::StartTimeEntry::getStartTime(int mjd) const {
+   return DVBTime::getTime(mjd >> 8, mjd & 0xff, s->start_time_h, s->start_time_m, s->start_time_s);
+}
+
+void PremiereContentTransmissionDescriptor::StartTimeEntry::Parse() {
+   s=data.getData<const item_premiere_content_transmission_reference>();
+}
+
 void ApplicationSignallingDescriptor::Parse() {
    entryLoop.setData(data+sizeof(descr_application_signalling), getLength()-sizeof(descr_application_signalling));
 }
diff --git a/libsi/descriptor.h b/libsi/descriptor.h
index 476da3fb..338a1fd5 100644
--- a/libsi/descriptor.h
+++ b/libsi/descriptor.h
@@ -6,7 +6,7 @@
  *   the Free Software Foundation; either version 2 of the License, or     *
  *   (at your option) any later version.                                   *
  *                                                                         *
- *   $Id: descriptor.h 1.13 2005/09/03 15:17:35 kls Exp $
+ *   $Id: descriptor.h 1.14 2006/04/14 10:53:44 kls Exp $
  *                                                                         *
  ***************************************************************************/
 
@@ -121,6 +121,25 @@ protected:
    virtual void Parse();
 };
 
+class TeletextDescriptor : public Descriptor {
+public:
+   class Teletext : public LoopElement {
+   public:
+      char languageCode[4];
+      int getTeletextType() const;
+      int getTeletextMagazineNumber() const;
+      int getTeletextPageNumber() const;
+      virtual int getLength() { return sizeof(item_teletext); }
+   protected:
+      virtual void Parse();
+   private:
+      const item_teletext *s;
+   };
+   StructureLoop<Teletext> teletextLoop;
+protected:
+   virtual void Parse();
+};
+
 class CaDescriptor : public Descriptor {
 public:
    int getCaType() const;
@@ -281,6 +300,15 @@ private:
    const descr_component *s;
 };
 
+class PrivateDataSpecifierDescriptor : public Descriptor {
+public:
+   int getPrivateDataSpecifier() const;
+protected:
+   virtual void Parse();
+private:
+   const descr_private_data_specifier *s;
+};
+
 class SubtitlingDescriptor : public Descriptor {
 public:
    class Subtitling : public LoopElement {
@@ -377,17 +405,42 @@ protected:
    virtual void Parse();
 };
 
+class LocalTimeOffsetDescriptor : public Descriptor {
+public:
+   class LocalTimeOffset : public LoopElement {
+   public:
+      char countryCode[4];
+      virtual int getLength() { return sizeof(local_time_offset_entry); }
+      int getCountryId() const;
+      int getLocalTimeOffsetPolarity() const;
+      int getLocalTimeOffset() const;
+      time_t getTimeOfChange() const;
+      int getNextTimeOffset() const;
+   protected:
+      virtual void Parse();
+   private:
+      const local_time_offset_entry *s;
+   };
+   StructureLoop<LocalTimeOffset> localTimeOffsetLoop;
+protected:
+   virtual void Parse();
+};
+
 class LinkageDescriptor : public Descriptor {
 public:
    int getTransportStreamId() const;
    int getOriginalNetworkId() const;
    int getServiceId() const;
    LinkageType getLinkageType() const;
+   int getHandOverType() const;
+   int getOriginType() const;
+   int getId() const;
    CharArray privateData;
 protected:
    virtual void Parse();
 private:
    const descr_linkage *s;
+   const descr_linkage_8 *s1;
 };
 
 class ISO639LanguageDescriptor : public Descriptor {
@@ -422,6 +475,41 @@ private:
    const descr_pdc *s;
 };
 
+class AncillaryDataDescriptor : public Descriptor {
+public:
+   int getAncillaryDataIdentifier() const;
+protected:
+   virtual void Parse();
+private:
+   const descr_ancillary_data *s;
+};
+
+// Private DVB Descriptor  Premiere.de
+// 0xF2  Content Transmission Descriptor
+// http://dvbsnoop.sourceforge.net/examples/example-private-section.html
+
+class PremiereContentTransmissionDescriptor : public Descriptor {
+public:
+   class StartTimeEntry : public LoopElement {
+   public:
+      virtual int getLength() { return sizeof(item_premiere_content_transmission_reference); }
+      time_t getStartTime(int mjd) const; //UTC
+   protected:
+      virtual void Parse();
+   private:
+      const item_premiere_content_transmission_reference *s;
+   };
+   StructureLoop<StartTimeEntry> startTimeLoop;
+   int getOriginalNetworkId() const;
+   int getTransportStreamId() const;
+   int getServiceId() const;
+   int getMJD() const;
+protected:
+   virtual void Parse();
+private:
+   const descr_premiere_content_transmission *s;
+};
+
 //a descriptor currently unimplemented in this library
 class UnimplementedDescriptor : public Descriptor {
 protected:
diff --git a/libsi/headers.h b/libsi/headers.h
index 69350cdd..a238ca67 100644
--- a/libsi/headers.h
+++ b/libsi/headers.h
@@ -10,7 +10,7 @@
  *   the Free Software Foundation; either version 2 of the License, or     *
  *   (at your option) any later version.                                   *
  *                                                                         *
- *   $Id: headers.h 1.5 2005/09/03 15:18:16 kls Exp $
+ *   $Id: headers.h 1.6 2006/04/14 10:53:44 kls Exp $
  *                                                                         *
  ***************************************************************************/
 
@@ -769,6 +769,57 @@ struct ait_app {
    /* descriptors  */
 };
 
+/* Premiere Content Information Table */
+
+#define PCIT_LEN 17
+
+struct pcit {
+   u_char table_id                               :8;
+#if BYTE_ORDER == BIG_ENDIAN
+   u_char section_syntax_indicator               :1;
+   u_char dummy                                  :1; // has to be 0
+   u_char                                        :2;
+   u_char section_length_hi                      :4;
+#else
+   u_char section_length_hi                      :4;
+   u_char                                        :2;
+   u_char dummy                                  :1; // has to be 0
+   u_char section_syntax_indicator               :1;
+#endif
+   u_char section_length_lo                      :8;
+   u_char                                        :8;
+   u_char                                        :8;
+#if BYTE_ORDER == BIG_ENDIAN
+   u_char                                        :2;
+   u_char version_number                         :5;
+   u_char current_next_indicator                 :1;
+#else
+   u_char current_next_indicator                 :1;
+   u_char version_number                         :5;
+   u_char                                        :2;
+#endif
+   u_char section_number                         :8;
+   u_char last_section_number                    :8;
+
+   u_char contentId_hi_hi                        :8;
+   u_char contentId_hi_lo                        :8;
+   u_char contentId_lo_hi                        :8;
+   u_char contentId_lo_lo                        :8;
+
+   u_char duration_h                             :8;
+   u_char duration_m                             :8;
+   u_char duration_s                             :8;
+
+#if BYTE_ORDER == BIG_ENDIAN
+   u_char                                        :4;
+   u_char descriptors_loop_length_hi             :4;
+#else
+   u_char descriptors_loop_length_hi             :4;
+   u_char                                        :4;
+#endif
+   u_char descriptors_loop_length_lo             :8;
+};
+
 /*
  *
  *    The following describes the different descriptors that can be used within
@@ -1010,6 +1061,21 @@ struct descr_linkage {
    u_char linkage_type                           :8;
 };
 
+#define DESCR_LINKAGE_8_LEN 3
+struct descr_linkage_8 {
+#if BYTE_ORDER == BIG_ENDIAN
+   u_char hand_over_type                         :4;
+   u_char reserved                               :3;
+   u_char origin_type                            :1;
+#else
+   u_char origin_type                            :1;
+   u_char reserved                               :3;
+   u_char hand_over_type                         :4;
+#endif
+   u_char id_hi                                  :8;
+   u_char id_lo                                  :8;
+};
+
 /* 0x4B nvod_reference_descriptor */
 
 #define DESCR_NVOD_REFERENCE_LEN 2
@@ -1364,7 +1430,10 @@ struct descr_multilingual_component {
 struct descr_private_data_specifier {
    u_char descriptor_tag                         :8;
    u_char descriptor_length                      :8;
-   /* TBD */
+   u_char private_data_specifier_hi_hi           :8;
+   u_char private_data_specifier_hi_lo           :8;
+   u_char private_data_specifier_lo_hi           :8;
+   u_char private_data_specifier_lo_lo           :8;
 };
 
 /* 0x60 service_move_descriptor */
@@ -1717,6 +1786,34 @@ struct descr_application_icons_descriptor_end {
    u_char icon_flags_lo                          :8;
 };
 
+// Private DVB Descriptor  Premiere.de
+// 0xF2  Content Transmission Descriptor
+// http://dvbsnoop.sourceforge.net/examples/example-private-section.html
+
+#define DESCR_PREMIERE_CONTENT_TRANSMISSION_LEN 11
+
+struct descr_premiere_content_transmission {
+   u_char descriptor_tag                         :8;
+   u_char descriptor_length                      :8;
+   u_char transport_stream_id_hi                 :8;
+   u_char transport_stream_id_lo                 :8;
+   u_char original_network_id_hi                 :8;
+   u_char original_network_id_lo                 :8;
+   u_char service_id_hi                          :8;
+   u_char service_id_lo                          :8;
+   u_char mjd_hi                                 :8;
+   u_char mjd_lo                                 :8;
+   u_char start_time_loop                        :8;
+};
+
+#define ITEM_PREMIERE_CONTENT_TRANSMISSION_LEN 3
+
+struct item_premiere_content_transmission_reference {
+   u_char start_time_h                           :8;
+   u_char start_time_m                           :8;
+   u_char start_time_s                           :8;
+};
+
 } //end of namespace
 
 #endif //LIBSI_HEADERS_H
diff --git a/libsi/section.c b/libsi/section.c
index 68af9918..6dd43df7 100644
--- a/libsi/section.c
+++ b/libsi/section.c
@@ -6,7 +6,7 @@
  *   the Free Software Foundation; either version 2 of the License, or     *
  *   (at your option) any later version.                                   *
  *                                                                         *
- *   $Id: section.c 1.4 2006/02/18 10:38:20 kls Exp $
+ *   $Id: section.c 1.5 2006/04/14 10:53:44 kls Exp $
  *                                                                         *
  ***************************************************************************/
 
@@ -341,4 +341,20 @@ void AIT::Application::Parse() {
    applicationDescriptors.setData(data+offset, HILO(s->application_descriptors_length));
 }
 
+/******************* PremiereCIT *******************/
+
+void PremiereCIT::Parse() {
+   int offset=0;
+   data.setPointerAndOffset<const pcit>(s, offset);
+   eventDescriptors.setData(data+offset, HILO(s->descriptors_loop_length));
+}
+
+int PremiereCIT::getContentId() const {
+   return (HILO(s->contentId_hi) << 16) | HILO(s->contentId_lo);
+}
+
+time_t PremiereCIT::getDuration() const {
+   return DVBTime::getDuration(s->duration_h, s->duration_m, s->duration_s);
+}
+
 } //end of namespace
diff --git a/libsi/section.h b/libsi/section.h
index 5b43f05f..29af7f4b 100644
--- a/libsi/section.h
+++ b/libsi/section.h
@@ -6,7 +6,7 @@
  *   the Free Software Foundation; either version 2 of the License, or     *
  *   (at your option) any later version.                                   *
  *                                                                         *
- *   $Id: section.h 1.3 2004/02/20 13:45:45 kls Exp $
+ *   $Id: section.h 1.4 2006/04/14 10:53:44 kls Exp $
  *                                                                         *
  ***************************************************************************/
 
@@ -260,6 +260,21 @@ protected:
    virtual void Parse();
 };
 
+/* Premiere Content Information Table */
+
+class PremiereCIT : public NumberedSection {
+public:
+   PremiereCIT(const unsigned char *data, bool doCopy=true) : NumberedSection(data, doCopy) {}
+   PremiereCIT() {}
+   int getContentId() const;
+   time_t getDuration() const;
+   PCIT_DescriptorLoop eventDescriptors;
+protected:
+   virtual void Parse();
+private:
+   const pcit *s;
+};
+
 } //end of namespace
 
 #endif //LIBSI_TABLE_H
diff --git a/libsi/si.c b/libsi/si.c
index bbd3f1af..c7f23e88 100644
--- a/libsi/si.c
+++ b/libsi/si.c
@@ -6,7 +6,7 @@
  *   the Free Software Foundation; either version 2 of the License, or     *
  *   (at your option) any later version.                                   *
  *                                                                         *
- *   $Id: si.c 1.15 2006/02/18 10:38:20 kls Exp $
+ *   $Id: si.c 1.16 2006/04/14 10:53:44 kls Exp $
  *                                                                         *
  ***************************************************************************/
 
@@ -373,6 +373,9 @@ Descriptor *Descriptor::getDescriptor(CharArray da, DescriptorTagDomain domain,
          case MultilingualComponentDescriptorTag:
             d=new MultilingualComponentDescriptor();
             break;
+         case PrivateDataSpecifierDescriptorTag:
+            d=new PrivateDataSpecifierDescriptor();
+            break;
          case ServiceMoveDescriptorTag:
             d=new ServiceMoveDescriptor();
             break;
@@ -400,9 +403,16 @@ Descriptor *Descriptor::getDescriptor(CharArray da, DescriptorTagDomain domain,
          case ParentalRatingDescriptorTag:
             d=new ParentalRatingDescriptor();
             break;
+         case TeletextDescriptorTag:
+         case VBITeletextDescriptorTag:
+            d=new TeletextDescriptor();
+            break;
          case ApplicationSignallingDescriptorTag:
             d=new ApplicationSignallingDescriptor();
             break;
+         case LocalTimeOffsetDescriptorTag:
+            d=new LocalTimeOffsetDescriptor();
+            break;
          case LinkageDescriptorTag:
             d=new LinkageDescriptor();
             break;
@@ -412,6 +422,9 @@ Descriptor *Descriptor::getDescriptor(CharArray da, DescriptorTagDomain domain,
          case PDCDescriptorTag:
             d=new PDCDescriptor();
             break;
+         case AncillaryDataDescriptorTag:
+            d=new AncillaryDataDescriptor();
+            break;
 
          //note that it is no problem to implement one
          //of the unimplemented descriptors.
@@ -436,13 +449,9 @@ Descriptor *Descriptor::getDescriptor(CharArray da, DescriptorTagDomain domain,
          //defined in ETSI EN 300 468
          case StuffingDescriptorTag:
          case VBIDataDescriptorTag:
-         case VBITeletextDescriptorTag:
          case CountryAvailabilityDescriptorTag:
          case MocaicDescriptorTag:
-         case TeletextDescriptorTag:
          case TelephoneDescriptorTag:
-         case LocalTimeOffsetDescriptorTag:
-         case PrivateDataSpecifierDescriptorTag:
          case CellListDescriptorTag:
          case CellFrequencyLinkDescriptorTag:
          case ServiceAvailabilityDescriptorTag:
@@ -453,7 +462,6 @@ Descriptor *Descriptor::getDescriptor(CharArray da, DescriptorTagDomain domain,
          case CaSystemDescriptorTag:
          case AC3DescriptorTag:
          case DSNGDescriptorTag:
-         case AncillaryDataDescriptorTag:
          case AnnouncementSupportDescriptorTag:
          case AdaptationFieldDataDescriptorTag:
          case TransportStreamDescriptorTag:
@@ -500,6 +508,27 @@ Descriptor *Descriptor::getDescriptor(CharArray da, DescriptorTagDomain domain,
             break;
       }
       break;
+   case PCIT:
+      switch ((DescriptorTag)da.getData<DescriptorHeader>()->descriptor_tag) {
+         case ContentDescriptorTag:
+            d=new ContentDescriptor();
+            break;
+         case ShortEventDescriptorTag:
+            d=new ShortEventDescriptor();
+            break;
+         case ExtendedEventDescriptorTag:
+            d=new ExtendedEventDescriptor();
+            break;
+         case PremiereContentTransmissionDescriptorTag:
+            d=new PremiereContentTransmissionDescriptor();
+            break;
+         default:
+            if (!returnUnimplemetedDescriptor)
+               return 0;
+            d=new UnimplementedDescriptor();
+            break;
+      }
+      break;
    }
    d->setData(da);
    return d;
diff --git a/libsi/si.h b/libsi/si.h
index c8910ffb..6922cdcd 100644
--- a/libsi/si.h
+++ b/libsi/si.h
@@ -6,7 +6,7 @@
  *   the Free Software Foundation; either version 2 of the License, or     *
  *   (at your option) any later version.                                   *
  *                                                                         *
- *   $Id: si.h 1.13 2006/02/18 10:38:20 kls Exp $
+ *   $Id: si.h 1.14 2006/04/14 10:53:44 kls Exp $
  *                                                                         *
  ***************************************************************************/
 
@@ -43,7 +43,8 @@ enum TableId { TableIdPAT = 0x00, //program association section
                TableIdTOT = 0x73, //time offset section
                TableIdDIT = 0x7E, //discontinuity information section
                TableIdSIT = 0x7F, //service information section
-               TableIdAIT = 0x74  //application information section
+               TableIdAIT = 0x74, //application information section
+               TableIdPremiereCIT = 0xA0 //premiere content information section
              };
 
 
@@ -139,13 +140,15 @@ enum DescriptorTag {
                MHP_PrefetchDescriptorTag = 0x0C,
                MHP_DelegatedApplicationDescriptorTag = 0x0E,
                MHP_ApplicationStorageDescriptorTag = 0x10,
+  // Premiere private Descriptor Tags
+               PremiereContentTransmissionDescriptorTag = 0xF2,
 
                //a descriptor currently unimplemented in this library
                //the actual value 0xFF is "forbidden" according to the spec.
                UnimplementedDescriptorTag = 0xFF
 };
 
-enum DescriptorTagDomain { SI, MHP };
+enum DescriptorTagDomain { SI, MHP, PCIT };
 
 enum RunningStatus { RunningStatusUndefined = 0,
                      RunningStatusNotRunning = 1,
@@ -411,6 +414,12 @@ public:
    MHP_DescriptorLoop() { domain=MHP; }
 };
 
+//Premiere Content Information Table
+class PCIT_DescriptorLoop : public DescriptorLoop {
+public:
+   PCIT_DescriptorLoop() { domain=PCIT; }
+};
+
 //The content of the ExtendedEventDescriptor may be split over several
 //descriptors if the text is longer than 256 bytes.
 //The following classes provide base functionality to handle this case.